Leaf Water Use Research Articles

Increased stomatal conductance and leaf biochemical capacity, not mesophyll conductance, contributing to the enhanced photosynthesis in Oryza plants during domestication.

Leaf biochemical capacity and the ratio of leaf biochemical capacity to stomatal conductance are promising to enhance leaf photosynthetic rate and water use efficiency in rice plants, respectively. Domestication may have great impact on crop photosynthetic rate, which has not been fully understood, especially from the perspective of stomatal conductance, mesophyll conductance, and leaf biochemical capacity simultaneously. In this study, we constructed a database consisting of 141 and 92 sets of data from wild and cultivated rice, respectively, including leaf gas exchange parameters, hydraulic conductance, structural traits, and nitrogen content. We found that, compared to wild rice, enhanced leaf photosynthetic rate in cultivated rice was mainly resulted by the increased stomatal conductance and leaf biochemical capacity, rather than mesophyll conductance. The unchanged mesophyll conductance observed during domestication suggested that it might have been optimized during plant evolution in wild rice. Additionally, the positive relationship between stomatal density and stomatal conductance disappeared in Oryza plants during domestication, suggesting that stomatal conductance in cultivated rice is less restricted by stomatal density, compared to wild rice. Moreover, in both wild and cultivated rice, leaf photosynthetic rate was mainly determined by leaf biochemical capacity, rather than stomatal conductance and mesophyll conductance. This study highlighted the important role of stomatal conductance and leaf biochemical capacity in improvement of leaf photosynthetic rate in rice during domestication. Leaf biochemical capacity and the ratio of leaf biochemical capacity to stomatal conductance should be further investigated to enhance leaf photosynthetic rate and water use efficiency in rice plants, respectively.

Morfofisiologia de gravioleira sob estresse salino e aplicação de H2O2 na fase de pré-floração

ABSTRACT In the semi-arid region of the Brazilian Northeast, water sources generally have high levels of salts, standing out as one of the abiotic stresses that restrict the growth and development of plants. In this context, the objective of the present study was to evaluate the effects of foliar applications of hydrogen peroxide on the morphophysiology of soursop under salt stress in the pre-flowering phase. The experiment was carried out in a greenhouse, using a randomized block design and a 4 × 4 factorial arrangement, with four values of electrical conductivity of the irrigation water - ECw (0.8, 1.6, 2.4, and 3.2 dS m-1) and four concentrations of hydrogen peroxide - H2O2 (0, 10, 20, and 30 μM), with three replicates. An increase in water electrical conductivity from 0.8 dS m-1 reduced stomatal conductance, CO2 assimilation rate, instantaneous carboxylation efficiency, and leaf water saturation deficit. It inhibited the growth of soursop plants at 370 days after transplanting. Hydrogen peroxide at concentrations of up to 10 μM increased leaf transpiration and water use efficiency of soursop plants irrigated with 1.8 dS m-1 water in the pre-flowering phase.

Productivity of Cherry Tomato Cultivars as Influenced by Watering Capacities and Microclimate Control Designs

Background: Cherry tomatoes remain relatively expensive due to limited public knowledge, few producers, and lower productivity rates in Indonesia. Although cherry tomatoes are increasingly popular in modern marketplaces, they are still uncommon in traditional markets. Cherry tomatoes have an enormous economic impact on many regions, particularly Indonesia, in the broader agricultural environment. Their cultivation, however, may be impacted by problems with water supply and climatic regulation. By evaluating how various watering capacity and microclimate control strategies affect cherry tomato productivity, this study seeks to address these challenges. The research is anticipated to offer farmers and agricultural practitioners useful information to improve cherry tomato output in response to market demands and sustainability concerns. Objectives: The objective of this study is to determine the effect of cultivars on the growth, yield, and quality of cherry tomatoes. Methods: The research is designed to determine the effect of each cultivar (Ruby, Fortesa), watering capacities (100% ETc, 75% ETc, 50% ETc), and microclimate control designs (Greenhouse, Rain shelter, Screen house) on the growth, yield, and quality of cherry tomatoes. Results: The cultivar Fortesa produced the highest possible fruit, biological yield per plant, maximum marketable fruit output, greater growth index, maximum fruit firmness, and water use efficiency. The cultivar Ruby performed better in terms of root-shoot ratio and fruit elasticity. The greenhouse produced the highest possible fruit and biological yield per plant, marketable fruit yield, growth index, leaf chlorophyll content, fruit firmness, elasticity and water use efficiency. In the watering capacities treatment condition, 100% ETC was more significant for parameters, such as marketable fruit yield, root-shoot ratio, growth index, leaf chlorophyll content, fruit firmness, and elasticity. Conclusion: Growing cherry tomato cultivar Fortesa in a greenhouse using a watering capacity of 100% ETc under the results is recommended. These conditions have improved fruit quality, making them favorable options for successful cherry tomato cultivar production.

