种子引发处理对旱直播水稻种子萌发和幼苗生长的影响及其机理研究

The shortage of rural labors and too much water requirement are two constraints to rice production in China. A new technology, "dry direct-seeded rice" has been developed to reduce water input, save labor demand, and be liable to mechanization. Dry direct-seeded rice technology is also one of the best options for stabilizing rice planting area and improving rice production during the transitional period of rice cultivation technology. However, poor stand establishment is the major constraint to the high and stable yield of dry direct-seeded rice in large cultivation areas with mechanization. One of the main reasons for the poor stand establishment is uneven soil surface and sowing depth, which results in seeds sown in different depth experienced different water conditions. A lot of study revealed that seed priming significantly reduced mean germination time and increased germination percentage, germination index, seedling vigor index, and stress resistance. Few researches focus on seed priming in traditional irrigated rice because the crop establishment of traditional irrigated rice is nursing seedlings and transplanting. Seed priming may be one of the promising strategies to resolve poor stand establishment of dry direct-seeded rice. The aims of our proposed project are (1) to explore the best priming conditions for dry direct-seeded rice and the mechanisms; (2) to identify the appropriate seeding rate after seed priming for different rice varieties; (3) to examine the minimum threshold for soil water content under which primed seeds can germinate; (4) to identify the genotypic variations in responses to seed priming among different rice varieties and the mechanisms. The output of the proposed project will provide a scientific basis for ensuring good stand establishment for dry direct-seeded rice under mechanization.

农村劳动力短缺和用水量过大是我国水稻生产的重要限制因素。水稻旱直播是一项新型高效省工、节水和易于机械化的栽培技术，也是当前水稻生产技术转型期稳定种植面积、提高产量的优选技术之一。然而，成苗率低和出苗不整齐是旱直播水稻高产和稳产的关键制约因子。究其原因主要为田面不平整，播种深度不均匀而使种子所处的水分条件不同。在很多植物上的研究表明，种子引发处理可以显著提高出苗速度、出苗率和整齐度, 而且能增强种子抗逆性。由于常规的水稻种植系统采用育秧移栽，种子引发在水稻上的研究相对较少。种子引发处理有可能是解决旱直播水稻成苗率低和出苗不整齐问题的有效措施。本项目旨在探索适宜旱直播的最佳引发条件及其机理，探明引发处理后种子萌发出苗所需的土壤含水量最低阈值，阐明不同类型水稻品种对种子引发反应的基因型差异及其机理，确定不同类型水稻品种引发后的适宜播种量，为确保机械化旱直播条件下一播全苗提供理论依据和技术指导。

农村劳动力短缺和用水量过大是我国水稻生产的重要限制因素。水稻旱直播是一项新型高效省工、节水和易于机械化的栽培技术。然而，成苗率低和出苗不整齐是旱直播水稻高产和稳产的关键制约因子。在很多植物上的研究表明，种子引发处理可以显著提高出苗速度、出苗率和整齐度, 而且能增强种子抗逆性。因此，本项目围绕种子引发在旱直播水稻上的应用及作用机理进行了系列研究，主要研究结果如下：一、筛选出了适宜旱直播的最佳引发剂、引发浓度、引发时间和引发处理后适宜的播种量，并在低温、渍水、干旱胁迫等逆境条件下对引发处理促进旱直播水稻早生快发的作用效果进行了验证，结果表明不同逆境胁迫下，引发处理显著提升了旱直播水稻的发芽速度和发芽率，促进了水稻幼苗的生长。二、探究了引发处理促进旱直播水稻种子早生快发的作用机理，试验结果表明逆境条件下，引发处理显著上调了水稻种子赤霉素合成基因的相对表达量、下调了脱落酸合成基因的相对表达量，诱导相应α淀粉酶酶基因显著表达，从而显著提升了旱直播水稻萌发过程中的α淀粉酶活及可溶性糖含量。同时，引发处理加速了种子萌发过程中线粒体和细胞器的修复和再合成过程，从而有效提高了呼吸作用。此外，逆境胁迫下，引发处理通过提升相关抗氧化酶活性并抑制丙二醛的积累降低了水稻种子萌发过程中膜脂过氧化的程度。总体而言，逆境胁迫下引发处理促进旱直播水稻的早生快发主要是通过加速水稻种子萌发过程的呼吸作用和淀粉代谢过程，同时增强抗逆性来实现的。三、研究了引发水稻种子的最适贮藏环境和贮藏时间，结果表明引发过的水稻种子放在室温条件15天以上便会丧失活性，而低温、真空、低湿贮藏则可以有效延长引发稻种的贮藏时间。四、将种子引发与丸粒化技术结合进行了系列研究，筛选出了适宜直播的丸粒化配方并探明了其作用机理。本项目为种子引发在旱直播上的应用提供了基础支撑，并为确保机械化旱直播条件下一播全苗提供了理论依据和技术指导。