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Many studies have been conducted on maize to study the effect of drought on yield at the flowering stage, but understanding biochemical and photosynthetic response against drought at the seedling stage needs to be well established. Thus, to understand differential changes and interaction of biochemical and photosynthetic parameters at the seedling stage under drought, a greenhouse experiment with twelve maize genotypes under severe drought (30% field capacity) and irrigated (90-100% field capacity) conditions were performed. Drought differentially altered biochemical and photosynthetic parameters in all genotypes. A sharp increase in hydrogen peroxide, malondialdehyde (MDA), and total antioxidant capacity (TAOC) were seen and a positive association between H2O2 and TAOC, and MDA and transpiration rate (E) was observed under drought. Nonphotochemical quenching increased under drought to avoid the photosystem damage. PCA biplot analysis showed that reducing E and increasing photosynthetic efficiency would be a better drought adaptation mechanism in maize at the seedling stage. [ABSTRACT FROM AUTHOR]

To study the light intensity suitable for Bletilla ochracea Schltr., morphology, photosynthetic parameters, and polysaccharide content of seedlings were evaluated under different light intensities. All shade treatments promoted plant growth and net photosynthetic rate while having no significant effect on transpiration rate. The maximum photochemical efficiency and potential photochemical efficiency reached the lowest values under full sunlight. The electron transport rate and photochemical quenching under shade were significantly higher than those under full light, while nonphotochemical quenching was the highest under full light. This indicated that the shade alleviated photoinhibition in summer and improved the utilization of light. B. ochracea could adapt to different light intensities, enhancing photosynthetic efficiency under low light by improving the electron transport and the degree of opened PS? reaction centers, and adapting to high light by increasing heat dissipation. Plant growth, photosynthesis, and polysaccharide accumulation of B. ochracea greatly increased under 76.4% shade. [ABSTRACT FROM AUTHOR]

Active control of photosynthetic activities is important in plant physiological study. Although models of plant photosynthesis have been built at different scales, they have not been fully examined for their application in plant growth control. However, we do not have an infrastructure to support such experiments since current plant growth chambers usually use fixed control protocols. In our current paper, an open IoT-based framework is proposed. This framework allows a plant scientist or agricultural engineer, through an application programming interface (API), in a desirable programming language, (1) to gather environmental data and plant physiological responses; (2) to program and execute control algorithms based on their models, and then (3) to implement real-time commands to control environmental factors. A plant growth chamber was developed to demonstrate the concept of the proposed open framework. [ABSTRACT FROM AUTHOR]

Melatonin (MT) is involved in physiological processes in plants under abiotic stress. In this study, we investigated the effects of melatonin on maize photosynthetic and antioxidant capacities under salinity stress. Our findings indicated salinity stress significantly inhibited maize growth. However, exogenous MT promoted maize growth and antioxidant capacity. Superoxide dismutase, peroxidase, and catalase increased by 138.8, 38.7, and 32.0%, respectively, while H2O2 and malondialdehyde decreased by 23 and 31%, respectively. Exogenous MT also improved maize photosynthesis under salinity stress. Net photosynthetic rate, transpiration rate, and stomatal conductance increased by 134, 67.2, and 46.3%, respectively. Maximum quantum yield of PSII photochemistry, effective quantum yield of PSII photochemistry, photochemical quenching coefficient, and electron transport rate increased by 5.8, 70.4, 65.3, and 41.0%, respectively. Therefore, our findings suggested exogenous MT significantly ameliorated maize physiological and photosynthetic adaptation under salinity stress, thereby providing helpful guidance for maize cultivation in areas of high salinity. [ABSTRACT FROM AUTHOR]