Divergences in leaf CO2 diffusion conductance and water use efficiency of soybean coping with water stress and its interaction with N addition

Drought and nitrogen (N) additions have been shown to affect plant photosynthesis, but the effect of their interaction on CO2 diffusion conductance (i.e., stomatal conductance, gsc, mesophyll conductance, gm) and water use efficiency (WUE) at the leaf level (i.e., instantaneous water use efficiency, WUEins; intrinsic water use efficiency, WUEint) has rarely been reported. Herein, we examined the interactive effects of drought and N addition on gsc and gm and WUE (i.e., WUEins and WUEint) in soybean (Glycine max (Linn.) Merr.) and analysed the interaction mechanisms mitigating water stress based on leaf anatomy and molecular activity. Drought decreased gsc,gm and WUEins, but N addition had a positive interactive effect with water stress on leaf physiological traits. The variables gsc, gm and WUEins were significantly increased by the additions of 7.5 and 15.0 g urea m−2 under moderate water stress (MW) conditions (P < 0.05), but they decreased under the interaction effect of SW and N addition. The decreased Tcw and increased Sm and Sc under the water stress × N addition interaction positively affected gm, and the increased SS dominated the gsc increase. In addition, these positive effects were further enhanced with increased AQP, CA and Rubisco activities and a decrease in the ABA content. Accordingly, moderate soil N additions of 7.5 and 15.0 g urea m−2 greatly mitigated the negative effects of droughts, especially the MW effects, by enhancing CO2 diffusion conductance and WUE.

Photosynthetic characteristics, yield and quality of sunflower response to deficit irrigation in a cold and arid environment.

In arid regions, deficit irrigation stands as an efficacious strategy for augmenting agricultural water conservation and fostering sustainable crop production. The Hexi Oasis, an irrigation zone situated in Northwest China, serves as a pivotal area to produce grain and cash crops. Nonetheless, due to the predominant conditions of low rainfall and high evaporation, the scarcity of irrigation water has emerged as a critical constraint affecting crop growth and yield in the area. In order to evaluate the effects of deficit irrigation on photosynthetic characteristics, yield, quality, and water use efficiency of sunflower, a two-year field experiment with under-mulched drip irrigation was conducted in the cold and arid environment of the Hexi Oasis region. Water deficits were implemented at sunflower seedling and maturity and consisted of three deficit levels: mild deficit (65-75% field capacity, FC), moderate deficit (55-65% FC), and severe deficit (45-55% FC). A total of six combined water deficit treatments were applied, using full irrigation (75-85% FC) throughout the entire crop-growing season as the control (CK). The results illustrated that water deficit engendered a decrease in leaf net photosynthetic rate, transpiration rate, and stomatal conductance of sunflower compared to CK, with the decrease becoming significant with the water deficit increasing. A mild water deficit, both at the seedling and maturity phases, precipitated a significant enhancement (p< 0.05) in leaf water use efficiency. Under mild water deficit, stomatal limitation emerged as the predominant factor inducing a reduction in the photosynthetic capacity of sunflower leaves, while as the water deficit escalated, non-stomatal limitation progressively assumed dominance. Moreover, a mild/moderate water deficit at seedling and a mild water deficit at maturity (WD1 and WD3) significantly improved sunflower seed quality under consistent yield conditions and significantly increased irrigation water use efficiency, with an average increase of 15.3% and 18.5% over the two years, respectively. Evaluations utilizing principal component analysis and membership function methods revealed that WD1 attained the highest comprehensive score. Consequently, a mild water deficit at both seedling and maturity (WD1) is advocated as the optimal deficit irrigation strategy for sunflower production within the cold and arid environment of Northwest China.

