Effect of drought stress on plant morphological traits and dry matter accumulation of various super rice varieties

With pot-cultivation and drought stress simulation from the panicle initiation to grain filling stage,the effect of drought stress on plant morphological traits and dry matter accumulation of different panicle type rice varieties(more or middle grains per panicle) was studied.The moisture content in soil was monitored by using a W.E.T Sensor(ML2x type) and an electronic balance.The results showed that a moderate drought stress in different stages had varying degrees of influence on the plant morphological traits and dry matter accumulation.The drought stress affected more on the biomass in 15-30d after panicle initiation and 0-15d after flowering,followed by 0-15d after panicle initiation and 15-30d after flowering.Moderate drought stress during panicle initiation affected panicle development and inhibited the elongation of the flag leaf and the 2nd leaf from top.This led to a reduced leaf photosynthesis and plant height.Moderate drought stress during panicle initiation and grain filling also resulted in reduction of biomass and dry matters,as compared to normal water supply.Sensitivity to drought stress varied among different varieties.Thus,the degree of change on plant morphological characteristics and dry matter accumulation differed among them.In general,the effects on super rice varieties were less than those on common hybrid rice variety(e.g.,Shanyou 63).On the rice varieties with more grains per panicle(e.g.,Guodao 6 and Liangyoupeijiu),influence of drought stress on plant morphological traits and dry matter accumulation was less than the rice varieties with less grains per panicle(e.g.,II-you 602 and Tianyou 998),indicating the changes were variety-specific.