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Background and aims: Plant nutrients play a fundamental role in regulating ecosystem functioning and are sensitive to global changes such as precipitation change and nitrogen (N) deposition. However, the mechanisms by which resource availability and community composition mediate canopy nutrients remain unclear. Methods: We investigated soil resource availability, plant productivity, community composition and canopy nutrient status in a 6-year water and N addition experiment in a desert shrubland of northern China. Results: Water addition overall negatively affected canopy N content but had no effect on canopy phosphorus (P) content, and these effects were mediated by ambient precipitation. In drier years, water addition reduced canopy N and P contents via decreasing shrub-herb ratio and increasing community productivity. In wetter years, higher precipitation levels weakened water effects on plant community, causing a neutral water effect on canopy N content. Furthermore, this increased precipitation intensified soil calcium leaching, which, in turn, had a positive water effect on canopy P content. Accordingly, canopy N and P contents showed negative logarithmic and concave-shaped relationships with precipitation, respectively. Nitrogen enrichment increased canopy N but reduced P content through increasing soil N availability and reducing shrub-herb ratio. Conclusions: Our results suggest that both ambient precipitation levels and plant functional composition play pivotal roles in mediating desert canopy nutrient responses to precipitation change and N deposition. Our findings also highlight the fundamental role of soil calcium in regulating plant P responses to precipitation change, which provide new insights into our understanding of biogeochemical coupling under global change. [ABSTRACT FROM AUTHOR]

Water availability is the main factor affecting the forage productivity of artificial grasslands, particularly in semi-arid regions. Generally, intercropping of gramineous grass and leguminous grass can achieve high productivity. However, how different water availability levels affect the productivity of intercropping system remains unclear. Here, we conducted a 3-year (2015-2017) study by manipulating the water conditions (CK equivalent to the annual precipitation, C50% treatment equivalent to 50% increase over the average precipitation, and -50% treatment equivalent to 50% decrease over the average precipitation) to explore the responses of plant traits, nitrogen use efficiency, and biomass of the monoculture of Medicago sativa (a leguminous grass, M.s), monoculture of Elymus nutans (a gramineous grass, E.n), and intercropping of M.s and E.n in a semi-arid region in Inner Mongolia, China. The results showed that the biomass obtained by intercropping of M.s and E.n decreased by 24.4% in -50% treatment compared to the CK treatment, while that of the monoculture of M.s decreased by 34.4% under the -50% treatment compared to the CK treatment. However, there was no significant difference in the biomass between intercropping artificial grassland and monoculture M. sativa under +50% treatment. Compared to monoculture, M.s can obtain more nitrogen by biological nitrogen fixation and decrease the proportion of nitrogen absorbed from soils under intercropping in the same water conditions. Under the intercropping system, the proportions of nitrogen absorbed from soils by M.s were 87.4%, 85.1, and 76.9% in -50%, CK, and C50% treatments, respectively. Under monoculture, these proportions were 91.9, 89.3, and 82.3% in -50%, CK, and C50% treatments, respectively. Plant trait, but not soil nitrogen content, was the main regulator for the productivity responses to water level changes. Our results highlight that intercropping can achieve higher productivity in both dry and wet conditions. Therefore, considering the fluctuating rainfall events in the future, it might be useful to alter the proportions of intercropped forage species in an artificial grassland to obtain optimal productivity by reducing the limitations of nitrogen availability. However, the economic viability of intercropping M. sativa and E. nutans should be evaluated in the future. [ABSTRACT FROM AUTHOR]

Background: Water stress is one of the serious abiotic stresses that negatively influences the growth, development and production of sugarcane in arid and semi-arid regions. However, silicon (Si) has been applied as an alleviation strategy subjected to environmental stresses. Methods: In this experiment, Si was applied as soil irrigation in sugarcane plants to understand the mitigation effect of Si against harmful impact of water stress on photosynthetic leaf gas exchange. Results: In the present study we primarily revealed the consequences of low soil moisture content, which affect overall plant performance of sugarcane significantly. Silicon application reduced the adverse effects of water stress by improving the net photosynthetic assimilation rate (Anet) 1.35–18.75%, stomatal conductance to water vapour (gs) 3.26–21.57% and rate of transpiration (E) 1.16–17.83%. The mathematical models developed from the proposed hypothesis explained the functional relationships between photosynthetic responses of Si application and water stress mitigation. Conclusions: Silicon application showed high ameliorative effects on photosynthetic responses of sugarcane to water stress and could be used for mitigating environmental stresses in other crops, too, in future. [ABSTRACT FROM AUTHOR]

A two years study was carried out during 2017-18 to investigate the effect of planting date and sowing depth on some qualitative traits, yield and water consumption efficiency of potato cultivars in autumn and spring cultivations in Ardebil, IRAN, as split factorial based on RCBD with three replicates. The main plots were sowing dates (1st of November and December and 30th of April) and factorial combination of potato cultivars (Esprit, Marfona, Savalan and Agria) and tuber sowing depths (10, 15, 20 and 25 cm) were considered as subplots. The results showed that iron content, tuber yield and water use efficiency affected by cropping date and nitrogen content, fat and fiber percentages and soluble sugars affected by sowing depths. Water consumption efficiency was higher by sowing Esprit cultivar in 1st of November and December at depths of 10, 15 and 25 cm. [ABSTRACT FROM AUTHOR]

This experiment was conducted in a field of clay soil to study the effect interaction between of spermine and amino fertilizer and water stress on the antioxidants of wheat plant Triticum aestivum L, the experience included water holding (3, 7 and 14) day that gave the symbols (D1, D2, D3) respectively, and (0, 2, 4 and 8) ml. L-1 amino fertilizer with or without spermine (1) mM., the vegetative leaf was harvested to study some biochemical characteristics, including the content of chlorophyll a, b and total chlorophyll, Carotenods, Proline, Tocopherol and Ascorbic acid. showed the results when foliar spray of amino fertilizer had a positive effect on plant growth as the concentration of (8) ml.L-1of amino fertilizer had a significant effect in an increase the content of chlorophyll a, b, total chlorophyll, Carotenods, Proline, Tocopherol, except Ascorbic acid which value decreased significantly, The study also showed that foliar spermine with a concentration of (1) mM has an effect similar to the effect of reduce the effect of water stress on wheat plant. [ABSTRACT FROM AUTHOR]

The goal of this study is evaluation of the effect of different levels of plant water stress on their subsequent performance in the first growing season after planting. The most noticeable manifestation of current global climate change are more frequent drought periods of greater intensity and different duration. For successful artificial forest restoration, the basic factor is the use of high-quality planting stock showing both morphological quality and desired physiological status. The physiological status of the plants is one of the most important factors predisposing survival rates and growth after planting. For objective evaluation of their water regime a water potential (stress) of plants was measured using the pressure chamber, water content, water deficit and relative electrical conductivity. For the reforestation of large clear cuts, which area is increasing currently, it is necessary to use also artificial renewal using preparatory (pioneer) trees. The results showed that all the methods used to evaluate the physiological quality responded to the stress of silver birch and European aspen seedlings exposed to deliberate drying and corresponded to losses and reduced growth after planting. The birch seedlings were more sensitive to drying when compared to aspen. [ABSTRACT FROM AUTHOR]

Groundwater level is crucial for wetland plant growth and reproduction, but the extent of its effect on plant growth can vary along with changed precipitation and temperature at different seasons. In this context, we investigated the effect of two groundwater levels (10 cm vs. 20 cm depth) on growth and reproductive parameters of Carex cinerascens, a dominant plant species in the Poyang Lake wetland, during three seasons (spring, summer, and autumn) and during two consecutive years (2015 and 2016). Carex cinerascens showed low stem number, height, and individual and population biomass in summer compared to spring and autumn. 10 cm groundwater level was overall more suitable for plant growth resulting in higher stem height and biomass. However, the interactive effect between groundwater level and season clearly demonstrated that the effect of groundwater level on plant growth occurred mainly in autumn. After the withering of the plant population in summer, we observed that C. cinerascens growth recovered in autumn to similar values observed in spring only with 10 cm groundwater level. Consequently, we could deduce that lowering groundwater level in the studied Poyang Lake wetland will negatively impact C. cinerascens regeneration and growth particularly during the second growth cycle occurring in autumn. Additionally, our results showed that, independently of the season and groundwater level, population biomass of C. cinerascens was lower during drier year. Altogether, our findings suggest that water limitation due to both reduction in precipitation and decreased groundwater level during the year can strongly impact plant communities. [ABSTRACT FROM AUTHOR]