Ecological adaptation strategies of plant functional groups in the upper reaches of the Tarim River based on leaf functional traits

Plant functional traits can reflect plants' long-term adaptive responses to the environment. However, the ecological adaptation strategies adopted by desert plants in plant functional groups to cope with extreme environments remain unclear. Therefore, in this study, plants belonging to 16 common desert species were collected to measure leaf chemical and physiological traits in the extremely arid region along the northern edge of the Tarim Basin. Cluster analysis was used to divide the plants into different functional groups to reveal the response and adaptation mechanisms of plants to environmental and resource changes at a higher level. The results showed that (1) based on plant leaf functional traits, the 16 desert plants could be divided into three plant functional groups, showing significant differences in chemical element contents and ratios, osmoregulatory substance content, and water use efficiency (p＜0.05). (2) Functional group 1 (FG1) had the highest leaf nutrient and water use efficiency and soluble sugar content, lower N and P content and the lowest soluble protein content, indicating a passive strategy of high consumption. Plants in functional group 2 (FG2) were poor in leaf N, rich in P and had the lowest organic carbon content, soluble sugar content, and water use efficiency, indicating a relatively conservative strategy. Members of functional group 3 (FG3) were rich in leaf C, N and P, and their proline, soluble protein and sugar content were all high, indicating a rapid resource acquisition and growth strategy. (3) There were significant correlations among most leaf traits of each functional group (p＜0.05); although the relationships were inconsistent, extremely significant correlations existed between the organic carbon and nonstructural carbon contents in FG1, C/P and soluble sugar contents in FG2, and total N and proline contents in FG3 (p＜0.01). These results indicate that desert plant functional groups adopt different ecological strategies and contribute to a comprehensive understanding of how plants adapt and respond to extremely arid environments, providing a scientific basis for the protection of desert vegetation.

Variations of deep water uptake and water use efficiency indicated divergence in tree growth stability

Insights into forest growth stability in response to intensified climate change and disturbances is critical to maintain the continued flow and stability of forest services. However, the underlying drivers for tree growth stability remain poorly understood. In this study, we quantified the spatiotemporal pattern in tree growth stability of Chinese pine (Pinus tabulaeformis) plantations and its relationship to diverse driving factors (climate, stand structure, ecophysiological traits, soil properties, and topography) across a great climatic gradient in northern China in the period of 1979–2018. We calculated the coefficient of variation of tree ring chronology (TRIcv) to characterize tree growth stability and revealed that the TRIcv increased significantly with increasing multiyear mean aridity index (MAI) and vapor pressure deficit (VPD) spatially. Temporally, TRIcv displayed increasing trend in 25 of 40 study sites. Constrained redundancy analysis revealed that TRIcv was strongly mediated by water availability, water uptake from different soil layers, wood density, tree height, leaf stable carbon isotope discrimination (δ13C), and leaf nutrients. The ratio of water uptake from 60 to 80 cm soil layer and leaf δ13C were the two most important ecohydrological-related factors determining TRIcv, highlighting that the water uptake strategy and leaf water use efficiency play critical role in reshaping the tree growth stability of Chinese pine to cope with the intensifying climate change.

Effect of water and nitrogen coupling regulation on the growth, physiology, yield, and quality attributes and comprehensive evaluation of wolfberry (Lycium barbarum L.).

