Rates of photosynthesis by isolated chloroplasts.

Abstract

The low rates of CO2 assimilation that first characterized the reconstruction of complete photosynthesis by isolated chloroplasts have been traced to elements of the experimental procedure (especially the use of sodium chloride and a relatively long and drastic preparative technique) that were initially introduced to guard against external sources of energy and metabolites and against contaminating cellular components. By replacing NaCl with a sugar (or a sugar derivative), using new buffers, inorganic phosphate, and a shorter and milder preparative technique, isolated spinach chloroplasts consistently gave photosynthetic rates of about 50 [mu] moles CO2/mg chlorophyll/hour. These rates represent about 30% of the photosynthetic activity of the intact leaf and are about 30 times greater than the first reported rate of CO2 assimilation by isolated chloroplasts but yield no significant change in products.