Leaves lose approximately 400 H2O molecules for every 1 CO2 gained during photosynthesis. Most long-distance water transport in plants, or xylem sap flow, serves to replace this water to prevent desiccation. Theory predicts that the largest vessels contribute disproportionately to overall sap flow because flow in pipe-like systems scales with the fourth power of radius. Here, we confront these theoretical flow predictions for a vessel network reconstructed from X-ray μCT imagery with in vivo flow MRI observations from the same sample of a first-year grapevine stem. Theoretical flow rate predictions based on vessel diameters are not supported. The heterogeneity of the vessel network gives rise to transverse pressure gradients that redirect flow from wide to narrow vessels, reducing the contribution of wide vessels to sap flow by 15% of the total. Our results call for an update of the current working model of the xylem to account for its heterogeneity. Plants require long-distance water transport to avoid desiccation. Here, via μCT and MRI of grapevine stem, Bouda et al. show evidence of pressure gradient heterogeneity and flow redirection from wide to narrow vessels that suggests narrow vessels contribute more to xylem sap flow than previously appreciated. [ABSTRACT FROM AUTHOR]

Understanding how trees respond to extreme events is important to predict how climate change will impact forests in the future. In this study, we report changes in radial growth and tree‐ring carbon (δ13C) and oxygen (δ18O) stable isotope ratios of Pseudotsuga menziesii (Douglas‐fir) in western Mexico. Tree growth was compared with δ13C and δ18O ratios recorded during dry and wet periods caused by El Niño‐Southern Oscillation since 1850. The three driest and three wettest events during the studied period caused tree growth decline of up to 50% followed by 6–10 years of slow recovery until baseline growth was regained. Wet events resulted in up to 17% growth increase, a positive effect that persisted for no more than 3–5 years. Stable isotope ratios recorded physiological adjustments that in some cases correlated significantly with tree growth. Excursions in tree‐ring Δ13C and δ18O isotope ratios suggest that trees cope with dry and wet periods with proportional but divergent adjustments in photosynthesis versus stomatal conductance. Notably, the intrinsic water‐use efficiency—that is, the ratio between carbon assimilation and water loss through transpiration—was positively correlated with tree basal growth only during dry periods. We found no significant correlations between growth and intrinsic water‐use efficiency during wet periods. Contrary to expectations, rising CO2 levels over the past ~160 years did not affect tree growth response to precipitation variability. Key Points: To quantify the response of Douglas‐fir trees to dry and wet events, we measured tree rings and C and O stable isotopes since 1850Tree growth decreased up to 50% following extreme drought events, an impact that lasted up to 10 yearsEach extreme wet event resulted in up to 17% of growth increase, an effect that lasted up to 5 years [ABSTRACT FROM AUTHOR]

Highlights • Effects of water and N input on maize yield and water productivity (WP) were assessed. • Effects of water and N input on maize nitrogen use efficiency (NUE) were studied. • Achieved values were lower than the attainable one by 28% (yield), 28 (WP), 21 (NUE). • Global mean water and N saving potentials was 10 and 18%. • Above-optimal water input increased both yield and WP by 3%. Abstract Global maize (Zea mays) yields are limited by water and nutrient availability. Although water and nitrogen (N) have long been recognized for their beneficial effects (alone or interactively) on maize production, synthetic analysis on the effects of water and N inputs on maize yield, water productivity (WP, yield per unit water usage) and N use efficiency (NUE, yield per unit N applied) at a global scale is lacking. The objectives of this study were to quantify the effects of water and/or N inputs on both yield, WP and NUE, and water and N saving potential. Based on yield (n = 1406), WP (n = 1406), and NUE (n = 1131) observations from 83 studies conducted in 15 countries, the meta-analysis found that the optimal maize yield was achieved when maize planting density (number of plants per unit area) was 8.7 plants m−2. Generally speaking, maize yield, WP, and NUE were inversely correlated to mean annual temperature. The positive effect of inputting either water or N on all variables faded away when the optimal input levels were exceeded. The achieved yield, WP, and NUE were significantly lower than the attainable values by 27.9%, 27.9%, and 20.5%, respectively. The overall global mean water and N saving potential was 10 and 18%, respectively. Meanwhile, optimizing water or N input separately did not consistently enhance yield, WP, or NUE, while above-optimal water input increased yield and WP more than below-optimal water input by 3.4% and 3.3%, respectively. These results showed that current water and N management practices have created large gaps between the actual and attainable productivity and efficiency indices (e.g. yield, WUE, and NUE), and that simultaneous optimization of water and fertilizer N inputs is crucial for achieving maximum maize yield. [ABSTRACT FROM AUTHOR]

5-Aminolevulinic acid relieves the effects of environmental stresses in plants. Therefore, the aim of our study was to evaluate the effects of 5-aminolevulinic acid (5-ALA) on the activity of the photosynthetic apparatus in spring wheat. Other analyzed parameters involved plant height, relative turgidity, membrane status, and chlorophyll level. The plant material consisted of three genotypes of spring wheat (J × Z, R × K, K × M), subjected to mild and severe drought in the early phase of vegetative development. 5-ALA showed a positive effect on the activity of the photosynthetic apparatus under water stress. The relieving action of 5-ALA on PSII was the most evident in J × Z genotype during severe soil drought. 5-ALA positively influenced the maximum photochemical efficiency of PSII (Fv/Fm), the overall performance index of PSII photochemistry (PI) and the effective quantum field of PSII (φEo). In the same genotype, the investigated acid stimulated light energy absorption (ABS/CSm), and enhanced the amount of excitation energy trapped in PSII reaction centers (TRo/CSm) and the amount of energy used for electron transport (ETo/CSm). Moreover, 5-aminolevulinic acid showed its potential to overcome the adverse effects of water deficit on Triticum aestivum L. by increasing plant growth, relative turgidity, and chlorophyll content and reducing the degree of damage to cell membranes at the early phase of vegetative development. [ABSTRACT FROM AUTHOR]

Highlights • LWP values clearly decreased during periods of water stress. • The CWSI and rs values increased with increasing water stress. • CWSI, LWP and rs were significantly affected by irrigation regimes and levels. • Partial root drying regimes result in high WUE and IWUE values. • There are significant relationships between AW and CWSI, LWP and rs in the study. Abstract A study was conducted to analyse the physiological response of red pepper (Capsicum annuum L.) to different irrigation regimes by means of periodical measurements of leaf water potential (LWP) and stomatal resistance (rs) and crop water stress index (CWSI) at midday during 2010 and 2011 seasons in the Mediterranean region of Turkey. The treatments consisted of full irrigation (FI), deficit irrigation (DI-75, DI-50), partial root zone drying (PRD-A, PRD-F, A: alternative, F: fixed). The greatest yield was obtained from the FI treatment followed by DI-75, PRD-A, DI-50 and PRD-F treatments resulted in the smallest yield. The FI irrigation treatment had less stomatal resistance (17.4 s cm−1 in 2010 and 16.4 s cm−1 in 2011) and CWSI (0.25 in 2010 and 0.27 in 2011) in comparison with deficit irrigation treatments. Red pepper performed best at FI with a corresponding leaf water potential of -0.65 to -0.53 MPa for experimental years. There were large differences among treatments in LWP, CWSI and rs, indicating that crop responded differently to different soil water levels. Significant relationship between stomatal resistance, water use and yield were obtained. The results also revealed significant dependency among CWSI, rs and LWP were found. [ABSTRACT FROM AUTHOR]