Photosynthetic capacity plays an important role in plant vegetative growth, and is often regarded as a key determinant of adaptability in plant species, including the hybrids. Interspecific hybridizations are common and can easily occur in Buddleja. The F1 hybrid investigated in this study is a newly discovered interspecific hybrid between B. crispa and B. officinalis, and it was found in the Sino-Himalayan region. In this study, the morphological traits, the stoichiometric characteristics and the gas-exchange traits in F1 hybrids and their parents were measured under the cultivation conditions. Buddleja F1 hybrids showed the high leaf mass per area, which was similar to B. officinalis. Although F1 hybrids presented a low light-saturated net photosynthetic rate, they did not reduced carbon cost by increasing the specific leaf area or decreasing the leaf dry mass per unit area. Compared to the parental species, F1 hybrids had low leaf C:N and C:P ratios, C concentration, as well as photosynthetic nitrogen-use efficiency. However, they had a great respiration efficiency through a markedly reduced rate of respiration. Furthermore, F1 hybrids showed similar photochemical efficiency to B. officinalis, which was significantly higher than that in B. crispa. These findings suggest that the F1 hybrids in our study show a high similarity to their parental species in the leaf economic spectrum and photosynthetic capacity. [ABSTRACT FROM AUTHOR]

Growth and gas-exchange traits of Capsicum annuum var. glabriusculum under flooding and water deficit (WD) stress were measured in a greenhouse experiment. Flooding was applied to a group of plants for 0 (control), 5, and 10 d, and WD to another set at 100 (control field capacity), 70, 50, and 25% of the water applied to control. Flooding negatively affected stomatal conductance, photosynthetic and transpiration rate from 20 d after transplanting (DAT), with a significant decrease in biomass at 120 DAT. WD at 70, 50, and 25% severely affected the plant aerial and root biomass and the gasexchange traits from 80 DAT, inhibiting both flowering and fructification. This study showed the sensitivity of amashito chili plants to water stress which could have implications for the survival of local populations in natural conditions. Results should be considered for the development of small-scale cultivation. [ABSTRACT FROM AUTHOR]

Through its impact on morphogenesis, light is the key environmental factor that alters plant structural development; however, the understanding how light controls plant growth and developmental processes is still poor and needs further research. For this purpose, a Petri dish and pot experiment was conducted to investigate the effects of different LEDs, i.e., white light (WL), red light (RL), blue light (BL), and orange light (OL) on morphology, gas-exchange parameters, and antioxidant capacity of Brassica napus. Compared with WL, RL significantly promoted plant growth and biomass, contents of photosynthetic pigments, and gas-exchange parameters in comparison to BL and OL. However, RL also helped decline malondialdehyde and proline contents and superoxide anion and peroxide production rate. In contrast, BL and OL significantly reduced plant growth and biomass, gas-exchange attributes and increased the activities of superoxide dismutase and peroxidase in Petri dish as well as in pot experiment. These results suggest that red light could improve plant growth in B. napus plants through activating gas-exchange attributes, reduce reactive oxygen species accumulation, and promote antioxidant capacity. [ABSTRACT FROM AUTHOR]

Our experiment was conducted to understand the effects of foliar sprays of paclobutrazol (PBZ), its mixture with abscisic acid (ABA), or water (control) on leaf carbon-use efficiency (CUEl), photosynthesis, and respiration of Euonymus japonicus seedlings. Plants were pot-grown in a greenhouse. The study revealed that elevated stomatal conductance, mesophyll conductance, and maximum rate of Rubisco carboxylation (Vcmax) in plants treated with PBZ could strongly improve net photosynthetic rate (PN). ABA could antagonize the increase of mesophyll conductance and stomatal conductance by PBZ, thereby inhibiting the improvement of photosynthesis by PBZ. The combination of PBZ and ABA significantly reduced day respiration (Rd) and dark respiration (Rdk), resulting in the increased CUEl, PN/Rd, and PN/Rdk. The increased PN in the PBZ treatment led to slightly increased PN/Rd and CUEl. Thus, the CUEl could be improved by PBZ and its mixtures with ABA by regulating leaf photosynthesis and respiration. [ABSTRACT FROM AUTHOR]

