Epidermis integrity and epicotyl growth in azuki bean

Abstract

In order to verify if epidermis integrity played a determinant role in epicotyl elongation induced by fusicoccin (FC), buffers at different pH's, and indoleacetic acid (IAA), we studied the short-term kinetics of elongation growth, the increase of fresh weight in long-term treatment, and the H+ excretion in intact, abraded, and peeled azuki bean epicotyl sections. We demonstrated that the epidermis is more sensitive to IAA, whereas the cortex is highly responsive to protons. Our data are consistent with the “acid growth theory.” In addition, our studies support the idea that the epidermis may be the tissue target for auxin, but its integrity is necessary for IAA-induced elongation.