CRASSULACEAN ACID METABOLISM IN 3 SPECIES OF COMMELINACEAE

Diurnal patterns of CO2 exchange and fluctuations of tissue malic acid concentrations were investigated in three species of Commelinaceae: C allisia fragans and Tripogandra multiflora from Jamaica; and Tradescan tia brevifolia from southern Texas. Very low levels of CAM gas exchang e were induced by drought stress in C. fragrans and T. multiflora. In addition, past indications of CAM-cycling in the two Jamaican species were confirmed in drought-stressed plants; however, only C. fragrans e xhibited CAM-cycling under well-watered conditions. CAM-cycling under drought stress was also found in T. brevifolia. This constitutes the f irst report of CAM (sensu lato) in the genus Tradescantia, The importa nce of low-level CAM in these three species is discussed as a potentia l adaptation to drought.