Highlights • Effects of irrigation and harvest moment were study in the grapevine leaves. • Antioxidant properties and phytochemicals content were assessed in grapevine leaf. • Increasing irrigation reduced phytochemicals content and the antioxidant activity. • The antioxidant activity suffered a reduction over time, presenting higher values in veraison. Abstract The cultivation of grapevines (Vitis vinifera L.) has extended worldwide, with great economic importance. From this crop, we can obtain grapes for fresh consumption, raisins, juices, wine, and other derived products. The cultivation of grapevines also generates some byproducts, such as seeds, skins, wood and leaves. The leaves can be removed from the plant, as is common agricultural practice, to improve the production and quality of the grapes at certain periods in the crop cycle. In the present work, the phytochemical composition (total phenols content, hydroxycinnamic acids derivatives and flavonols) and antioxidant potential (reducing power, ABTS and DPPH radical scavenging capacity) of grapevine leaves from cv. Touriga Nacional were evaluated. The studied cultivar was under three severities of regulated deficit irrigation (RDI60, RDI40, and RDI20; providing 60, 40 and 20% of reference evapotranspiration, respectively) and non-irrigation (NI; exclusively rain-fed), in a vineyard located in the Demarcated Douro Region (Portugal). The leaves were collected at three different phenological stages: veraison, maturation, and grape harvest. For the first time, the interactions between different irrigation regimes and the collection period were evaluated on grapevine leaves. The results obtained for the phytochemical composition revealed that increasing irrigation reduced total phenols content, hydroxycinnamic acids derivatives, and flavonols in all of the phenological stages studied. For instance, compared to that of the control treatment (NI), the total phenols content reduced 19% in RDI20 (from 189 mg GAE g−1 to 153 mg GAE g−1), 28% in RDI40 (136 mg GAE g−1), and 33% in RDI60 (127 mg GAE g−1). The antioxidant activity suffered a reduction when the irrigation amount was increased for all assays. Additionally, the antioxidant activity suffered a reduction over time, presenting higher values in veraison. For harvest sampling, the loss of antioxidant activity was more notable, with EC 50 values varying between 0.092 mg mL−1 (NI) and 0.187 mg mL−1 (RDI60). Altogether, the results suggest that grapevine leaves are a potential source of natural compounds with valuable antioxidant properties that could be explored by the pharmaceutical, chemical and food industries. [ABSTRACT FROM AUTHOR]

Accurate estimation of reference evapotranspiration (ETo) is a major task in hydrology, water resources management, irrigation scheduling and determining crop water requirement. There are many empirical equations suggested by numerous references in literature for calculating ETo using meteorological data. Some such equations have been developed for specific climatic conditions while some have been applied universally. The potential for usage of these equations depends on the availability of necessary meteorological parameters for calculating ETo in different climate conditions. The focus of the present study was a global cross-comparison of 20 ETo estimation equations using daily meteorological records of 10 weather stations (covering a period of 12 years) in a semi-arid region of Iran. Two data management scenarios, namely local and cross-station scenarios, were adopted for calibrating the applied equations against the standard FAO56-PM model. The obtained results revealed that the cross-station calibration might be a good alternative for local calibration of the ETo models when proper similar stations are used for feeding the calibration matrix. [ABSTRACT FROM AUTHOR]

Water availability is often described as one of the main drivers of phenology of tropical dry forests but experimental studies to identify the cues triggering phenological changes are few. In a greenhouse trial, we exposed seedlings of thirteen origins, seven from West and six from East Africa, respectively, of Adansonia digitata L.(baobab) to a well‐watered control treatment and a water withholding treatment in combination with exposure to three different daylengths (11.5, 12.0, and 12.5 hr). Responses were measured in terms of meristematic activity, number of leaves, and height growth followed over 6.5 months. Multi‐level mixed‐effects statistical models were used to analyze how environmental and inter‐population variables affected phenological behavior. Flushing was influenced by the daylength with the lowest degree of meristematic activity observed in the short daylength treatment. Daylength also influenced the number of leaves through an interaction with the water regime. The water regime influenced all variables through interactions with the origins. Seedlings subjected to water stress had higher meristematic activity, but initially lower numbers of leaves than continuously watered plants. Height growth in continuously watered plants was fastest or at par with water‐stressed plants, depending on the origin. Origins from West Africa tended to have higher meristematic activity and their phenology was found to be less influenced by water withholding than East African origins. There were no signs of significant differences between origins in their response to photoperiod. In conclusion, baobab seedlings show opportunistic behavior, setting leaves when water is available, but larger activity is found when days are long. We discuss the results in terms of triggering factors for baobab phenology and adaptation to specific environmental conditions at the site of origins. There are very few studies on triggering factors for phenology of dry zone tropical tree species, and even fewer studies that investigate how phenology is varying among origins in common garden experiments. In this study, we tested 13 baobab origins and their phenological response to drought stress and different daylengths. Our results demonstrate that both water availability and daylength influence flushing of leaves, and that origin react differently to these signals. [ABSTRACT FROM AUTHOR]

Copyright of Revista Brasileira de Engenharia Agricola e Ambiental - Agriambi is the property of Revista Brasileira de Engenharia Agricola e Ambiental and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Atmospheric CO2 concentration continues to rise and is predicted to reach approximately 700 ppm by 2100. Some predictions suggest that the dry season in West Africa could be extended with climate change. This study examined the effects of elevated CO2 concentration and water deficit on growth and photosynthesis of juvenile cacao. Light-saturated photosynthesis (Pmax), quantum efficiency, and intrinsic water-use efficiency increased significantly in response to elevated CO2, as did a range of growth and development responses (e.g. leaf area and leaf number), but the magnitude of the increase was dependent on the water treatment. Stomatal index was significantly greater in the elevated CO2 treatment; an atypical response which may be a reflection of the environment in which cacao evolved. This study shows a positive effect of elevated CO2 on juvenile cacao which may help to alleviate some of the negative impacts of water deficit stress. [ABSTRACT FROM AUTHOR]

Copyright of Agronomía Colombiana is the property of Universidad Nacional de Colombia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Root-hemiparasitic plants of the genus Rhinanthus acquire resources through a water-wasting physiological strategy based on high transpiration rate mediated by the accumulation of osmotically active compounds and constantly open stomata. Interestingly, they were also documented to withstand moderate water stress which agrees with their common occurrence in rather dry habitats. Here, we focused on the water-stress physiology of Rhinanthus alectorolophus by examining gas exchange, water relations, stomatal density, and biomass production and its stable isotope composition in adult plants grown on wheat under contrasting (optimal and drought-inducing) water treatments. We also tested the effect of water stress on the survival of Rhinanthus seedlings, which were watered either once (after wheat sowing), twice (after wheat sowing and the hemiparasite planting) or continuously (twice and every sixth day after that). Water shortage significantly reduced seedling survival as well as the biomass production and gas exchange of adult hemiparasites. In spite of that drought-stressed and even wilted plants from both treatments still considerably photosynthesized and transpired. Strikingly, low-irrigated plants exhibited significantly elevated photosynthetic rate compared with high-irrigated plants of the same water status. This might relate to biochemical adjustments of these plants enhancing the resource uptake from the host. Moreover, low-irrigated plants did not acclimatize to water stress by lowering their osmotic potential, perhaps due to the capability to tolerate drought without such an adjustment, as their osmotic potential at full turgor was already low. Contrary to results of previous studies, hemiparasites seem to close their stomata in response to severe drought stress and this happens probably passively after turgor is lost in guard cells. The physiological traits of hemiparasites, namely the low osmotic potential associated with their parasitic lifestyle and the ability to withstand drought and recover from the wilting likely enable them to grow in dry habitats. However, the absence of osmotic adjustment of adults and sensitivity of seedlings to severe drought stress demonstrated here may result in a substantial decline of the hemiparasitic species with ongoing climate change. [ABSTRACT FROM AUTHOR]