The characteristics of the growing environment (arid and semi-arid regions with abundant light), wastage of water, types of fertilizers used, quality of the plants, and the decline in yield due to the need for large quantities of water and fertilizers are the most significant obstacles to wolfberry cultivation. To cope with the scarcity of water caused by the increase in the area of wolfberry cultivation and to improve the efficiency of the utilization of water and fertilizers, a two-year field experiment was conducted in a typical area of the central dry zone of Ningxia in 2021 and 2022. The effects of different water and nitrogen coupling on the physiology, growth, quality, and yield of wolfberry were investigated, and a water and nitrogen management model with better indicators was constructed based on the TOPSIS model and a comprehensive scoring method. In the experiment, three irrigation quotas of 2,160, 2,565, and 2,970 m3 ha-1 (I1, I2, and I3) and three N applications of 165, 225, and 285 kg ha-1 (N1, N2, and N3) were established; the local conventional management served as the control (CK). The results showed that the growth index of wolfberry was most significantly affected by irrigation, followed by the water and nitrogen interaction effect, and the nitrogen application had the least effect. The growth and development of wolfberry plants mainly takes place during the fruit ripening and flowering periods, and growth almost stops after entering the fruit ripening period. The chlorophyll (SPAD) values were affected by irrigation and nitrogen application to a significant level, except for during the spring tip period, but the effect of water and nitrogen interaction was not significant. The SPAD values of N2 treatment were better under different irrigation. The daily photosynthetic activity of wolfberry leaves peaked between 10:00 am and noon. The daily photosynthetic dynamics of wolfberry were affected by irrigation and nitrogen application to a significant level during the fruit ripening period, and the transpiration rate and leaf water use efficiency were affected by water and nitrogen interaction to a significant level during 8:00 am and noon, while the effect was not significant during the spring tip period. The yield, dry-to-fresh ratio, and 100 grain weight of wolfberry were significantly affected by the irrigation, nitrogen application, and their interaction effects. Specifically, the two-year yield with I2N2 treatment increased by 7.48% and 3.73%, respectively, compared to CK. The quality indices were significantly affected by irrigation and nitrogen application, except for the total sugars; other indexes were also significantly affected by water and nitrogen interaction effects. The evaluation of the TOPSIS model showed that the I3N1 treatment yielded the best quality of wolfberry, and the results of the integrated scoring method based on the growth, physiology, yield, and quality indicators and water-saving objectives showed that the I2N2 (2,565 m3 ha-1, 225 kg ha-1) treatment was the optimal water and nitrogen management mode for drip-irrigated wolfberry. Our findings provide a scientific basis for the optimal irrigation and management of fertilization of wolfberry in arid regions.

Salinity stress amelioration and morpho-physiological growth stimulation by silicon priming and biochar supplementation in Chenopodium quinoa

The effect of silicon (Si) priming and soil amendment with biochar (BC) was analysed in Chenopodium quinoa under normal and salinity stressed conditions. Reduced growth parameters, chlorophyll content, and photosynthesis under salinity stress were significantly ameliorated by Si priming and soil amendment with BC. Applied Si and BC treatment also enhanced the chlorophyll content, stomatal conductance, transpiration rate, net photosynthesis, and maximal photochemical efficiency. In addition to this, Si and/or BC amendments alleviated the oxidative damage by reducing the generation of toxic reactive oxygen species including hydrogen peroxide and superoxide. Moreover, the activities of antioxidant enzymes and the content of ascorbate and glutathione increased significantly in Si and BC treated plants reflecting efficient alleviation of oxidative damage. Besides, the content of compatible osmolytes was increased in Si and/or BC treated seedlings, thereby contributing to improved growth and salinity tolerance by maintaining higher leaf water potential and water use efficiency. Si and BC treatment increased the uptake of key mineral elements. Moreover, salinity induced decline in the nutritional components of seeds of C. quinoa were considerably increased under Si and BC treatments.

Optimizing drip fertigation at different periods to improve yield, volatile compounds and cup quality of Arabica coffee.

How to improve and regulate coffee bean yield and quality through split fertilization in the whole life cycle of coffee is still unclear and deserves further study. A field experiment of 5-year-old Arabica coffee trees was conducted for 2 consecutive years from 2020 to 2022. The fertilizer (750kg ha-1 year-1, N-P2O5-K2O:20%-20%-20%) was split in three times at early flowering (FL), the berry expansion (BE), and the berry ripening (BR). Taking equal fertilization throughout the growth cycle (FL250BE250BR250) as the control check, variable fertilizations including FL150BE250BR350, FL150BE350BR250, FL250BE150BR350, FL250BE350BR150, FL350BE150BR250, and FL350BE250BR150. Leaf net photosynthetic rate (A net), stomatal conductance (g s), transpiration rate (T r), leaf water use efficiency (LWUE), carboxylation efficiency (CE), partial factor productivity of fertilizer (PFP), bean yield, crop water use efficiency (WUE), bean nutrients, volatile compounds and cup quality, and the correlation of nutrients with volatile compounds and cup quality was evaluated. FL350BE250BR150 had the maximum A net and g s, followed by FL250BE350BR150. The highest dry bean yield and WUE were obtained from FL250BE350BR150, which increased by 8.86% and 8.47% compared with FL250BE250BR250 in two-year average. The ash, total sugar, fat, protein, caffeine and chlorogenic acid in FL250BE350BR150 were 6.47%, 9.48%, 3.60%, 14.02%, 4.85% and 15.42% higher than FL250BE250BR250. Cluster analysis indicated FL150BE350BR250, FL250BE350BR150, FL350BE150BR250 and FL350BE250BR150 under medium roasted degree increased pyrazines, esters, ketones and furans, FL150BE350BR250 and FL250BE350BR150 under dark roasted degree increased ketones and furans. The aroma, flavor, acidity and overall score of medium roasted coffee were higher than dark roasted coffee, while the body score of dark roasted coffee was higher than medium roasted coffee. The nutrient contents were correlated with the volatile compounds and cup quality. TOPSIS indicated that FL250BE350BR150 was the optimal fertilization mode in the xerothermic regions. The obtained optimum fertilization mode can provide a scientific basis for coffee fertilization optimization and management.