Low temperature (LT) and low irradiation (LI) are common factors posing a great risk to plants. The study aimed to elucidate the effects of LT and LI and recovery on the photosynthetic apparatus, photoinhibition of PSII, and reactive oxygen metabolism of strawberry seedlings. The results showed that strawberry growth slowed down or even stopped and total chlorophyll content, stomatal conductance, net photosynthetic rate, and maximal quantum yield of PSII photochemistry decreased, while intercellular CO2 concentration increased under LI, LT, and combined stress (LL). Additionally, JIP-test showed that compared to LI or LT stress, LL-stressed plants had lower quantum yields and efficiencies and functional antenna size, and higher reaction center activity. Besides, the contents of hydrogen peroxide and malondialdehyde increased, while the activity of superoxide dismutase, peroxidase, and catalase were significantly inhibited compared with the control. After the stress was relieved, the photosynthesis of LL-stressed plants recovered poorly. [ABSTRACT FROM AUTHOR]

We investigated the role of nitric oxide (NO) in the regulation of ascorbate-glutathione (AsA-GSH) cycle and water physiological characteristics of Arabidopsis thaliana by sodium hydrosulfide (NaHS). NaHS markedly increased the contents of H2S, NO, chlorophyll (Chl), and carotenoids, the activity of AsA-GSH cycle, ascorbate/dehydroascorbate ratio, net photosynthetic rate, Chl fluorescence parameters, transpiration rate, stomatal conductance, and relative water content in leaves and the biomass of wild-type Arabidopsis. However, NaHS markedly decreased malondialdehyde content and electrolytic leakage. Except H2S, above NaHS-induced promotions were suppressed by nitrate reductase (NR) inhibitor sodium azide (NaN3). Application of sodium nitroprusside (SNP) to (NaN3+NaHS)-treated wild type Arabidopsis (NaN3+SNP+NaHS) reversed above effects of NaN3+NaHS. However, NaN3+NaHS and NaN3+SNP+NaHS had no significant effects on H2S content. Meanwhile, we proved above results by using NO-associated NR gene mutant nia1,nia2. Above results suggested that NO participated in the regulation of AsA-GSH cycle and water physiological characteristics of Arabidopsis by NaHS. [ABSTRACT FROM AUTHOR]

We selected the elite clone of Pinus sylvestris var. mongolica 'GS1' from 365 clones in a primary seed orchard in Liaoning Province, China. To understand the photosynthesis characteristics and mechanisms, 40-year-old 'GS1' trees were compared with a common clone 'H524' of the same age at the same seed orchard. Results showed that 'GS1' had higher net photosynthetic rate because of higher stomatal conductance (gs); the larger external and inner diameters of stomata were the structural factors enabling maintenance of higher gs. The higher light-saturated net photosynthetic rate of 'GS1' was mainly due to higher electron transfer activity, demonstrated by the lower relative fluorescence intensity from O-step to P-step. The increase in density of active reaction centers resulted in an increase in energy flux per cross section, which led to higher photosynthetic performance. [ABSTRACT FROM AUTHOR]

Two spring wheat varieties were used to study alleviating effects of exogenous spermine (Spm) and spermidine (Spd) on agronomic traits and photosynthesis under high temperature treatment (HT). Our results showed that HT significantly decreased grain mass per panicle of heat-resistant variety (XC 6) by 25% and heat-sensitive variety (XC 31) by 32%. After HT, i.e., at 13 d after flowering, the decrease in net photosynthetic rate of XC 6 (38%) was lower than that of XC 31 (53%); the reason for this was related to XC 6, which could maintain correspondingly normal chlorophyll content (Chl), stomatal conductance (gs), transpiration rate (E), and intercellular CO2 concentration. Exogenous Spm and Spd could increase relative water content, Chl, gs, E, the maximal quantum yield of PSII photochemistry, effective quantum yield of PSII photochemistry, antenna conversion efficiency, and photochemical quenching coefficient of flag leaves under HT. Our results indicated that the heat resistance of XC 6 is better than that of XC 31 and exogenous Spm and Spd could alleviate the heat injury of photosynthesis of wheat flag leaves. [ABSTRACT FROM AUTHOR]

The aim of this work was to evaluate the impact of Si fertilization on the resilience capacity of chestnut plants growing under high air temperatures and its recovery capacity after returning to optimal temperatures. Castanea sativa plants were supplied with 0, 5, 7.5, and 10 mM potassium silicate (SiK®) and exposed for a month at each temperature, 25, 32, and 25°C. The results demonstrated that phytoliths were accumulated in the leaf tissues, both on the cell wall and xylem vessels, suggesting their role in the plant's tolerance to heat. Under high temperature, Si fertilization in chestnut plants increased the gas exchange and the photochemical efficiency of the PSII as the increase of 50% on performance index suggests. The presence of Si also induced higher contents of photosynthetic pigments and promoted a better adaptation of chloroplasts to high temperatures. The present study suggests that the application of Si may be used to enhance the high temperature tolerance of chestnut plants. [ABSTRACT FROM AUTHOR]