As a common plant in the Momoge National Nature Reserve (MNNR), China, Bolboschoenus planiculmis has been acknowledged as a key species in Siberian Crane ( Grus leucogeranus ) habitat by providing food for this migratory waterfowl. Water shortage and salinization have severely impacted B. planiculmis vegetation in this area. In order to restore the degraded B. planiculmis wetlands, tuber transplantation is tentatively used in MNNR. However, the effects of the abiotic factors on tuber emergence and growth of B. planiculmis are poorly understood. In this study, emergence, growth, biomass accumulation and tuber reproduction were investigated experimentally using four water levels (5 cm below soil surface, 0 cm, 10 cm and 20 cm above soil surface) and three soil planting depths (5 cm, 10 cm and 15 cm). Results indicated that emergence, growth and production were closely related with the water level and planting depth. Increasing the water level and planting depth generally decreased the emergence rate and speed of planted tubers. The water table at 5 cm below soil surface significantly increased emergence rate and emergence speed of tubers planted at 5 cm soil depth. Water table at soil surface and 10 cm above soil surface facilitated subsequent growth, biomass accumulation and tuber reproduction of B. planiculmis at soil depth of 5 cm. In addition, planting tubers at this depth increased root/shoot ratio across the four water levels. Therefore, the tuber transplanting method can be selectively ameliorated to promote the plant establishment, plant growth and productivity of B. planiculmis . Results of this study provide technical support for the restoration of B. planiculmis wetland and the improvement in the quality of Siberian Crane habitat. [ABSTRACT FROM AUTHOR]

Endogenous hormones and polyamines (PAs) could interact to regulate growth and tolerance to water stress in white clover. The objective of this study was to investigate whether the alteration of endogenous indole-3-acetic acid (IAA) level affected other hormones level and PAs metabolism contributing to the regulation of tolerance to water stress in white clover. Plants were pretreated with IAA or L-2-aminooxy-3-phenylpropionic acid (L-AOPP, the inhibitor of IAA biosynthesis) for 3 days and then subjected to water-sufficient condition and water stress induced by 15% polyethylene glycol 6000 for 8 days in growth chambers. Exogenous application of IAA significantly increased endogenous IAA, gibberellin (GA), abscisic acid (ABA), and polyamine (PAs) levels, but had no effect on cytokinin content under water stress. The increase in endogenous IAA level enhanced PAs anabolism via the improvement of enzyme activities and transcript level of genes including arginine decarboxylase, ornithine decarboxylase, and S-adenosylmethionine decarboxylase. Exogenous application of IAA also affected PAs catabolism, as manifested by an increase in diamine oxidase and a decrease in polyamine oxidase activities and genes expression. More importantly, the IAA deficiency in white clover decreased endogenous hormone levels (GA, ABA, and PAs) and PAs anabolism along with decline in antioxidant defense and osmotic adjustment (OA). On the contrary, exogenous IAA effectively alleviated stress-induced oxidative damage, growth inhibition, water deficit, and leaf senescence through the maintenance of higher chlorophyll content, OA, and antioxidant defense as well as lower transcript levels of senescence marker genes SAG101 and SAG102 in leaves under water stress. These results indicate that IAA-induced the crosstalk between endogenous hormones and PAs could be involved in the improvement of antioxidant defense and OA conferring tolerance to water stress in white clover. [ABSTRACT FROM AUTHOR]

Aims: Addressing plant responses to water stress is critical to understand the structure of plant communities in water-limited environments and to forecast their resilience to future changes in climate. In a semiarid agroforestry system in the Sahelian savannah of Leona (Senegal), we selected nine common tree species and explored their stress-resistance mechanisms. These species represent a variety of life forms and are of high regional socio-economic importance. We hypothesized that different species would show different suites of traits to cope with water stress and expected to identify functional groups differing in strategies to withstand water shortage. Methods: Along a dry and a wet season, we monitored four traits reflecting above- and below-ground strategies of resource acquisition such as predawn leaf water potential (ψpd), specific leaf area (SLA), leaf thickness and leaf area index (LAI). We also measured two morphological traits: trunk diameter and tree height. LAI and ψpd were measured six times during the dry and rainy seasons, and the other traits were measured once. Important Findings: We identified two functional classes subdivided into two functional groups of each class. The first class included deciduous and semi-deciduous species that generally had large SLA, low leaf thickness and small-to-intermediate inter-seasonal variations in ψpd. The second class included evergreen species of two functional groups that differ in SLA, leaf thickness and the magnitude of inter-seasonal variations of ψpd throughout the year. The four functional groups identified in this study represent plant strategies differing in their response to changing environmental conditions. [ABSTRACT FROM AUTHOR]

Microbial symbionts increase plant growth and eco-physiological performance under abiotic stress. In this study, we evaluated how the colonization of two fungal endophytes isolated from wild Nicotiana species from areas of drought-prone northern Australia, and a plant virus, yellowtail flower mild mottle virus (genus Tobamovirus ), improved water stress tolerance in N. benthamiana plants. Inoculation with both of the two fungal strains used and the virus significantly increased plants tolerance to water stress as manifested by their significant delay in wilting of shoot tips. The water stress tolerance of fungus-inoculated plants was correlated with increases in plant biomass, relative water content, soluble sugar, soluble protein, proline content, increased activities of the antioxidant enzymes catalase, peroxidase and polyphenol oxidase, decreased production of reactive oxygen species, and decreased electrical conductivity. In addition, there was significant upregulation of several genes previously identified as drought induced. The influence of the virus was similar to the fungi in terms of increasing the plant osmolytes, antioxidant enzyme activity and gene expression. Although separate infection of fungi and virus increased plant water stress tolerance responses, their co-infection in plants did not have an additive effect on water stress responses. These findings show that presence of both fungi and viruses can initiate plant responses to water stress in a similar way. [ABSTRACT FROM AUTHOR]

Although water stress reduces fruit yield, it also increases capsaicinoid accumulation in hot pepper. The aim of this study was to investigate the effect of different water regimes on capsaicinoid production in Capsicum chinense Jacq. having different pungency levels. Four hot pepper ( C. chinense ) cultivars were planted with four water regimes after anthesis: daily irrigation (control; S1), every 2 days (S2), every 3 days (S3) and every 4 days (S4). The results found that Akanee Pirote with the S2 treatment gave the highest capsaicinoid yield, and the increase of capsaicinoid yield was attributed from increasing the absolute capsaicinoid content and reducing the dry fruit yield as compared to the control. Capsaicinoid yield of Bhut Jolokia, Orange Habanero, and BGH1719 responded to the water stresses, but produced less capsaicinoid yield as compared to the control. This study reveals that appropriate water stress could increase capsaicinoid yield in some, but not all, hot pepper cultivars. [ABSTRACT FROM AUTHOR]

Requiring water and minerals to grow and to develop its organs, Maize (Zea mays L.) production and distribution is highly rainfall-dependent. Current global climatic changes reveal irregular rainfall patterns and this could represent for maize a stressing condition resulting in yield and productivity loss around the world. It is well known that low water availability leads the plant to adopt a number of metabolic alterations to overcome stress or reduce its effects. In this regard, selenium (Se), a trace element, can help reduce water damage caused by the overproduction of reactive oxygen species (ROS). Here we report the effects of exogenous Se supply on physiological and biochemical processes that may influence yield and quality of maize under drought stress conditions. Plants were grown in soil fertilized by adding 150 mg of Se (sodium selenite). We verified the effects of drought stress and Se treatment. Selenium biofortification proved more beneficial for maize plants when supplied at higher Se concentrations. The increase in proline, K concentrations and nitrogen metabolism in aerial parts of plants grown in Se-rich substrates, seems to prove that Se-biofortification increased plant resistance to water shortage conditions. Moreover, the increase of SeMeSeCys and SeCys2 forms in roots and aerial parts of Se-treated plants suggest resistance strategies to Se similar to those existing in Se-hyperaccumulator species. In addition, epigenetic changes in DNA methylation due to water stress and Se treatment were also investigated using methylation sensitive amplified polymorphism (MSAP). Results suggest that Se may be an activator of particular classes of genes that are involved in tolerance to abiotic stresses. In particular, PSY (phytoene synthase) gene, essential for maintaining leaf carotenoid contents, SDH (sorbitol dehydrogenase), whose activity regulates the level of important osmolytes during drought stress and ADH (alcohol dehydrogenase), whose activity plays a central role in biochemical adaptation to environmental stress. In conclusion, Se-biofortification could help maize plants to cope with drought stress conditions, by inducing a higher drought tolerance. [ABSTRACT FROM AUTHOR]

