Abstract
The envelope of the spinach chloroplast is a yellow membrane system with a unique carotenoid composition. Envelopes prepared from dark-treated leaves had a violaxanthin content up to 3.5 times the lutein plus zeaxanthin content, whereas in chloroplast envelopes from illuminated leaves this ratio was only 0.75. Light-catalyzed changes in violaxanthin content also occurred in the thylakoid fraction.The role of this reversible light-catalyzed de-epoxidation of violaxanthin in the function of the envelope of the chloroplast is discussed.