Distribution of Indoleacetic Acid Oxidase, Peroxidase, and Esterase Activities in Relation to Elongation Growth in Pearl Millet Internode

Abstract

Summary The mean cell length along a differentiating internode, and the associated changes in total phenolic content and activities of IAA oxidase, peroxidase, and non-specific esterase were examined in pearl millet. The rate of cell elongation per mm showed an inverse relation with cytoplasmic IAA oxidase activity. Cytoplasmic peroxidase activity when assayed with ferulic acid and caffeic acid as hydrogen donors, showed similar trends to that of IAA oxidase, whereas with chlorogenic acid as hydrogen donor, it revealed an entirely different trend. Ionically bound wall peroxidase activity increased as the distance from the nodal plate increased, showing a peak activity in the 15-20 mm zone, which was much before the cessation of the elongation zone. Total phenolic content exhibited a clear inverse relationship with the rate of cell elongation. Wall-bound non-specific esterases also showed an increasing trend and maximum activity was recorded in the maturation zone. These results are discussed in relation to the proposed function of peroxdases and esterases in the cessation of elongation growth.