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• Xcc infection lead the chlorophyll degraded, net photosynthetic rate decreased. • Xcc infection reduced the activity of the PSⅡ reaction center and affected the chlorophyll fluorescence intensity. • Activities of the most enzymes in the Calvin cycle decreased after Xcc invasion. • Xcc can affect cabbage photosynthesis through multiple pathways. Cabbage is one of the most important cruciferous vegetables. Black rot, caused by Xanthomonas campestris pv. campestris (Xcc) seriously affects cabbage production; therefore, it is important to study the resistance mechanism to black rot in cabbage. In this study, cabbage photosynthetic physiology changes in the early stages of Xcc infection were analyzed using physiological index determination and transcriptome analysis. The results showed that the Xcc infection can lead the chlorophyll degradation and decreased the net photosynthetic rate (Pn), and the decrease in Pn was mainly due to non-stomatal factors. In addition, the maximum photosynthetic efficiency (Fv/Fm), actual photosynthetic efficiency of photosystem II (PSII) gradually decreased, and the OJIP curve tended to be flat, indicating that Xcc infection reduced the activity of the PSII reaction center and affected the chlorophyll fluorescence intensity. Moreover, the primary photochemical reaction of cabbage leaves was damaged, and electron transfer on the PSII receptor side was inhibited after Xcc infection. NADP-GAPDH and FBPase activities in the Calvin cycle decreased after Xcc invasion. Using transcriptome analysis, 173, 77, 63, and 53 differentially expressed genes (DEGs) were enriched in "carbon metabolism", "photosynthesis", "carbon fixation in photosynthetic organisms", and "metabolism of porphyrins and chlorophyll" metabolic processes, respectively. These results suggest that Xcc infection affects cabbage photosynthesis via multiple pathways. Our results provide a theoretical basis for further research on black rot-resistant breeding and cabbage resistance mechanisms. [ABSTRACT FROM AUTHOR]

• Chromium toxicity impaired leaf photosynthesis and pepper seedling growth. • Melatonin increased leaf photosynthetic efficiency and pigments content. • Melatonin maintained membrane stability and increased antioxidant defense system. • Melatonin decreased chromium uptake in shoot and enhanced pepper seedlings growth. Chromium (Cr) is widely recognized as a highly toxic metal pollutant that adversely affects the agricultural productivity and poses considerable risks to human health. The regulatory role of melatonin (MEL) in Cr stress is well recognized, however, the potential role of MEL in enhancing Cr stress tolerance in pepper is rarely investigated. This study examined the possible effect of MEL in alleviating the adverse effects of Cr toxicity in pepper seedlings. When pepper seedlings were exposed to Cr toxicity, they showed a significant reduction in growth traits, photosynthetic efficiency, root morphological characteristics, and biochemical attributes. Cr treatment greatly caused oxidative damage that was directly related to increased EL, H 2 O 2 , O 2 •−, and MDA production. Conversely, MEL supplementation significantly mitigated the phytotoxic effects of Cr on root morphology, gas exchange elements, and leaf photosynthetic capacity, and restored the growth of pepper seedlings. MEL application stimulated the plant's defense system by enhancing the modulation of antioxidant enzymes, AsA-GSH pools, maintaining the glyoxalase enzymes activity, and reducing oxidative damage. Notably, MEL supplementation significantly reduced Cr accumulation from root to shoot. Hence, MEL supplementation might be regarded as a successful approach for reducing Cr accumulation and its adverse effects in pepper seedlings cultivated in contaminated soils. The research may also provide novel perspectives on the potential application of MEL in mitigating heavy metal toxicity in pepper seedlings. [Display omitted] [ABSTRACT FROM AUTHOR]

• Whether and how soil AMF enhance heat stress tolerance of cucumber were studied. • Heat stress decreased root AMF colonization and soil hyphal length. • AMF increased cucumber biomass and leaf gas exchange under heat stress. • Most cshsp70s and cspips were up-regulated in inoculated plants under HS versus ST. • Under HS, AMF up-regulated expressions of 11 of 12 cshsp70s and 12 of 14 cspips. Cucumbers are frequently subjected to heat stress (HS) during the summer, which severely limits their growth and fruit yield and quality. Soil arbuscular mycorrhizal fungi (AMF) can enhance the abiotic stress tolerance of host plants, but it is unclear whether and how soil arbuscular mycorrhizal fungi (AMF) enhance the HS tolerance of cucumber. This work aimed to assess the effects of an arbuscular mycorrhizal fungus, Diversispora versiformis , on plant growth, leaf gas exchange, and expressions of plasma membrane intrinsic proteins (PIPs) and heat shock protein 70 (Hsp70) genes in roots of cucumber under HS (38 °C/30 °C, day/night temperature, 16 h/8 h) and suitable temperature (ST) (25 °C/18 °C, day/night temperature, 16 h/8 h) conditions. The HS treatment significantly decreased root mycorrhizal colonization and soil mycelium length by 0.26- and 0.55-fold, respectively, compared with the ST treatment. The biomass inhibition of cucumber by HS versus ST was more pronounced in uninoculated plants than inoculated plants. Inoculation with D. versiformis , however, significantly increased cucumber biomass and leaf gas exchange under both ST and HS conditions when compared to the uninoculated treatment. The HS treatment had almost no effect on or down-regulated the expression of CsHsp70s and CsPIPs genes in uninoculated plants, while most CsHsp70s and CsPIPs gene expressions were up-regulated in inoculated plants under HS versus ST conditions, suggesting the active heat resistance of mycorrhizal plants. Additionally, under ST conditions, D. versiformis up-regulated CsHsp70–11, CsPIP1;2 , and CsPIP2;6 expressions. Under HS conditions, D. versiformis increased the expression of 11 of 12 CsHsp70s by 1.17‒6.14 folds as well as 12 of 14 CsPIPs by 1.82‒144.43 folds, with CsPIP1.5 and CsPIP2;7 up-regulated up to 144.43- and 82.46-fold, respectively. It is concluded that D. versiformis -inoculated cucumbers exhibited higher heat tolerance than uninoculated plants, associated with up-regulated expression of most CsHsp70s and CsPIPs genes. [ABSTRACT FROM AUTHOR]

• Exogenous IAA improved photosynthetic capacity and carbohydrate metabolism in Zizania latifolia. • IAA could significantly improve plant yield. • IAA obviously promoted the integration of plant cell wall and hyphae of Ustilago esculenta Henn. • TIBA can reversely prove that exogenous IAA to improve plant yield, photosynthesis capacity, carbon assimilation. The effects of plant hormones on plant growth of Zizania latifolia are still considered to be the difficult and hot spots. The present study was carried out to investigate the regulation mechanism of exogenous indole-3-acetic acid (IAA) and IAA transport inhibitor (2,3,5-triiodobenzoic acid, TIBA) on yield, photosynthesis capacity, carbon assimilation and interaction of plant-fugal of Ustilago esculenta Henn. These results displayed that exogenous IAA led to significant increases in gall growth rate, swollen gall volume and biomass accumulation, promoting yield per unit of swollen gall in Z. latifolia. Exogenous IAA could improve the net photosynthetic rate (Pn), which contributed to higher stomatal conductance (Gs) and transpiration rate (Tr) in plant. TIBA treatment markedly inhibited the plant growth and photosynthetic rate. Contents of sucrose, glucose, fructose and total soluble sugar by IAA were significantly higher than control, whereas these parameters were declined by TIBA. Exogenous TIBA resulted in accumulation of starch (unfavorable to sugar metabolism) and crude fiber contents (declined swollen gall quality). Additionally, it was firstly reported the stimulation of exogenously applied of IAA and TIBA on plant growth and hyphae growth of U. esculenta. Microscopic analyses revealed that abundant hyphae were well-distributed closely to cell wall after IAA treatment, which could produce endogenous plant hormones, promoting the swollen cell structure enlargement. And hyphal aggregation over-growth by TIBA treatment indicated the vigorously increase of hyphae was surpassed the plant self-growth. These changes were greatly contributed to the increase of endogenous IAA content. The utilization of exogenous IAA and TIBA in present study proved IAA played a dominant role in regulating Z. latifolia growth. [ABSTRACT FROM AUTHOR]

Highlights • The use of interstocking method consists in two consecutive grafts. • Double grafting reduced CO 2 assimilation due to stomatal limitation. • Double grafting seedlings were more sensitive to high atmospheric evaporative demand. • Grafting operations affected gas exchange but not growth characteristics of seedlings. Abstract Interstocked seedlings are produced by making two successive grafts. In one of the methods used, interstocked seedlings can be produced by introducing a rootstock by inarching and a scion by budding in a previously formed seminiferous seedling. The hypothesis of the present research is that double grafting may reduce shoot hydraulic conductivity and reduce water supply to the scion, affecting leaf gas exchanges and photochemical efficiency. Thus, in the present study the effect was assessed of sequential grafting (inarching and budding) during the production process of interstocked 'Pêra' sweet orange plants on their net photosynthesis and growth capacity. The grafts were made on 'Seleta' (S) sweet orange or Rangpur lime (R) nucellar seedlings. First the seedlings were inarched with Poncirus trifoliata var. monstrosa 'Flying Dragon' (FD) and in the second stage, they were budding with 'Pêra' orange (P), to form the scion. A completely randomized design was used, with three treatments, seven replications and one plant per plot. The treatments consisted of the following combinations between scion, interstock and rootstock: P/S/FD; P/R/FD and P/R, and the latter combination was used as control. At 390 days after sowing, the seedlings had two functional root systems and their height and diameter were measured. The net CO 2 assimilation rate (A), stomatal conductance (g s), transpiration (E), internal CO 2 concentration in mesophyll (Ci), maximum quantum efficiency of Photosystem II (F v /F m), photosynthetic index (Pi), leaf temperature (°C) at 8:00 and 13:00 and the SPAD reading were determined on the leaves. The seedlings did not differ in its height or in diameter of their inarch. Among the seedlings with double rootstocks, higher diameter was observed in the 'Seleta' sweet orange stem. The connections in the plant, caused by inarching and budding, and the gradual rootstock substitution, made these plants more sensitive to high atmospheric evaporative demand during nursery stage, and reduced photosynthetic carbon assimilation. [ABSTRACT FROM AUTHOR]

