Plant Water Use Efficiency Research Articles

The interspecific interactions in agroforestry systems enhance leaf water use efficiency and carbon storage in cocoa

Global climate changes include more intense and concentrated rainy seasons and severe and longer-lasting dry seasons. In this context, the benefits carried out within agroforestry systems (AFS) have played a significant role, especially for tropical crops such as cocoa. The present study evaluated the changes in photosynthetic traits and the physical, chemical, and microbiological soil properties in response to variations in the shading tree species. Three cocoa genotypes (CCN51, TCS01, and TCS19) were cultivated under three AFS designs, differing in the accompanying shade tree species ( Cariniana pyriformis , Tabebuia rosea, and Terminalia superba ). No significant differences in CO 2 assimilation rates among the different cocoa genotypes were observed. However, TCS01 exhibited a 20% higher leaf water use efficiency (WUEl) than the TCS19 genotype, associated with decreased stomatal conductance. The designs combining C. pyriformis with CCN51 and TCS01, as well as the design associating CCN51 with T. rosea, exhibited significantly higher WUEl for cocoa plants as compared to the systems involving T. superba combined with TCS19. In addition, the cocoa genotype TCS01 exhibited the highest potential for carbon storage when combined with C. pyriformis , whereas TCS19 exhibited the lowest potential for this feature under the T. superba association. The chemical, physical and biological properties of soils were evaluated, and an orthoPLS-DA multivariate analysis was performed to contrast the differences between TCS01 associated with C. pyriformis (higher WUEl and C sequestration) with the combination of TCS19 with T. superba (lower WUEl and carbon sequestration). The results highlight the importance of soil pH, [Al], [Mn], and [Mg] for a better physiological performance exhibited by TCS01 under C. pyriformis AFS as compared to TCS19 under T. superba . Thus, taken together the data obtained here suggest that species-genotype-dependent interactions in AFS-cocoa may determine soil characteristics, which may indirectly affect important physiological traits, such as leaf water use efficiency and long-term carbon storage of cocoa plants. • Advantageous interspecific interactions can generate improve leaf-level water use efficiency and carbon storage in cocoa. • Cocoa TCS01 associated with C pyriformis shows better leaf-level water use efficiency and carbon storage as compared with TCS19 associated with T. superba . • The evaluated shade tree species contrasted regarding their effects on the chemical features of adjacent soils. • Soil acidity, aluminium, manganese and magnesium concentrations were the soil features most correlated with the contrasts observed in the cocoa genotypes.

Water Use Efficiency of Long Staple Cotton Varieties in Southern Zone of Uzbekistan

Previous research established field capacity (Fc) based irrigation scheduling for upland cotton (Gossypium hirsutum L.) varieties in Uzbekistan. In this paper, the irrigation scheduling Fc for two long staple cotton (Gossypium barbadense L.) varieties and its effect on seed-lint yield and irrigation water use efficiency and water consumption of plants were reported. The field experiments were conducted in the condition of takyr soils with mechanical composition of silt loam in southern zone of Uzbekistan, at the Kashkadarya Experimental Station of Uzbekistan’s Cotton Breeding, Seed Production and Agrotechnologies Research Institute in 2018, 2019 and 2020. In research, cotton growth stages such as germination to flowering, flowering to boll formation, and maturation were considered for the development of irrigation scheduling with respect to field capacity water content (Fc). Irrigation scheduling based on percentages of Fc and mineral fertilizer application rate of N250P175K125 should be considered applicable practices for long staple cotton varieties on silt loam soils of the southern zone of Uzbekistan and for similar soil-climatic conditions of Central Asian countries.

