种子是高等植物特有的繁殖和储存器官，决定着物种延续，而种子又是人类和动物食物结构的重要组成部分。因此关于植物种子发育尤其是种子大小的研究一直以来都是植物学研究的热点问题。对于植物而言，种子的大小对植物生态适应性至关重要；而在农业生产中，种子大小则是决定粮食产量的重要因素之一。近年来，对于植物种子大小的调控网络有了一定的阐述，但关于外部环境如何影响种子大小缺少研究。我们前期工作发现，光周期显著影响拟南芥种子的大小，进一步研究发现响应光周期的关键因子CONSTANS(CO)直接影响种子大小，这为我们深入揭示光周期如何影响种子的发育提供了切入点。在此基础上，本项目将探讨：(1) 光周期及其响应因子CO在种子发育中的重要功能，(2)CO调控种子大小的具体分子机制，以促进对植物种子大小调控机制的认知，同时为农业生产中作物改良、粮食产量的提高提供潜在的理论依据。

Seed is a special reproductive and storage organ of higher plants, which determines the continuation of species. Therefore, the research on seed development especially on seed size has always been a hot topic in botany. For plants, the size of seeds is crucial to the ecological adaptability of plants. In agricultural production, seed size is one of the important factors that decide grain yield. Seed development is a very complex and delicate process. In recent years, the regulation network of plant seed size has been uncovered to some extent, but there are few reports on how the external environment affects the seed size. we found that photoperiod significantly affected the seed size of Arabidopsis, and further research found that the key factor CONSTANS(CO) in response to photoperiod directly affected the seed size, which provided a breakthrough point for us to further reveal how photoperiod affected the seed development. On this basis, this project will explore the important function of photoperiod response factor CO in seed development, and reveal the detailed molecular mechanism of CO-regulated seed size, so as to promote the understanding of the mechanism of plant seed size regulation, and provide potential theoretical basis for crop improvement and grain yield improvement in agricultural production.