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Abstract Background Spring irrigation with freshwater is widely used to reduce soil salinity and increase the soil water content in arid areas. However, this approach requires a huge amount of freshwater, which is problematic given limited freshwater resources. Utilizing brackish water for spring irrigation in combination with magnetized water technology may be a promising alternative strategy. Results The objective of this study was to evaluate the effects of four spring irrigation methods (freshwater spring irrigation (FS), magnetized freshwater spring irrigation (MFS), brackish water spring irrigation (BS), and magnetized brackish water spring irrigation (MBS)) on soil water and salt distribution, emergence, growth, and photosynthetic characteristics of cotton seedlings. The results showed that for both freshwater and brackish water, magnetized water irrigation can increase the soil water content for improved desalination effect of irrigation water. Additionally, spring irrigation with magnetized water promoted cotton emergence and seedling growth. Compared with FS treatment, cotton finial emergence rate, emergence index, vigor index, plant height, stem diameter, and leaf area index of MFS treatment increased by 6.25, 7.19, 12.98, 15.60, 8.91, and 20.57%, respectively. Compared with BS treatment, cotton finial emergence rate, emergence index, vigor index, plant height, stem diameter, and leaf area index of MBS treatment increased by 27.78, 39.83, 74.79, 26.40, 14.01, and 57.22%, respectively. Interestingly, we found that spring irrigation with magnetized water can increase the chlorophyll content and net photosynthetic rate of cotton seedlings. The rectangular hyperbolic model (RHM), non-rectangular hyperbolic model (NRHM), exponential model (EM), and modified rectangular hyperbolic model (MRHM) were used to fit and compare the cotton light response curve, and MRHM was determined to be the optimal model to fit the data. This model was used to calculate the photosynthetic parameters of cotton. Compared with FS treatment, the net photosynthetic rate (P nmax ), dark respiration rate (R d ), light compensation point (I c ), light saturation point (I sat ), and the range of available light intensity (ΔI) of MFS were increased by 5.18, 3.41, 3.18, 2.29 and 2.19%, respectively. Compared with BS treatment, the P nmax , R d , I c , I sat and ΔI of MBS were increased by 26.44, 29.48, 30.05, 5.13, and 2.27%, respectively. Conclusion The results show that spring irrigation with magnetized brackish water may be a feasible method to reduce soil salt and increase soil water content when freshwater resources are insufficient.