Deteriorating Harmful Effects of Drought in Cucumber by Spraying Glycinebetaine

In order to alleviate the shortage of irrigation water in dry regions, refining water use efficiency (WUE) is a key issue in sustainable productivity. Furthermore, glycinebetaine (GlyBet) is a vital osmoprotectant produced in crops for improving drought tolerance; however, little is known about its role in improving plant WUE under field conditions in non-accumulating plants such as cucumber. In order to elucidate the effectiveness of GlyBet concentrations (0, 2000, 4000, and 6000 mg/L) in mitigating the deleterious effects of drought (e.g., well-watered (1250 m3/fed), moderate drought (950 m3/fed), and severe drought (650 m3/fed)), field experiments were conducted at Elmia village, Dakahlia, Egypt in the 2020 and 2021 seasons on vegetative growth, some physiological attributes, as well as yield and quality. Drought considerably decreased vegetative growth, yield and its components, leaf relative water content, and photosynthetic pigment concentrations compared with well-watered plants while increasing electrolyte leakage. The most harmful causes were severe drought. However, exogenous spraying with GlyBet substantially boosted the mentioned attributes, but reduced electrolyte leakage within well-watering. Commonly 6000 mg/L contributed to the maximum growth and productivity, preserving cucumber plant water status above other concentrations or untreated plants. Under extreme drought, the application of 6000 mg/L GlyBet had a beneficial effect on moderating the damage of water deficit on cucumber plant growth and productivity. Overall, using GlyBet as a cost-effective and eco-friendly biostimulant six times (10, 20, 30, 40, 50, and 60 days from sowing) has the potential to mitigate drought damage while also increasing yield; however, more research is needed to determine the optimal rate and timing of application.

Impacts of CO2 Enrichment on Water Use Efficiency in Terrestrial Ecosystems: A Meta-Analysis of Experimental Manipulations

Elevated CO2 (eCO2) has important impacts on plants, especially on water use efficiency (WUE). A meta-analysis was performed to determine the responses of WUE to enriched CO2. We summarized 242 studies on WUE research under ambient and enriched CO2 conditions that were published between 1989 and 2019. Our results showed that WUE had positive responses to elevated CO2 with an increase of about 46% and high heterogeneity. Elevated CO2 increased leaf, grain, biomass and whole plant WUE by 76%, 9%, 30% and 37%, respectively. The effect size on leaf WUE was higher than the other three WUE types, and the effect size on whole plant WUE was higher than grain WUE (P<0.05). In another respect, the response of WUE in forests was higher than in cropland (P<0.05). Regarding different experimental methods, WUE had a stronger response to elevated CO2 by the method of climate-controlled chamber than by the methods of OTC (Open Top Chamber) or greenhouses (P<0.05). However, the effect size obtained by the method of greenhouse was higher than that obtained by the methods of either OTC or climate chamber for whole plant WUE (P<0.05). Furthermore, our results found WUE had a positive linear relationship with the magnitude of CO2 enrichment (P<0.05). Meanwhile, the effect size of elevated CO2 on grain WUE had a positive linear relationship with the duration of CO2 enrichment. This study found that the impacts of CO2 enrichment on WUE are unique and specific for different WUE types and the various experimental conditions.

Variations of stomata development in tea plant (Camellia sinensis) leaves in different light and temperature environments and genetic backgrounds.

Stomata perform important functions in plant photosynthesis, respiration, gas exchange, and interactions with environments. However, tea plant stomata development and functions are not known. Here, we show morphological changes during stomata development and genetic dissection of stomata lineage genes regulating stomata formation in tea developing leaves. Different tea plant cultivars displayed clear variations in the stomata development rate, density and size, which are closely related to their tolerance against dehydration capabilities. Whole sets of stomata lineage genes were identified to display predicted functions in regulating stomatal development and formation. The stomata development and lineage genes were tightly regulated by light intensities and high or low temperature stresses, which affected stomata density and function. Furthermore, lower stomatal density and larger size were observed in triploid tea varieties as compared to those in diploid plant. Key stomata lineage genes such as CsSPCHs, CsSCRM, and CsFAMA showed much lower expression levels, whereas negative regulators CsEPF1 and CsYODAs had higher expression levels in triploid than in diploid tea varieties. Our study provides new insight into tea plant stomatal morphological development and the genetic regulatory mechanisms on stomata development under abiotic stresses and genetic backgrounds. The study lays a foundation for future exploring of the genetic improvement of water use efficiency in tea plants for living up to the challenge of global climate change.