Ziziphus spina-christi (L.) Willd., known as Christ's thorn jujube, is a multipurpose species of the Rhamnaceae family. Seedlings were subjected to various NaCl concentrations (0 to 200 mM) for 21 d. They grew well under control conditions, however, biomass production and relative growth rate decreased with increasing NaCl salinity. This decline in growth was closely associated with a reduction in photosynthetic characteristics and plant water relations. However, the intrinsic water-use efficiency significantly increased as salt stress intensified. The relative water content declined although it still maintained high values (= 57%). At high salinity, plants displayed more negative stem water potential (w) and osmotic potential values of -2.0 and -4.0 MPa, respectively. The net photosynthetic rate and stomatal conductance were positively correlated and the former variable also had a strong positive relationship with w. These findings suggest that this fruit tree is quite tolerant to NaCl-salinity during its seedling stage. [ABSTRACT FROM AUTHOR]

This study tried to evaluate the influence of high temperatures (HT) on carbon assimilation of two oak species (Quercus cerris and Quercus robur). The screening of their populations, which are assumed to have a different resistance and acclimatization potential to adverse environmental conditions, can provide essential information for its implementation in reforestation strategies. By employing principal component analysis, the aim was to determine the most variable physiological characteristics of plants exposed to extremely HT during vegetation periods. After 2 d of HT treatment, a significant decline of photosynthetic and transpiration rates, and stomatal conductance were observed in plants of all investigated populations. The decrease of photosynthetic parameters after 2 d of HT treatment was regulated by the stomatal closure which caused the limitation of CO2 assimilation. Contrary, a chronic HT stress led to an increase in gs and inhibition of photosynthesis at the level of carboxylation. [ABSTRACT FROM AUTHOR]

Physiological and molecular responses of maize seedlings (Zea mays L. cv. Troinaya sladost) to 5-d drought and rehydration for 48 h were investigated. Plant water status was determined by a new method of water potential measurement in mesophyll cells' apoplast in substomatal cavity (ψwa). Drought caused the changes in water status, plant growth, the rates of photosynthetic CO2/H2O gas exchange, and metabolism of carbohydrates and proline. The increase in carbohydrate and proline content under drought was observed simultaneously with the decline in ψwa. Rewatering of seedlings for 24 and 48 h resulted in restoration of growth, rapid increase in ψwa as well as in the rates of photosynthetic gas exchange, and a sharp decline in the content of soluble sugars and proline. Data on close correspondence between the changes in osmolyte content and ψwa under drought and recovery support the assumption that osmolytes might participate in regulation of ψwa. [ABSTRACT FROM AUTHOR]

