The senescence of isolated chloroplasts.
Because previous work indicated that senescence of oat leaves in darkness probably centers in the cytoplasm, the senescence of chloroplasts isolated from the same material and carefully purified was studied. The rate of loss of chlorophyll was about one-tenth of that which takes place in the isolated leaves at the same temperature, while the loss of protein, though slightly more rapid, was still only 36% of the rate observed in the leaf after 7 days. This unexpected stability of the chloroplasts is matched by their photosynthesis, 81% of photosystem I and 35% of photosystem II being present after 3 days at 25°. Traces of system I, but not of system II, were still detectable even after 7 days.
The Thimann Laboratories, University of California, 95064, Santa Cruz, California, USA.
H T
HT
Choe
K V
KV
Thimann