Rice Genomics and Genetics 2024, Vol.15, No.1, 36-47 http://cropscipublisher.com/index.php/rgg 43 4.2 Accumulation of antioxidant substances and protection of chloroplasts from oxidative damage In the context of high temperature stress in rice, plants respond to oxidative stress by accumulating antioxidant substances, thereby protecting chloroplasts from oxidative damage. Ascorbic acid (a scorbate, Asc) is a key antioxidant substance. The content of ascorbic acid in rice increases significantly under high temperature stress. Ascorbic acid, as a non-enzymatic antioxidant, can directly neutralize reactive oxygen species and prevent oxidative damage to chloroplasts. Experimental data show that the increase in ascorbic acid content in rice leaves after high temperature treatment is closely related to slowing down lipid peroxidation of the chloroplast membrane and maintaining the stability of the chloroplast structure (Lee et al., 2000). Another important antioxidant substance is glutathione (GSH). Studies have found that under high temperature stress conditions, the accumulation of glutathione in rice also shows an upward trend. Glutathione participates in the reduction of oxidized proteins. For example, reduced glutathione removes intracellular hydrogen peroxide by reducing the activity of catalase, thus protecting chloroplasts from oxidative stress damage. Experimental data show that the increase in glutathione content in rice leaves under high temperature stress is closely related to maintaining the integrity of the chloroplast membrane and the oxidation degree of antioxidant proteins. The accumulation of these antioxidant substances is closely related to their protective role in rice against high temperature stress. By maintaining intracellular redox balance and reducing the damage caused by oxidative stress, it provides key support for the physiological adaptability of rice. An in-depth understanding of the regulatory mechanisms of these antioxidant substances is expected to provide a theoretical basis for improving rice resistance to high temperature stress. 4.3 Response mechanism of antioxidant system to high temperature stress Under high temperature stress, rice regulates antioxidant enzyme activity to remove excess reactive oxygen species and maintain intracellular red oxygen balance. Among them, enzymes such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) play key roles in this process. Experimental results show that the activities of these antioxidant enzymes in rice leaves significantly increased after high temperature treatment, thereby enhancing resistance to oxidative stress (Pang et al., 2021). Rice responds to oxidative stress by increasing the accumulation of antioxidant substances under high temperature stress conditions. For example, the levels of glutathione (GSH) and ascorbic acid (Asc) increased significantly. These antioxidant substances can neutralize reactive oxygen free radicals and reduce oxidative damage. Experimental data showed that the contents of GSH and Asc in rice leaves after high temperature treatment were significantly increased compared with the control group, indicating a positive response to antioxidant stress (Table 2). Table 2 Changes in antioxidant content of rice leaves under high temperature stress Processing Group Glutathione content (μmol/g fresh weight of leaves) Ascorbic acid content (μmol/g fresh weight of leaves) Control group 8.2 2.5 High temperature treatment group 15.6 5.83.2 High temperature treatment group 10.3 3.2 Together, these examples and data reveal the response mechanism of the rice antioxidant system to high temperature stress. By regulating antioxidant enzyme activity and accumulating antioxidant substances, rice can maintain intracellular redox balance and reduce oxidative damage under high temperature conditions. Provides important physiological support for survival in inhospitable climatic environments. This in-depth understanding provides a theoretical basis for cultivating rice varieties with greater resistance to high temperatures in the future. 5 Potential Strategies to Improve Resistance to High Temperature Stress in Rice 5.1 Methods of plant breeding and genetic improvement In order to improve the resistance of rice under high temperature stress conditions, scientists and agricultural researchers use a variety of methods, including traditional breeding, molecular marker-assisted breeding, gene
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