Diurnal CO2 assimilation patterns in nine species of CAM-type succulent plants

Abstract

CO2 assimilation rate of Crassula hybrid 'Himaturi', a succulent ornamental species with the crassulacean acid metabolism (CAM) photosynthetic pathway, was affected by light intensity (50, 100, 300 μmol·m -2·s-1), photoperiod (16/8, 8/16 h day/ night), and temperature (30/25, 25/20°C day/night). Maximum assimilation of CO 2 occurred at 300 μmol·m-2·s-1 of diurnal irradiance, 16/8 h day/night photoperiod, and a day/night temperature of 30/25°C. Diurnal CO2 assimilation patterns of nine succulent ornamental CAM species were evaluated (300 μmol·m -2·s-1 35/25°C day/night and a 16/8-h day/niglit photoperiod) for CO2 fixation. Of the nine ornamentals, Crassula 'Himaturi' had the highest and Echeveria derembergii the lowest maximum CO2 absorption rate (13.0 vs 2.4 μmol·kg -1·s-1), total nighttime (179.3 vs 13.4 mmol·kg-1), and 24 h total (200.6 vs 19.0 mmol·kg -1) absorption. Based on the CO2 assimilation patterns, the nine ornamentals were separated into two groups: 1) full CAM (Faucaria tigrina, Gasteria gracilis var. minima, Haworthia cymbiformis, and Haworthia fasciata); and 2) weakly CAM (Adromischus clarifolius, Crassula hybrids 'Moonglow' and 'Himaturi', E. derembergii, and Haworthia retusa).