INTERACTION BETWEEN CHLOROPLAST BIOGENESIS and PHOTOREGULATION OF AMYLASES IN Pennisetum americanum LEAVES

Abstract

In pearl millet (Pennisetum americanum) seedlings, light acting via phytochrome stimulates amylase activity in the leaves. The maximum photostimulation of amylase is observed in the segment proximal to the leaf base. This photostimulation mainly results from an enhancement in β‐amylase activity (EC 3.2.1.2.), which constitutes80–90% of leaf amylase activity. The subcellular fractionation studies revealed that while p‐amylase is localized only in the extraplastidic compartment, a‐amylase (EC 3.2.1.1.) is localized both in the cytosol and in the chloroplasts. The mesophyll cells contained both a‐ and β‐amylase activity, but only a‐amylase activity was present in the bundle sheath cells. The Norflurazon‐mediated photooxidation of chloroplasts during leaf development also eliminated plastidic α‐amylase activity, confirming dependence of its photoregulation on the chloroplast biogenesis. Copyright © 1991, Wiley Blackwell. All rights reserved