Triticeae Genomics and Genetics, 2025, Vol.16, No.4, 156-165 http://cropscipublisher.com/index.php/tgg 159 4 Mechanistic Insights and Physiological Responses 4.1 Root development and water uptake efficiency Wheat roots are responsible for absorbing water and are a key part of water use. The role of the root system is particularly evident under different irrigation frequencies and drought conditions. Drought-tolerant wheat varieties usually grow thicker and larger roots. These roots can grow and absorb water better, and can also activate genes related to carbon metabolism and hormone signaling, thereby enhancing drought resistance (Hu et al., 2018). Root shape and structure, such as lateral root length and number of root tips, are directly related to water absorption efficiency. Using molybdenum fertilizer can make roots grow better, such as making roots more permeable to water, and can also increase the expression of water channel proteins, thereby enhancing water absorption capacity. The method and time of irrigation can also affect root distribution. If irrigation is more frequent, there will be more roots in the upper soil layer and the ability to absorb water will also be stronger (Jha et al., 2017). In addition, wheat with long root hairs and heavy root sheaths can also absorb water more easily and help control water evaporation. 4.2 Leaf morphology and transpiration The coordination between leaves and roots also affects how water is used, especially during droughts or when there is little water. Sometimes wheat grows thinner roots to improve water absorption efficiency. Stable isotopes in leaves can be used to determine the current water status and transpiration rate of the plant (Brunel-Saldias et al., 2020). Studies have found that using molybdenum fertilizer can reduce leaf transpiration and allow roots to absorb more water, indicating that the direction of water flow has changed, and water is more concentrated in the roots for use rather than evaporating from the leaves (Wu et al., 2019). In addition, the relationship between some substances secreted by the roots and the surrounding microorganisms will also affect soil water retention, and these factors will also change the transpiration process (Rabbi et al., 2021). 4.3 Hormonal and molecular signals Plants use hormones to regulate their response to water. One of the most important is abscisic acid (ABA). When the soil dries out, the roots sense it and produce ABA. This hormone travels to the leaves, closing the stomata, which reduces water loss and helps the plant save water during later droughts (Saradadevi et al., 2017). Drought-tolerant wheat generally has stronger protective mechanisms, such as stronger antioxidant capacity and more active hormones related to root growth (Hu et al., 2024). There is also a substance called nitric oxide, which is also involved in regulating root development and enhancing water absorption during drought, and these regulations may also be affected by the trace element molybdenum (Wu et al., 2019). From a molecular perspective, some transcriptome and metabolome studies have found that drought-tolerant wheat activates some special pathways, such as synthesizing flavonoids, osmoprotectants, and enhancing energy metabolism. These changes can help roots grow better and cope with drought. 5 Agronomic and Environmental Considerations 5.1 Yield stability under different irrigation schemes Many studies have shown that wheat yield and water use efficiency (WUE) can be kept stable or even improved if irrigation time is chosen appropriately and water use is well controlled (Gao et al., 2022). This method will be even more effective if variety improvement is combined. Even in years with significant climate change, timely irrigation before sowing, during jointing or flowering can keep yields on track and reduce yield differences between years. In some places where water is scarce, appropriate reduction in water use (called "deficit irrigation") can increase WUE, and will have little impact on yield if soil conditions are suitable (Yu et al., 2020). In addition, combining scientific fertilization with water-saving irrigation can further improve yield stability and resource utilization efficiency (Huang et al., 2024). 5.2 Soil health and sustainability To ensure sustained high wheat yields, the soil must be kept healthy. Reducing irrigation and applying fertilizers properly are effective methods. For example, controlling the amount of water and combining it with appropriate nitrogen fertilizers can make the soil healthier, reduce nitrogen loss, and reduce pollution to the environment (Xu
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