Evolution of O2 in Brown Algal Chloroplasts

A METHOD IS DESCRIBED FOR THE ISOLATION OF PHOTOSYNTHETICALLY ACTIVE CHLOROPLASTS FROM FOUR SPECIES OF BROWN ALGAE: Fucus vesiculosis, Nereocystis luetkeana, Laminaria saccharina, and Macrocystis integrifolia. When compared to lettuce and spinach chloroplasts, the algal chloroplasts all showed lower activities for both photosystems II and I. Chloroplasts from all the plants produced H(2)O(2), with photosystem I functioning as the O(2) reductant in the light. In contrast to the green plants, however, brown algal chloroplasts strongly reduced O(2) under conditions where both photosystems II and I remain active. Relative variable fluorescence values were lower both in intact plants and chloroplasts of the brown algae than for either spinach or lettuce. It is suggested that although light harvesting activities appear similar in all the plants, details of electron transport in brown algae may differ from those of green plants.