Highlights • Fruit load altered water and carbon cycles of date palm. • Fruit growing increased gas exchange and decreased frond elongation. • Post-harvest water use in fruited palms was high for carbohydrate refilling. • Irrigation management must consider fruit load to achieve optimal yield. Abstract The cultivation of date palms in Israel's Arava Valley, which is characterized by a high evaporative demand, is widespread and exclusively depends on high-frequency irrigation. Fruit sets are usually thinned early in their development to produce large, high-quality dates. However, no effort has yet been made to comprehensively examine fruit load effects on date palm water use, CO 2 fluxes and growth. The objective of this study was to investigate the effects of fruit load on these factors. Twelve date palms, six with fruit removed ("without fruit") and six untreated ("with fruit"), were irrigated with equal amounts of water at sufficient levels for maintaining optimal soil water conditions. Sap flow and frond elongation were continuously measured. Gas exchange parameters (i.e., stomatal conductance and CO 2 assimilation rate) and fruit growth (i.e., fruit size, mass, and sugar content) were monitored periodically. No significant differences were found in gas exchange, water consumption and frond elongation between the two treatments several weeks after the onset of the fruit load differentiation. However, a pronounced increase in stomatal conductance and CO 2 assimilation rates in palms with fruit compared to those without fruit was identified during the sugar accumulation and post-harvest periods. Continuously increasing water consumption in palms with fruit was also observed during these periods, probably as a result of the progressive recovery of depleted carbohydrate and water storage in the tree. In addition, the frond elongation rate of palms with fruit was remarkably lower than those without fruit until the end of the harvest. It is concluded that crop load has a pronounced effect on physiological behaviors and water use of the cultivated date palm. Therefore, irrigation management must consider fruit load to achieve optimal yield. [ABSTRACT FROM AUTHOR]

Alkali stress on crops has gained importance around the world in recent years. Avocado ( Persea americana Mill.) is considered a salt-sensitive species, but the effect of alkaline water on avocados has not been sufficiently studied. Biomass, gas exchange, chlorophyll- a fluorescence, photosynthetic pigments and tocopherols were evaluated in response to alkali salt (NaHCO 3 ) and neutral salt (NaCl) stresses on avocado. Three irrigation treatments were applied: Control (no added salt), 1 g l −1 NaCl and 1.5 g l −1 NaHCO 3 for a period of 5 months. Six clonally propagated avocado rootstocks were employed, four local selections of West Indian and two Mexican race rootstocks. Biomass reduction was observed in both salt treatments, especially in the roots under the alkali stress. A reversible photoinhibition, a lower photochemical efficiency of PSII and a greater oxidative stress were detected in the alkali stressed avocados. Although biomass was reduced under salt and alkali stress, alkali stress harmed the photosynthetic apparatus to a greater extent than salt stress. Further research is necessary, the problem of alkali stress is increasing, especially in places with alkali waters where salt sensitive species such as avocado is cultivated. [ABSTRACT FROM AUTHOR]

High concentration of salts in the irrigation water causes plant water stress due to decreased water availability and nutrients uptake from the soil. However, these effects may be minimized by the presence of soil microorganisms, which increase plant tolerance to abiotic stress. The experiment described was performed using three-year-old laurustinus ( Viburnum tinus L.), in which the combined effect of two irrigation treatments (EC < 0.9 dS m −1 as control and EC: 6 dS m −1 as the saline water) and microbial complex inoculation and non-inoculation were applied under field conditions during six months. The chemical properties of the soil as well as physiological behavior of the plants were evaluated. The higher salinity irrigation water produced plants that were lower than the control plants in the last phase of the experiment, while inoculated plants had a better visual appearance minimizing the decrease of chlorophyll levels. Salinity caused a decrease in g s and P n from the beginning of the experiment, the enhanced g s due to bacterial inoculation increased the photosynthetic activity, which was accompanied by the better uptake of water by the roots (higher Ψ stem values). Bacterial inoculation led to a significant decrease in Na and Cl in the aerial part of the plants. The leaf Ca, Fe, Mg and Mn contents were higher in the inoculated control plants than in non-inoculated control plants, while P decreased and K content was similar. Salinity did not affect the enzymatic activity (phosphatase and chitinase activity) or the nitrogen and total carbon content of the soil, while the total carbon was higher in inoculated plants than in non-inoculated plants. The bacterium did not significantly influence the soil phosphorus content, although it showed a slight tendency to increase at the end of experiment. Although laurustinus has natural mechanisms against saline stress, the inoculation with the selected soil microbial complex improves plant physiological behavior, which is important for plant establishment and soil protecting. [ABSTRACT FROM AUTHOR]

Plant growth is key determinant for leaf yield and biomass accumulation in mulberry. Accurate prediction of yield ensures brushing of right quantum of silkworms for silk production. Repeated harvesting of leaves/shoots leads to stress with physiological and biochemical changes. This necessitates in-depth analysis of growth attributes leading to rejuvenation and biomass production. A total of 22 contrasting genotypes for growth (CSG) were shortlisted from a diverse set of germplasm based on Number of Days required for Bud Sprouting (NDBS), Shoot Elongation Rate (SER) and Number of Branches (NB) in two distinct seasons. The logistic regression analysis of CSG expressed in odds ratio showed positive regression coefficients for important traits viz ., inter-nodal distance (2.71), NB (1.31), Total Shoot Length (TSL, 1.38), Length of the Longest Shoot (LLS, 1.17) and Number of Leaves on the Longest Shoot (NLLS, 1.18) for high growth in August 2016. The growth curve estimates for SER was significantly (P < 0.0001) higher among High Growth Genotypes (HGG; 4–6.2 cm/day) compared to Low Growth Genotypes (LGG; 2.6–4.1 cm/day). Repeated measure ANOVA showed significance A (P < 0.0001), gs (P < 0.01), IWUE (P < 0.01) between three growth periods. A , Tr , and gs were higher among HGG compared to LGG and opposite was true in case of IWUE. Similarly, Amax and AQL were higher in HGG whereas Vcmax and Jmax were higher in LGG. Significant linear relationship of Tr , gs and IUWE was observed with NB, TSL and LLS. The study concludes that mulberry growth can be predicted using important morpho-metric traits and gas exchange parameters as supported by logistic and linear regression analysis. [ABSTRACT FROM AUTHOR]

Although grafting has become an effective tool to enhance many traits in horticultural crops, its role in improving the performance of local landraces is yet to be proven. The aim of this work was to assess the performance of the ‘Ramellet’ tomato, a landrace from the Balearic Islands, when grafted onto different rootstocks. For this purpose, two ‘Ramellet’ genotypes were grafted on two commercial (‘Beaufort’ and ‘Maxifort’) and a wild ( Solanum pimpinellifolium ) tomato rootstock species, and cultivated in greenhouse under commercial conditions. Plant yield, morphology and photosynthetic traits were measured in all combinations, with non-grafted and self-grafted ‘Ramellet’ plants used as controls. A significant effect of the rootstock on key parameters related to yield, plant growth and photosynthesis was found in both ‘Ramellet’ genotypes. Stomatal conductance increased, resulting in a decreased water-use efficiency in both genotypes grafted on the commercial rootstocks. Oppositely, when grafted on S. pimpinellifolium , stomatal conductance decreased and water-use efficiency increased in one of the ‘Ramellet’ genotypes. Remarkably, there was a significant correlation between water-use efficiency, plant growth and yield. Overall, the results highlight the potential of grafting to alter several physiological traits of local landraces and to provide new clues towards advancing our understanding in the underlying determinants of water-use efficiency and plant yield. [ABSTRACT FROM AUTHOR]

Most modern and traditional grape-growing regions are facing challenging times due to the unpredictability of weather conditions and warming trends. Innovative and sustainable tools such as seaweed-based biostimulants may play a key-role in the development of environment-friendly viticultural strategies to improve yields, biotic/abiotic stress tolerance and fruit and wine quality. A sprayable Ascophyllum nodosum extract was tested on grapevines cv. Sangiovese grown under Mediterranean conditions (central Italy) and on grapevines cv. Pinot Noir and Cabernet Franc within a cool-climate viticulture region (Michigan, USA). The product was sprayed on the canopies at label doses (1.5 kg/ha) five times during the season, starting two weeks before veraison. The seaweed extract did not affect leaf gas exchanges, yield or cluster and berry size, but hastened veraison, improved anthocyanins accumulation in all cultivars and increased phenolic content particularly in Sangiovese. Therefore, medium-late application of the seaweed extract can be a simple way to favour chromatic and chemical proprieties of grapes and wines. This is the first report of positive effects of Ascophyllum nodosum extracts on the quality of cultivated wine grapes. The adoption of the technique can be particularly suitable to cool-climate viticulture, especially as it pertains to short growing seasons and genotypes with a limited phenolic profile. [ABSTRACT FROM AUTHOR]

Plants perceive environmental stress and use this information to modulate their regular pattern of development. Abscisic acid (ABA) mediates plant responses to many abiotic stresses. This study investigated the efficiency of short- versus long-term ABA exposure on critical morphological and physiological responses linked to functional changes in stomata, stomatal density, plant water status, photosynthetic activity and overall growth in bell pepper ( Capsicum annuum L.). ABA was applied to pepper seedlings as foliar at 0, 0.1 or 1.0 mM for 5, 10 or 15 consecutive days. A depressive effect of ABA on net photosynthetic rate (A CO2 ) and stomatal conductance (g s ) compared to control was found after 5-day ABA-exposure at 1.0 mM, and after 15-day ABA-exposure at 0.1 mM and 1.0 mM ABA. Plants quickly resumed the photosynthetic activity since no effect of ABA was found after a longer recovery. Temporary higher leaf water potential was observed in seedlings treated with ABA compared to control. At 17 days after the beginning of the experiment, the number of stomata at adaxial and abaxial side was reduced at 1.0 mM ABA-rate compared to 0.1 mM ABA for each ABA-day of exposure. ABA-rate at 1.0 mM decreased leaf weight, number and area with a more pronounced effect as ABA-days of exposure increased. Stem dry weight was almost unaffected by ABA-rate at 0.1 mM, but 1.0 mM decreased stem weight by 30% after 15-day ABA-exposure. The increased specific root length at 1.0 mM ABA-rate after 5- or 15-day ABA exposure suggested that ABA induced the growth of thinner roots. The delayed effect of ABA-rate and ABA-days of exposure was measured for plants allowed to recover for 23 days after the last application for the longest treatment. Growth parameters were generally affected by ABA after longer recovery. The effect of ABA on modulation of pepper seedlings growth and physiology was dependent on rate and length of exposure but recovery duration was important as well. These results provide new evidences that application of ABA at a specific rate and length of exposure could eliminate the risk of stressing young seedlings to the point of physiological injury as previously reported for some hardening techniques. [ABSTRACT FROM AUTHOR]