Physiological responses of the beet crop under agricultural environment and saline stress

The deleterious effects of salts on plants exposed to high solar radiation tend to be more accelerated due to the increase of toxic ions in the aerial plant part. Consequently, the physiological and biochemical processes will be affected. These effects can be minimized, however, with the use of management strategies, such as the use of a shading screen and a protected environment. In this sense, the objective of this work was to evaluate the physiological responses of sugar beet cultivated in different environments and irrigated with saline water. The experiment was conducted in an experimental design entirely randomized, using the factorial scheme 3 × 2, equivalent to three environments (FS = full sun; SSOS = shading screen open on the sides and PE = protected environment) and two electrical conductivities of the irrigation water (0.5 and 6.2 dS m-1), with four repetitions. At 45 days after sowing (DAS) the following variables were analyzed: stomatal conductance, liquid photosynthesis, transpiration, internal CO2 concentration, leaf temperature, instantaneous water use efficiency, instantaneous carboxylation efficiency, intrinsic water use efficiency, and relative chlorophyll index. Irrigation with water of higher salinity negatively affected stomatal conductance, net photosynthesis, leaf temperature and instantaneous water use efficiency of sugar beet plants grown in a full sun environment. The protected environment and open shading on the sides partially mitigated the deleterious effects of salinity.&#x0D; Keywords: Beta vulgaris L., gas exchange, salinity levels.

Xylem functionality controlling blossom-end rot incidence in transgenic ALC::NCED tomato plants

Fruit susceptibility to the physiological disorder known as blossom-end rot (BER) is an important limitation in tomato production. Abscisic acid (ABA) is known to reduce leaf transpiration, which can enhance plant water use efficiency (WUE), as well as increase fruit xylem functionality, Ca2+ uptake and oxidative stress defenses, which has been suggested to reduce BER incidence. However, the role of ABA on most of these factors determining fruit susceptibility to BER remains poorly understood. ABA production is mainly regulated by the expression of 9-cis-epoxycarotenoid dioxygenase (NCED) genes. Manipulation of NCED gene expression by the alcohol inducible promoter (ALC) could be an alternative approach to stimulate ABA production and its beneficial effects on inhibiting BER incidence. The objectives of this study were to use ALC::NCED transgenic tomato plants to decrease BER incidence and investigate which mechanisms were involved in BER. In this study, two transgenic tomato lines (1 and 2) were developed with the ALC::NCED construct. This construct allows the inducible activation of the ALC promoter by treating the plants with ethanol vapor that drives NCED expression and ABA synthesis. According to the results, after full bloom, weekly spraying transgenic plants with ethanol (2%) decreased BER incidence in both transgenic lines, compared to the wild type ‘New Yorker’ plants. The transgenic line 1 had higher NCED expression in response to ethanol than the transgenic line 2 and wild type ‘New Yorker’. At 15 and 30 days after pollination, transgenic lines 1 and 2 had higher number of functional xylem vessels which helped to increase Ca2+ concentration in the distal end of the fruit, compared to the wild type fruit. In response to higher NCED expression, WUE and antioxidant content in leaves and fruit were higher in both transgenic lines, compared to the wild type, helping to explain the lower BER incidence. Therefore, our study shows that stimulating NCED expression with an inducible system increases the number of functional xylems and Ca2+ uptake into the fruit, improving plant WUE and reducing BER incidence.