Savin juniper has green, photosynthetic branchlets with scale and/or needle leaves and these heteromorphic forms may contribute differentially to its success in open, arid environments. To test differences in photoprotection between fully sun-exposed scale-holding branchlets (SHB) and needle-holding branchlets (NHB), we measured gas exchange, chlorophyll (Chl) fluorescence, and pigment concentrations. NHB had higher net photosynthetic rate, stomatal conductance, and intrinsic water-use efficiency. In contrast, SHB had higher nonphotochemical quenching. Chl a, Chl b, and antheraxanthin concentrations were higher in NHB. SHB had higher zeaxanthin, lutein, and carotenoids (Car), and higher Chl a/b, Car/Chl, and a-carotene/ß-carotene ratios. The results indicate greater engagement of xanthophyll-based thermal dissipation in SHB. Branchlet types acclimate to strong light using different strategies; SHB by investing in photoprotective mechanisms, and NHB by having a high photosynthetic capacity. Heterophylly may allow savin juniper to be more functionally flexible under variable environmental conditions. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S) is regarded as gaseous signaling molecule in plant response to various biotic and abiotic stresses. In this study, we investigated potential role of H2S in modulating photosynthesis in low light (LL) stress-induced tall fescue (Festuca arundinacea Schreb.) seedlings. Results demonstrated that LL significantly reduced the plant height, leaf width, tiller number, dry mass, turf quality, chlorophyll content, net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, maximal quantum yield of PSII photochemistry, photochemical efficiency of PSII, photochemical quenching, electron transport rate, and enzymatic activity of ribulose-1,5-bisphosphate carboxylase. Then, these parameters were found to be considerably alleviated by H2S donor application. Moreover, exogenous application of NaHS decreased the concentration of malondialdehyde, increased activities of peroxidase, superoxide dismutase, ascorbate peroxidase, total soluble sugar, soluble protein, and endogenous concentration of H2S. In addition, these responses could be reversed by treatment with hypotaurine (H2S scavenger) and aminooxy acetic acid (H2S biosynthesis inhibitor). These results suggested that H2S was possibly involved in the regulation of photosynthesis to strengthen LL tolerance by maintaining a high level of photochemical efficiency and improving antioxidant enzyme activities in tall fescue. [ABSTRACT FROM AUTHOR]

Long-term CO2 enrichment (1,000 µmol mol-1) leads to photosynthetic acclimation in cucumber. Here, through hydroponic experiments in an open-top climate chamber system, we investigated key photosynthetic parameters of cucumbers using potassium stimulation (120 or 240 mg L-1). Short-term CO2 enrichment (less than 25 days) significantly increased the net photosynthetic rate in cucumber. However, long-term CO2 enrichment (43 d) led to photosynthetic acclimation and decrease in stomatal conductance. The increase in potassium alleviated the decrease in photosynthetic rate and stomatal conductance, which reduced photosynthetic acclimation. In addition, 13C isotope tracing showed that under CO2 enrichment, plants with higher potassium concentrations showed higher sink/source and flow/source ratios of photosynthetic assimilative C (d13C) abundance. Moreover, the abnormal accumulation of soluble carbohydrates and starch resulted in photosynthetic acclimation in cucumber. Increasing potassium significantly reduced the accumulation of soluble carbohydrates and promoted the transport of soluble carbohydrates to the sink, which alleviated photosynthetic acclimation. [ABSTRACT FROM AUTHOR]

We studied the effects of melatonin on soybean photosynthesis and seed growth at different developmental stages under drought stress induced by polyethylene glycol in the growth medium. Experimental groups were supplied with a normal nutrient solution after seven days of continuous treatment; overall, five treatments were completed when the early maturity stage was reached. Under normal water supply, melatonin supplementation had no significant effect on the photosynthetic characteristics or soybean seed growth. However, drought stress reduced leaf relative water content, chlorophyll content, and relative photosynthetic gas-exchange parameters, while it increased a leaf content of osmoregulatory substances, antioxidant-related enzyme activities, and seed growth-related indicators. Compared to the drought-stressed group, the melatonin treatment under drought stress improved the above indicators; specifically, melatonin effectively increased the photosynthetic rate, 100-seed mass, and total seed mass per plant. All the effects were most significant during the first seven days after the early seed-filling stage. [ABSTRACT FROM AUTHOR]

Sinopodophyllum hexandrum (Royle) Ying, a medicinal plant, has been endangered due to alpine habitat and overuse at Southeastern Tibet Plateau. This study aimed to examine the phenotypic traits and photosynthesis of S. hexandrum, including their relationship with main environmental factors, under low light (LL), moderate light (ML), and high light (HL) regimes. Low specific leaf mass was observed under LL, but the stomatal density and apparent quantum yield were the highest under this regime. The phenotypic traits, except for stomatal density and net photosynthetic rate, were the most notable under ML. The leaf area, stomatal density, apparent quantum yield, dark respiration, and stomatal conductance showed the smallest values under HL. Air temperature, photosynthetically active radiation, and air vapour pressure deficit significantly affected the stomatal characteristics and photosynthesis of S. hexandrum individuals. Our results suggested that a moderately shaded habitat could promote leaf development and the photosynthetic ability of S. hexandrum. [ABSTRACT FROM AUTHOR]