World recent concerns about the shortage of water resources and contamination of groundwater supplies have motivated scientists seeking for more efficient techniques in irrigation and fertilization of farms while taking the advantage of models. The objective of this study is to address how water and nitrogen (N) dynamics are affected by efficient management strategies and to evaluate the application of HYDRUS-1D model in these conditions. In terms of using management policies, different irrigation strategies, planting methods, and different N fertilization rates applied on safflower (Carthamus tinctorius L.) in volumetric field lysimeters. The irrigation regimes were ordinary furrow irrigation (OFI) and variable alternate furrow irrigation (VAFI) as a partial root drying (PRD) technique. The planting methods were on-ridge planting (P1) and in-furrow planting (P2) methods. The fertilizer levels were 0 (N0), 100 (N1), and 200 (N2) kg ha−1 of urea as 0, 46, and 92 kg N ha−1. Results showed that VAFI regime and in-furrow planting method favorably reduced the amount of drainage water below safflower root zone in comparison with the ordinary methods. Furthermore, VAFI regime satisfactorily decreased the seasonal nitrate (NO3-N) leaching below the root zone, whereas differences between the leached NO3-N in in-furrow and on-ridge planting methods were not significant. Moreover, VAFI regime did not show any negative effects on total N uptake in safflower seed and straw, whereas in-furrow planting accumulated higher N in comparison with the on-ridge planting method. In addition, safflower nitrogen (N) uptake was responsive to application of nitrogen, although the rate of increase in N accumulation was not significant between the application rates of 46 and 92 kg N ha−1. The soil nitrate concentration decreased during the growing season indicating that safflower root system has a great ability in absorption of NO3-N from soil N supplies. HYDRUS-1D model favorably predicted the drainage water, nitrate concentration of drainage water, crop N uptake, and residual soil NO3-N concentration for safflower field. Therefore, it can be an applicable model for prediction of water and nitrogen dynamics, despite of two-dimensional flow conditions in furrow irrigation. It was concluded that VAFI strategy and in-furrow planting method are suitable alternatives helping farmers produce food while conserving water and preserving the environment. [ABSTRACT FROM AUTHOR]

In plants, water deficiency can result from a deficit of water from the soil, an obstacle to the uptake of water or the excess water loss; in these cases, the similar consequence is the limitation of plant growth and crop yield. Silicon (Si) has been widely reported to alleviate the plant water status and water balance under variant stress conditions in both monocot and dicot plants, especially under drought and salt stresses. However, the underlying mechanism is unclear. In addition to the regulation of leaf transpiration, recently, Si application was found to be involved in the adjustment of root hydraulic conductance by up-regulating aquaporin gene expression and concentrating K in the xylem sap. Therefore, this review discusses the potential effects of Si on both leaf transpiration and root water absorption, especially focusing on how Si modulates the root hydraulic conductance. A growing number of studies support the conclusion that Si application improves plant water status by increasing root water uptake, rather than by decreasing their water loss under conditions of water deficiency. The enhancement of plant water uptake by Si is achievable through the activation of osmotic adjustment, improving aquaporin activity and increasing the root/shoot ratio. The underlying mechanisms of the Si on improving plant water uptake under water deficiency conditions are discussed. [ABSTRACT FROM AUTHOR]

Although the flowerpot is widely used for indoor flowers, it cannot meet the needs of intelligent management during the uncared-for period. The objective of this study was to design a new microcontroller-based smart flowerpot. Its overall system was composed of three parts: information collection layer, automatic control layer and data transmission layer. Firstly, in the process of collecting information, the Laiyite criterion and the normalized weighted average algorithm were adopted to improve the accuracy of information collection. Secondly, for making precise control decisions, the fuzzy control was used to achieve automatic on-demand watering. Finally, the method for comparative analysis of regional light intensity was utilized to achieve light-seeking and light-supplementing. Experimental results showed that the smart flowerpot had strong anti-jamming performance for information collection, the relative soil moisture of flowers could be stably maintained near the optimum humidity (65%), and the light was well-distributed on the flower with the error angle of light-supplementing ranged from -3° to 3°. [ABSTRACT FROM AUTHOR]

The effect of rain shelters on the performance of the day-neutral strawberry ( Fragaria × ananassa ) Monterey cultivar was studied in northern Québec in trials extending over 2 years. The main objective of the study was to evaluate the benefits of growing strawberry crops under plastic rain shelters in terms of yield, fruit quality, disease incidence and economical returns for soilless strawberry production. Five treatments were carried out and these included four − under rain shelters cultivation (T1 to T4) and one under open-air conditions (the Control, C). Under rain shelters conditions, plants were grown in either peat (PE; T1 treatment) or peat-sawdust (PS25; T2 treatment) substrates. Early forcing of bare-root plants (T3) in combination with a rain shelter cover was also carried out in an attempt to generate consistent early yields by the end of July as such would allow producers to capture a niche market for strawberries in Québec. Finally in T4, the PE substrate was laid onto a capillary mat to determine the potential of sub-surface water retention technology to minimize water use. In comparison to the Control treatment, protected cultivation led to a significantly lower incidence of strawberry mildew [ Sphaerotheca macularis (Wall. ex Fries)] and consistently higher marketable yields which largely compensated for the initial costs associated with the rain shelters. When grown under greenhouse conditions, forced plants had a significant production peak earlier, coinciding with the period of high prices for fresh strawberries in 2013. However, the economical analysis revealed that this method was not always profitable. Balancing economical and environmental considerations, the conditions of the T4 treatment were found to be best for generating both consistent water savings and profits (CAD $ 724–1356 per 0.1 ha) compared to the Control. Taken together, our results highlight the potential for rain shelters for soilless strawberry production, and should be a more profitable and environmentally friendly cultivation method for strawberry producers. [ABSTRACT FROM AUTHOR]

Effect of plant bio–regulators (PBRs) viz. , potassium nitrate (KNO 3 , 15 g L −1 ), thio–urea (TU, 500 ppm), salicylic acid (SA, 10 μM), gibberellic acid (GA 3 , 25 ppm) and sodium benzoate (SB, 150 mg L −1 ) for two years (2015–17) under various levels of deficit irrigation created using line source sprinkler system (LSS) was evaluated in onion ( Allium cepa L.). The crop could sustain little water deficits and its bulb yield declined to 0.84, 0.66, 0.48, 0.35, 0.24 and 0.16 when irrigation water (IW) applied equalled 0.85, 0.70, 0.55, 0.40, 0.25 and 0.10 times the pan evaporation (CPE) against maximum yield at full irrigation (IW:CPE 1.00). Application of PBRs helped to mitigate the water stress through maintenance of leaf water content, modulating the canopy temperature and better water usage thereby improving average bulb yields by 10.1–25%. Especially KNO 3 and TU were more effective under low to medium water deficits. The water productivity ranged between 7.78 and 9.61 with PBRs against 7.36 kg m −3 under control. The overall water saving was 18.3, 25.7, 48.4 and 63.8% with PBRs namely GA 3 , SA, TU and KNO 3 , respectively. The marketable quality monitored in terms of bulb weight, geometric mean diameter and sphericity was significantly reduced with water deficits while it improved with PBRs. Among the other physicochemical and functional quality characteristics of the onion bulb, rehydration ratio, protein content, total soluble sugar, total phenolics content and pyruvic acid were lowered by water deficits. These were improved significantly with PBRs. Thus it was concluded that combining PBRs like KNO 3 and TU can further facilitate to implement deficit irrigation technology for sustaining productivity and quality of onion under water scarce conditions. [ABSTRACT FROM AUTHOR]