Root characteristics explain greater water use efficiency and drought tolerance in invasive Compositae plants

Root characteristics explain greater water use efficiency and drought tolerance in invasive Compositae plants

Relationship between Water Use and Energy Generation from Different Power Generation Types in a Megacity Facing Water Shortages: A Case Study in Shenzhen

Using less water to generate more power is a goal of the worldwide power industry, but this is difficult to achieve because of the lack of long-term, operational data-based studies. This challenge is especially severe for megacities facing water shortages. This study used long-term data (2005–2015) from Shenzhen, a megacity of over 20 million people that faces severe water shortages, to determine the relationship between water and energy for different types of power generation. It was found that power generation consumed huge amounts of water and that cooling water was the biggest water use category. Smaller power plants, such as the Yueliangwan power plant, which uses the closed cooling method, consume 2.36 million m3 of tap water per year, equivalent to the water supply of a small reservoir. However, larger power plants, such as the Mawan power plant and Dayawan nuclear power plant (using the open cooling method), use 0.92 and 3.42 billion m3 of seawater for cooling every year, respectively, equivalent to about 60% and 200% of the total annual water supply in Shenzhen, respectively. Therefore, large thermal power plants and nuclear power plants should be built in coastal areas with rich water resources rather than in arid or semi-arid areas. Additionally, the water use efficiency of nuclear power plants was found to be 0.22 m3/kWh, which was significantly lower than that of coal-fired power plants (0.10 m3/kWh) and gas-fired power plants (0.09 m3/kWh). Third, the water use efficiency of the closed cooling method was ten times higher than that of the open cooling method. Therefore, the closed cooling method is suitable for power plants constructed in areas without rich water resources. These results are useful for balancing the water and energy demands in the changing world.

Mitigation fluctuations of inter-row water use efficiency of spring wheat via narrowing row space in enlarged lateral space drip irrigation systems

Water use efficiency (WUE) is key indicator of balance between crop water demand and artificial water input in irrigation management. This makes specific importance of accurate evaluating largely diverse WUE of plants differently distant from the drip tube in the enlarged lateral space (ELS) drip irrigation wheat systems. To achieve this, we compared WUE calculated from differentiation of stable carbon isotopes (δ13C, WUE13 C), with those from grain yield (WUEYield) or dry matter accumulation (WUEDM) per evaportranspirated water in a two-year field trial with different ELS patterns in Xinjiang. Seven patterns were included, the normal ELS pattern by simply expanding drip tube to plant rows ratio from four (TR4, conventional pattern) to six (TR6) and eight (TR8) with row space (RS) of 15 cm; modified ELS by narrowing RS (NRS) to 10 cm to leave large inter-block space (IBS) of 35 cm and 45 cm for TR6L and TR8L, respectively; and Shortened IBS to 25 cm of TR6S and TR8S. Compared with TR4, ELS effectively improved all WUE parameters due to significant WUE increase in the outermost rows to drip tube, probably as a result of reduced received irrigation water (RIW). This led to large variations in WUE between rows, with inter-row coefficient of variation (C.V) of 6.2 %− 13.6 % for TR6 and TR8 (only 0.2 %− 2.3 % for TR4), respectively. The modified ELS patterns effectively reduced inter-row C.V to 2.9 %− 7.0 % for TR6L and TR8L, and 2.2 %− 5.7 % for TR6S and TR8S, respectively. NRS and SIBS effectively reduced the inter-row WUE heterogeneity, and facilitated overall yield and WUE. Considering satisfied WUE and high yield, TR6S was recommended the optimum ELS drip irrigation pattern. Moreover, WUE13 C was less fluctuant in response to reduced RIW as WUEDM and WUEYield, and was suggested proper indicator reflecting WUE of different rows in ELS patterns. The results should help guide better WUE evaluation under complex conditions and optimize more water-saving and productive drip irrigated wheat patterns.

Hourly water-carbon interactions modulate decadal water-use efficiency trends inferred from ecosystem-scale measurements

