The effect of copper on chlorophyll organization during greening of barleyleaves

The effect of copper on chlorophyll organization and function during greeni ng of barley was examined, using chlorophyll fluorescence and photoacoustic techniques. Copper was found to inhibit pigment accumulation and to retard chlorophyll integration into the photosystems, as evident from low tempera ture (77 K) fluorescence spectra. Resolution of the minimal fluorescence (F -0) into active and inactive parts, indicated a higher inactive fraction wi th copper treatment. This was attributed to chlorophyll molecules which fai led to integrate normally, a conclusion supported by the longer fluorescenc e lifetime observed in copper treated plants. A lower ratio of chlorophyll a to b and fluorescence induction transients, showing accelerated Photosyst em II closure, both indicate that copper treatment resulted in a larger lig ht-harvesting antenna. Another effect of copper treatment was the suppressi on of oxygen evolution, indicating a decrease in photosynthetic capacity. W e suggest that the non-integrated chlorophyll fraction sensitizes photodama ge in the membrane, contributing to disruption of electron flow and pigment accumulation.