A great challenge for agricultural production is to produce more food with less water, which can be possibly achieved by increasing crop water use efficiency (WUE). This study systematically reviewed 52 cases from 49 empirical studies with field experimental results on wheat and cotton. This research investigated yield-water use relations under both furrow and micro irrigation systems, compared optimal water use to achieve maximum WUE and maximum yield, calculated water saving potentials under various scenarios, and evaluated the effects of influential factors using meta-regression analysis. The results suggest that to achieve maximum WUE rather than maximum yield, water use for wheat can be reduced by 30.4% with a grain yield decrease of 14.8%, and water use for cotton can decrease by 51.4% with a yield reduction of 51.7%. Compared with furrow irrigation, micro irrigation reduces wheat water use by 22.7% and increases yield by 36.7%. While for cotton, micro irrigation reduces water use by 36.8% and decrease yield by 21.4%. Under the scenario of a 10% yield reduction, water use decreases by 25% for wheat and by 20–22% for cotton. Compared with maximum yield, other yield levels reduce water use by 2–15% on average for wheat, and by 15–17% for cotton. Achieving maximum WUE reduces water use by 14–31% compared with other sub-optimal WUE levels. The meta-regression analysis showed adoption of micro irrigation systems, and farm management practices on soil and water significantly improved wheat and cotton WUE. Assessments of the publication selection bias and genuine effects illustrate the application of weighted least squares in conducting meta-regression analysis. [ABSTRACT FROM AUTHOR]

Although atmospheric evaporative demand is increasingly recognized as significant roles in coupling water transport and carbon acquisition, potentials to reduce irrigation demand and improve photosynthesis performance via regulating evaporative demands is highly uncertain. To bridge this gap, plant water status in combination with photosynthetic carbon acquisition under contrasting evaporative demand was examined in two cultivars of tomato ( Solanum lycopersicum L.). Experiments were conducted from May to August in 2016. Evaporative demand gradients were achieved via regulating vapor pressure deficit (VPD) at two adjacent greenhouses of similar characteristics: High VPD was maintained in natural greenhouse condition without environmental regulation (Control); Moderate VPD was achieved by artificially humidification when evaporative demand exceeded optimal ranges (Humidification). VPD regulation by humidification reduced the excessive driving force for water flow, which efficiently prevented the declines in plant water potential and alleviated hydraulic limitation. Transpiration rate and irrigation demand over experimental period were substantially reduced via reducing evaporative driving force in humidification treatment. Moderation in plant water stress sustained stomatal openness for CO 2 acquisition and utilization. Photosynthetic capacity was significantly improved by humidification, as indicated by the substantial increases in photosynthesis rate(P n ), rubisco carboxylation capacity(V cmax ), maximum electron transport capacity (J max ) and net assimilate rate (NAR). At long-term scales, fruit yield was increased by 14.6% and 16.7% for two cultivars. Whole plant biomass was increased by 22.6% and 16.9% for two cultivars. Plants irrigation amount in humidification treatment over the experimental period was significantly saved by 16.9% and 17.4% for two cultivars. Taken together, VPD regulation had great potentials to reduce irrigation demand and improve photosynthetic capacity via reducing water driving force and sustaining stomatal function. The present study provided novel information to improve photosynthetic and reduce irrigation demand for sustainable crop production. [ABSTRACT FROM AUTHOR]

The common bean (Phaseolus vulgaris L.) low phytic acid (lpa1) biofortified genotype produces seeds with improved nutritional characteristics and does not display negative pleiotropic effects. Here we demonstrated that lpa1 plants establish an efficient nitrogen-fixing symbiosis with Rhizobium etli CE3. The lpa1 nodules showed a higher expression of nodule-function related genes than the nodules of the parental wild type genotype (BAT 93). We analyzed the response to water stress of lpa1 vs. BAT 93 plants grown under fertilized or under symbiotic N2-fixation conditions. Water stress was induced by water withholding (up to 14% soil moisture) to fertilized or R. etli nodulated plants previously grown with normal irrigation. The fertilized lpa1 plants showed milder water stress symptoms during the water deployment period and after the rehydration recovery period when lpa1 plants showed less biomass reduction. The symbiotic water-stressed lpa1 plants showed decreased nitrogenase activity that coincides with decreased sucrose synthase gene expression in nodules; lower turgor weight to dry weight (DW) ratio, which has been associated with higher drought resistance index; downregulation of carbon/nitrogen (C/N)-related and upregulation of stress-related genes. Higher expression of stress-related genes was also observed in bacteroids of stressed lpa1 plants that also displayed very high expression of the symbiotic cbb3 oxidase (fixNd). [ABSTRACT FROM AUTHOR]

Grindelia covasii is an endemic species of the Lihue Calel Sierras. In this semiarid enviroment soil water availability is a limiting factor for seedling establishment. This greenhouse experiment evaluated the growth and survival of juvenile G. covasii plants by exposing four plant sizes (G=large, M=medium, and P=small plant sizes) to three irrigation levels, simulating high (Rf), moderate (R7) and low soil water availability (R14). Plant growth and physiological measurements were taken during the experiment. Results showed that growth parameters were affected by increasing waterstress. Leaf senescence was high under severe water limitation (R14) with larger individuals showing highest drought tolerance. No changes were observed in resource allocation from aboveground parts to roots in response to water stress. Survival was also affected by reduced water availability, with smaller plants being the most affected. The lower tolerance of juvenile stages of G. covasii to severe water stress observed in this experiment, suggest that this species would require moist conditions for successful seedling establishment. This study provides useful information regarding G. covasii recruitment. [ABSTRACT FROM AUTHOR]

Rainfall interception is a process scarcely studied in arid and semiarid environments. The aim of this study was comparatively analyze two field techniques to evaluate the water storage capacity in Chuquiraga erinacea Don., characteristic shrub species of the CaldenalMonte Occidental ecotone region, Argentina The study was conducted in the annexed field of INTA in Chacharramendi, La Pampa. Water storage capacity was measured on whole plants from two techniques on field: rainfall simulation and immersion. Water storage capacity, expressed in percentage of biomass was determined by difference wet weight fresh weight. Equality of results from field techniques for whole plants of Chuquiraga erinacea justified the application of immersion method in the study to be more expeditious implementation and more economical in terms of time and costs. [ABSTRACT FROM AUTHOR]

For species to persist on floodplains and in temporary wetlands in arid climates, where large and unpredictable water level fluctuations are common, at least one life history stage must be able to survive inundation. We investigated the survival and performance (RGR, total biomass and above-to-belowground biomass (A:B)) of three common and often coexisting arid zone floodplain species: Xanthium strumarium, Cyperus gymnocaulos and Ludwigia peploides. Observations suggested the species had different responses to inundation, which was tested in a controlled pond experiment. Plants were held at three elevations (+ 10 cm, − 20 and − 70 cm) and subjected to three hydrological regimes (static 90 cm, 1 and 5 cm day inundation) for 16 weeks. Xanthium strumarium died when completely inundated for longer than 4 weeks but when partially flooded survived, showed lower growth rates, increased A:B and produced adventitious roots. C. gymnocaulos showed reduced growth rates when partially flooded and senesced to rhizomes when completely inundated for longer than 4 weeks, which re-sprouted after inundation pressure was removed. L. peploides responded positively to flooding with increased A:B and the production of adventitious roots. The species exhibited three contrasting responses to inundation, which do not necessarily fit neatly within existing water regime functional classification frameworks. [ABSTRACT FROM AUTHOR]

Oxidative indices including peroxide value (PV), para-anisidine value (p-AnV), and extinction coefficients K232 and K268, instrumental texture attributes (hardness and chewiness) and colour parameters ( L, a, b, and total colour difference) were measured to find the proper water activity ( aw) corresponding to the proper quality of peanut kernels during a certain period of storage. The highest and lowest oxidation rates were recorded for the samples kept in aw values of 0.11 and 0.32-0.43, respectively. The stress required to obtain 25% deformation (MPa) decreased significantly ( p < .05) with the increasing moisture content of the samples. In summary, less hardness, colour properties closer to fresh kernels as well as slower oxidation progress were measured for the samples stored at a higher aw, especially those stored at 0.32-0.43 at 40°C (equivalent to 0.33-0.43 at 25°C). Practical applications Peanuts ( Arachis hypogaea) are grown in tropical, subtropical, and warm temperate climates in more than 70 countries. Like other nuts, peanuts are being consumed as snack foods after roasting or are used as chopped ingredients in cereal bars, confectionery, and breakfast cereals. Therefore, controlling peanut storage conditions (specially aw and temperature) should be considered before use for different purposes. In this study, color, texture, and oxidative changes of peanuts grown in northern Iran, as affected by aw were investigated in order to determine the best aw corresponding to proper quality during storage before being used in various applications at industrial scales. [ABSTRACT FROM AUTHOR]

