Su Wenhua, Zhang Guangfei
Institute of Ecology and Geobotany, Yunnan University, Kunming 650091.
Zhong Yao Cai. 2003 Mar;26(3):157-9.
With LiCor-6400 Portable Photosynthesis System, carbon dioxide exchange pattern for leaves of Dendrobium nobile during 24 hours were studied in sunny day and rainy day, and the variation of CO2 exchange rate to light intensity was analysed. The results showed that in sunny day D. nobile absorbed CO2 in all day except at midday, at noon photorespiration took place. The CO2 exchange pattern was similar to Crassulacean Acid Metabolism(CAM). In rainy day CO2 uptake was in all day, at night CO2 uptake was monitored at 21:00, then CO2 released from 23:00 to dawn. Light saturation point was 1000 mumol/m2s. Over light saturation point photosynthesis, photoinhibition of photosynthesis will be induced by high-light. Exposed to high-light, the light saturation point and the CO2 uptake velocity would be decreased. With variation of environmental factors, photosynthetic pathway in D. nobile could change from CAM to C3 photosynthetic metabolism. It may be one of main reasons for D. nobile to adapt to the shade-requiring environment, the slow growth and rareness in nature.
利用LiCor-6400便携式光合作用系统，研究了晴天和雨天时金钗石斛叶片24小时的二氧化碳交换模式，并分析了二氧化碳交换率随光照强度的变化。结果表明，晴天时金钗石斛除中午外全天吸收二氧化碳，中午发生光呼吸作用。其二氧化碳交换模式类似于景天酸代谢（CAM）。雨天时全天吸收二氧化碳，21:00监测到夜间吸收二氧化碳，然后从23:00至黎明释放二氧化碳。光饱和点为1000μmol/m²·s。超过光饱和点进行光合作用时，高光会诱导光合作用的光抑制。暴露于高光下，光饱和点和二氧化碳吸收速度会降低。随着环境因素的变化，金钗石斛的光合途径可从CAM转变为C3光合代谢。这可能是金钗石斛适应喜阴环境、生长缓慢且在自然中稀少的主要原因之一。