Apple orchards are being increasingly installed with high tree density, using different training systems. Although, some information about how training systems affect fruit parameters, few are known regarding the physiological performance under different tree architecture. Consequently, in this study, leaf gas exchange parameters, but also leaf biochemistry and antioxidant activity were assessed. The study was carried out in an orchard located in Carrazeda de Ansiães, northeast of Portugal, during the year of 2015, in two years old apple trees of “Royal Gala” cultivar (first harvest), grafted onto M9 rootstock, grown using the central leader and the bi-axis training systems. While minor influence was found on leaf biochemical and antioxidant parameters, namely only an increase of the starch content in the bi-axis training system, leaf gas exchange parameters showed to be strongly influenced by the training system. Higher A, E, g s and C i rates, were recorded for the bi-axis training system, however A/g s was higher in the central leader training system. These results clearly illustrate the effect of the training system on apple trees that can ultimately influence fruit production and quality. [ABSTRACT FROM AUTHOR]

• Open-flow photosynthesis system was assembled using an Arduino development board. • System provided a disinfection condition during air ventilation with near-saturated moisture content. • Accurate sampling was conducted by a real-time clock library programmed on the Arduino board. • In vitro pitaya achieved a positive net photosynthetic rate during the daytime period. • Open-flow system yielded a four-phase gas exchange pattern. A non-facultative crassulacean acid metabolism (CAM) profile has been documented in pitaya, in which closed flow photosynthesis systems have been used to evaluate the CAM capacity and characteristics of plants, albeit with overestimation. By contrast, open-flow systems promote measurement reliability and continuously monitor the photosynthetic profile, which has not been reported in pitaya. Therefore, this study aimed to overview the diel gas exchange capacity of Hylocereus polyrhizus 'Da Hong' in an open-flow system, in which the explants were incubated in vitro to prevent measurement deviations caused by microorganism activity. The experimental conditions were 80 µmol/m2/s light intensity at 25 °C under a 16/8 h (D/N) photoperiod. The Arduino-based assembled system contained three subsystems: explant growth, air supplementation, and air sampling and environmental monitoring. The growth vessel had an 83.5% light transmittance with a 3.8 mol/m2/day light intensity. Air ventilation was performed at a flow rate of 1,000 mL/min with 99.9% relative humidity through the filters, which precluded infection and provided a high moisture content environment in the growth vessel during the experiments. A real-time clock library programmed on the development board realized an accurate sampling point and period. The diel gas exchange pattern of pitaya exhibited four phases; explants had a net photosynthetic rate (P n) of 2.63 μmol/m2/s at midnight, and the total net CO 2 uptake over 24 h was 73.98 mmol/m2/day. The positive P n observed during the daytime was noteworthy. This study successfully measured the photosynthetic profile of pitaya in vitro , providing a diel gas exchange reference. An open-flow whole-canopy system could be used in other explants to evaluate the photosynthesis profile in the era of climate change. [Display omitted] [ABSTRACT FROM AUTHOR]

The recently bred Korean strawberry ( Fragaria × ananassa ) cultivar ‘Sulhyang’ accounts for more than 83% of the strawberry cultivation area in Korea. Although strawberry growth properties vary among cultivars, knowledge related to those of ‘Sulhyang’ remains insufficient. We examined gas exchange characteristics in leaves of this cultivar in autumn and winter to obtain basic data related to this cultivar. The light saturation point of the net photosynthetic rate ( P n ) at 25 °C leaf temperature and 400 μmol mol −1 CO 2 was about 1750–2000 μmol m −2 s −1 PPFD. The optimum leaf temperature of P n was about 29 °C, but values did not differ greatly between 19 °C and 31 °C, at 1200 μmol m −2 s −1 PPFD and 400 μmol mol −1 CO 2 . These results indicate that a high light condition is the most important factor affecting the strawberry cultivation in plastic houses and that temperature is the second most important. Results show that P n did not saturate at 1400 μmol mol −1 CO 2 under 1200 μmol m −2 s −1 PPFD and 25 °C leaf temperature, with its enrichment effect as high as 60–80% ( P n at 1400 vs. 400 μmol mol −1 CO 2 ). The P n and dark respiration rate ( R d ) among the first to fifth leaves from the top expanded leaf showed no great difference. However, P n was generally higher in autumn plants at initial flowering than in winter plants at vigorous fruit setting. These findings constitute important fundamental information to support the technological development of strawberry cultivation, especially of ‘Sulhyang’. [ABSTRACT FROM AUTHOR]

• Exogenous IAA (100 mg/L) could significantly improve the adverse growth states of Syringa villosa in summer. • IAA application promoted photosynthetic capacity and endogenous favourable hormones levels such as IAA and GA 3 in Syringa villosa. • The transcriptome of Syringa villosa was first sequenced which revealed the vital biological processes and potential target genes regulated by exogenous IAA as a growth promoter. Auxin is a core regulator of plant growth and an effective promoter of cell division and cell expansion. Effects of auxin on improving plant growth of Syringa plants remain poorly elucidated. The present study was carried out to investigate the effects of exogenous indole-3-acetic acid (IAA) on morphogenesis, endogenous hormone content, photosynthesis capacity and find the basis of IAA-induced physiological effects of Syringa villosa by transcriptome sequencing technology. The results indicated that exogenous IAA significantly contributed to the plant height, stem diameter, leaf area and leaf number, which improved the accumulation of whole plant quality. Contents of endogenous IAA and gibberellic acid (GA 3) were markedly higher than control after IAA treatment, while abscisic acid (ABA) content was significantly declined. For photosynthetic parameters, photosynthesis capacity was promoted by the application of IAA, as evidenced by a significant increase in net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (Tr) and a lower intercellular CO 2 concentration (Ci). In addition, the transcriptome of S. villosa was first sequenced which revealed that genes related to the synthesis and signal transduction of growth-promoting hormones such as IAA, GA 3 , cytokinin (CTK), and brassinolide (BR) were significantly up-regulated within 2 h of IAA treatment. The expression levels of genes related to photosynthesis, antenna proteins, and carbon fixation of photosynthetic organisms were also enhanced by exogenous IAA. Additionally, the application of exogenous IAA had a positive effect on growth and development by rapidly inducing genes related to cell division and cell expansion. By profiling the transcriptome of IAA response, potential target genes were identified based on the hormone levels and photosynthesis. These results provide insights for further functional genomic studies on the regulatory mechanisms of IAA underlying Syringa plants architecture. [ABSTRACT FROM AUTHOR]

Whole-canopy gas exchange provides a more accurate measurement of CO 2 assimilation (A c ) and transpiration (E c ) compared to single-leaf. The objectives of this study were to evaluate whole-canopy gas exchange of 2 coffee species: Coffea arabica cv. Catuaí Amarelo-Catuaí and Coffea canephora cv. Emcapa 8111 Clone 02–Clone 02 during two different seasons varying in temperature. Six plants >1-year-old of each species were grown in pots (100L) in a greenhouse. Soil moisture was maintained at field capacity. Data were continuously collected for 10 days during spring (September 2014—moderate temperatures) and summer (February 2015 with high temperature) and micrometeorological variables were monitored inside the greenhouse. Catuaí had a lower area leaf and higher branch angle resulting in greater light distribution within the canopy that contributed to higher net photosynthesis and transpiration as compared to Clone 02 in both seasons. Catuaí had reduced whole-canopy CO 2 assimilation and transpiration during summer, mainly linked to reduced whole-canopy conductance. However, Clone 02 had similar whole-canopy CO 2 assimilation and transpiration values in both seasons. Despite reduced gas exchange for Catuaí during summer, the relationship between A c and E c indicated that Catuaí had a greater instantaneous WUE c than Clone 02 during spring and there were no differences between species during summer. The dense canopy architecture of Clone 02 limited whole-canopy gas exchange due to poor light distribution within the canopy whereas Catuaí had better canopy light distribution resulting in higher photosynthetic rates than Clone 02 during spring. Additionally, the architecture had a negative effect when Catuaí experiences increased temperature that reduced whole-canopy conductance. High temperatures may limit the growth and production of coffee plants in tropical areas. [ABSTRACT FROM AUTHOR]

Due to the rise in anthropogenic greenhouse gas concentrations, the earth's climate is expected to change, with precipitation being reduced in some areas resulting in growth-limiting drought and, as a consequence, reduced plant productivity. We investigated the physiological and growth responses of cassava ( Manihot esculenta Crantz) to approximate present-day ambient (390 μL L −1 ) and elevated (750 μL L −1 ) atmospheric CO 2 concentrations under well-watered and water deficit conditions, aiming at understanding how cassava would face those problems. Water deficits led to reductions in the Leaf Elongation Rate of plants grown at ambient as well as CO 2 -enriched concentrations. However, plants grown at 750 μL L −1 of CO 2 maintained leaf growth two days longer than plants grown at 390 μL L −1 . Three Days After Withholding Water (DAWW), photosynthesis and stomatal conductance were reduced in plants grown under ambient CO 2 , while in plants under an elevated CO 2 concentration, these physiological functions remained similar to that of control plants grown under good water availability. Five DAWW plants grown with 750 μL L −1 continued to have enhanced gas exchange compared with plants grown under 390 μL L −1 . Under drought stress, the instantaneous transpiration efficiency was always greatest for plants grown under elevated CO 2 . The positive response of elevated CO 2 levels on total dry mass was 61% in the water-stressed plants and only 20% for the plants grown under good water availability. Stomatal limitation was an important factor reducing CO 2 assimilation in cassava growing under drought conditions. [ABSTRACT FROM AUTHOR]