BACKGROUND: The integration of inorganic and organic fertilizers is increasingly being recommended to address the demand for sustainable cotton cultivation and to mitigate the ecological impacts of reliance on inorganic fertilizers. However, the nuanced effects of this combined fertilization approach on soil quality, cotton growth, yield, and their interaction mechanisms, remain unclear. METHOD: To elucidate this, a 2‐year field trial (2022–2023) was conducted, incorporating five fertilization treatments: low inorganic fertilizer (BI1), high inorganic fertilizer (BI2), organic fertilizer (BO), combined low inorganic and organic fertilizer (BIO1), and combined high inorganic and organic fertilizer (BIO2). This study aimed to evaluate the influence of these treatments on soil quality, cotton growth, and yield. RESULTS: The results indicate that the BO treatment significantly enhanced plant height growth rate, and BIO1 treatment increased leaf area index and dry matter accumulation growth rate. Critical soil parameters such as alkali‐hydrolyzed nitrogen and available potassium emerged as pivotal determinants of soil quality over the trial period, corresponding to soil quality index (SQI) values of 0.482 and 0.478, and yields of 7506.19 kg ha−1 and 6788.02 kg ha−1, respectively. Water productivity reached optimum levels at SQI values of 0.461 and 0.462, with corresponding efficiencies of 13.31 kg (ha mm)−1 and 12.16 kg (ha mm)−1. Partial least squares path modeling revealed that integrating organic fertilizer with reduced inorganic fertilizer usage significantly boosts cotton yield by enhancing soil quality (path coefficient: 0.842). CONCLUSION: In conclusion, this integrated fertilization strategy not only improves soil health but also increases agricultural productivity. It presents a promising approach for optimizing crop yields while fostering sustainable agricultural practices. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND: The development of agricultural practices requires an understanding of the improvement of salt tolerance and crop growth in agricultural systems through magnetized‐ionized water irrigation. METHOD: This study examined the impacts of fresh water (F), brackish water (B), magnetized‐ionized fresh water (MIF), and magnetized‐ionized brackish water (MIB) on soil properties and the growth of cotton seedlings through microbial analysis during the cotton seedling period. RESULTS: The results revealed that magnetized‐ionized water irrigation improved soil water retention and promoted salt leaching. In comparison with F irrigation, plant height, leaf area index (LAI), dry matter accumulation (DM), and chlorophyll content (SPAD) levels increased by 3.61%, 4.07%, 5.76%, and 1.33%, respectively, under MIF irrigation. Similarly, when compared with B irrigation, LAI, DM, and SPAD increased by 5.13%, 6.12%, and 3.12% under MIB irrigation. Magnetized‐ionized water irrigation also led to a notable rise in the relative abundance of beneficial soil bacterial communities, particularly Pseudomonas and Azoarcus, as well as fungal communities like Trichoderma, while reducing the prevalence of pathogenic fungi, such as Lasionectria, Gibberella, and Alternaria. Notably, this irrigation approach induced alterations in soil properties, and partial least squares path modeling revealed significant links between soil properties and both cotton growth and fungal community structure (with path coefficients of −0.884 and 0.693, respectively). CONCLUSION: This study elucidated the distinct effects of soil properties and growth indices on cotton yield during the seedling period, providing a crucial scientific foundation for enhancing future agricultural production through the use of magnetized‐ionized water irrigation. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Soil salinization, a significant global challenge, threatens sustainable development. This study explores the potential of magnetized ionized water irrigation and Bacillus subtilis application to mitigate this issue. The former method is hypothesized to enhance soil salt leaching, while the latter is expected to improve soil nutrient availability, thereby increasing microbial diversity. To address the unclear impact of these interventions on soil quality and cotton productivity, this study employs four different experimental methods: magnetized ionized water irrigation (M), application of 45 kg ha−1 B. subtilis (B), a combination of 45 kg ha−1 B. subtilis with magnetized ionized water irrigation (MB), and a control treatment with no intervention (CK). This study aims to clarify the effects of these treatments on soil bulk density (BD), field capacity (FC), salinity and alkalinity, nutrient content, microbial activity, and cotton crop yield and quality. Additionally, it aims to evaluate the efficacy of these methods in improving saline soil conditions by developing a soil quality index. The results showed that using magnetized ionized water for irrigation and applying B. subtilis, either alone or together, can effectively lower soil pH and salt levels, enhance microbial diversity and abundance, and improve the yield and quality of cotton. Notably, B. subtilis application significantly decreased BD and enhanced FC and nutrient content (p < 0.05). A correlation was found where soil nutrient content decreased as pH and salt content increased. Furthermore, a strong correlation was observed between the major soil bacteria and fungi with BD, FC, and salt content. Comparatively, M, B, and MB significantly boosted (p < 0.01) the soil quality index by 0.21, 0.52, and 0.69 units, respectively, and increased (p < 0.05) cotton yield by 5.7%, 14.8%, and 20.1% compared to CK. Therefore, this research offers eco-friendly and efficient methods to enhance cotton production capacity in saline soil. [ABSTRACT FROM AUTHOR]

The foliar application of biostimulants at specific concentrations under magnetic–electric water irrigation has a positive effect on water and fertilizer use efficiency and yield of cotton, which is crucial for green and sustainable agricultural development. As a new type of fertilizer, biostimulants have demonstrated remarkable effects in improving crop yield and quality by enhancing nutrient uptake, promoting plant growth, and increasing resilience to environmental stress. In this study, the effects of magnetic–electric-activated water irrigation and foliar biostimulant application on cotton growth and yield were investigated, with the aim of understanding the underlying mechanisms. The field experiment included various irrigation treatments (brackish water, fresh water, magnetic–electric brackish water, and magnetic–electric fresh water) and biostimulant concentrations (1600, 1200, 800, 400 times dilution, and no spraying). SEM analysis indicated that under magnetoelectric water irrigation, the foliar application of biostimulants enhances physiological growth of cotton, improving the water and nutrient uptake efficiency, and thereby increasing yield. Specifically, the effective boll number and single boll weight under magnetic–electric fresh water irrigation with an 800 times biostimulant concentration increased by 21.84–48.78% and 5.50–18.91%, respectively, compared to the no-spraying treatment. The seed cotton yield rose by 16.61–38.63%, water-use efficiency improved by 24.35%, the harvest index reached 0.33, and nitrogen absorption increased by 76.21%. Thus, integrating magnetic–electric water irrigation with foliar biostimulants offers a theoretical and technical foundation for advancing green, high-quality agriculture and sustainable production. [ABSTRACT FROM AUTHOR]

