Translocation and Distribution of Carbon-Nitrogen in Relation to Rice Yield and Grain Quality as Affected by High Temperature at Early Panicle Initiation Stage

Abstract

Due to climate change, extreme heat stress events have become more frequent, adversely affecting rice yield and grain quality. Accumulation and translocation of dry matter and nitrogen substances are essential for rice yield and grain quality. To assess the impact of high temperature stress (HTS) at the early panicle initiation (EPI) stage on the accumulation, transportation and distribution of dry matter and nitrogen substances in organs, as well as its effects on rice yield and grain quality, pot experiments with indica rice Yangdao 6 (YD6) and japonica rice Jinxiangyu 1 (JXY1) were conducted under normal temperature (NT, 32 ºC / 26 ºC) and HTS (38 ºC / 29 ºC). The results indicated that exposure to HTS at the EPI stage significantly decreased rice yield by reducing spikelet number per panicle, grain filling rate and grain weight. In addition, it improved the nutritional quality of rice grains by increasing protein and amylose contents. The reduction in nitrogen and dry matter accumulation accounted for the changes in spikelet number per panicle, grain filling rate and grain size. Under HTS, the decrease in nitrogen accumulation accompanied by the reduction in dry matter may due to the down-regulation of leaf net photosynthesis and senescence as evidenced by the decrease in nitrogen content. Furthermore, the decrease in sink size limited the translocation of dry matter and nitrogen substances to grains, which was closely related to the reduction in grain weight and deterioration of grain quality. These findings contribute significantly to our understanding of the mechanisms of HTS on grain yield and quality formation from the perspective of dry matter and nitrogen accumulation and translocation. Further efforts are needed to improve the adaptation of rice varieties to climate change in near future.

Topics & Concepts