There is a trade-off between leaf structures and photosynthesis physiology. While numerous reports have shown a difference in photosynthesis between Gossypium hirsutum L. (upland cotton) and G. barbadense L. (pima cotton), the potential contribution of leaf structures on this difference was not fully clarified. Here, we investigated the differences in area- and mass-based photosynthetic traits and leaf structures between upland and pima cottons. Our results showed that upland cotton had higher area-based net photosynthetic rate (Parea) than that of pima cotton, which was attributed to the coordination of stomatal conductance (gs), area-based mesophyll conductance (gm-area), and maximum carboxylation rate (Vcmax-area). Parea, gm-area, and Vcmax-area correlated positively with leaf mass per area. But upland and pima cotton had similar mass-based PN (Pmass), gm (gm-mass), Vcmax (Vcmax-mass), suggesting that they have a similar photosynthetic capacity of single cells. Consequently, the higher area-based values in upland cotton were only due to a higher leaf thickness (Tleaf). [ABSTRACT FROM AUTHOR]

The effects of different concentrations of ferulic acid, chlorogenic acid, and protocatechuic acid were studied in a pot experiment to assess the response of Rhododendron delavayi seedlings. The results showed that three kinds of phenols promoted increases in chlorophyll (Chl) a, Chl b, total Chl, and carotenoid contents, but inhibited the accumulation of biomass. Low concentrations of ferulic acid significantly inhibited stomatal opening, the stomatal opening ratio, stomatal length and width. Chlorogenic acid and the moderate and high concentrations of ferulic acid also significantly inhibited stomatal density. Ferulic acid significantly inhibited net photosynthetic rate and stomatal conductance in seedlings, whereas chlorogenic acid significantly inhibited stomatal conductance. The low and moderate concentrations of chlorogenic acid significantly inhibited transpiration rate, and high concentrations of ferulic acid significantly inhibited the stomatal limitation value. The moderate concentration of protocatechuic acid significantly inhibited net photosynthetic rate and stomatal conductance. Ferulic acid exhibited a greater toxic effect than that of chlorogenic acid and protocatechuic acid for R. delavayi seedlings. [ABSTRACT FROM AUTHOR]

Photosynthesis is sensitive to water deficit (WD) stress. Maize (Zea mays L.) yield is vulnerable to water stress, especially if it occurs during the reproductive stage. In this study, the expression patterns of photosynthesis-related genes, together with photosynthetic gas-exchange and fluorescence parameters were investigated in a maize inbred line exposed to 50% of field water capacity (moderate WD) for 15 d after tassel emergence. The results demonstrated that WD down-regulated expression of psbA, psbB, psbC, psbP, psaA, psaB, and cab, especially at later periods of WD stress. Besides, with the increased WD stress, the steady decline in the value of photosynthesis performance index, maximum quantum yield of primary photochemistry, quantum yield for electron transport, quantum yield for the reduction of end acceptors of PSI per photon absorbed, and the efficiency of an electron beyond QA - that reduced PSI acceptors, and a clear increase in the J-step and I-step, K-band as well as L-band were observed. The results suggested that WD might restrict light-harvesting and electron transport. Interestingly, leaf transcript levels of rbcL and rbcS were up-regulated at the later stage of water stress in maize inbred line, which helped repair injury to PSII centers and maintain PSII activity (increased quantum yield of dissipation and effective antenna size of an active reaction center) under 15-d lasting WD. [ABSTRACT FROM AUTHOR]

In order to explore whether leaf area of developing leaves was regulated by systemic irradiance signal from mature leaves, we investigated the leaf area, leaf anatomy, photosynthesis, auxin, gibberellin, and cytokinin contents of new developing leaves in soybean growing under conditions of shaded mature leaves (MS), shaded whole plants (WS), and under full sunlight (NS). The results showed that developing leaves under MS exhibited the higher leaf area and leaf mass than that of WS. Blade thickness, palisade tissue thickness, sponge tissue thickness, cell size, cell numbers, net photosynthetic rate, stomatal conductance, transpiration rate, and cytokinin content of developing leaves under MS were lower, while auxin and gibberellin contents were higher than that of NS. These results indicate that the leaf area, leaf anatomy, and photosynthesis of developing leaves were regulated by the shading environment of mature leaves. Growth hormones may possibly act as candidate signal substances to systemic regulation of leaf area development. [ABSTRACT FROM AUTHOR]