Plant stomatal conductance regulates photosynthesis and transpiration. This physiological link affects ecosystem responses to microclimate and harmonizes carbon, energy, and water exchanges between the biosphere and atmosphere. The relationship between water losses via transpiration and carbon gains via photosynthesis can be quantified by plant water-use efficiency (WUE). While leaf- and ecosystem-scale observations both suggest rising WUE in recent decades, WUE trends inferred from the ecosystem scale are much larger than those inferred from the leaf scale or implied by theory. The unexpectedly large ecosystem-scale WUE trends complicate interpretation of ecophysiological responses to changing environmental conditions. Here, we analyze ecosystem-scale WUE inferred from 40 FLUXNET sites, each with at least 10 years of measurements. Our results demonstrate that observed ecosystem-scale WUE trends are more sensitive to hourly weather conditions than longer-term changes in atmospheric carbon dioxide or vapor pressure deficit. Our analysis shows that Earth System Models participating in CMIP6 did not capture the observed WUE sensitivity to inter-site variability and microclimatic conditions. Collectively, our findings suggest that ecosystem-scale WUE trends reflect water-carbon interactions across multiple temporal scales, and disentangling factors contributing to emergent ecosystem responses is needed to infer ecophysiological relationships and model structures from observations.

Evaluation of the rhizospheric microbiome of the native colonizer Piptatherum miliaceum in semiarid mine tailings

The study of the rhizospheric microbiome in native plants should be a prerequisite before carrying out the phytomanagement of mine tailings. The goal of this work was to evaluate the rhizospheric microbiome of Piptatherum miliaceum in semiarid mine tailings. A comprehensive edaphic characterization was performed including the description of soil microbial composition in the rhizosphere of P. miliaceum growing at a mine tailings pile and at a control site. Plant nutritional and isotopic compositions were also determined. Neutral pH of the tailings (7.3) determined low metal extractability in 0.01 M CaCl2 (e.g. < 1 mg/kg for Zn). In spite of the contrasting edaphic fertility conditions of both sites, N (~ 15 g kg−1) and P (~ 400 mg kg−1) leaf concentrations were similar. The lower δ15N at the tailings plants (− 4.50‰) compared to the control (6.42‰) indicated greater efficiency of P. miliaceum for uptaking N under the low fertility conditions of the tailings (0.1% total soil nitrogen). The presence at the tailings of bacterial orders related to the cycling of N, such as Rhizobiales, could have contributed to enhance N acquisition. The lower leaf δ13C values at the tailings (− 30.22‰) compared to the control (− 28.47‰) indicated lower water use efficiency of the tailing plants. Some organotrophic bacterial and fungal groups in the tailings’ rhizospheres were also found in the control site (e.g. Cytophagales, Sphingobacteriales for bacteria; Hypocreales, Pleosporales for fungi). This may indicate that P. miliaceum is able to shape its own specific microbiome at the tailings independently from the initial microbial composition of the tailings.

Basin management inspiration from impacts of alternating dry and wet conditions on water production and carbon uptake in Murray-Darling Basin

The impacts of alternating dry and wet conditions on water production and carbon uptake at different scales remain unclear, which limits the integrated management of water and carbon. We quantified the response of runoff efficiency (RE) and plant water-use efficiency (PWUE) to a typical shift from dry to wet episode of 2003–2014 in Australia's Murray-Darling basin using good and specific data products for local application, including Australian Water Availability Project, Penman-Monteith-Leuning Evapotranspiration V2 product, MODIS MCD12Q1 V6 Land Cover Type and MODIS MOD17A3 V055 GPP product. The results show that there are significant power function relationships between RE and precipitation for basin and all ecosystems, while the PWUE had a negative quadratic correlation with precipitation and satisfied the significance levels of 0.05 for basin and the ecosystems except the grassland and cropland. The shrubs can achieve the best water production and carbon uptake under dry conditions, while the evergreen broadleaf trees and evergreen needleleaf trees can obtain the best water production and carbon uptake in wet conditions, respectively. These findings help integrated basin management for balancing water resource production and climate change mitigation.

Effects of high Ca and Mg stress on plants water use efficiency in a Karst ecosystem.

