College of Agronomy and Biotechnology, China Agricultural University, Beijing, China.
College of Agronomy, South China Agricultural University, Guangdong, China.
Plant Commun. 2023 Nov 13;4(6):100629. doi: 10.1016/j.xplc.2023.100629. Epub 2023 May 23.
Heat waves induced by climate warming have become common in food-producing regions worldwide, frequently coinciding with high temperature (HT)-sensitive stages of many crops and thus threatening global food security. Understanding the HT sensitivity of reproductive organs is currently of great interest for increasing seed set. The responses of seed set to HT involve multiple processes in both male and female reproductive organs, but we currently lack an integrated and systematic summary of these responses for the world's three leading food crops (rice, wheat, and maize). In the present work, we define the critical high temperature thresholds for seed set in rice (37.2°C ± 0.2°C), wheat (27.3°C ± 0.5°C), and maize (37.9°C ± 0.4°C) during flowering. We assess the HT sensitivity of these three cereals from the microspore stage to the lag period, including effects of HT on flowering dynamics, floret growth and development, pollination, and fertilization. Our review synthesizes existing knowledge about the effects of HT stress on spikelet opening, anther dehiscence, pollen shedding number, pollen viability, pistil and stigma function, pollen germination on the stigma, and pollen tube elongation. HT-induced spikelet closure and arrest of pollen tube elongation have a catastrophic effect on pollination and fertilization in maize. Rice benefits from pollination under HT stress owing to bottom anther dehiscence and cleistogamy. Cleistogamy and secondary spikelet opening increase the probability of pollination success in wheat under HT stress. However, cereal crops themselves also have protective measures under HT stress. Lower canopy/tissue temperatures compared with air temperatures indicate that cereal crops, especially rice, can partly protect themselves from heat damage. In maize, husk leaves reduce inner ear temperature by about 5°C compared with outer ear temperature, thereby protecting the later phases of pollen tube growth and fertilization processes. These findings have important implications for accurate modeling, optimized crop management, and breeding of new varieties to cope with HT stress in the most important staple crops.
气候变化引起的热浪在世界范围内的粮食产区已变得普遍，常与许多作物的高温（HT）敏感阶段相吻合，从而威胁到全球粮食安全。了解生殖器官对 HT 的敏感性对于提高结实率具有重要意义。种子结实对 HT 的响应涉及雄性和雌性生殖器官中的多个过程，但我们目前缺乏对世界三大主要粮食作物（水稻、小麦和玉米）这些响应的综合和系统总结。在本研究中，我们定义了开花期水稻（37.2°C ± 0.2°C）、小麦（27.3°C ± 0.5°C）和玉米（37.9°C ± 0.4°C）种子结实的临界高温阈值。我们评估了这三种谷物从花粉期到滞后期的 HT 敏感性，包括 HT 对开花动态、小花生长和发育、授粉和受精的影响。我们的综述综合了现有关于 HT 胁迫对小穗张开、花药开裂、花粉散落数、花粉活力、雌蕊和柱头功能、花粉在柱头上的萌发以及花粉管伸长的影响的知识。HT 诱导的小穗闭合和花粉管伸长停止对玉米的授粉和受精有灾难性影响。由于底部花药开裂和闭花授粉，水稻在 HT 胁迫下受益于授粉。闭花授粉和二次小穗张开增加了小麦在 HT 胁迫下授粉成功的可能性。然而，谷类作物本身在 HT 胁迫下也有保护措施。与空气温度相比，冠层/组织温度较低表明，谷类作物，特别是水稻，可部分免受热损伤。在玉米中，苞叶叶片使内穗温度比外穗温度低约 5°C，从而保护花粉管生长和受精过程的后期阶段。这些发现对准确的模型、优化的作物管理和培育新的品种以应对最重要的主食作物的 HT 胁迫具有重要意义。