Soil salinisation poses a significant threat to global agricultural production and food security. China is among the countries most severely impacted by soil salinisation. To investigate the improvement technology for saline–alkali stress in buckwheat, a typical multigrain crop in northwest China, a coupling regulation study using desulfurisation gypsum and polyacrylamide (PAM) was conducted in 2019 and 2020. Desulfurisation gypsum was applied at 0, 5.5, 11, 16.5 and 22 kg·ha−1, while PAM was applied at 0, 15, 30, 45 and 60 kg·ha−1. The results demonstrated that applying 11 t·ha−1 desulfurisation gypsum and 30 kg·ha−1 PAM effectively reduces soil salinity and pH, averaging 81.79% and 6.07%, respectively. Furthermore, it did not cause soil heavy metal pollution and created the best soil environment for buckwheat growth. Among the models tested, the nonrectangular hyperbolic model was the most accurate in describing buckwheat's photosynthetic light response. The optimal treatment for achieving the best photosynthetic performance—measured by apparent quantum efficiency, maximum net photosynthetic rate, light compensation point, light saturation point, dark respiration rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, leaf water use efficiency and yield—was achieved through applying 11 t·ha−1 desulfurisation gypsum and 30 kg·ha−1 PAM. Therefore, desulfurised gypsum and PAM should be applied at 11 t·ha−1 and 30 kg·ha−1, respectively, to improve buckwheat's adaptability to different light intensities while promoting its photosynthetic response in saline–alkali soils. This study provides an effective technical scheme for reducing salt and promoting the growth of crops under salinity stress, which is of great significance for improving salinity land in arid areas. [ABSTRACT FROM AUTHOR]

In the southern Xinjiang region of China, developing efficient irrigation and fertilization strategies to enhance resource utilization and prevent desertification is of critical importance. This study focuses on jujubes in Xinjiang, China, and involves a three-year field experiment aimed at exploring the optimal application strategy of magnetically treated water combined with microbial organic fertilizer to provide scientific support for high-quality jujube production. The experiment included a control group (using only fresh water, denoted as CK) and combinations of magnetically treated water drip irrigation with varying amounts of microbial organic fertilizer: in 2021, treatments included M0 (only irrigating with magnetically treated water), M6 (0.6 t/ha), M12 (1.2 t/ha), M18 (1.8 t/ha), and M24 (2.4 t/ha); in 2022 and 2023, treatments included M0, M6 (0.6 t/ha), M12 (1.2 t/ha), M24 (2.4 t/ha), and M48 (4.8 t/ha). This study investigated the effects of magnetically treated water drip irrigation combined with microbial organic fertilizer on soil physical properties, hydraulic parameters, enzyme activity, aggregate stability, and jujube yield and quality. The application of microbial organic fertilizer significantly reduced the soil bulk density by 3.07% to 11.04% and increased soil porosity by 1.97% to 14.75%. Soil saturated hydraulic conductivity gradually decreased with the increasing amount of microbial organic fertilizer, with a reduction range of 5.95% to 13.69%, while the water-holding capacity significantly improved (from 0.217 cm3/cm3 to 0.264 cm3/cm3). Additionally, microbial organic fertilizer significantly enhanced the activities of urease, catalase, and sucrase in the soil and significantly increased the proportion of large soil aggregates. Jujube yield increased by 3.66% to 21.38%, and the quality significantly improved, as evidenced by the increase in soluble sugar and flavonoid content. The Gauss model calculation results recommended 3.09 t·hm2 as the optimal amount of microbial organic fertilizer for comprehensively improving jujube yield and quality. These findings indicate that magnetically treated water drip irrigation combined with high amounts of microbial organic fertilizer significantly improved soil physical properties, hydraulic parameters, enzyme activity, aggregate stability, and jujube yield and quality, providing scientific evidence for desert soil improvement and agricultural production. [ABSTRACT FROM AUTHOR]

