Energetic basis of the light-induced chloroplast shrinkage in vivo

摘要

A light-induced chloroplast shrinkage occurring invivowas measured with a Coulter counter and a packed weight technique using chloroplasts isolated within two minutes of harvesting pea plants. Introduction of the photosynthetic inhibitor DCMU (5μM) into the plant either by bathing the cut stem or injection through a fine hypodermic needle decreased the light-induced chloroplast shrinkage in vivo 11 to 20. The uncoupler tri-Fl-CCP (5μM) inhibited the light-induced shrinkage 80, while nigericin (0.5μM) completely abolished it. An action spectrum for the chloroplast volume decrease invivohad a shoulder at 700-715 mμ. These results are considered in terms of the various forms of energy available during photosynthesis. A consistent interpretation is that the lightinduced chloroplast shrinkage invivodepends either on a high energy state created by electron flow or onATP.This chloroplast volume change upon illumination of the plants may increase the photosynthetic efficie