Studies On The Physiological Basis And Regulation Of Preharvest Sprouting In Rice

Preharvest sprouting is seed germination in the spike suffering successive high-temperature-damp climate before harvest. During seed production in hybrid rice, preharvest sprouting is one of the main restricting factors for yield and quality. Seed germination, preharvest sprouting and their related physiological and biochemical characteristic were studied by using two rice varities as the experimental materials with different preharvest sprouting abilities. Effect of exogenous plant growth substance on the preharvest sprouting formation, endogenous phytohormones and related physiological and biochemical characteristic and agronomic properties were studied by spraying the exogenous GA3 and ABA on rice on the seventh day after tasseling, the results are as follows:Rice variety with high germinating potential is easier for preharvest sprouting. Besides the genetic factors, the contents of endogenous phytohormones GA3 and ABA is closely related with the preharvest sprouting ability, especially the ratio of GA3/ABA, then easier preharvest sprouting rice variety has higher ratio of GA3/ABA. The results showed that the rice with easier preharvest sprouting has higher a-amylases activity, soluble sugar contents, soluble protein contents and water content than one with the uneasy preharvest sprouting rice from preharvest germination to sprouting.The treatment with exogenous plant growth substances on rice can affect preharvest sprouting formation in a certain degree. The treatment with exogenous GA3 on Jin 23B which has uneasy preharvest sprouting can remarkably improve the ratio of preharvest sprouting. Maybe this is the result that the exogenous GA3 led to the change of endogenous GA3 and many other physiological and biochemical characters,caused increases in the ratio of GA3/ABA, a-amylases activity, soluble sugar content,speeded up the starch decompose and decreased seed dormancy,eventually the preharvest sprouting took place without dormancy.Exogenous ABA treatment on V20B, an easy preharvest sprouting ,remarkably decreased its ratio of preharvest sprouting, increased endogenous ABA content and changed a serious of related physiological and biochemical indexes, therefore, promoted seed dormancy and inhibited preharvest...