Photosynthetic Effects To Doubled CO2in Three Species Of Dendrobium

Dendrobium has an important medicinal and ornamental value, which is one big genus of Orchidaceae. The research on photosynthetic characteristics of three dendrobia to doubled CO2helps to acknowledge the adaptablity when growing at elevated CO2of the future. Chose three dendrobia(Dendrobium.chrysotoxum, D.nobile and D.primulinum), gas exchange and chlorophyll fluorescence kinetic parameters of the three dendrobia under two Carbon dioxide concentration (380±20μmol·mol-1and800±20μmol·mol-1) were measured. The conclusion were as followings:1The net photosynthesis rate and water use efficiency of D.chrysotoxum and D.nobile was increased and the net photosynthesis rate of D.primulinum decreased in high CO2concentration environment. The carbon assimilation of D.chrysotoxum showed a significant character of C3pathway while the D.primulinum showed the character of CAM pathway. The carbon assimilation pathway of D.nobile showed more C3characters in high CO2concentration environment, however, D.nobile is CAM carbon assimilation pathway in low CO2concentration environment.2Under the high CO2concentration environment, the light use efficiency of D.chrysotoxum and D.nobile was raised, the apparent quantum yield, light saturate point and the maximum photosynthesis rate in light saturate point were increased compared with growing in low CO2concentration environment, However, the light saturate point and the maximum photosynthesis rate of D.primulinum was decreased in high CO2concentration environment.3Grown in high CO2concentration, the carboxylation efficiency at low CO2concentration of D.chrysotoxum and D.nobile decreased and the CO2saturate point and the maximum photosynthesis rate raised insignificantly. Howerer, the photorespiratory rate of D.primulinum increased significantly while the CO2saturate point and the maximum photosynthesis rate decreased.4The high CO2concentration promoted the activity of PSII in D.chrysotoxum and D.nobile, elevated the relative electron transport rate and actual photochemistry efficiency. The activity of PS II in D.primulinum was restrainted in high CO2concentration environment, the relative electron transport rate and actual photochemical efficiency descreased.