It was reported that exogenous hydrogen peroxide(H2O2) can induce primary root bend in Arabidopsis and pea. However, the mechanism remains unclear. Here we explored the mechanism underlying this phenomenon by using the pea(Pisum sativum L.) variety ‘‘longwan No. 1''.The results showed that the endogenous indole-3-acetic acid(IAA) content decreased and gibberellin A3(GA3)content increased in the curving primary pea root induced by H2O2. Meanwhile, both of the two hormones asymmetrically distributed in the inside and outside parts of the curving root. Also, the starch content decreased due to the increased a-amylase activity in this process. However,exogenous Ca2?can relieve the horizontal bending of pea root induced by H2O2 and altered the contents of endogenous IAA and GA3. A working model was proposed:Exogenous H2O2 causes the increase in GA3 content, and GA3 stimulates the activity of a-amylase, which leads to the hydrolysis of starch, and then the root lost the gravityperceiving. The asymmetric distribution of IAA and GA3 in two sides of curving root may cause the horizontal bending.Exogenous Ca2?can relieve root bending through altering the endogenous IAA and GA3 contents.
Sheng LiLi-Rong SuShao-Ying MaZhen-Zhen ShiXiao-Ming Yang