Effects of Poultry Manure on the Growth, Physiology, Yield, and Yield-Related Traits of Maize Varieties.

Industries play a significant role in the improvement of lifestyle and in the development of a country. However, the byproducts from these industries are a source of environmental pollution. The proper use of the byproducts of these industries can help to cope with environmental pollution. Some byproducts have high nutritional content and are good for crop plants. The purpose of this research was to investigate the effect of different rates of poultry manure on the soil chemical properties, growth, and yield of maize. A pot experiment was conducted in the botanical garden of the Department of Botany, University of Sargodha, Pakistan to investigate the effect of various treatments of poultry manure (0, 25, 50, 75, and 100 g/pot) on the morphological, physiological, and yield attributes of two maize varieties, Pearl and MMRI. Treatment T1 was a mixture of soil and 75 g/pot poultry manure, T2 was a mixture of soil and 50 g/pot poultry manure, T3 was a mixture of soil and 25 g/pot poultry manure, and T4 was 100 g/pot poultry manure. Soil without any industrial byproduct (100% soil only) was used as the control (T0). The results revealed that the use of poultry manure enhanced the physical properties of the soil. Available P and soil organic matter were improved in soil amended with poultry manure. It is evident from the results that the vegetative growth of both maize varieties was significantly enhanced by growing in soil amended with poultry manure as compared to their respective control. Similar responses were also recorded for the physiological attributes of leaf area, photosynthetic rate, transpiration rate, stomatal conductance, and water use efficiency of both varieties. Yield and yield-contributing traits of both maize varieties were significantly improved by growing plants in soil amended with 50 and 75 g/pot of poultry manure. It is also inferred that the use of 50 g/pot poultry manure in soil amendment is an eco-friendly and economically effective option for maize growers of arid and semiarid regions to enhance the kernel yield and profit per annum. Poultry manure could be useful to ameliorate the adverse effects of salinity stress on all parameters, particularly the grain yield. Furthermore, this would be a useful and economical method for the safe disposal of byproducts.

Soil enzyme activities, soil physical properties, photosynthetic physical characteristics and water use of winter wheat after long-term straw mulch and organic fertilizer application.

Inappropriate residue and nutrient management leads to soil degradation and the decline of soil quality and water storage capacity. An ongoing field experiment has been conducted since 2011 to investigate the effects of straw mulching (SM), and straw mulching combined with organic fertilizer (SM+O), on winter wheat yield, including a control treatment (CK, no straw). We studied the effects of these treatments on soil microbial biomass nitrogen and carbon, soil enzyme activity in 2019, photosynthetic parameters, evapotranspiration (ET), water use efficiency (WUE), and yields over five consecutive years (2015-2019). We also analyzed the soil organic carbon, soil structure, field capacity, and saturated hydraulic conductivity in 2015 and 2019. Results indicate that compared with CK, SM and SM+O treatments increased the proportion of >0.25mm aggregates, soil organic carbon, field capacity, and saturated hydraulic conductivity, but decreased the soil bulk density. In addition, the SM and SM+O treatments also increased soil microbial biomass nitrogen and carbon, the activity of soil enzymes, and decreased the carbon-nitrogen ratio of microbial biomass. Therefore, SM and SM+O treatments both increased the leaf water use efficiency (LWUE) and photosynthetic rate (Pn), and improved the yields and water use efficiency (WUE) of winter wheat. The combination SM (4.5 t/ha)+O (0.75 t/ha) was more effective than SM alone, and both treatments were superior to the control. Based on the results of this study, SM+O is recommended as the most effective cultivation practice.

