Chloroplast Movement Can Be Impeded by Crowding

Abstract A nuclear magnetic resonance (NMR) technique was used to detect chloroplast reorientational movement in Acer platanoides shade leaves. Sporadic movement was observed during incubation in darkness as well as during exposure to high-intensity light, but never during exposure to light within the range of moderate intensities to which the leaves were adapted. Movement occurred significantly more often at high water potentials. Results suggest that severe crowding among the chloroplasts inhibited reorientational movement.