Biennial cropping is typically characterized as having ‘ON’ and ‘OFF’ years in which the ‘ON’ year produces an excessive crop load and the ‘OFF’ year has a very small crop load. Frost damage during the bloom period or winter freeze damage is another means of reducing the crop load that can initiate biennial bearing in an otherwise consistent cropping system. The objectives were to determine what effect single and multiple year crop loss had on the current and subsequent year’s dry matter partitioning and photosynthesis. Dry matter partitioning and whole tree photosynthesis ( A ) were being measured in biennial bearing ‘Empire’ apple trees when 2 consecutive frosts occurred following an ‘OFF’ year. This provided an opportunity to evaluate two cycles of conventional biennial bearing and the effect of 3 years of suppressed crop load on dry matter partitioning and whole tree photosynthesis. Frost events reduced fruit dry weight to levels equivalent to the ‘OFF’ years but the ‘SUPPRESSED’ years (1 ‘OFF’ and 1 or 2 frost years) reduced partitioning to wood dry matter and leaf + fruit more than the ‘OFF’ years while increasing the fruit dry matter partitioning compared to the ‘OFF’ years despite similar fruit yield and crop load. The ‘ON’ years had the highest fruit dry weight and% dry weight partitioned to fruit and leaf + fruit. Conversely, the ‘ON’ year had the least leaf area index (LAI) and% dry weight partitioned to wood and leaf tissue. There were no differences in canopy area, however, the ‘ON’ years had a significantly reduced LAI. Radiation use efficiency RUE; Annual biomass (kg)/PAR [(MegaMoles/growing season) × canopy area (m 2 )] was linearly correlated with the% dry mass partitioned to fruit and negatively correlated with LAI. For a specified LAI, the ‘ON’ year had a greater RUE than the ‘OFF’ or ‘SUPPRESSED’ years and there were no differences between ‘OFF’ and ‘SUPPRESSED’ years. Analysis of daily photosynthesis ( A ) indicated that all three treatments were significantly different. The ‘ON’ years had the highest mean daily A (3.8 μmol/m 2 /s), ‘SUPPRESSED’ years were intermediate (3.0 μmol/m 2 /s) and the ‘OFF’ years had the lowest A (2.5 μmol/m 2 /s). It appears that in years when fruiting is suppressed more than a single year, dry matter partitioning to wood is also suppressed and a great partitioning occurs to the remaining fruit and leaf tissue. This may be a response to a continued deficit of the hormonal complex supplied by fruit as they develop. [ABSTRACT FROM AUTHOR]

Papaya canopy architecture enables all the leaves to receive sufficient amounts of sunlight to optimize leaf gas exchange due to the spiral phyllotaxis. Thus, there may be a close relationship between photosynthesis and transpiration measurements at single-leaf and whole-canopy levels. We tested this hypothesis by simultaneously measuring single leaf and whole canopy gas exchange of ‘Gran Golden’ papaya during two seasons. Whole-canopy gas exchange was measured on five plants during four days in July (winter) from 08:00 to 1700 h and three days in December (summer) from 06:00 to 1700 h in 2006. Single-leaf gas exchange measurements were performed using the fully exposed 12th and 13th leaf from the apex on five plants adjacent to those with whole canopy chambers at the same time of the day. Net photosynthetic rate ( A ) values on a single-leaf or whole-canopy basis in field-grown papaya were similar and highly correlated under clear sky conditions since the open canopy architecture of papaya plants allowed saturating light intensities for photosynthesis to reach all leaves. Conversely, whole-canopy transpiration ( E c ), was approximately 50% of single-leaf transpiration ( E l ) likely due to high air temperature and VPD leaf-air and increased leaf fan speed in the LI-6200 leaf chamber (single leaf) compared to the whole canopy chamber. Therefore, water use efficiency measured on a single-leaf basis seems to have reduced applicability in papaya water relations studies. [ABSTRACT FROM AUTHOR]

• The silencing of FaCRY2 not only delayed flowering time, but also delayed growth (plant height) in cultivated strawberry. • The down-regulation of cell development genes and decrease of IAA accumulation could be responsible for the delayed growth of cry2 based on RNA-seq analysis and IAA determination. • The silencing of FaCRY2 deepen the lignification of strawberry petiole tissue cells. • The silencing of FaCRY2 reduced stomatal conductance and transpiration rate. As a plant blue light receptor, CRY2 plays pleotropic roles in regulating photomorphogenesis, flowering time and stress response. However, the function of CRY2 in the octoploid cultivated strawberry (Fragaria × ananassa Duch.) has not been identified. In this study, certain variation and functional divergences of the FaCRY2 protein were found in compared with its homologs in diploid model plants (AtCRY2 and SlCRY2). Quantitative RT-PCR analysis of the FaCRY2 showed the highest expression level in the leaf and flower tissues. The subcellular localization results indicate that the FaCRY2 was a nucleus-localized protein. The cry2 mutants, silenced by artificial micro-interfering RNA interference (AmiRNAi) using 'Benihoppe' strawberry as genetic background, showed a growth retardation, including dwarf phenotype, decreased free IAA content, delayed flowering time, deepened the lignification degree of petiole cells, decreased stomatal conductance and transpiration rate. RNA-seq analysis showed that there were 910 significantly differentially expressed genes (DEGs) between wild-type (WT) and cry2. They were mainly enriched in hormone regulation, cell development and stress response, etc. The decrease of IAA accumulation could be the main factor responsible for the delayed growth of cry2. Taken together, our results suggested the complex roles of FaCRY2 in the plant growth regulation in cultivated strawberry. [ABSTRACT FROM AUTHOR]

• Glycinebetaine (GB) increased net photosynthetic rate of albino tea by 45.3% at low temperature. • GB raised the methylation of photosynthetic-related genes and chlorophyll contents. • Facilitating photosynthesis by GB was correlative to related gene methylation. • GB may play as a methyl donor for gene methylation of albino tea leaves. The frequent occurrence of adverse weather conditions in early spring caused by global climate change has seriously restricted the physiological metabolism and growth of plants in recent years. As a low temperature sensitive albino tea cultivar, white leaf No. 1 (WL-1) has been seriously affected. Regulation of DNA methylation (an epigenetic regulator) due to global climate change by glycinebetaine (GB, a bioactive methyl donor) has been often observed in animals/humans, but little is known about whether it is linked to gene methylation priming responses of plants to low temperature. Herein, the effects of foliar application of GB on photosynthesis, photosynthetic pigment synthesis and related genes methylation of WL-1 functional leaves under low temperature were investigated. Results showed that the transpiration efficiency and chlorophyll contents of WL-1 functional leaves under low temperature condition were significantly improved by the application of GB (P < 0.05), and the net photosynthetic rate was increased by 45.3%. In addition, the application of GB promoted the methylation of most methyltransferase and demethylase genes, PSⅡ component genes and some chlorophyll synthesis genes in WL-1 functional leaves under low temperature. It was verified that the changes of photosynthetic parameters and chlorophyll content may be correlative to related gene methylation. Together, present study suggests important roles of GB in facilitating photosynthesis of albino tea functional leaves under low temperature by regulating related gene methylation. [Display omitted] [ABSTRACT FROM AUTHOR]

Two urban biowaste materials, fermented under anaerobic and aerobic conditions, their soluble and insoluble alkaline hydrolysates, and a commercial biostimulant product, were compared for their capacity to boost Hibiscus crop production and quality. Plants were grown in 4‐litre pots, containing peat and pumice as substrate, under optimal growing conditions. A randomized-block experimental design was adopted. Two types (main factors of variability) of treatments were applied, i.e. by blending the above products with the substrate at transplant, and by fertigation using the soluble hydrolysates only. Plant biomass characteristics and ecophysiological parameters were measured. Mean effect of factors and their interactions were assessed by two‐way ANOVA. Principal component analysis was performed by using the different dependent variables to summarize the most relevant differences among treatments. Compared with the control (untreated plants), the applied treatments enhanced most of the investigated parameters. The most valuable effects were observed for total biomass accumulation (+25%), plant height (+10%), leaf chlorophyll SPAD index (+15%) and net photosynthesis (+24%). The hydrolysates performed better than the pristine materials. The former ones were comparable to the commercial biostimulant. The results confirmed the hypothesis that biowaste derived products induce biostimulant activity on Hibiscus ; their application can improve cultivation sustainability. [ABSTRACT FROM AUTHOR]

The response of different deficit irrigation strategies on physiological and morphological parameters on table grapes (cv. Crimson Seedless) grown in pots was studied three times a day to evaluate how such strategies could be safely used for hardening and to ascertain their tolerance to drought. Five preconditioning treatments were applied: (i) CTL-1 and CTL-2; both irrigated daily to field capacity; (ii) DI, watered to 50% of CTL-1; (iii) PRDFIX, permanently watered to 50% of CTL-1 in a pot, and (iv) PRDALT, the root was split into two pots, and the pots alternatively watered to 50% of CTL-1 when the volumetric substrate water content ( θ v ) reached 12%. 30 days after the application of the preconditioning treatments, vines were subjected to drought for 7 days, except for CTL-1. After that, vines were re-irrigated and their recovery was studied for 7 days. Crimson Seedless displayed different responses to water stress, depending on the diurnal course. At predawn ( t 1) and early morning ( t 2), the cultivar showed near-anisohydric behaviour, through a less effective stomatal control of drought, whereas at midday ( t 3) the behaviour was near-isohydric. Although the total amount of irrigation water was the same for DI, PRDALT and PRDFIX, the vines from the last had a reduced photosynthetic activity, probably due to a limited sap flow. Water stress conditions induced avoidance mechanisms to drought such as stomatal closure, partial defoliation and a reduction in leaf insertion angle. Osmotic adjustment was only observed in un-preconditioned vines (CTL-2) but it was not enough to reach full turgor. In addition, PRDFIX and CTL-2 vines suffered serious dehydration damages to biomass accumulation and vine quality, regardless of the recovery of gas exchange parameters. PRDALT and DI can be used as safe techniques for irrigation scheduling in the nursery stage, because of their adaptability to water stress and so improve the survivability of the young table grapes plantations. [ABSTRACT FROM AUTHOR]