Drought-triggered leaf transcriptional responses disclose key molecular pathways underlying leaf water use efficiency in sugarcane (Saccharum spp.).

Drought is a major constraint to sugarcane (Saccharum spp.) production and improving the water use efficiency (WUE) is a critical trait for the sustainability of this bioenergy crop. The molecular mechanism underlying WUE remains underexplored in sugarcane. Here, we investigated the drought-triggered physiological and transcriptional responses of two sugarcane cultivars contrasting for drought tolerance, 'IACSP97-7065' (sensitive) and 'IACSP94-2094' (tolerant). After 21 days without irrigation (DWI), only 'IACSP94-2094' exhibited superior WUE and instantaneous carboxylation efficiency, with the net CO2 assimilation being less impacted when compared with 'IACSP97-7065'. RNA-seq of sugarcane leaves at 21 DWI revealed a total of 1,585 differentially expressed genes (DEGs) for both genotypes, among which 'IACSP94-2094' showed 617 (38.9%) exclusive transcripts (212 up- and 405 down-regulated). Functional enrichment analyses of these unique DEGs revealed several relevant biological processes, such as photosynthesis, transcription factors, signal transduction, solute transport, and redox homeostasis. The better drought-responsiveness of 'IACSP94-2094' suggested signaling cascades that foster transcriptional regulation of genes implicated in the Calvin cycle and transport of water and carbon dioxide, which are expected to support the high WUE and carboxylation efficiency observed for this genotype under water deficit. Moreover, the robust antioxidant system of the drought-tolerant genotype might serve as a molecular shield against the drought-associated overproduction of reactive oxygen species. This study provides relevant data that may be used to develop novel strategies for sugarcane breeding programs and to understand the genetic basis of drought tolerance and WUE improvement of sugarcane.

Physiological and morphological characterization of avocado creole (Persea americana Mill.) accessions for elite rootstocks

The selection of a suitable cultivar as a seed source for rootstock production can be considered of great importance since the success or failure after the plantation establishment depends on the attributes of the material used as a pattern in the production of seedlings. This research aimed to characterize morphologically and physiologically different creole cultivars of avocado to identify elite materials that can be used as rootstocks. The research was carried out in Supia, Caldas - Colombia (5°26'39'' N; 75°38'56'' W). A completely randomized experimental design was used with 17 treatments (accessions) and 20 replications. The variables evaluated were rootstock stem diameter, rootstock height, leaves number, leaf area index (LAI), specific leaf area (SLA), dry matter, net photosynthesis (A), stomatal conductance (gs), transpiration (E), and water use efficiency (WUE). The largest records were for rootstock stem diameter ID08, ID-06 (˃ 9 mm), rootstock height ID01, ID-15 (˃ 60 cm), leaf area ID08 and ID15 (&gt; 2000 cm2), LAI ID14 (1.99), SLA ID06 and ID17 (164.23 and 167.57), total dry matter ID01, ID08, ID15 (43.50, 42.91 and 42.80), A: ID01 and ID02 (˃6 μmol CO2 m-2 s-1), gs: ID-16 (0.15 mol H2O m-2 s-1), E: ID-16 (5.93 mmol H2O m-2 s-1) and WUE: ID02 (1.70 μmol CO2/mmol H2O) accessions. The origin of the avocado cultivars significantly influenced physiological and morphological behavior, thus enabling the detection of early attributes for selecting materials that can be used as rootstocks.

Influence of Silicon on Tolerance to Water Deficit of Peach Trees

Water deficit in young fruit trees can reduce growth and future orchard productivity. Exogenous silicon (Si) applications have been associated with induced resistance to biotic and abiotic stresses such as water deficit, but the role of Si in fruit trees is still largely unexplored. The aim of the study was to evaluate the effect of Si applications on water status and gas exchange of young peach trees. This study comprises two experiments arranged in a factorial design with two water regimens (well-irrigated or water-stressed) and three Si concentrations (0, 10, or 20 mg⋅L−1 in the first experiment; 0, 20, or 40 mg⋅L−1 in the second experiment). Si applications via foliar spray were performed weekly after the water regimens were clearly established. Tree water status (midday stem water potential), and gas exchange parameters (CO2 assimilation, leaf transpiration, stomatal conductance, leaf water use efficiency) were measured. Si application at 10 or 20 mg⋅L−1 improved water status of water-stressed trees without affecting gas exchange, but 40 mg⋅L−1 reduced CO2 assimilation. Thus, foliar applications of Si could be a promising strategy for nonirrigated, nonbearing orchards to maintain their water status during dry periods and/or improve their recovery from water deficit.

