Subcellular distribution of (35)S-sulfur in spinach leaves after application of (35)SO 4 (2-) , (35)SO 3 (2-) , and (35)SO 2.

(35)SO2, (35)SO 3 (2-) , and (35)SO 4 (2-) , respectively, were applied to leaves of Spinacia oleracea L. for 60 min in the light. Thereafter, the specific activity was determined in the organelles separated by means of sucrose density gradient centrifugation. In mitochondria and peroxisomes, the specific activity was equally distributed in their protein moieties. After application of (35)SO2 or (35)SO 3 (2-) , the chloroplast lamellae are characterized by elevated specific activity, which is not found after application of (35)SO 4 (2-) . Chloroplast stroma shows a low specific incorporation rate after application of either compound, which may be due to the low turnover rate of Fraction I protein.