SOLUBLE PEROXIDASE GRADIENTS IN LUPIN HYPOCOTYLS AND THE CONTROL OF THE LEVEL OF POLARLY TRANSPORTED INDOLE-3YL-ACETIC ACID

The distribution of basic soluble isoperoxidases along the growth gradient of lupin hypocotyl was studied in order to establish the role of these isoenzymes in controlling polarly transported indole-3yl-acetic acid (IAA) levels. The observation that the levels of basic isoperoxidases, which diminish from the young (vascular differentiating) to the older (vascular differentiated) tissues, are related with previously reported IAA oxidation rates in decapitated plants, suggests that these isoenzymes can play a role in the oxidation of IAA during polar transport. The fact that the level of basic isoperoxidases is controlled by IAA in hypocotyl sections harvested from different growth zones is in accordance with the previously described adaptative activation of basic isoperoxidases to IAA content. This adaptative activation of basic isoperoxidases might constitute the basic characteristic of a system of subcellular oscillators, coupled at the cellular level, necessary to generate the supracellular auxin-wave associated with auxin transport.