Mode of photosynthesis during different life stages of hemiepiphytic Clusia species

Abstract

Carbon isotope fractionation and nocturnal acid accumulation in Clusia osaensis Hammel-ined., C. peninsulae Hammel-ined. and C. valerii Standl. were investigated during the seedling, epiphytic and hemiepiphytic phases in a lowland tropical forest in Costa Rica to study photosynthetic adaptations of different plant growth stages to their habitat. Foliar δ13C values around -24 to -32‰ indicate predominant C3 fixation of CO2 and low crassulacean acid metabolism (CAM) activity in all three Clusia species. Only terrestrially rooted plants of C. osaensis showed increased CAM expression. However, all developmental stages exhibited significant CAM cycling as shown by significant day-night fluctuatio..