Rice Genomics and Genetics 2024, Vol.15, No.1, 36-47 http://cropscipublisher.com/index.php/rgg 37 and threaten the stability of chloroplasts. It will study how rice resists through antioxidant enzymes and antioxidant substances. oxidative stress to maintain cellular homeostasis. Through transcriptomic research, we can understand the gene expression patterns of rice under high temperature stress, especially genes related to photosynthesis and antioxidant systems, which helps to identify potential high temperature resistance genes and provides a basis for breeding improvement. In addition, this study will also propose a series of potential strategies to improve high temperature stress resistance in rice, which include methods of plant breeding and genetic improvement, suggestions for agricultural management practices, and new technologies and innovative methods in improving high temperature stress resistance in rice. By deeply studying the physiological mechanisms of rice under high temperature stress, we can better understand its adaptability and resistance. This research is critical to ensuring the stability and sustainability of global food supplies, while also helping to address the challenges of climate change to the agricultural industry. We expect this review to provide valuable insights and directions for solving the problem of high temperature stress in rice. 2 Physiological Response of Rice to High Temperature Stress 2.1 Effects of high temperature stress on rice growth and yield High temperature stress is one of the main factors that decreases rice yield. Under high temperature conditions, the development of the reproductive organs of rice is inhibited, including the formation of inflorescences and spikelets, the development of pollen, and the fertilization process. Impairment of these reproductive processes directly results in a reduction in grain quantity and quality. In addition, high temperatures can also cause abnormal development of embryos, endosperm and ovules, further reducing the yield per ear. High temperature stress can also cause premature plant senescence, resulting in immature grains. The combined impact of these factors has led to a significant decline in rice yields, posing a major challenge to agricultural systems and global food supply (Pickson et al., 2021). High temperature stress can shorten the growth period of rice. Generally, high temperature accelerates the growth and development process, but it also reduces the quality and function of reproductive organs. According to research, the maximum temperature exceeding 35 °C is the temperature causing high temperature stress in rice. Among the 17 days of high temperature treatment, the maximum temperature exceeded 35 ℃on 14 days, and the maximum temperature exceeded 40 ℃on 9 days. The average daily maximum temperature of high temperature treatment reached 40.16 ℃, while the average daily maximum temperature of normal temperature control was 30.6℃(Figure 1) (Miao et al., 2017). Sterility and early seedling growth are major components of seedling vigor. Prolonged temperature increases reduce the germination potential of seeds, resulting in reduced germination rates and seedling vigor (Figure 2). The optimal growth temperature for rice in the seedling stage is 25~28 °C. Heat stress (42~45 °C) in the seedling stage will cause increased water loss, yellowing of leaves, damage to seedling and root growth, and even death of seedlings. The resistance of rice to HS in the seedling stage varies with different genetic backgrounds. After exposure to HS (45 °C for 72 h), seedlings of the japonica rice variety Nipponbare almost completely withered, whereas seedlings of the indica rice variety HT54 could tolerate up to 48°C for 79 h. Plants treated with HS at the tillering stage showed various morphological symptoms, such as leaf wilting, curling and yellowing, and reduced tiller number and biomass. Under HS (40 °C day/35 °C night) for 15 days, the panicle number and total yield per plant of rice were about 35% lower than those under 28 °C. The impact of HS on tillers and panicle number in japonica rice is more serious than that in indica rice. The number of tillers under HS is often used as a marker for selecting heat-tolerant rice varieties (Xu et al., 2021).
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