Isolation and Propeties of Chloroplasts from the Siphonous Green Alga Cualerpa simpliciuscula

Abstract

Isolated chloroplasts fixed CO*2 and evolved oxygen at rates equal to or greater than rates measured in segments of plant frond, with a maximum hourly value of 73 �mol per mg chlorophyll (a+ b). They were equally active whether isolated in a sorbitol-based medium or in an artificial sea water medium. Their activity declined after isolation, although they were relatively resistant to lysis in hypotonic medium. The products of photosynthesis included both sucrose and alanine as well as hexose monophosphates, and organic acids. There was much less 1,3-�-glucan formation in the chloroplasts than in the intact plant fronds. These chloroplasts appeared to be free of gross contamination when seen under the light microscope, but material which could not be distinguished from cytoplasm was attached to some chloroplasts. A maximum value of 17% contamination was calculated from the distribution of the mitochondrial marker enzyme succinate dehydrogenase.