Light-induced structural changes of thylakoids in normal and carotenoid deficient chloroplasts of maize

Summary Changes of membrane thickness and loculi were studied after red (650 nm) and far-red (707 nm) light in thylakoids of maize with different stacking and pigment compositions.The most intensive shrinkage of thylakoid membranes occurred in grana and under red light. Membranes of stroma thylakoids responded more to far-red light. Bundle sheath thylakoid membranes did not change in thickness. Loculi decreased in all types of thylakoids under both, red and far-red light. Thylakoids obtained from a -carotenic mutant exhibited a contrasting response: swelling under red light followed by photodestruction. Changes under far-red light were similar to that of normal stroma thylakoids.The data on normal chloroplasts show that the light induced shrinkage of membranes and the decrease of loculi are coupled to a different degree in various kinds of thylakoids; that the thylakoid flattening can be correlated with the Photosystem content of the membranes; and that two kinds of single thylakoids (stroma lamellae and bundle sheath lamellae) are different in molecular structure and function.Data on carotenoid deficient chloroplasts indicate a photooxidative destruction of the thylakoids by Photosystem 2 that occurs in the absence of normal carotenoids.