The Regulation Of Jasmonic Acid On Growth And Leaf Senescence In Rice Seedlings Under Low Potassium

Rice is one of the main food crops in China,but the potassium content is generally low in Chinese paddy fields,and low potassium stress affects rice growth and development.Jasmonic acid(JA),one of the anti-stress hormones,participates in the response of plant to many stresses.However under low potassium stress,the mechanism of JA on rice growth and senescence is unclear.In this study,the seedlings of rice 9311(Oryza sativa L.)grown in hydroponic cultures were treated with control treatment(CK),low potassium treatment(LK),low potassium plus JA biosynthetic inhibitor(Ibuprofen,IBU)treatment(LK+IBU),and the effects of CK,LK,and LK+IBU on root growth,potassium uptake and transportation and leaf senescence in rice were investigated.The main results are as follows:1.LK promoted the expression of JA biosynthetic genes such as OsLOXs,OsAOSs,OsAOC,OsOPRs and OsACXs,increased JA content of roots,and reduced many indicators of root growth,including root length,root diameter,root surface area,root number,root volume and root fresh weight.IBU treatment not only effectively alleviated the promotion effect of LK on JA biosynthesis of rice seedling roots,but also effectively alleviated the inhibition of low potassium on root growth.The above results indicate that low potassium stress promotes JA biosynthesis,and then inhibits root growth of rice seedlings.2.LK promoted the expression of JA biosynthetic genes in roots,and greatly increased JA content,and then significantly promoted the expression of genes involved in potassium uptake and transportation,and promoted root potassium uptake and upward transportation of potassium.However,IBU treatment not only effectively alleviated the promotion effects of LK on the expression of genes(OsKATs,OsAKTs and OsHAKs)involved in potassium uptake and transportation,but also effectively alleviated the promotion effects of LK on potassium uptake and transportation.The above results indicate that LK stress promotes JA biosynthesis,and then promotes potassium uptake and upward transportation in rice seedlings.3.LK promoted the expression of JA biosynthetic genes,and greatly increased JA content of leaves,and then promoted the expression of genes involved in chlorophyll degradation and leaf senescence,reduced chlorophyll content,and then promoted leaf senescence.However,the promotion effects of LK on the expression of genes involved in JA biosynthesis,leaf chlorophyll degradation and leaf senescence were significantly alleviated by IBU treatment.The above results demonstrate that LK stress promotes JA biosynthesis in leaves,and then promotes leaf senescence in rice seedlings.Taken together,LK stress promotes the expression of JA biosynthetic genes,increases JA content of roots and leaves of rice seedlings,and then promotes potassium uptake and upward transportation,inhibits root growth,and promotes leaf senescence.