The lack of trace element iron has become a key factor restricting vegetable yield and quality improvement. To address the low production efficiency of water–fertilizer coupling in agricultural production, we used a combination of experimental research, theoretical analysis, and mathematical modeling to systematically determine the effects of magneto-electric water irrigation with iron application on spinach growth and physiology, its yield and quality, and soil water transport characteristics. Compared with conventional water irrigation, under magneto-electric water irrigation, the water volume and applied iron concentration average increased the total accumulation of nitrogen, carbon, and iron in the aboveground part of spinach by 3.71%, 10.16%, and 14.14%, respectively, and the aboveground part of spinach had the highest total accumulation of nitrogen and carbon when irrigation water was 3300 m3 ha−1 and iron fertilizer application at 0.15%. Additionally, magneto-electric water irrigation increased spinach aboveground fresh weight and soluble sugar and protein content by an average of 13.34, 18.26, and 11.61%, respectively. Based on a comprehensive quantitative evaluation and analysis of aboveground nutrient accumulation in spinach, aboveground fresh weight, water use efficiency, and soluble sugar and protein content, we determined the optimal irrigation water and iron fertilizer application for spinach growth. [ABSTRACT FROM AUTHOR]

The problem of poor water and fertilizer retention in sandy soils can lead to physiological growth restriction and yield and quality decline in apples. Sodium carboxymethyl cellulose (CMC) formula can improve the soil structure and increase the water- and fertilizer-holding capacity of the soil, and Biogenic Stimulant (BS) can improve the drought stress resistance of crops and promote the physiological growth of crops. Considering that CMC and BS may improve the physiological characteristics of sandy soil apples, in this study, CMC was coupled with BS in sandy apples, and the effects on the physiological characteristics, yield, and quality of apples were systematically investigated. The results showed that CMC and BS could increase leaf N, P, and K content, with the greatest increases seen in the Y2C2 treatment (9.28, 0.61, and 0.56 g kg−1, respectively) compared with the CK treatment. The SPAD values of leaves following the coupled CMC and BS treatment compared to the CK treatment were elevated in the range of 4.47–24.29% at the flowering and fruiting stage, 2.84–26.50% at fruit expansion stage, and 6.64–19.41% at maturation stage. In the light response data of different treatments, the maximum net photosynthetic rate occurred in the Y2C2 treatment, and the net photosynthetic rate, transpiration rate, and stomatal conductance were all the highest in the Y2C2 treatment during the fruit expansion stage, with the net photosynthetic rate being higher than that of the CK treatment by 5.09 µmol m−2 s−1. The combination treatments of CMC and BS increased apple yield by 10.69 to 27.62% as compared to the CK treatment, and also increased soluble reducing sugar, soluble solids, and VC and reduced the titratable acid content. There was no correlation between the SPAD value during fruit expansion (p > 0.05) and the other physiological indexes (p < 0.05). Through the established functional relationship between the application rate of CMC and BS and apple yield, the recommended BS application rate of 27 kg ha−1 and CMC application rate of 20.625 kg ha−1 could yield up to 43,357.8 kg ha−1. [ABSTRACT FROM AUTHOR]

