Study On The Young Spike And Caryopsis Development Of Rice Under High Temperature Stress

Rice,one of the most crucial food resources in the world,is consumed by more than half of the global population.Under the premise of explosive population growth,people pay more and more attention to the yield and the quality of rice.However,global warming would affect the development of rice at different growth stages,decreasing rice yield and deteriorating grain quality.Rice can be divided into indica rice and japonica rice.Different types of rice have various responses to high temperature.In order to clarify high temperature effects at different periods on the growth of different types of rice,pot experiments were conducted in 2017 and 2018.Rapid viscosity analyzer,FTIR and NMR spectroscopy were applied to investigate the high temperature effects at panicle stage on the development of indica rice and at grain filling stage on that of japonica rice.The changes of physicochemical properties of rice starch under high temperature stress were studied by analytical techniques.The key results are as followings:1.High temperature stress at pollen filling stage during the young panicle differentiation period had a significant effect on the development of young panicle of indica rice,which was mainly manifested as promoting the early development and accelerating the differentiation process of young panicle,obstructing the pollen enrichment process under high temperature stress,and insufficient pollen grain deformation or accumulation.2.Compared with rice under normal temperature,high temperature-stressed rice showed accelerated growth rate,smaller caryopsis and decreased yield,along with lower apparent amylose content,resulting in higher order degree,gelatinization temperatures,and increased peak,trough and final viscosities in starch.3.High temperature during primordial differentiation stage inhabited cell development and starch deposit,leading to smaller starch granule and lower retrogradation,whereas that during pollen filling stage increased starch accumulation and granule size.4.High temperature during grain filling period inhibited the overall growth of japonica rice,reduced the seed setting rate,1000-grain weight and other agronomic traits,meanwhile promoted the early development of rice caryopsis.This study showed that high temperature effects at different stages of panicle on caryopsis development and starch properties of indica rice were partly similar,but also significantly different.The high temperature during the filling period leads to the deformation of japonica rice pollen grains,thus reducing the yield of mature rice.The findings will not only promote in-depth study of high temperature-stressed rice,but also provide an important basis for rice starch production and utilization.