EFFECT OF NAPHTHALENEACETIC ACID ON ENDOGENOUS INDOLE-3-ACETIC-ACID, PEROXIDASE AND AUXIN OXIDASE IN HYPOCOTYL CUTTINGS OF SOYBEAN DURING ROOT-FORMATION

The effect of exogenous naphthaleneacetic acid (NAA) on the internal l evels of indole-3-acetic acid (IAA) in rooting hypocotyls of Glycine m ax was studied. The hypocotyls of NAA-treated cuttings grew significan tly higher numbers of adventitious roots with an increase in endogenou s IAA levels that corresponded with a decrease in IAA oxidase activity (32 kDa) examined. Moreover, a decline of peroxidase activity was acc ompanied by a decrease of lignin content during root formation. Caffei c acid and ferulic acid, two critical phenolic compounds for lignin sy nthesis, accumulated in NAA-treated tissues. Consequently, the increas ed IAA levels with a decrease of IAA oxidase activity accompanied a lo wer lignin content and a reduced peroxidase activity in NAA-treated ti ssues suggests that the induction of adventitious roots by NAA in soyb ean cuttings may be due to to the higher IAA levels accumulated in tis sues.