CO2 gas exchange and the occurrence of CAM in tropical woody hemiepiphytes

Abstract

CO 2 gas exchange and nocturnal acidification was studied in situ and in the laboratory on 7 woody hemiepiphytes representing 6 genera in 4 families. CAM activity was detected only in the genus Clusia , but a species of another genus in the same family (Havetiopsis flexilis) showed very high but constant levels of organic acidity. This is frequently observed in C 3 /CAM intermediates when operating in C 3 mode. The rates of net CO 2 uptake during the day ranged from 1.4–24 μmol m −2 S −1 , thus covering the same range as found in tropical trees. The correlation of the maximum rates of net CO 2 uptake and diel carbon balances was the same as previously found in other tropical species providing further evidence for the generality of this relationship.