The short-term benefits of biochar application on crop yield await confirmation with long-term effects when initial liming or nutritional benefits are attenuated. In this study, we determined the above-ground silage maize yield in soils under historical charcoal kilns (black spots, >150 years enrichment) and adjacent soils in southern Belgium in three consecutive years (2014–2016). Maize yield in these well fertilized arable soils was, on average, 23% higher (P < 0.05) in black spots than in the adjacent soils and the charcoal-C concentration was, on average, 2.2 g 100 g −1 soil (63% of total SOC) in the black spots. The factor yield increase decreased with average rainfall during the growing season (P < 0.05). Water retention curves of both soil types revealed 11% higher (P < 0.05) available water content, determined between pF 1.8 and pF 4.2, in soils under black spots. The δ 13 C analysis of maize leaves at final harvest determined in one season indicated lower water stress for plants grown on black spots. Nutrient concentrations in maize leaves were unaffected by charcoal even though significant positive effects of charcoal on soil CEC and concentrations of available Ca and Mg were detected. This study shows, for the first time, that historical charcoal amendment can increase maize yield in fertile, temperate soils considerably. These effects are most likely related to soil physical effects, rather than to nutritional effects. [ABSTRACT FROM AUTHOR]

Ebb-and-flow subirrigation is a closed system that applies water to the bottom of the containers, reducing water and nutrient losses due to recirculation of fertilizer solution (FS). The technology can improve plant growth and eliminate the improper disposal of salts into the environment. Subirrigation is widely used in the ornamental industry, and sensor-based ebb-and-flow benches can be used by the citrus nursery industry. There is a need for establishing water and fertilizer guidelines to produce citrus rootstocks. The objectives of this study were: 1) design and build an ebb-and-flow subirrigation equipment, 2) automate the system operation using soil moisture sensors, 3) evaluate the system performance on plant growth, and 4) determine the water and fertilizer guidelines to produce Rangpur lime ( Citrus × limonia ) liners in 56-cm 3 cone-shaped containers. The treatments were four volumetric water content (VWC) to trigger subirrigation (0.12, 0.24, 0.36 and 0.48 m 3 m −3 ), three FS concentrations (25%, 50% and 75% of the fertilizer recommendation) and a control (nursery manual overhead irrigation using breaker nozzles), arranged in a completely randomized 4 × 3 + 1 factorial plus design, with three replications. The system was automated by 39 capacitance sensors connected to a data logger, multiplexer and relay drivers, which controlled independent submersible pumps. Subirrigation was turned on when VWC dropped below the set thresholds. Sensors effectively monitored the substrate moisture and controlled subirrigation. Treatments with highest VWC had higher substrate moisture and number of irrigations over time ( p < 0.0001). The volume of water applied doubled from treatments 0.12–0.48 m 3 m −3 ( p < 0.0001). Subirrigation increased shoot height, stem diameter, dry weight, leaf area, physiological parameters (leaf intracellular concentration of CO 2 , transpiration, stomatal conductance, and net photosynthesis), and water use efficiency in response to increase in VWC and FS ( p < 0.0001). Subirrigation shortened the crop cycle in 30 days, anticipating the liners transplant for grafting, allowing another cultivation cycle in the nursery during the year. VWC of 0.48 m 3 m −3 and FS concentration of 50% of the recommended value for overhead irrigation are indicated for Rangpur lime liner production in 56-cm 3 containers. [ABSTRACT FROM AUTHOR]

Plains cottonwood trees (Populus deltoides subsp. monilifera (Aiton) Eckenw.) occur in riparian and urban areas in semi-arid regions of western United States. The amount of water necessary to maintain healthy trees while reducing water use are management objectives along the High Line Canal in Denver, Colorado, U.S. Canal-flow days, soil moisture, precipitation, cottonwood predawn leaf water potentials (ψpd) and crown dieback were measured annually from 1997-2008. Five key findings were: 1) percent soil moisture did not correlate with ψpd, 2) trees became moderately water-stressed (ψpd < -0.3 MPa) and severely water-stressed (< -0.5 MPa) 45 and 51 days after canal flow ended, respectively, 3) ψpd of water-stressed trees increased 24-48 hours after water was added, 4) only 22% of rain events of 25 mm relieved stressed conditions for seven days, and 5) yearly average autumn and growing season ψpd correlated with autumn crown dieback at low soil moisture sites (few canal-flow days), but not at moderate or high sites (more canalflow days). Trees with ψpd > -0.30 MPa generally had low crown dieback, whereas trees with ψpd < -0.50 MPa exhibited moderate or severe crown dieback. Plains cottonwoods are relatively resilient to single-year drought, and moderately stressed trees may recover and can withstand 25%-40% crown dieback if water is available the following year for >14 days. Irrigation timing and the frequency needed to minimize cottonwood future crown dieback can be obtained from autumn and growing season predawn leaf water potentials. [ABSTRACT FROM AUTHOR]

Rising energy costs, decreasing soil depth, and best management practices that require on-farm water retention have led to interest in flood-tolerant bioenergy crops for production in the Everglades Agricultural Area (EAA) of Florida. Information on the effects of high water tables on sugarcane ( Saccharum spp. L.) is available; however, little is known about the bioenergy crops elephant grass ( Pennisetum purpureum Schumach.), energycane ( Saccharum spp. L.), and giant reed ( Arundo donax L.). The objective of this study was to evaluate the role of water-table depth on the yields, morphology, physiology, and early season growth of these three bioenergy species in relation to sugarcane. The species were grown in a greenhouse and subjected to three water management strategies, −40 or −16 cm constant water-table depths, and bi-weekly flooding with drainage to −40 cm. The experiment was conducted in plant-cane, first-ratoon, and successive plant-cane crop cycles. Periodic flooding relative to a −40 cm constant water table significantly reduced dry weights and leaf area index and increased aerenchyma development. Averaged among crops, dry weight declined by 32, 49, 37, and 52% while leaf area index (LAI) decreased by 31, 50, 46, and 57% for giant reed, elephant grass, energycane, and sugarcane, respectively, in response to flooding. Aerenchyma proportional area of the stalk increased by 52, 90, and 95% for elephant grass, energycane, and sugarcane, respectively, but aerenchyma in giant reed decreased by 11%. High yields and stalk populations for all water tables were observed in energycane and elephant grass. These two species show potential for bioenergy production in the EAA. Field trials are recommended to confirm production scale yield. [ABSTRACT FROM AUTHOR]

Contrasting phenotypes of foundation species are known to differentially affect understorey plants. However, there is little knowledge on both the mechanisms of competition (resource competition versus interference) of stress-tolerant phenotypes and the importance of indirect interactions. In an oromediterranean community from Mount Lebanon we assessed the effects on understorey forbs of two contrasting phenotypes, a tight competitive from stressful habitat and a loose facilitative from more benign habitat. In a dry south and a wet north exposure we assessed short-term resource effects removing shrub canopy and long-term soil effects (including litter interference) with the comparison of forb performances in adjacent naturally open areas vs no shrub. Indirect effects were quantified through the removal of grasses. Abundance, richness and biomass of forbs were measured in all treatments after one year of experiment, together with litter depth and soil moisture. We found strong direct negative soil effects of the tight phenotype on all forb performances and in particular in south exposure. These effects were due to litter interference on water availability, but not to resource competition. They were likely explained by the high hydrophobicity of organic matter accumulating in the stressful habitat of the tight phenotype. We also found an indirect competition of the loose phenotype for forb richness, due to its direct positive soil effect on competitive grasses, and in particular in south exposure. Our results improve our knowledge on the importance of litter interference in dry nutrient-poor habitats and the role of indirect interactions in phenotypic effects on understorey species. [ABSTRACT FROM AUTHOR]

