Photoinhibition of Photosynthesis in Lemna gibba: The Effect of O(2), CO(2) and the Selective Inhibition of Photosystem II.

This study demonstrates that photoinhibition of Lemna gibba can be induced by exposing the plants in a N(2) atmosphere to a light intensity which exceeds that used for cultivation. The lack of O(2) and CO(2) appeared to be more important than the sudden increase in photon-flux rate for the induction of photoinhibition. Photoinhibition had no effect on the O(2) inhibition of photosynthesis. Moreover, Lemna exhibited a rather fast recovery to photoinhibition, which suggests that Lemna has some mechanism of protection that may be related to the presence of high CO(2) stored in their air sacs. Studies using selected monochromatic light during photoinhibitory treatment show that in vivo photoinhibition maybe due to reactions connected to the excitation of PS II.