Leaf gas exchange and growth responses of three melon cultivars, i.e., Mission, Da Vinci (var. reticulatus), and Super Nectar (var. inodorus) to two irrigation regimes, 50 and 100% crop evapotranspiration (ETc) were investigated under water-limited conditions of southwest Texas. In 2012, deficit irrigation (50% ETc) significantly decreased above-ground biomass, leaf area, leaf number, and specific leaf area, while leaf gas exchange, relative water content, water potential, chlorophyll fluorescence (Fv/Fm), and chlorophyll content (SPAD index) were not affected. However, in the drier year 2011, deficit irrigation significantly reduced net photosynthetic rate (PN) and stomatal conductance (gs). Further, the responses to water deficit varied with cultivars. At 50% ETc, PN and gs were maintained in cv. Da Vinci while decreased in Mission and Super Nectar. Thus, the late maturing cv. Super Nectar appeared to be more sensitive to drought stress, possibly due to the decrease in leaf area and PN. [ABSTRACT FROM AUTHOR]

Photosynthetic characteristics of sugar beet cultivars KWS0143 and Beta464 were studied under alkaline conditions, including 0 (A0, control), 25 (A1), 50 (A2), 75 (A3), and 100 mM of mixed alkali (Na2CO3:NaHCO3, 1:2). A2, A3, and A4 reduced net photosynthetic rate (PN), stomatal conductance, and transpiration rate, but rose intercellular CO2 concentration. Reduction in PN occurred probably due to nonstomatal limitation. The decrease in efficiency of photosynthetic electron transport might be the main reason for the decrease of PN. The concentrations of photosynthetic pigments were significantly reduced by high (A3 and A4) alkalinity. Changes in chloroplast ultrastructure are the reason for the decrease in chlorophyll content. Sugar beet could resist injury from alkali owing to osmotic substances and antioxidant enzymes if alkaline stress was at a lower level. The better performance of KWS0143 under alkalinity might be associated with its more efficient osmotic and antioxidant systems to resist injury of photosynthetic apparatus caused by alkalinity. [ABSTRACT FROM AUTHOR]

Climate models predict an increase in atmospheric CO2 concentration and prolonged droughts in some parts of the Amazon, but the effect of elevated CO2 is still unknown. Two experiments (ambient CO2 400 ppm and elevated CO2 ? 700 ppm) were conducted to assess the effect of drought (soil at 50% field capacity) on physiological parameters of Carapa. At ambient CO2 concentration, light-saturated net photosynthetic rate (PNsat) was reduced by 33.5% and stomatal conductance (gs) by 46.4% under drought, but the effect of drought on PNsat and gs was nullified at elevated CO2. Total plant biomass and leaf area production were also reduced (42?47%) by drought. By changing leaf traits, Carapa is able to endure drought, as the consumptive use of water was reduced under drought (32?40%). The improvement of PNsat under elevated CO2 and water stress and the leaf plasticity of Carapa broaden our understanding of the physiology of Amazonian trees. [ABSTRACT FROM AUTHOR]

Increased attention has been paid to effects of coal mining subsidence on the growth of plants. Studying the changes of plants photosynthetic physiology under the disturbance of coal mining subsidence is the basis for understanding dynamic exchanges of plant energy and water at that mining area. The 52302 working face of the Shendong mining area was selected as the experimental site, with Artemisia ordosica, Caragana korshinskii, and Populus spp. as the research targets. Changes in leaf photosynthesis were monitored in plants at a subsidence crack area. We showed collapse cracks decreased soil moisture and caused drought stress. The photosynthetic capacity of leaves was reduced. Compared with plants from the control area, stomatal conductance, photosynthetic CO2 assimilation, and transpiration rate were reduced in all three plant species. The activity of PSII reaction center and electron transport at the donor and acceptor sites significantly decreased. [ABSTRACT FROM AUTHOR]