Correlation between Photosynthetic Activity and Membrane Integrity in Isolated Pea Chloroplasts

Abstract

Pea chloroplasts, isolated in sucrose media were examined under the phase contrast microscope. The proportion of otherwise entire chloroplasts which showed the granular appearance characteristic of membrane loss varied between 10% and 50% in in individual preparations. Exposure to hypotonic media was followed by immediate membrane loss. Membrane-free chloroplasts showed an enhanced ability to catalyse cyclic photophosphorylation and a reduced ability to catalyse carbon dioxide fixation. Expressed as a fraction of the rate achieved by membrane-free chloroplasts, photophosphorylation by chloroplasts with intact membranes varied between 12% and 65%.