Aiming at improved knowledge on water use, productivity and irrigation scheduling of processing pea, the soil water balance model SIMDualKc was calibrated and validated using field data observed in two farmers’ fields in a wet and a dry year. The model uses the dual crop coefficient approach for partitioning crop evapotranspiration into crop transpiration and soil evaporation. Calibration was performed by minimizing differences between measured and simulated soil water content with a root mean square error representing 2% of the measured mean. The calibrated basal crop coefficients for the initial, mid-season and end-season were respectively 0.15, 1.15 and 1.10. Pea commercial yield (5084–8197 kg ha −1 ), obtained from the total yield using industry textural and quality criteria, was influenced by climatic conditions and the harvesting date. Using the global water-yield function with K y = 1.15 and the actual crop transpiration computed with SIMDualKc, the fresh and commercial yields were estimated with errors smaller than 3.5%. Water productivity relative to the commercial yield varied 1.51–2.67 kg m −3 , mainly depending on the yield achieved rather than on water use. Results from the economic water productivity ratio (EWPR), which compares the commercial yield value with the corresponding production costs, varied 1.07–1.82. Because irrigation costs were a small fraction of the total costs, EWPR values mainly varied with the commercial yield and less with irrigation costs. Irrigation scheduling alternatives for wet and dry years showed that water saving is achievable without considerably affecting peas’ yield and economic results. Results show that the SIMDualKc model is appropriate to support irrigation advising. [ABSTRACT FROM AUTHOR]

Climate change is projected to increase water resources limitation and to impact significantly agricultural production. A big challenge for agriculture will be to reduce the amount of water used to fit the environmental constraints, while maintaining a level of production that ensure food security. In this context, we develop a methodology based on high spatial and temporal resolution remote sensing data combined with a semi-empirical crop model coupling the Simple Algorithm For Yield estimates (SAFY, Duchemin et al., 2008, 2015) with the new formulation (Battude et al., 2016) to a water balance model adapted from the FAO-56 method (Allen et al., 1998). A module was added to automatically simulate irrigation. The model was used to assess the dynamics of actual Evapotranspiration (ETca) and water supplies of maize crop over large areas and during contrasted climatic years in the south west of France. It was first calibrated and evaluated over an experimental field using four years of ETca measurements. The validation was done over 18 maize fields and larger irrigated zones (135 ha to 450 ha) using total irrigation depths. This work permitted to quantify the ability of different methods to estimate the storage capacity (soil map vs in situ data) and the basal crop coefficient Kcb (standard vs remotely sensed values) and their impact on total irrigation depths. Good estimations were obtained for ETca (R = 0.88; RRMSE = 20%). The model also reproduced correctly the total irrigation depth over the 18 maize fields (R = 0.79; RRMSE = 18.8%) and three larger irrigated zones (R = 0.8; RRMSE = 42%). The underestimation (Bias = −93 mm) is due to several reasons such as errors in soil water storage capacity estimates, but also to an overestimation of water needs by water managers or a potential over-irrigation carried out by farmers. Finally, the work demonstrates the high potential of combining a simple agro-meteorological model using only few parameters with satellite imagery for a large-scale monitoring of total irrigation depth. [ABSTRACT FROM AUTHOR]

Climate warming increases vulnerability to drought in Mediterranean water-limited forests. However, we still lack knowledge of the long-term physiological responses of coexisting pine species in these forests regarding their ability to cope with warming-induced drought stress., We investigated spatiotemporal patterns of tree performance for five isohydric pines with partially overlapping ecological niches in the eastern Iberian Peninsula along an altitudinal gradient: Pinus halepensis = Pinus pinaster ≤ Pinus nigra ≤ Pinus sylvestris ≤ Pinus uncinata., Using indexed tree-ring widths ( TRW i), we assessed the changes in the temporal coherence of radial growth (growth synchrony, â C) over the period 1902-2011 across three elevation belts: low ≈1100 m; mid = 1615 m; high = 2020 m. We also examined by mixed modelling whether TRW i showed an increased coupling with leaf-level gas exchange (inferred from indexed carbon isotope discrimination, Δ13C i) by enhanced stomatal regulation in response to an amplified regional drought stress., Increasingly negative annual water balances (decrease in annual precipitation minus evapotranspiration = −4·8 mm year−1; 1970-2011) prompted more synchronous growth of coexisting pines between low- and mid-elevation belts, with â C rising from 0·25 ± 0·04 (1902-1951) to 0·62 ± 0·05 (1962-2011). This effect was coupled with tighter stomatal regulation at mid-elevation as indicated by high correlations between TRW i and Δ13C i (>0·60 from the mid-1970s onwards) which resembled those found at low elevation. Simultaneously, TRW i vs. Δ13C i uncoupling occurred at the high-elevation belt across species., Weaker growth-climate relationships as elevation increased highlighted the major role of the altitude-dependent thermal gradient in growth responsiveness to drought; however, an intensified Δ13C i response to spring water availability across elevation belts observed from mid-1970s onwards suggested regional shifts in tree physiological activity linked to earlier seasonal drought impacts. Warming-induced drought stress is spreading to higher altitudes in Iberian pinewoods as multispecies growth is linked to progressively tighter stomatal control of water losses reflected in wood Δ13C. [ABSTRACT FROM AUTHOR]

This research was carried out in 2014 and 2015 to assess the effects of salicylic acid (SA) (0 and 1 mM) and abscisic acid (ABA) (0 and 50 µM) on essential oil content and yield of ajowan (Carum copticum L.) organs under different irrigation intervals (I1, I2, I3, I4: irrigation after 70, 100, 130 and 160 mm evaporation, respectively). Plants were sprayed by SA and ABA at vegetative and reproductive stages. In both years, the biomass of vegetative organs (leaves and stem), flower production and seed yield per unit area of ajowan decreased with decreasing water availability. All organs mass improved by application of ABA and particularly SA. Essential oil percentage of all organs increased, but essence yield decreased as a result of water limitation. Reduction in essential oil yield of ajowan organs due to water stress strongly related with the reduction of individual organ mass under stress. Foliar spray of ABA and especially SA improved the medicinal and commercial value of ajowan under different irrigation intervals by enhancing plant organs biomass and accumulation of more essential oil. [ABSTRACT FROM AUTHOR]

Agricultural drought causes serious yield losses for rainfed crops (including C 4 crops) and is a cause of higher costs incurred by irrigation use. Drought episodes have been more frequent in Central Europe in recent years and have caused problems in terms of crop and livestock production due to a lack of available feed. The main aim of this study is to examine 16 water availability indicators (suitable for the evaluation of agricultural drought) to help explain maize silage yields. A parallel aim is to determine the period during which current maize hybrids for silage are the most vulnerable to water availability shortages. These aims reflect a current need for accurate drought impact assessment methods that can be applied as an early warning system or as part of a decision making protocol. For the purposes of this study, data from rainfed silage maize field experiments conducted between 2011 and 2015 in 4 locations (throughout the Czech Republic) were used. Relatively high correlations were found using precipitation totals for July alone, as this simple indicator explained 64% of the observed variability in the average silage yields of maize. Overall, the highest R 2 (coefficient of determination) of 0.77 was obtained when the sum of actual evapotranspiration (ETa) for May to August was applied as an independent variable. This indicator also gave the most consistent response for all of the individually assessed months. The lowest ETa totals from May to August occurred during an extremely dry year (2015). The significance of this drought episode was exacerbated by its spatial extent and severe impacts on regional maize silage yields throughout the entire Czech Republic. The selection of hybrids according to FAO numbers has not been proven (based on included data) to serve as an adequate adaptation measure for severe episodes of drought, although higher FAO values should provide slightly higher yields in such cases. The recommendation for farmers is not to rely on one hybrid alone, but instead use hybrids with different FAO values for a given year. [ABSTRACT FROM AUTHOR]