• Sooty mould (SM) black coatings reduced the photosynthetic activity of tea plants. • Exogenous application of 10 mM melatonin could protect plants from SM by reduction of fungal growth and melanin pigment production. • Melatonin improved photosynthetic parameters and increased antioxidant enzymes in SM tea plants. • Melatonin triggers plant defence and chlorophyll a & b degradation associated genes expression. Studies have been estimated the economic risk of sooty mould (SM) disease in various economical crops, however, the effects of SM on growth and development of tea plants are still unclear. The study investigates the impact of sooty mould on photosynthetic pigments, chlorophyll fluorescence (Fv/FM) and gas exchange parameters and recovery of plants by exogenous melatonin. The morphological and multilocus phylogenetic analyses showed that the sequences of ITS, EF1-α and ACT of these pathogenic isolates belong to the Cladosporium tenuissimum. Exogenous melatonin (10 mM) inhibits mycelial growth and melanin production of C. tenuissimum causing SM. The higher chlorophyll contents and more chloroplasts with starch granules were observed in the SM leaves. SM on tea plants reduced Fv/FM, net photosynthetic (Pn), transpiration rate (Tn), stomatal conductance (gsw) and intercellular CO 2 (Ci) were 39, 88, 90 and 29%, respectively compared to control. Whereas, exogenous melatonin (10 mM) increased Fv/FM, Pn, Tn, gsw and Ci were 26, 63, 74 and 17%, respectively than SM infected. Besides, melatonin enhanced CAT, SOD, PPO and PAL activities by 27.6, 32.2, 65.3 and 27.1%, respectively compared to SM, but no significance in POD activity. CLH and NYC1 genes were down-regulated in SM plants and the genes expression was higher in the melatonin treatment. Meanwhile, melatonin up-regulated WRXY, PAL and β-gly genes expression involved in plant defence. This study provided the fundamental knowledge of SM and its impact on tea plants and the recovery of plants by exogenous melatonin. [ABSTRACT FROM AUTHOR]

Papaya ( Carica papaya , L.) is an important economic crop in tropical and subtropical countries. It is a giant herbaceous species; maintaining adequate tissue turgidity and water availability is necessary to maintain the rigidity of the stem as well as increase productivity. Water-saving irrigation techniques for papaya will be needed in the future due to the possibility of water shortages related to climate change. The morphological and physiological responses of ‘Grand Golden’ papaya to partial root drying (PRD), regulated deficit irrigation (RDI) and no irrigation followed by re-hydration (NI-gh) in a greenhouse study or no irrigation (NI-field) in a field study were compared with full irrigation (FI). In the greenhouse study, plants were grown in pot with roots split equally between two soil columns. In the field study, drip emitters on opposite sides of the plant delivered irrigation water. In FI, the whole root system was irrigated at 100% of water use; in RDI 50% or 70% of FI water use was supplied to the whole root system (greenhouse and field study, respectively); in PRD 100% of FI was supplied to half the root zone while the other was allowed to dry to 50% or 70% of FI (greenhouse, and field study, respectively). In the field study, PRD was achieved by applying different amounts of irrigation water to alternate sides of the root system within the plant row. The application of 50% water use in PRD and RDI in the greenhouse study decreased shoot and root dry weight production, with a more pronounced effect on root dry weight compared to FI. This decrease in biomass was associated with a decrease in the net photosynthetic rate in the day of most intense water stress for the plants in NI-gh. In the field study, a 30% water deficit in both PRD and RDI treatments did not significantly reduce vegetative growth or yield components (number fruit plant −1 , average weight (g) fruit −1 , kg fruit ha −1 , kg fruit plant −1 ), compared to FI. In greenhouse conditions there was evidence of a non-hydraulic signal in the PRD treatments decreasing G s compared to RDI at comparable soil water tension but it was insufficient to affect shoot growth or yield components in field conditions. There was no difference in the instantaneous leaf water use efficiency (WUE, A/E) of PRD or RDI treatments in the greenhouse or the agronomic water use efficiency (AWUE) (kg fruit L −1 and number fruit L −1 ) in the PRD and RDI treatments in the field but both treatments improved AWUE compared to FI. It appears that papaya can tolerate some water deficits without a significant reduction in yield components indicating that <100% ET 0 irrigation replacement can be scheduled but there is little or no benefit to PRD. [ABSTRACT FROM AUTHOR]

Papaya fruit ( Carica papaya L.) were exposed continuously to ozone fumigation (0, 1.5, 2.5, 3.5 and 5.0 μL L −1 ) for 96 h prior to ambient storage (25 ± 3 °C and 70 ± 5% RH) for an additional 10 days. The rate of ethylene formation and changes in the activities of the plant defence enzymes, phenylalanine ammonia-lyase (PAL) (EC 4.3.1.5), peroxidase (POD) (EC 1.11.1.7) and polyphenol oxidase (PPO) (EC 1.14.18.1), were measured in ozone treated and untreated papaya fruit after 0, 2, 4, 6, 8, 10, 12 or 14 days. The fruit treated with ozone at concentrations lower than 5 ppm had lower respiration rate and delayed ripening compared to the control. However the fruit that had received high ozone concentrations (>3.5 μL L −1 ) produced more ethylene and caused injury to fruit tissue. Enzyme activities were higher in ozone treated papaya fruit than in untreated fruit throughout the storage period. The greatest changes in enzyme activities were obtained with the highest ozone dose (5 μL L −1 ). [ABSTRACT FROM AUTHOR]

Understanding how water use efficiency (WUE) changes under drought is crucial for interpreting adaptive responses of species and cultivars to such abiotic stress. Several recent papers have concluded that in grapevine these responses and the guidelines stemming therefrom can differ, depending upon the parameter chosen to express WUE. In the present paper a complete set of WUE expressions, including the physiological and agronomical, were compared in potted, fruiting cv. Montepulciano ( Vitis vinifera L.) grapevines which were either well watered (WW) or subjected to progressive pre-veraison drought (WS) by supplying decreasing fractions (i.e. 70%, 50% and 30% of daily vine transpiration, T g ) determined gravimetrically before vines were fully rewatered. While single-leaf intrinsic water-use efficiency (WUE i ) increased with water stress severity, seasonal and diurnal whole-canopy WUE were similar at pre-stress, 70% T g , and upon rewatering but dropped in WS during severe water stress. Agronomic WUE calculated as mass of dry weight stored in annual biomass (leaves, canes and bunches) per L of water used, was also lower in WS, whereas WS had similar must composition with WW despite a 37% reduction in the yield per vine. Results warn that whole-canopy WUE is a much better index than any single-leaf based WUE parameter for extrapolation to agronomic WUE and actual grape composition. Under our specific case study, it can be recommended that, to avoid significant profit loss, water supply to drought stressed Montepulciano at pre-veraison should not be lower than 70% of daily vine water use. [ABSTRACT FROM AUTHOR]

Daily patterns of leaf and stem water potentials, leaf gas exchanges (net photosynthesis, stomatal conductance and transpiration), fruit growth, vascular (phloem and xylem) and transpiration in/outflows were determined in two subsequent years at regular time intervals during the season on pear trees of the cv. Abbé Fétel. Leaf gas exchanges showed higher values in the morning, while fruit shrank due to high transpiration water losses which were not balanced by xylem flows. Despite the high rates of transpiration, fruit were fully rehydrated in the afternoon thanks to high xylem flows, while phloem import occurred mostly in the midday hours. During most of the season, fruit growth was sustained above all by the xylem flux which represented upto 85% of fruit total inflows. Later, fruit growth rate decreased while dry matter accumulation increased following a rise in the phloem relative contribution to growth, which reached 50% of fruit total inflows. This is the first report to show how the biophysical mechanism of fruit growth in “Abbé Fétel” pear is based on high water exchanges by xylem and transpiration during most of the season. The simultaneous monitoring of leaf gas exchanges and fruit vascular flows during the day suggests how until about 95 days after full bloom (DAFB), leaves are stronger “sinks” for water in the morning while fruit import water mainly during the afternoon, thanks to the increase in leaf water potential following stomatal closure. [ABSTRACT FROM AUTHOR]

• Under different VPDs, two tomato cultivars had different physiological responses and these responses are related to stomatal sensitivity. • Low VPD reduced the stomatal limitation of photosynthesis and improves photosynthesis and growth. • High VPD would not always lead to an increase in the nutrient uptake. For tomato cultivar, with higher stomatal sensitivity, high VPD limited its nutrient absorption and accumulation. Vapor pressure deficit (VPD) is the main driving force of plant water transport and affects the nutrient absorption of plants. Exploring the nutrient absorption, growth, and photosynthetic characteristics of different tomato cultivars under different VPDs is of great importance for the cultivation of tomato. This experiment featured two levels of VPD (high 2.2/low 0.9 kPa) and two tomato cultivars (Solanumlycopersicum L., cv. Jinpeng and cv. Zhongza) for a total of four treatments in two controlled environment growth chambers. After about 4 weeks, the seedlings (at the three true-leaf stage) were transplanted into pots flled with inorganic medium and watered with nutrient solution. The stomatal characteristics, leaf moisture status, net photosynthetic rate (An), and plant growth of Jinpeng were not significantly different under the two VPD treatments, but high VPD resulted in a significantly increased transpiration rate (E) and whole plant hydraulic conductance (K plant), as well as significantly increased absorption of potassium (K) and calcium (Ca) in various organs. In contrast, Zhongza had lower biomass, smaller stem height, and lower total leaf area under high vs. low VPD conditions. At high VPD, the reduction of photosynthesis in Zhongza was mainly caused by anatomical modifications of the stomata; significant reductions in stomatal aperture and length restricted photosynthesis and biomass accumulation. Moreover, the E and K plant of Zhongza were reduced by stomatal state changes that prevent excessive transpiration. High VPD limited plant transpiration and mass flow of water, which reduced the absorption and accumulation of nutrients. Overall, these results suggest tomato cultivars differ in their stomatal sensitivity. Specifically, increasing VPD resulted in increased levels of some nutrients in certain organs in the cultivar with lower stomatal sensitivity; however, the cultivar with higher stomatal sensitivity demonstrated opposite trends. [ABSTRACT FROM AUTHOR]

