Rice Genomics and Genetics 2024, Vol.15, No.1, 19-27 http://cropscipublisher.com/index.php/rgg 24 conditions, the leaf water content of Yangdao 6 and Shanyou 63 did not significantly decrease under 10% PEG drought stress, but significantly decreased under 20% and 30% drought stress. They decreased by 5% and 2% under 20% PEG stress, and by 7% and 6% under 30% PEG stress, respectively. Both under normal water conditions and drought stress, the water content of Yangdao 6 is lower than that of Shanyou 63 (Figure 3). Figure 3 Effects of drought stress on leaf water content (Adopted from Ding et al., 2014) Leaves may activate signal transduction pathways under drought conditions to more effectively transmit drought signals. Signal transduction pathways are a series of complex biochemical and molecular events that involve interactions between molecules such as protein kinases, kinase substrates, and transcription factors. In leaves, dehydration hormone signaling pathways, protein kinase cascade reactions, and other key signaling networks may be involved. The activation of these signal transduction pathways helps plants perceive drought signals more quickly and trigger corresponding physiological and biochemical responses to improve their drought resistance. These molecular level leaf response mechanisms provide strong support for the survival of rice under drought stress. By regulating gene expression and activating signal transduction pathways, rice leaves can more flexibly cope with drought stress, achieving survival and growth in arid environments. A deep understanding of these molecular level regulatory mechanisms will provide a crucial scientific basis for developing rice varieties with stronger drought resistance and formulating agricultural management strategies. 4 Compare the Differences in Response Between Roots and Leaves 4.1 Differences in morphological structure between roots and leaves When rice faces drought conditions, its roots and leaves exhibit significant morphological differences, which play an important role in the plant's adaptability to drought. Firstly, from the comparison of morphological structures, the root system and leaves exhibit different adjustment strategies under drought conditions. In terms of root system, rice may exhibit more significant morphological changes. Under drought stress, the main changes in the root system include an increase in root length, adjustments in the number of lateral roots, and changes in the growth and distribution of root hairs. These adjustments help the root system to explore soil moisture more deeply and increase the surface area for absorbing water and nutrients. In contrast, the morphological changes of leaves are relatively small, which may mainly manifest as wrinkling, curling, or reduction of leaves to reduce transpiration and water loss. The morphological differences between roots and leaves directly affect the performance of plants in drought resistance. For example, under drought conditions, rice roots typically increase in length to search deeper for water sources in the soil. In addition, it may increase the number and length of lateral roots to expand the water absorption area. The root system may enhance the water absorption capacity of the soil by adjusting the density and length of root hairs. At the same time, the adjustment of leaf morphology reduces water transpiration and reduces water loss. This synergistic adjustment of roots and leaves can be seen as a stress response of plants in the face of drought stress (Sarabi et al., 2019).
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