Water and nitrogen management are crucial for food security and the efficient use of water and fertilizer, especially in arid regions. Three irrigation levels, namely, 80% crop water requirement (ETC) (W1), 100% ETC (W2), and 120% ETC (W3), and three nitrogen application levels, namely, 0 kg/ha (N1), 207 kg/ha (N2), and 276 kg/ha (N3), were used as the experimental treatments, and a control group, denoted as CK, was created. The results show that the maximum height achieved was 82.16 cm under W3N3. There was a single-peak variation trend throughout the growth stages of SPAD. It peaked at 58.44 under W3N3 and then at 27.9 under W2N2. The net photosynthetic and transpiration rates displayed bimodal peaks and the phenomenon of a "photosynthetic midday depression". And the prominent peaks in leaf water use efficiency occurred at 14:00 and 18:00, alongside noteworthy enhancements observed under the W3 treatment. Water and nitrogen and their interactions significantly affected the dry matter (DM) of winter wheat, with the spike accounting for the highest percentage. The W2N2 treatment demonstrated superior effectiveness in enhancing winter wheat water use efficiency, offering the potential to decrease irrigation requirements by 20% and nitrogen application by 25%. Moreover, the maximum PFPN attained under W2N2 reached 60.13, representing a noteworthy 35.25% increase compared to the control group (CK), but the HI of the W2N2 treatment only reached 0.56. The highest HI was achieved with W3N2 (0.73), and the nitrogen application of 207 kg/ha was more conducive to obtaining a higher HI. The highest yield was achieved under W3N3 (13.599 t/ha), followed by W2N2 (12.447 t/ha), and the spike proportion exceeded 60% with W2N2, and its production cost and economic benefit ratio of under 0.31 were superior to those for other treatments. Multiple regression analysis revealed that the maximum yield reached 12.944 t/ha with an irrigation amount of 3420.1 m3/ha and a nitrogen application of 251.92 kg/ha. Overall, our study suggests using an optimal water–nitrogen combination, specifically an irrigation level of 2829 m3/ha and a nitrogen application rate of 207 kg/ha, leading to increased winter wheat yields and economic benefits. These research results provide a pragmatic technique for improving winter wheat production in southern Xinjiang. [ABSTRACT FROM AUTHOR]

Water scarcity and the overuse of chemical fertilizers present significant challenges to modern agriculture, critically affecting crop photosynthesis, yield, quality, and productivity sustainability. This research assesses the impact of organic fertilizer on the photosynthetic attributes, yield, and quality of pakchoi under varying irrigation water conditions, including fresh water and brackish water. Findings reveal that the modified rectangular hyperbolic model most accurately captures the photosynthetic reaction to organic fertilization, outperforming other evaluated models. The maximum net photosynthesis rate (Pnmax), yield, soluble sugar (SS), and soluble protein content (SP) all exhibited a downward-opening quadratic parabolic trend with increasing amounts of organic fertilizer application. Specifically, under fresh-water irrigation, the optimal Pnmax, yield, SS, and SP were obtained at organic fertilizer rates of 65.77, 74.63, 45.33, and 40.79 kg/ha, respectively, achieving peak values of 20.71 µmol/(m2·s), 50,832 kg/ha, 35.63 g/kg, and 6.25 g/kg. This investigation provides a foundational basis for further research into the intricate relationship between water salinity stress and nutrient management, with the goal of crafting more sophisticated and sustainable farming methodologies. The insights gained could significantly influence organic fertilizer practices, promoting not only higher yields but also superior quality in agricultural outputs. [ABSTRACT FROM AUTHOR]

In order to eliminate the limitations of traditional winter wheat yield prediction methods, the prediction models based on machine learning are used to improve the accuracy of winter wheat yield prediction. In this study, by collecting a large amount of domestic literature about wheat growth characteristics, the irrigation amount, fertilization amount, soil nutrient status, planting density, maximum leaf area index (LAImax), maximum aboveground dry matter accumulation (Dmax) and yield (Y) were chosen to develop the learning models. Using the data of the irrigation amount, fertilization amount, soil nutrient status and planting density as the training set, the regression prediction models (Gaussian process regression mode, linear regression model, regression tree mode and support vector machine model) were used to train and learn the data of the LAImax, Dmax and Y, respectively. The results show that the Gaussian regression model has the best precision compared to the other models. The coefficients of determination (R2) of the learning results of the Gaussian regression model for the LAImax, Dmax and Y are 0.9, 0.93 and 0.86, and the root mean square error (RMSE) is 0.57, 1125.1 and 640.41. Based on the data of the irrigation amount, nitrogen application amount, potassium application amount, phosphorus application amount, organic matter content, total nitrogen content, alkali-hydrolyzable nitrogen content, available phosphorus content, available potassium content and planting density, the method proposed in this paper can reliably predict the LAImax, the Dmax and Y of winter wheat. The results also have certain reference significance for the yield prediction of other crops. [ABSTRACT FROM AUTHOR]