Photosynthetic Physiological Basis of No Tillage with Wheat Straw Returning to Improve Maize Yield with Plastic Film Mulching in Arid Irrigated Areas

Surface mulch is an efficient plant production technique widely used in arid and water-scarce areas. In this study, a field experiment was conducted to determine whether plastic film combined with wheat straw returning could boost grain yield of maize via optimizing photosynthetic physiological characteristics and coordinating yield components. The results showed that no tillage with wheat straw mulching and straw standing treatments had better regulation on photosynthetic physiological characteristics and had a greater impact on the increase in grain yield than conventional tillage with wheat straw incorporation and without wheat straw returning (the control treatment) in plastic film-mulched maize. Meanwhile, no tillage with wheat straw mulching had a relatively higher yield than no tillage with wheat straw standing through better regulation of photosynthetic physiological characteristics. No tillage with wheat straw mulching decreased the leaf area index (LAI) and leaf area duration (LAD) of maize before the VT stage and maintained higher LAI and LAD after the VT stage, which effectively regulated the growth and development of maize at early and late stages of development. From VT to R4 stage of maize, no tillage with wheat straw mulching had greater chlorophyll relative content, net photosynthetic rate, and transpiration rate by 7.9-17.5%, 7.7-19.2%, and 5.5-12.1% than the control, respectively. In addition, leaf water use efficiency was increased by 6.2-6.7% from the R2 to R4 stage of no tillage with wheat straw mulching in comparison to the control treatment. Thus, no tillage with wheat straw mulching had a greater grain yield of maize by 15.6% than the control, and the high yield was attributed to the synchronous increase and cooperative development of ear number, grain number per ear, and 100-grain weight. Collectively, no tillage with wheat straw mulching had a positive effect on regulating the photosynthetic physiological traits and can be recommended to enhance the grain yield of maize in arid conditions.

Leaf gas exchange characteristics, biomass partitioning, and water use efficiencies of two C4 African grasses under simulated drought

AbstractBackgroundFew studies have evaluated the effect of drought on the morpho‐physiological characteristics of African C4 grasses. We investigated how drought affects leaf gas exchange characteristics, biomass partitioning, and water use efficiencies of Enteropogon macrostachyus and Cenchrus ciliaris.MethodsThe grasses were grown in a controlled environment under optimum conditions, that is, 70% of the maximum water‐holding capacity (WHC) for the first 40 days. Thereafter, half of the columns were maintained under optimum or drought conditions (30% of maximum WHC) for another 20 days.ResultsUnder optimum conditions, C. ciliaris showed a significantly higher photosynthetic rate, stomatal conductance, and transpiration rate than E. macrostachyus. Drought decreased the photosynthetic rate, stomatal conductance and transpiration rate only in C. ciliaris. The net photosynthetic rate, stomatal conductance, and leaf transpiration of E. macrostachyus did not differ significantly under optimum and drought conditions. E. macrostachyus showed an increase in its water use efficiencies under drought to a greater extent than C. ciliaris.ConclusionsOur results demonstrate that C. ciliaris is more sensitive to drought than E. macrostachyus. The decrease in the intercellular CO2 concentration and the increase in stomatal limitation with drought in C. ciliaris and E. macrostachyus suggest that stomatal limitation plays the dominant role in photosynthesis of the studied African C4 grasses.

No-tillage with straw mulching boosts wheat grain yield by improving the eco-physiological characteristics in arid regions