A field experiment was conducted to study the influence of exclusion of solar UV components on the growth responses, gas exchange rates, chlorophyll fluorescence, pigmentation, carboxylation enzymes and foliage yield of four Amaranthus tricolor varieties; Arka arunima, Arka suguna, Pusa lalchaulai and Pusa kiran. The plants were grown in specially designed UV exclusion chambers, wrapped with filters that excluded UV-B (<315nm), UV-A/B (<400nm) or transmitted ambient UV or lacked filters. Plants grown under ambient UV radiation (280-400nm) were compared with those grown without UV-B or UV-A/B. The results indicated increased plant height, leaf weight ratio, specific leaf weight and foliage yield in all the four varieties of A. tricolor grown without UV-B and UV-A/B compared with those grown under ambient UV. Exclusion of UV significantly increased the total chlorophyll while Chl a/b ratio decreased. The efficiency of PS II (Fv/Fm), rate of photosynthesis and stomatal conductance significantly enhanced along with a remarkable increase in Carbonic anhydrase, PEP carboxylase and total soluble proteins. Thus UV excluded plants have higher reducing power and increased CO2 fixation and decreased UV-B absorbing compounds, channelling the additional fixation of carbon towards the improvement of yield in A. tricolor varieties. The response for UV exclusion was higher in variety Arka arunima and Arka suguna compared with Pusa kiran and Pusa lalchaulai. UV sensitivity of the A. tricolor varieties was in the following sequence - Pusa lalchaulai>Pusa kiran>Arka suguna>Arka arunima. Thus Arka arunima and Arka suguna were most sensitive and Pusa lalchaulai and Pusa kiran the least sensitive varieties to ambient level of UV. The least sensitive varieties may be used in the development of UV-B tolerance mechanisms and also developing new varieties tolerant to higher levels of UV-B in future attempts in plant breeding programmes. [ABSTRACT FROM AUTHOR]

Highlights: [•] Leaf age and light intensity substantially affect photosynthesis within the canopy of papaya. [•] Mature leaves in the upper canopy were the major contributors to papaya photosynthesis. [•] The first study of LAI and extinction coefficient was estimated in the papaya canopy. [•] Relative gas exchange measurements could be verified between intrinsic and environmental effects. [•] Photosynthesis is highly adaptable in a field net-house cultivation system. [Copyright &y& Elsevier]

• Entropy weight method was used to determine the best water saving method for mango. • Sugarcane leaf mulching was significantly increased fruit yield and IWUE. • Sugarcane leaf mulching decreased the titratable acid by 31.3%. • Sugarcane leaf mulching with 50% ETC had the best fresh fruit quality. Rational application of field-management technology can not only improve mango (Mangifera indica L.) fresh fruit yield and quality but also improve irrigation water use efficiency (IWUE). However, few studies have involved the simultaneous use of mulch and irrigation-management techniques in hot and dry environments to achieve a relatively good level of performance. We used the entropy weight method (EWM) to explore an optimal mulching and irrigation-management technology for mango production in a dry hot environment. Three irrigation levels [FI, 100% mango evapotranspiration (ET C); DI 75 , 75% ET C ; DI 50 , 50% ET C ] were designed with (SM) and without (NM) sugarcane leaf mulching in 2018 and 2019 in a dry hot environment. The results showed that the photosynthetic rate, stomatal conductance, transpiration rate, leaf water-use efficiency, and carboxylation efficiency in the SM treatment were 12.5% to 83.7% higher than those in the NM treatment in both years. Compared with the NM treatment, the SM treatment increased the fresh fruit yield and IWUE by 45.7% and 49.7% in 2018 and by 46.1% and 63.2% in 2019. The solid-to-acid ratio and sugar-to-acid ratio in the SM treatment were 48.5% and 50.4% higher than those in the NM treatment, respectively, but the titratable acid content decreased by 31.3%. Compared with FI, DI 75 increased carotenoid content, total soluble solids, solid-to-acid ratio and sugar-to-acid ratio by 8.4%–40.7%, while it reduced titratable acid by 22.8%. Compared with FI, DI 50 reduced fresh fruit yield by 24.3% and 21.9% in 2018 and 2019, respectively, while it increased IWUE by 13.6% and 17.7%. The fresh fruit yield of SMDI 75 was the highest, which was 1.42 and 1.44 times that of NMFI in both years, respectively. A comprehensive evaluation by EWM also showed that the SMDI 50 treatment had the highest comprehensive scores of mango yield, quality and water-use efficiency, which could provide a basis for the scientific management of mango fertiliser in dry and hot areas of China. [ABSTRACT FROM AUTHOR]

Highlights: [•] Leaf gas-exchange rates of Japanese and Dutch tomato cultivars were surveyed. [•] Dutch cultivars generally had higher photosynthetic capacity than Japanese cultivars. [•] There is variation of photosynthetic capacity within Japanese and Dutch cultivars. [ABSTRACT FROM AUTHOR]

Abstract: The effects of variable water supply were investigated in 50-year-old Olea europaea (cv “Koroneiki”) L. trees grown in an experimental orchard located in northwest Crete. The trees were subjected to four irrigation treatments: rainfed (RF), full irrigation (FI) with 100% of the crop evapotranspiration (Etc.) level and two deficit irrigation treatments, FRDI-fully irrigated, that received no irrigation water from July 12 to August 18 and DRDI-irrigated with 60% of ETc level, that received no irrigation water from July 12 to August 18. The effects of watering regime on soil moisture content, plant water status, gas exchange characteristics, chlorophyll content, antioxidant enzyme activities, i.e. superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (APX; EC 1.11.1.11) and guaiacol peroxidase (GPX; EC 1.11.1.7) and on malondialdehyde (MDA) levels were evaluated. There were no marked differences between FI and FRDI treatments, except at the end of the no-watering period. On the contrary, stem water potential (Ψ) was affected by the level of water supply, leading to reduced stomatal conductance (gs) and carbon assimilation rate (Pn) in DRDI treatment. DRDI plants exhibited a close relation between photosynthetic rate (Pn) and stomatal conductance (gs), suggesting that stomatal closure is the dominant limitation to photosynthesis. Chlorophyll degradation and enhanced synthesis of carotenoids assisted plant to maintain its physiological processes under the water deficit and high light conditions. Olive tree was able to restore stem water potential (Ψ) after rewatering, and the recovery of leaf water status was coupled with an up-regulation of leaf gas exchange characteristics in DRDI plants. Leaves grown under rainfed conditions revealed signs of oxidative stress as indicated by the increased levels of lipid peroxidation, whereas irrigation mitigated the oxidative damage at leaf level in DRDI plants. Superoxide dismutase, ascorbate peroxidase and guaiacol peroxidase activity was increased in DRDI leaves, while catalase activity was inhibited. On the contrary, the lower expression of the enzymatic antioxidant system under rainfed conditions did not allow a better protection against a more pronounced oxidative stress. [Copyright &y& Elsevier]

Abstract: To investigate the role of brassinosteroids in the drought-tolerance of plants, leaf gas exchange and chlorophyll fluorescence parameters were examined in pepper (Capsicum annuum L. cv. Longkouzaojiao) plants with or without 24-epibrassinolide (EBR, 0.01mgL−1 EBR) treatment. Pepper plants were subjected to drought (45% relative soil water content, RSWC) for 10d and then returned to well-watered conditions for 5d. In this study, drought treatment impaired the pepper growth and reduced leaf photosynthetic rate, and drought-inhibition of photosynthesis may be due to non-stomatal factor. Drought also reduced the utilization of absorbed light energy in chloroplasts, and photoinhibition was caused by excess absorbed light energy in spite of drought-induced the increase of non-photochemical quenching coefficient (NPQ). Interestedly, EBR treatment significantly alleviated drought-induced inhibition of photosynthesis, which may be particularly attributed to the increase in capacity of CO2 assimilation and the efficiency of light utilization. EBR also significantly alleviated drought-induced photoinhibition by dissipation of excitation energy as heat from the light harvesting complex in photosystem II (PSII). We concluded that EBR could alleviate the detrimental effects of drought on photosynthesis by increasing the efficiency of light utilization and dissipation of excitation energy in the PSII antennae in leaves. [Copyright &y& Elsevier]

Abstract: Three greenhouse experiments were carried out to determine the effect of the nitrogen form and the nutrient solution pH on growth, yield, leaf gas exchange, carbohydrate, N-compound concentrations and mineral composition of tomato cv. Moneymaker (Solanum lycopersicum L.) self-grafted and grafted onto ‘Maxifort’ (S. lycopersicum L.× S. habrochaites S. Knapp and D. M. Spooner) grown in hydroponics. Exp. 1 included five pH levels in the nutrient solution (3.5, 4.5, 5.5, 6.5, and 7.5) while in the Exps. 2 and 3 four different ratios of NO3 − to NH4 + (100:0, 70:30, 30:70, and 0:100) were used. The Exps. 1 and 2 were performed in a short period of time (about 20 days) while Exp. 3 was a long-term experiment. No significant differences among treatments were observed in shoot and root dry biomass of tomato in the pH experiment (Exp. 1), whereas shoot dry biomass, Ca and Mg concentrations decreased sharply when N was exclusively provided as NH4 + (Exp. 2). When averaged over the pH level of the nutrient solution, the highest Ca, Fe, Zn, and Cu concentrations were recorded in grafted than self-grafted plants (Exp. 1), whereas in Exp. 2 shoot and root biomass values recorded in grafted plants were significantly higher than those observed for self-grafted plants, by 20%, and 24%, respectively. In the long-term experiment, the plant growth and yield decreased in response to an increase of NH4 + in the nutrient solution. The decrease in marketable yield with decreasing NO3 −:NH4 + ratio resulted mainly from the increase of blossom-end rot, which reduced the number of marketable fruits per plant. The adverse effects of an increased supply in NH4 + have been associated to a fall in Ca and Mg levels in plant tissues. The carbohydrate concentrations, amino acids and proteins increased under NH4 + in comparison to NO3 − based nutrition. Moreover, NH4 + toxicity was associated with reduced rates of net photosynthesis. Our results also demonstrated that grafting ‘Moneymaker’ into ‘Maxifort’ did not mitigate the negative effects of ammonium nutrition on tomato productivity. [Copyright &y& Elsevier]