Large-scale vegetation restoration campaigns have been implemented on the Chinese Loess Plateau, which have resulted in higher soil moisture deficits in this region. This, in turn, has hampered the healthy growth of planted trees, leading to a decline and, in severe cases, mortality of trees. Therefore, the rational regulation and utilization of rainwater, the primary water source in this region, may alleviate drought stress, ensuring the sustainability of the ecosystem. In this study, we investigated the impact of in situ rainwater collection and infiltration systems (IRCISs) on soil water, fine-root distribution, xylem vascular, and hydraulic conductivity characteristics in declining Robinia pseudoacacia forests. The results demonstrated that the application of an IRCIS can effectively increase plant available moisture content (0–5.0 m) of declining Robinia pseudoacacia forests. In particular, IRCIS treatment significantly increased xylem conduit diameter and plant hydraulic conductivity while substantially reducing the percentage loss of hydraulic conductivity in both roots and branches. Furthermore, IRCIS treatment significantly reduced the root biomass and distribution depth of Robinia pseudoacacia during both wet and dry years. This implies that IRCISs are beneficial for plant growth and survival. The findings of this study are significant for devising strategic methodologies for the planning and management of rainwater resources. [ABSTRACT FROM AUTHOR]

Introduction: Arid and semi-arid regions encompass nearly 40% of the Earth's land surface and are characterized by extensive undeveloped land, scarce water resources, and fragile ecosystems. The arid northwestern China is a representative arid and semi-arid region. It has developed rapidly in recent years, leading to a significant increase in human activity. This increased activity has had a pronounced impact on the ecosystem, posing a major challenge to the environment. The close relationship between human activities and ecosystem service value (ESV) is crucial for the healthy development of both humans and ecosystems. However, the intricate nature of this relationship and the degree to which they are codependent remain unclear and require further investigation. Methods: This study investigates the impact of human activities on land use intensity (LUI) and degree of urbanization (URB). It comprehensively evaluates the spatial and temporal distribution of human activities and ESV, quantifying their coordination through coupling models. Results: This work provides valuable insights and theoretical support for promoting the coordinated development of human activities and ESV. Overall, the LUI in the arid northwestern region decreased (from 0.485 in 2000 to 0.459 in 2020), while the URB increased (from 0.060 in 2000 to 0.087 in 2020). The ESV significantly increased, with a total growth of 556.58 billion yuan. In prefecture- level cities, the growth in ESV values ranges from 75.19 yuan/hm2 to 10,062.49 yuan/hm2.The coupling coordination degree between ESV and LUI has changed over time, transitioning from uncoordinated development to coordinated development. In addition, the coordination between ESV and URB has evolved from uncoordinated development to transitional coordination. The level of coordination between human activities and ESV in provincial capital cities significantly influences the coordination in surrounding cities. Discussion: In conclusion, effective development recommendations are provided based on the ESV, LUI, and URB of different cities, along with a proposed development strategy for ecosystem service functions that aligns with the 14th Five-Year Plan and "Vision 2035" of each province. This work provides important insights into the relationship between human activities and ESV, and its findings can be used to guide coordinated and sustainable urban development. [ABSTRACT FROM AUTHOR]

Tree species transitioning between different developmental phases requires homeostatic adjustments in order to maintain the integrity of the tree hydraulic system. Hence, adjustments related to hydraulic traits (e.g., xylem conduit diameter) are of key functional significance. However, critical information on the differences between different developmental stages is rare. Using sapwood samples from 36 black locust trees with different growth stages (actively growing and declining stages) and a soil water gradient along a hillslope, xylem conduits at stem apexes and breast height (1.3 m above ground) stems were measured. The results showed marked differences in vascular traits between actively growing and declining trees. In contrast to actively growing trees, declining trees exhibited a reduction in conduit diameters accompanied by increased frequency with a positively skewed distribution and a subsequent decline in cumulative theoretical hydraulic conductivity. Across all sampled trees, the hydraulically weighted mean conduit diameter tapered acropetally from breast height to the stem apex. The extent of conduit tapering in actively growing trees (0.244, 95% CI 0.201–0.287) aligned with predictions from the hydraulic optimality model. Conversely, trees in a declining status displayed significantly reduced conduit tapering (0.175, 95% CI 0.146–0.198), indicating an elevation in hydraulic resistance with increasing tree height. Variations in hydraulic properties predominantly resulted from differences in tree height rather than variations in stem diameter or soil water content. The correlation between conduit diameter and soil water content in both actively growing and declining trees stemmed indirectly from variations in tree height rather than presenting a direct response to drought stress. [ABSTRACT FROM AUTHOR]