Photosynthetic Response and Yield Formation Mechanisms of Rice Under Warming at Different Growth Stages in Cool Region.

The environmental temperature of rice in cool region varies greatly at the whole growth stage, and studies on warming at different stages are still rare. In this study, we set up warming treatments at six growth stages of rice in cool region: the before heading stage (T1), the whole growth stage (T2), the grain-filling stage (T3), the early grain-filling stage (T4), the middle grain-filling stage (T5), the late grain-filling stage (T6). The change trend of the yield of each treatment in 2019–2020 was the same. Among them, T1, T2, T3 and T5 increased significantly by 13.2%, 9.4%, 6.9% and 6.3%, respectively; T6 increased by 2%; T4 decreased significantly by 4.8%. The yield and inferior grains (IG) yield had a significant positive correlation with LAI at each stage. All warming treatments had a positive effect on A max to varying degrees at grain-filling stage. Among the photosynthetic parameters that affect A max under the warming treatment, g m and J max played a major role, V c , max and g s played a minor role, and R d had no effect on A max . Furthermore, g m was the most important factor that affected A max , and the correlation coefficients at the panicle initiation stage, the heading stage, the middle grain-filling stage and the late grain-filling stage were 0.88, 0.784, 0.639 and 0.932, respectively. These results suggested warming at most growth stages of rice in cool region would be beneficial to photosynthesis and promote the yield accumulation. However, it was adversely affected by the short-term warming at the early grain-filling stage of rice. [ABSTRACT FROM AUTHOR]