Abstract: Considering that adventitious root formation (ARF) relies on adequate supply of carbon, the objectives of this study were (I) to evaluate how CO2 assimilation contributes to the carbon balance of petunia cuttings and (II) to study the extent to which CO2 assimilation depends on the progress of ARF and environmental key factors. CO2 gas exchange and dry matter production of Petunia hybrida ‘Mitchell’ cuttings were monitored in a specifically designed multiple open chamber system using plastic covered rooting trays as measuring cuvettes connected to an infrared CO2 sensor. Excised cuttings were rooted for two weeks in a growth chamber at 22/20°C (day/night) at a photosynthetic photon flux density (PPFD) of 100μmolm−2 s−1 and a CO2 concentration of approximately 400ppm. An increase in dry matter of 186mg per cutting, or 158% of the initial dry matter, reflected high carbon assimilation. Whilst the shoot dry matter of cuttings increased substantially in the very first week root dry matter growth was not observed until day seven after planting. The short-term response of CO2 gas exchange to environmental conditions revealed that net photosynthesis (P N) enhanced with increasing PPFD, with a maximum P N of 7.8μmolm−2 s−1. Temperature response curves exhibited only minor changes of P N; dark respiration (R D) increased considerably when the temperature was temporarily increased. Furthermore, cuttings responded to an increase in CO2 concentration from 300 to 1200ppm by almost doubling P N. When cuttings were rooted permanently under PPFDs of 150μmolm−2 s−1 and 80μmolm−2 s−1 (22/20°C day/night; CO2 concentration 400ppm) P N and R D of cuttings at the higher PPFD were constantly higher than under the lower PPFD. The CO2 gas exchange of both treatments was relatively constant during ARF. The light response curves of P N differed after one week of exposure to the two light intensities. Light adaptation was comparable to that of stock plants measured using a portable infrared gas analyser equipped with a leaf chamber. The data indicates that petunia cuttings rooted under conditions frequently applied in young plant production in Central Europe show significant carbon assimilation from the first day onwards. The data also reveals that CO2 gas exchange under such conditions is not affected by ARF, but is subject to prevailing environmental factors such as light intensity, temperature and CO2 concentration. [Copyright &y& Elsevier]

Abstract: Lenticels are macroscopic openings occurring on the surface of mango fruit and are responsible for gaseous exchange and transpiration. Lenticel originates from the ruptured stomata during fruit enlargement and growth, reaching their maximum size at full maturity of fruit. Distribution of lenticel is 2–3 times higher in the apical region of the fruit than middle or shoulder portion at all growth stages. Although, the mechanism of lenticel discoloration (LD) is poorly understood, however few studies revealed that it is due to several factors including cultivar differences, movement of air and water through lenticel and membrane damage and liberation of phenolics, as a consequence of inadequate pre- and post-harvest handling. LD in mango cultivars is a serious problem, affecting the appearance and economic value of the fruit. A little information is available on the prevention of LD, which indicates that it can be prevented by adopting standardized pre- and post-harvest strategies like drying of orchard soil, fruit bagging, desapping of harvested fruit and storage in ventilated chamber. [Copyright &y& Elsevier]

Abstract: In the last decade, high-density olive planting systems have been developed to facilitate less costly mechanical harvesting and pruning by using straddle harvesters. High-density orchards allow faster production since the first crop of fruit starts a few years after planting. In high-density orchards the control of tree size is essential. It is possible to control the vigour and size of the tree by selecting suitable cultivars, by choosing rootstocks capable of controlling scion vigour and, finally, by applying deficit irrigation to reduce plant vegetative growth. Knowledge of tree water requirements is needed for precise irrigation scheduling. In this study, the dwarfing capacity of two Leccino clones, Leccino Dwarf (LD) showing low vigour, and Leccino Minerva (LM) highly vigorous, was investigated under two water regimens, well-watered (T 100) and water deficit (T 50). We analysed growth rates, dry matter production, gas exchanges and water relations of one-year-old plants of Leccino Dwarf (LD) and Leccino Minerva (LM), grown in pots in open fields. The two genotypes showed significant differences in vigour, demonstrated by measuring the trunk diameter, shoot length and leaf area; values were significantly lower in clone LD. Stem water potential, photosynthesis and stomatal conductance were similar in both genotypes under a well-watered regime; they decreased when subjected to water deficit with values significantly lower in LM clone during the summer months, indicating physiological differences among clones and that LD adapts better to water deficit. [Copyright &y& Elsevier]

Abstract: A continuous CO2 measurement system was developed to monitor the CO2 exchange rate of the whole canopy of grafted transplants using semi-open multiple chambers. Air heating or cooling and humidification inside a healing box were under control, if needed. To test the system, the gas exchange rate of the cucumber (Cucumis sativus L.) transplants grafted onto pumpkin (Cucurbita maxima cv. ‘New-Shintozwa’) was analysed. During the healing and acclimatisation of the grafted cucumber plants, the air temperature in the box remained constant at night but ranged above 1°C of a set value under high humidity in daytime. The relative humidity was kept within the set point during the daytime, and it nearly reached 100% at night when not controlled. The cucumber seedlings were exposed to different water stresses before grafting, and the water potentials of each treatment were −0.579 (non-stressed), −0.814 (mildly water-stressed), and −0.870MPa (strongly water-stressed) on grafting. At the water-stressed scions, leaf expansion was inhibited by 30.9–53.3% compared with the non-stressed scions. Therefore, the gas exchange rates of the strongly water-stressed scions based on the leaf area were decreased to 72.7% compared with the non-stressed scions. After grafting, the apparent photosynthesis of the transplants of all treatments was negative, with higher respiration in the strongly water-stressed scions during the initial period of healing. However, they turned to positive values and exceeded those of the non-stressed scions from three days after grafting. This result provides critical information that the water column is physiologically connected between the stock and scion within two days after grafting. As a result of water stress, the leaf area and dry weight of the transplants in the strongly water-stressed scions were inhibited by 67.5% and 83% compared with the non-stressed scions at the end of acclimatisation. In contrast, the relative growth rate and graft-take of the strongly water-stressed transplants were slightly increased, which suggests that the water stress prior to grafting alleviated the water demand of the scion. This system may provide useful information for diagnosis at the early stage by monitoring the whole canopy''s photosynthesis over a long term. [Copyright &y& Elsevier]

Abstract: Pistachio is a drought tolerant fruit tree that can be cultivated in rainfed and irrigated conditions. The water requirements of the tree, however, are considerable so in most of the commercial orchards deficit irrigation is a common practice. Regulated deficit irrigation in pistachio trees has been described in several works, which reported that the phenological stage of shell hardening, so called stage II, is the most drought tolerant. This paper proposes that such drought resistance is related to changes in water relations linked to the phenological stages, even in conditions of no water stress. In order to evaluate such changes, the daily pattern of stem water potential and gas exchange (net photosynthesis, P n, and leaf conductance, g s) was measured, determining also the pressure–volume curves, in three different phenological stages of mature pistachio trees (Pistacia vera cv Kerman on P. terebinthus L. rootstock.). The daily pattern of stem water potential and gas exchange were performed in three different irrigation treatments: control, regulated deficit irrigation and rainfed. The pressure–volume curves were made only in the control and rainfed treatments. Significant differences were found in the daily pattern of stem water potential in all the phenological stages considered, while only in the last one the net photosynthesis was affected by water stress. The daily pattern of gas exchange at the beginning of the season was not affected by the evaporative demand, with a constant value when radiation was not limiting. Moderate levels of water stress during the last measurement date reduced the maximum values of g s and P n resulting also in a clear change in the pattern of the daily curve, with maximum values only at the beginning of the day. The relationships between stem water potential and gas exchange parameters were different during stage II and almost the same in stages I and III. The parameters drawn from the pressure–volume curves also indicated a change in the elastic modulus of the leaf cells in stage II. In addition, differences in the osmotic adjustment (OA) index suggested different degree of osmotic adjustment of the phenological stages in the response to water stress. The results showed that different mechanisms of drought resistance are operating in the different phenological stages in pistachio trees. [Copyright &y& Elsevier]

Abstract: We investigated the effects of altered source/sink ratio by leaf or fruit pruning on leaf photosynthetic characteristics and whole-plant growth of ‘Momotaro York’, a Japanese cultivar, and ‘Dundee’, a Dutch cultivar and verified a hypothesis for sink-limitation of plant growth proposed by . Plants were grown hydroponically with a high-wire system in a greenhouse for 11 weeks. Light-saturated photosynthesis of young, fully expanded leaves measured at atmospheric CO2 partial pressure of 37Pa and at an intercellular CO2 partial pressure of 20Pa was not influenced by alteration of source/sink ratio for either cultivar. Although soluble sugars were accumulated in leaves under high source/sink conditions, the amount of ribulose-1,5-bisphosphate carboxylase/oxygenase, a rate-limiting factor for CO2-limited photosynthesis, was not affected by the altered source–sink balance. Net assimilation rate of a whole plant increased with decreasing source/sink ratio, but this can be accounted for by the changes in light interception per unit leaf area, without taking the source–sink relationship into consideration. It was concluded that the altered source/sink ratio did not change leaf photosynthetic capacity and the sink-limitation hypothesis cannot be applied to either cultivar under the conditions of the present study. [ABSTRACT FROM AUTHOR]

Abstract: This paper analyses the effect of different air temperatures (10, 20 and 30°C) on the response of sweet pepper plants (Capsicum annuum L. cv. Herminio) to foliar urea applications after growing plants for 20day with and without nitrogen (N) applied to the growing substrate. Leaf CO2 assimilation, chlorophyll fluorescence, root respiration, lipid peroxidation and antioxidative enzymes were analysed. Spraying plants with urea increased leaf CO2 assimilation of N-deficient plants when applied at 20 or 30°C, compared with non-sprayed plants. When plants were sprayed with urea at 10°C chlorophyll fluorescence of leaves was similar to that of plants that were supplied with full N in the nutrient solution. Root respiration was not affected by urea sprays whilst leaf NO3 − concentration was increased by urea but only when it was sprayed at 10 or 20°C. Lipid peroxidation and ascorbate peroxidase in N-deficient plants were reduced significantly by urea sprays, especially when plants were sprayed at 20°C with N-limitation in the growing substrate. This study shows that N-limitation in the growing substrate induces a temperature-dependant increase in the activities of antioxidant enzymes in leaves of pepper and applications of foliar urea can be optimised, when applied at the appropriate temperature, to partly replace the N supplied to the roots of sweet pepper. [Copyright &y& Elsevier]