BackgroundKarst ecosystems are widely distributed in the world, with one of the largest continuous Karst landforms in Southwest China. Karst regions are characterized by water shortage, high soil calcium (Ca) and magnesium (Mg) content, and soil nutrient leaching, resulting in drought stress and growth limitation of plants.MethodsThis study compared nitrogen (N), phosphorus (P), potassium (K), Ca, and Mg of herbaceous and woody plants in a small Karst ecosystem in Southwest China. The indexes of water use efficiency (WUE) were calculated to identify the drought stress of plants in this Karst ecosystem. Meanwhile, the relationship between Ca and Mg accumulation and WUE was evaluated in herbaceous and woody plants.ResultsHerbaceous plants showed a higher content of leaf N (13.4 to 40.1 g·kg−1), leaf P (2.2 to 4.8 g·kg−1) and leaf K (14.6 to 35.5 g·kg−1) than woody plants (N: 10.4 g to 22.4 g·kg−1; P: 0.4 to 2.3 g·kg−1; K: 5.7 to 15.5 g·kg−1). Herbaceous plants showed a significantly positive correlation between WUE and K:Ca ratio (R = 0.79), while WUE has a strongly positive correlation with K:Mg ratio in woody plants (R = 0.63).ConclusionHerbaceous plants suffered from nitrogen (N) limitation, and woody plants were constrained by P or N+P content. Herbaceous plants had higher leaf N, P, and K than woody plants, while Ca and Mg showed no significant differences, probably resulting from the Karst environment of high Ca and Mg contents. Under high Karst Ca and Mg stress, herbaceous and woody plants responded differently to Ca and Mg stress, respectively. WUE of herbaceous plants is more sensitive to Ca stress, while that of woody plants is more sensitive to Mg stress. These findings establish a link between plant nutrients and hydraulic processes in a unique Karst ecosystem, further facilitating studies of the nutrient-water cycling system in the ecosystem.

Genotype Variations in Water Use Efficiency Correspond with Photosynthetic Traits in Tempranillo Grapevine Clones

Mediterranean viticulture is highly dependent on soil water availability. Moreover, global warming is likely to increase average temperatures and the frequency of heat waves, thus leading to greater water scarcity. To cope with this situation, much research focused on the selection of genotypes with higher water use efficiency (WUE). Several previous studies indicated that WUE varies between genotypes of the Tempranillo cultivar with some showing interesting improvement in the leaf WUE. Here, we assessed the associations between the leaf WUE and physiological parameters in six selected Tempranillo clones. The plants were cultivated in pots and two water conditions were applied sequentially: a well-watered period followed by a moderate water stress and recovery phase. Growth parameters and intrinsic WUE were monitored during both periods. Pressure–volume and AN/Ci curves were measured after the plants were re-watered. At the end of the season, biomass accumulation and total irrigation water were used to calculate whole plant WUE (WUEWP). AN/Ci curves revealed significant differences in several photosynthetic parameters, including mesophyll conductance (gm), maximum velocity of carboxylation (Vcmax) and leaf respiration (R). Clones RJ51 and 1048 both exhibited high WUE, but presented distinct physiological traits: RJ51 had the highest gm, while genotype 1048, had the lowest R. This study confirms that physiological traits generally explain the intracultivar diversity in WUE observed in previous studies.

CO2 Elevation and Nitrogen Supply Alter the Growth and Physiological Responses of Tomato and Barley Plants to Drought Stress

Global climate change will modify plants in terms of growth and physiology. To better understand the consequences of this effect, the responses of the leaf water relations and nitrogen (N) use efficiency of barley and tomato plants to elevated CO2 (e[CO2], 800 ppm) combined with progressive drought stress at two levels of N supply (N1, 0.5 g N pot−1 and N2, 1.0 g N pot−1) were studied. The plants were grown in two separate phytotrons at ambient CO2 (a[CO2], 400 ppm) and e[CO2], respectively. The leaf physiological parameters as well as carbon (C) and N concentrations were determined; plant growth, water and N use efficiencies were evaluated. The results showed that e[CO2] increased photosynthesis and water use efficiency (WUE) while decreased specific leaf area (SLA) in both species, whereas N supply level differentially influenced WUE in barley and tomato plants. The abscisic acid (ABA)-induced stomatal closure during progressive soil drying varied between the two species where the stomatal conductance (gs) of barley plants was more sensitive to leaf ABA than tomato plants, though CO2 environment did not affect the response in both species. Compared to a[CO2], e[CO2] reduced plant transpiration rate (Tplant) in barley but not in tomato. e[CO2] increased the leaf C:N ratio ([C:N]leaf) in plants by enhancing leaf C concentration ([C]leaf) in barley and by dilution of leaf N concentration ([N]leaf) in tomato, respectively, but N2 substantially decreased [C:N]leaf, and thus, N treatment was the dominant factor controlling [C:N]leaf. Collectively, appropriate N supply may modulate the acclimation of plants to e[CO2] and soil water deficits. This study provides some novel insights into N management of different plant species for adapting to future drier and CO2-enriched environment.

