Studies on chloroplasts

Abstract

I. A method of isolating the chloroplast substance from leaf tissue at the rate of 2-3 g. per day is descr. This method is based on the flocculation of suspensions of the chloroplast substance by cations. A study of the factors affecting the rate of flocculation shows that it cannot be explained entirely as a neutralization of electrical charges. Several methods of calculating the chloroplast content of leaf tissue are compared; these methods are based on analysis for the plastid pigments. The results show that the completeness of extraction of these plgments is affected by unknown variables. A method based on analysis for chlorophyll gives satisfactory results.[long dash]II. Chloroplasts consist chiefly of protein and liplns. Cu, Fe, P and NH4 salts are conc. to a certain extent in the chloroplasts; Ca, Mg, Mn, Na, K and Cl show an opposite localization in the cell. SO4 and NO3 do not follow any general rule. The Cu in the chloroplasts is chiefly in organic combination. Part of the Fe and P is organically combined but Ca and Mg are present chiefly in the inorganic state. Most of the eatalase in the leaf cells is present in the chloroplasts. Carbonic anhydrase and ascorbic acid are found in appreciable quantities in the chloroplasts and in other parts of the cell.