Straw returning to the field is a technical measure of crop production widely adopted in arid areas. It is unknown whether crop yield can be further increased by improving the eco-physiological characteristics when straw returning is applied in the crop production system. So, a three-year field experiment was conducted with various straw returning treatments for wheat production: (i) no-tillage with straw mulching (NTSM), (ii) no-tillage with straw standing (NTSS), (iii) conventional tillage with straw incorporation (CTS), and (iv) conventional tillage with no straw returning (CT, control). The eco-physiological and yield formation indicators were investigated to provide the basis for selecting the appropriate straw returning method to increase wheat yield and clarifying its regulation mechanism on eco-physiology. The results showed that NTSM and NTSS treatments had better regulation of eco-physiological characteristics and had a higher yield increase than CTS and CT. Meanwhile, NTSM had a relatively higher yield than NTSS through better regulation of eco-physiological characteristics. Compared to CT, the leaf area index of NTSM was decreased by 6.1–7.6% before the Feekes 10.0 stage of wheat, but that of NTSM was increased by 38.9–45.1% after the Feekes 10.0 stage. NTSM effectively regulated the dynamics of the photosynthetic source of green leaves during the wheat growth period. NTSM improved net photosynthetic rate by 10.2–21.4% and 11.0–21.6%, raised transpiration rate by 4.4–10.0% and 5.3–6.1%, increased leaf water use efficiency by 5.6–10.4% and 5.4–14.6%, at Feekes 11.0 and 11.2 stages of wheat, compared to CT, respectively. NTSM had higher leaf water potential (LWP) by 7.5–12.0% and soil water potential (SWP) by 8.9–24.0% from Feekes 10.3 to 11.2 stages of wheat than CT. Meanwhile, the absolute value of difference on LWP and SWP with NTSM was less than that with CT, indicating that NTSM was conducive to holding the stability of water demand for wheat plants and water supply of soil at arid conditions. Thus, NTSM had a greater grain yield of wheat by 18.6–27.3% than CT, and the high yield was attributed to the synchronous increase and cooperative development of ear number, grain number per ear, and 1 000-grain weight. NTSM had a positive effect on regulating the eco-physiological characteristics and can be recommended to enhance wheat grain yield in arid conditions.

Silicon and bioagents pretreatments synergistically improve upland rice performance during water stress

Rice (Oryza sativa L.) is one of the most important food crops worldwide. Upland rice growing areas are susceptible to adverse conditions and drought represents the main limiting factor for its production and yield stability. Soil management strategies (e.g., chemical and biological treatments) are often implemented to mitigate drought and improve crop production. However, morpho-physiological responses of upland rice to drought under such management strategies remains poorly understood. Here, we studied the effect of silicon and bioagents pretreatments under water stress on an upland rice landrace, Samambaia Branco. Our results unraveled that these pretreatments improved robustness of the root system in water stressed plants with increase in 40.9% of surface area, 11.5% on diameter, 53.8% on volume and 30.8% of length density when measured at 45 cm soil depth. Furthermore, these treatments increased number of thick roots by more than 14.0 and 45.0% at 25 and 45 cm soil depths, respectively; and fine root by more than 25.0% at 45 cm soil depth. Consequently, pretreated water stressed plants exhibited greater yield stability (reduction of 14.6% in grain yield compared to pretreated well-watered plants), root/shoot ratio (26.8%), photosynthesis (50.0%), stomatal conductance (14.4%), leaf water potential (61.0%) and water use efficiency (49.1%) than untreated water stressed plants. Thus, we conclude that silicon and bioagent pretreatments significantly improve root and shoot performance under water stress. Our results provide a first step towards understanding the relevance of these pretreatments in upland rice for improving adaptive root system as a response to suboptimal environmental conditions.

The Interactive Effects of Deficit Irrigation and Bacillus pumilus Inoculation on Growth and Physiology of Tomato Plant.

The effects of inoculating plant growth promoting rhizobacteria (PGPR) and soil water deficits on crop growth and physiology remain largely unknown. Here, the responses of leaf gas exchange, growth, and water use efficiency (WUE) of tomato plants to Bacillus pumilus (B.p.) inoculation under four irrigation strategies (I1-I4) were investigated in a greenhouse. Results showed that soil water deficits, especially at I4 (20%, v/v), significantly decreased leaf stomatal conductance (gs), transpiration rate (Tr), and photosynthetic rate (An), and the decrease of gs and Tr were more pronounced than An. Reduced irrigation regimes significantly lowered dry matter and plant water use both in the non-B.p. control and the B.p. plants, while reduced irrigation significantly increased plant WUE, and B.p. inoculation had little effect on this parameter. Synergistic effects of PGPR and deficit irrigation on leaf gas exchange, leaf abscisic acid content, and stomatal density were found in this study, and specifically, B.p. treated plants at I4 possessed the highest WUE at stomatal and leaf scales, suggesting that B.p. inoculation could optimize water use and partly alleviate the negative effects of soil water deficit. These findings provide useful information for effective irrigation management and the application of PGPR in agriculture in the future.