The Cupric Ion as an Inhibitor of Photosynthetic Electron Transport in Isolated Chloroplasts

Open Access
Publisher Website
Google Scholar
Abstract
Strong inhibition of uncoupled photosynthetic electron transport by Cu2+ in isolated spinach chloroplasts was observed by measuring changes in O2 concentration in the reaction medium. Inhibition was dependent not only on the concentration of the inhibitor, but also on the ratio of chlorophyll to inhibitor. Binding of Cu2+ to the chloroplast membranes resulted in removal of Cu2+ from solution. When chloroplasts were exposed to preincubation in light, there was increased inhibition as a result of Cu2+ binding to inhibitory sites. Preincubation in the dark resulted in Cu2+ binding to noninhibitory sites and decreased inhibition. The degree of inhibition was lower at low light intensities than at high light intensities.