Rice Genomics and Genetics 2024, Vol.15, No.1, 19-27 http://cropscipublisher.com/index.php/rgg 21 2023) Therefore, while studying the adjustment of rice root structure, it is necessary to deeply understand the balance relationship between root sheath formation and biomass. This helps to comprehensively evaluate the adaptive strategies of rice under drought conditions and provides guidance for future breeding work and agricultural management. By conducting in-depth research on these physiological and morphological changes, we can better understand the ecological adaptability of rice under drought stress, providing scientific support for improving its drought tolerance. The growth adaptation strategy of the root system also involves adjusting the vertical and horizontal distribution of the root system. When there is more water in the deep soil, rice roots may grow deeper to better utilize potential water sources. On the contrary, in situations where the surface soil moisture is relatively abundant, the root system may be more distributed in the surface to quickly absorb available water. This dynamic adjustment helps rice to more flexibly utilize water resources in the soil under drought conditions. Rice roots exhibit multi-level structural adjustments and growth adaptation strategies when facing drought stress. These adjustments aim to optimize water absorption, improve water use efficiency, and enable plants to better adapt to arid environments. A deep understanding of the changes in root morphology and growth adaptation strategies is of great significance for developing drought resistant rice varieties and formulating agricultural water management policies. 2.2 Root physiological response Rice roots exhibit complex and coordinated physiological responses under drought conditions, with important aspects including root water absorption and regulation of nutrients. Under drought stress, rice roots maintain growth and survival by adjusting water absorption and nutrient uptake. It is crucial for rice roots to regulate water absorption under drought conditions. In order to adapt to the water scarce environment in the soil, the roots may optimize water absorption by adjusting the growth and distribution of root hairs. In addition, rice may adjust the osmotic pressure inside and outside the cells to adapt to different soil moisture conditions by regulating the osmotic regulation mechanisms of the root system, such as the synthesis and secretion of osmotic regulating substances. These physiological responses help rice maintain water balance more effectively under drought conditions, ensuring normal growth and development. The antioxidant system plays a crucial role in the drought response of rice roots. Due to oxidative stress caused by drought conditions, the root system may experience the accumulation of reactive oxygen species such as oxygen free radicals, leading to lipid peroxidation of cell membranes and protein oxidative damage. To combat this oxidative stress, rice roots activate the antioxidant system, including enzymes such as superoxide dismutase (SOD), peroxidase (POD), and ascorbic acid peroxidase (APX). The increased activity of these enzymes helps to clear intracellular reactive oxygen species, maintain cellular redox balance, and thus slow down or alleviate oxidative damage to roots (Bouabdelli et al., 2022). During this process, the physiological response of rice roots is not only a stress-induced adjustment, but also a survival strategy to combat drought stress. By regulating water absorption and nutrient uptake, as well as activating the antioxidant system, rice roots exhibit strong adaptability under drought conditions, providing physiological support for their survival and growth in harsh environments. A deeper understanding of the mechanisms underlying these root physiological responses can provide a theoretical basis for developing drought resistant rice varieties and offer more sustainable solutions for agricultural production. 2.3 Molecular level root response The molecular level response of rice roots is a key link in their resistance to drought stress, involving changes in gene expression and regulation of water channel genes. A deeper understanding of these molecular level reactions can help reveal the adaptive mechanisms of rice under drought conditions. Under drought stress, the gene expression in rice roots undergoes significant changes. This change is a direct response to environmental pressure, and by adjusting the expression levels of specific genes, plants can better adapt to arid environments. Some genes
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