Abstract: A greenhouse experiment was conducted to study the effects of boron (B) on growth, nutrient status, B distribution and gas exchange parameters of olive plants (Olea europaea L.). One-year-old own-rooted olive plants of the Greek cultivars Megaritiki, Chondrolia Chalkidikis, Amfissis and Kalamon were grown in a sand–perlite medium and irrigated with nutrient solutions containing: 0.27, 0.5, 1, 2.5, 5 and 10mgL−1 B (0.27 and 10mgL−1 were considered as control and excess B treatment, respectively). After culturing for 185 days, leaves and stems (from basal and apical part of the shoots) and roots were separately sampled. Our results showed that the final number of leaves per plant was negatively correlated with B concentration in the nutrient solution. Furthermore, in B10.0 treatment, ‘Megaritiki’ had decreased length and number of lateral stems, ‘Chondrolia Chalkidikis’ and ‘Amfissis’ showed decreased length of lateral stems and ‘Kalamon’ decreased length of lateral stems and plant height. In general, dry weight of stems and leaves was not significantly correlated with B concentration in the nutrient solution. B concentration in leaves and stems was linearly correlated with B supply. A linear correlation existed between B concentration of the nutrient solution and that of leaves and stems. At the end of the experiment, B levels in the leaves and stems of B0.27 and B0.5 treatments did not differ significantly. In general, the increase of B concentration in the nutrient solution, negatively affected the nitrogen (N) concentration of leaves and stems while phosphorus (P) and iron (Fe) concentrations were not affected. Furthermore, potassium (K) and calcium (Ca) concentration in stems of plants supplied with 10mgL−1 B was decreased. In addition, high B supply resulted in increased magnesium (Mg) and manganese (Mn) concentrations in ‘Chondrolia Chalkidikis’ and ‘Amfissis’ and in the decrease of zinc (Zn) concentrations, in all plants. A significant decline in photosynthetic rate at the end of the experiment was observed in the B5.0 treatment regardless of cultivar. [Copyright &y& Elsevier]

Abstract: The effects of NaCl stress on plant growth, gas-exchange, activity of superoxide dismutase (SOD), rate of lipid peroxidation, and accumulation of Na+ ion and sugar were investigated in leaves and fruits of pepper plants (Capsicum annuum L.). Especially, the gene expression of l-galactono-1,4-lactone dehydrogenase (GalLDH), which is the last enzyme of ascorbic acid (AsA) biosynthesis, and the relationships between AsA level and Na+ concentration in plant tissue were investigated with increasing salinity. Plants were treated with three treatments: the control (0mM NaCl) and two salinity levels (50 and 100mM NaCl) for 21 days under greenhouse conditions. Plant growth was markedly restricted due to the reduction of photosynthetic rate and the increase of Na+ accumulation in leaves with the increasing intensity of NaCl stress. Salinity had more effect on fruit growth comparing to leaf growth, suggesting that fruits could be more sensitive to salinity than leaves. In comparison with the control, salt stress significantly increased lipid peroxidation (as measured as malondialdehyde content) but decreased SOD activity in both fruits and leaves although the effect was larger in fruits; and the rate of the decrease in SOD activity was greater than that of the increase in lipid peroxidation. The AsA concentration transiently increased first 7 days but it slightly decreased from the initial level in the end of treatment day 21. The change in GalLDH gene expression was similar to AsA concentration. The accumulation of Na+, the reduction of AsA level at severe salinity stress were greater in fruits than in leaves; and AsA level had a negative relationship with Na+ concentration in both leaves and fruits. These results suggest that the difference in salt sensitivity between fruits and leaves in pepper plants can be related to the difference in inhibition of AsA synthesis, which in turn is probably due to the toxicity of extreme accumulation of Na+. [Copyright &y& Elsevier]

Abstract: Plants of cucumber (Cucumis sativus L. cv. Euphorbia) were grown in a traditional high-wire cultivation system to investigate the effects of three lighting regimes on photosynthetic characteristics, leaf area and yield. The lighting regimes included overhead lighting (OH), where all the lamps were mounted above the canopy and overhead+intracanopy lighting (OH+IC) which comprised 65% of overhead lamps and 35% of lamps mounted vertically along the plant rows. All overhead lighting was provided for 20hday−1 and intracanopy lighting was provided for either 20h or 24hday−1 lighting period. Intracanopy lighting improved the light distribution in the canopy. Gas exchange measurements showed that intracanopy lighting increased net photosynthesis (P N) and photosynthetic capacity (P max). Parameters calculated from CO2 response (A/C i ) curves showed that in vivo estimate of the maximum rate of Rubisco carboxylation (Vcmax) and the maximum rate of electron transport (J max) were affected by light regime. Intracanopy light increased yield by 11% compared to traditional overhead light. [Copyright &y& Elsevier]

Abstract: The effects of two types of hydrophilic polymers on drought and salt resistance of 1-year-old cuttings of Populus popularis 35–44 were investigated in this study. The polymers used in the experiments were Stockosorb 500 XL (Stockosorb) (a granular type, cross-linked poly potassium-co-(acrylic resin polymer)-co-polyacrylamide hydrogel) and Luquasorb® product (a powder type of potassium polyacrylate), which were manufactured by Stockhausen GmbH Krefeld and BASF Corporation in Germany, respectively. Drought or salt stress significantly decreased leaf photosynthesis and transpiration, as well as plant water-consumption and dry weight. A significant reduction occurred in Drought+NaCl-stressed plants. Soils treated by 0.5% Stockosorb or Luquasorb markedly alleviated the inhibition of plant growth and leaf gas-exchange that were caused by drought and/or salt stress treatments, and the occurrence of stress-induced leaf injury was delayed for 31 and 51 days, respectively. Experimental results showed that hydrophilic polymers in root media assisted P. popularis plants to tolerate the drought and salt stresses, due to the following reasons: (1) roots took up the retained water from hydrophilic polymers when water was deficient in the soil (Stockosorb-treated plants exhibited a higher rate of water uptake); (2) under saline conditions, Stockosorb and Luquasorb held Na+ and Cl− in the soil solution due to their high water-holding capacity, thus limiting an excessive accumulation of toxic ions in the plant organs; furthermore, the exchangeable K+ that contained in Stockosorb and Luquasorb resulted in an improved K+/Na+ homeostasis in salinized plants; (3) hydrophilic polymers aided the plants to tolerate an interactive impacts of drought and salt stresses, which was mainly accounted for their water- and salt-holding capacities. In comparison, the growth and survival enhancement effects of the hydrophilic polymers on Drought+NaCl-treated plants was more evident by Luquasorb application, because it supplied water to plants at a lower rate during soil drying, thus prolonging the duration of water supply and allowed roots to grow in an environment of lower salinity for a long period of salt and drought stresses. [Copyright &y& Elsevier]

Abstract: Physiological and growth responses of ‘Pantin’ and ‘Magana’ mamey sapote (Pouteria sapota) trees to continuous and cyclical flooding were studied in a series of experiments. Trees were grown in containers in a very gravelly loam soil and were subjected to continuous flooding of the root zone for 30–66 days (Experiments 1 and 2) or alternating flooding–unflooding cycles for 50 days (Experiments 3–5). For all experiments, the control treatment consisted of nonflooded trees. Net CO2 assimilation (A) and stomatal conductance (g s) decreased within 3 days of continuous flooding and internal CO2 concentration was significantly higher in leaves of flooded than nonflooded plants. In the cyclic flooding experiments, trees were flooded in 3- to 6-day cycles and then unflooded for the same time periods. Stomatal conductance and A decreased within 3 days of flooding, leaf epinasty occurred between days 5 and 10, leaf senescence and abscission occurred between days 15 and 30, and branch dieback and tree death occurred between days 30 and 60. Three cycles of 3-day flooding and 3-day recovery of trees had little effect on leaf gas exchange of ‘Magaña’ trees. Similarly, ‘Pantin’ trees survived 3 cycles of 6 days of flooding interspersed with 3–6 days of recovery despite consistent decreases in g s and A during flooding. Stomatal conductance and A of both mamey sapote cultivars decreased within a few days of flooding and this species appears to have intermediate flooding tolerance compared with other tropical fruit crops based on tree survival. [Copyright &y& Elsevier]

Abstract: Diurnal patterns of photosynthesis in two-year-old Myrica rubra young trees under natural conditions were studied by measuring gas exchange, chlorophyll fluorescence parameters and D1 protein. When measured on a clear day, the diurnal changes of net photosynthetic rate (P n), stomatal conductance (G s) and apparent quantum yield (AQY) show two daily maxima; the maximum value occurred at about 09:00h, then declined, and reached the lowest values at about 13:00h then increased to reach the second maxima at about 15:00h. However, with the consistent decline of P n and G s in the afternoon, the ratio of intercellular CO2 concentration (C i) to atmospheric CO2 concentration (C a) increased. In addition, carboxylation efficiency (CE) and RUBP regeneration declined as the afternoon progressed. In the morning, the maximum yield of fluorescence after dark adaptation (F m) and maximal photochemical efficiency of PSII (F v/F m) decreased continuously until it reached its minimum at 13:00h, while the reverse occurred in the later afternoon. The quantum yield of PSII (Φ PSII) declined after 09:00h; in contrast, initial fluorescence (F o) increased. A decrease in the rate of Q A reduction and an increase in inactive PSII reaction centers was observed as the day progressed. Non-photochemical quenching (qN) and its slow-relaxing (qS) component increased at about midday, while the fast-relaxing component (qF) declined. The amount of inactive PSII centers was significantly enhanced, while F v/F m, Φ PSII, qS and rate of Q A reduction were significantly reduced by DTT (dithiothreitol), an inhibitor of the xanthophyll cycle. The D1 protein was significantly degraded at 13:00h relative to that at 09:00h during the course of the day. These results suggest that stomatal and non-stomatal limitations, which decreased carboxylation and photochemical efficiency, may cause the midday depression; and that non-stomatal limitations may be due to the decrease in RuBPCase activity and degradation of D1 protein, which causes decreased photoprotection at midday. [Copyright &y& Elsevier]