Abstract
Photorespiration rates in tissue cultures of a C(4) plant, Portulaca oleracea, were compared to those in tissue cultures of a C(3) plant, Streptanthus tortuosus. The C(4) plant tissue cultures have one-half to one-third the photorespiration rate of the C(3) plant tissue cultures and respond to varying O(2) concentrations in a manner typical of C(4) plants. The results suggest that the lack of detectable photorespiration in C(4) plants is not related to leaf anatomy.