The acute effect of copper on the levels of indole-3-acetic acid and lignin in peanut roots

Cu-treated peanut (Arachis hypogaea L.) seedlings showed a significant inhi bition in peanut root growth, and a decrease in endogenous indole-3-acetic acid (IAA) content. The decline of IAA content in Cu-treated tissue was acc ompanied by an increase in the activity of cationic peroxidase (POD) isozym e P8.5, which was correlated with an increase in cationic POD transcripts. Cu might suppress the growth of peanut roots by inducing the synthesis of t he cationic POD isozyme that degrades endogenous IAA. The increase in the a ctivity of anionic POD isozyme P3.5 was correlated with the rise in lignin content in Cu-treated roots. We suggest that the increase in anionic POD is ozyme P3.5 induced by Cu might be responsible for lignin synthesis in peanu t roots, and may also remove excess hydrogen peroxide caused by Cu, thus pl aying a detoxifying role during Cu treatment.