The Effect of Deficit Irrigation on Yield and Quality of Second Crop Sesame (Sesamum indicum L.)

This study was carried out in Bursa, Turkey which has a sub-humid climate, in order to examine the water-yield relationships and responses of yield and quality components under deficit irrigation of second crop sesame plant (Sesamum indicum L.) irrigated with drip irrigation method. Experimental treatments were application of 100% (S1), 75% (S2), 50% (S3), 25% (S4) and 0% (S5) of soil water depleted at effective rooting depth at 7-day intervals. The experiment was applied in 3 replicates according to the completely randomized blocks experimental design. According to the study results, the total amounts of irrigation water applied were between 127.0-354.7 mm. Crop evapotranspiration values varied between 246.0-449.5 mm. Seed yield, oil content and protein content were obtained as between 76.3-189.2 kg da-1, 56.3-62.6% and 18.6-20.4%, respectively. In the study, the seasonal yield response factor (ky) was determined as 1.28. Water use efficiency (WUE) of the sesame plant was found between 0.31-0.43 kg m-3. Irrigation water use efficiency (IWUE) varied between 0.50-0.57 kg m-3. As a result, irrigation treatment S1 can be suggested as an irrigation schedule in order to reach the highest seed yield (189.2 kg da-1) in the second crop sesame plant. When water resources are limited, taking into account the WUE and IWUE values, the S2 treatment (25% water deficit) can be preferred as an irrigation program in terms of water saving.

Effect of Canopy Gaps on Growth and Water Use Efficiency of Seedling of Vulnerable Species, Hopea sangal Korth

Aims: Hopea sangal Korth. is listed as vulnerable species and recently its remnant habitat was rediscovered in the degraded forest near the springs area in East Java. In the forest, the regeneration of the seedling and saplings understory is affected by the heterogeneity in environmental factors especially various light levels due to the canopy gaps. H. sangal is considered a shade-tolerant species, hence the establishment of the seedling in its natural habitat occurs under the closed canopy. This study aimed to understand the Water Use Efficiency (WUE) and Relative Growth Rate (RGR) of Hopea sangal Korth seedling grown in two different levels of tree canopy shades.&#x0D; Study Design: This research was using a completely randomized design, with 9 replications.&#x0D; Place and Duration of Study: This study was conducted in the Purwodadi Botanic Garden, East Java, between March – July.&#x0D; Methodology: We used seedling of H. sangal collected from the field in Pasuruan which were planted in plastic pots and acclimatized to obtain seedling of a similar size. The microclimate was measured weekly using solarimetri and sling psychrometer at 08.00; 10:00; 12:00; 14:00 and 16:00. RGR was measured by harvesting the seedling and whole plant WUE was measured using the gravimetric method.&#x0D; Results: We observed the light level during the periodic opening of the canopy gap was significantly different at a specific time (8-12 am), with the highest light intensity at 10.00 of 333.57 µmol photon m-2s-1. The canopy shades differences did not affect the WUE of seedling (P = 0.333), meanwhile, there was a significant difference in the seedling RGR (P = 0.025). The seedling that were grown under a higher gap and received higher light intensity periodically during a day had higher RGR than those under a closed canopy. The WUE has a positive relationship with the RGR of seedling (R2 = 0.5; P &lt; 0.05).&#x0D; Conclusions: This study suggested that the H. sangal is one of the shade-tolerant species capable of responding to gap-opening sunlight. The study also showed RGR of the seedling positively correlated with the WUE of plants, indicating that the seedling could use the water supply efficiently to grow rapidly.

