Carbon dioxide and senescence in cotton plants

Glandless cotton plants (Gossypium hirsutum L. cv. Coker 100) were subjected to the influence of high CO(2)-bicarbonate. The content of protein decreased with no accompanying increase in its degraded products. The decrease in protein was correlated with the low content of chlorophyll and also with the reduced activity of carbonic anhydrase. The initiation of these correlations coincided with the time when the control leaves contained the highest enzyme activity during leaf growth. The high concentration of bicarbonate directly restricted the rate of photophosphorylation and that of the Hill reaction in isolated chloroplasts. The amount of ATP in leaves treated in vivo also diminished. High CO(2) as bicarbonate, however, did not directly inhibit the activity of carbonic anhydrase in vitro.