Properties of chloroplasts and chloroplast fragments, as deduced from internal chlorophyll → chlorophyllide conversion

Abstract

Summary 1. Fractions containing either small green particles with PS I or PS I + II properties, or «whole chloroplasts and large fragments» were isolated from spinach and endive leaf homogenates. 2. With spinach, internal chlorophyll → chlorophyllide conversion is shown to occur in small green particles dispersed in an aqueous medium and also, be it to a much lower degree, in «whole chloroplasts and large fragments». The effect can be increased by addition of Triton X-100 or acetone. 3. Reconversion of chlorophyllide into chlorophyll is shown to occur mainly in PS I particles, probably from stroma lamellae. 4. An aqueous extract from spinach acetone powder, containing dissolved chlorophyllase, more or less inhibits chlorophyllase activity in small spinach particles, while with «whole chloroplasts and large fragments» an increase occurs. Dissolved chlorophyllase is adsorbed by endive small green particles; a much lower adsorption occurs with «whole chloroplasts and large fragments». 5. Phytol inhibits chlorophyll → chlorophyllide conversion in green particles and in «whole chloroplasts and large fragments». 6. Oleic acid, at certain concentrations, increases chlorophyll → chlorophyllide conversion in small particles, while, at the same concentrations, an inhibition occurs with «whole chloroplasts and large fragments». 7. «Whole chloroplasts and large fragments» are «solubilized» completely, or nearly so, by 0.2 % Triton X-100; solubilization of small green particles is much less. 8. The results are discussed in terms of differences in lipid composition of the various membranes. The experiments provide new evidence for the hypothesis, put forward in an earlier paper (Terpstra, 1972), that «fraction 4 particles», with both PS I and PS II properties, are distinct particles, probably derived from stroma lamellae.