Vapour pressure deficit and endogenous ABA level modulate stomatal responses of tomato plants to soil water deficit

High vapour pressure deficit (VPD) in the air and water deficits in the soil are considered two key stress factors limiting crop growth and production. To explore their interactive effects on stomatal behaviour and plant water use and the role of abscisic acid (ABA) in mediating these responses, two tomato (Solanum lycopersicum) genotypes, Ailsa Craig (AC) and its ABA-deficient mutant (flacca), were grown at two VPD levels (VPD1, 0.71 kPa and VPD2, 1.25 kPa) and were exposed to progressive soil drying. The results showed that the relatively higher VPD, i.e. VPD2, decreased stomatal conductance only in AC, and increased transpiration rate and water consumption in both genotypes, which was associated with altered stomatal morphological traits, including lowered stomatal density, reduced stomatal size and pore aperture. During progressive soil drying, both AC and flacca grown at VPD2 closed stomata earlier than VPD1-plants with a low leaf ABA concentration, indicating that rising VPD advanced stomatal drought response in an ABA-independent way. At the end of soil drying, the stomata of VPD1-AC plants remained widely opened resulting in fast desiccation of the leaves excised from the plants upon exposure to VPD2, which implied an interaction of VPD and ABA in mediating short-term stomatal response. VPD2 increased the intrinsic water use efficiency (WUE) in AC plants but decreased the whole-leaf and plant WUE in both genotypes, as affirmed by the corresponding changes in leaf δ13C and δ 18O. Compared to δ 18O, δ13C was a more robust indicator of stomatal movement when plants were exposed to combined atmospheric and soil droughts. Collectively, these findings provide some novel insights into the stomatal regulation of tomato plants confronting combined atmospheric and edaphic droughts.

EFFECT OF OZONE ENRICHMENT AND SPRAYING WITH ORGANIC NUTRIENT ON NUTRIENT AND WATER USE EFFICIENCY AND FERTILIZER PRODUCTIVITY OF BROCCOLI PLANT CULTIVATED HYDROPONICALLY WITH MODIFIED NFT TECHNOLOGY.

This study was carried out at University of Baghdad - College of Agricultural Engineering Sciences - research station B during the fall season of 2019-2020, in order to evaluate the effect of Ozone enrichment and the foliar application of organic nutrient on nutrient and water use efficiency and fertilizer productivity of broccoli plant using the modified NFT film technology. A factorial experiment (2*5) was carried out within Nested Design with three replicates. The ozone treatment was distributed into the main plots which consisted of oxygen (O2) and ozone (O3). The foliar application of organic nutrients were distributed randomly within each replicate including five treatments, which were the control treatment (T0), Coconut water with two concentrations of 50 (T1) and 100 ml. L-1 (T2), and Moringa leaves extract at two concentrations 2% (T3) and 4% T4. Results revealed a significant effect of ozone and the foliar application of coconut water 100 ml. L-1 at the treatment of O3T2 on the leaves content of N, P, and K, and vegetative dry weight, vegetative to roots dry weight ratio, the recovering efficiency of N, P, k, the use efficiency of N, P, K, and fertilizer productivity, reaching 4.530, 0.674, 3.139%, 178.81 g. Plant-1, 5.74, 8.21, 8.29, 8.68%, 65.17, 36.35, 24.48%, and 3.616 kg yield. Kg fertilizer, respectively, compared to the control treatment (O2T0). The treatment of ozone enrichment and the foliar application of 2% Moringa leaf extract (O3T3) or with coconut water 100 ml. L-1 (O3T2) gave a significant increment in plant yield reached 919.33 and 917.00 g. Plant-1 (O2T0) which gave the lowest plant yield reached 624.00 g. Plant-1.