Rice Genomics and Genetics 2024, Vol.15, No.1, 1-11 http://cropscipublisher.com/index.php/rgg 6 The study also found that changes in pollen particle size caused by high temperatures may affect the buoyancy and propagation distance of pollen. Smaller pollen grains are subject to greater air resistance in wind or insect transmission, which may lead to a reduction in their drift distance. This may affect the effective dissemination and pollination range of pollen, ultimately reducing the fertilization rate and yield of rice. When rice is exposed to high temperature conditions, the average diameter of pollen grains significantly decreases, which is related to the decrease in protein content in pollen cells. The decrease in protein may lead to the relaxation of cell membranes and the reduction of pollen grain volume. This result suggests a direct regulatory effect of high temperature on the size of rice pollen grains. The impact of high temperature stress on the size of rice pollen grains often involves multiple aspects of cell physiology and morphology regulation, which may have far-reaching effects on the fertilization process and yield of rice. In depth research on the regulatory mechanism of high temperature on pollen morphology and structure can help to better understand the physiological response of rice in the face of climate change, provide scientific basis for cultivating high-temperature resistant rice varieties, and maintain global food security. 3 The Effect of High Temperature on Rice Pollination 3.1 The impact of pollination success rate High temperature stress is a major challenge in the context of global warming, which has a direct impact on the growth and reproduction of important crops such as rice. Among them, the success rate of pollination is one of the key factors affecting rice yield. The impact of high temperature on the success rate of rice pollination mainly involves two aspects. Firstly, high temperatures may directly affect the cracking process of anthers. Anther cracking is a crucial step in pollen release, and high temperature stress may lead to dehydration of anther cells and degeneration of cell membranes, preventing normal anther cracking and limiting pollen release. Secondly, the impact of high temperature on pollen vitality is another important reason for the decrease in pollination success rate. High temperature may cause denaturation and oxidation of pollen proteins, leading to damage to the structure and function of pollen particles. This weakens the ability of pollen to spread during pollination, reducing the likelihood of binding to the stigma and fertilization. Through case studies, we can gain a deeper understanding of the specific mechanism by which high temperatures affect the success rate of rice pollination. The spring and summer hybrid rice seed production often encounters high temperature weather during the flowering and pollination period, which has a serious impact on flowering and pollination. The basic conditions for a safe flowering and pollination period are summarized as follows: the daily average temperature is not continuously below 21 ℃or above 35 ℃for 3 days, and the temperature at the panicle during flowering is not continuously below 24 ℃or above 35 ℃for 3 days, with the most suitable temperature being 28 ℃; If the relative humidity is below 75% or above 90% for 3 consecutive days, the most suitable is 85%. However, there is a negative correlation between humidity and temperature. According to observations, the relative humidity of the ear at 35 ℃is only 75% (Zhao et al., 2023). It indicates that the success rate of rice pollination generally decreases under high temperature conditions. Meanwhile, high temperatures may hinder anther cracking, reduce pollen vitality, and even have adverse effects on the morphology and structure of pollen particles, thereby affecting the effectiveness of pollination. It can be seen that the impact of high temperature stress on the success rate of rice pollination is complex and multifaceted. By studying the specific mechanisms of high temperature on anther cracking and pollen vitality, we can gain a deeper understanding of the vulnerability of rice reproductive systems under high temperature stress. This helps to provide scientific basis for cultivating high-temperature resistant rice varieties to ensure the sustainability of agricultural production under constantly changing climate conditions.
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