三种石斛与大叶落地生根光合作用比较研究

石斛属为兰科大属,部分物种光合作用行景天酸代谢途径。为了检验石斛的光合作用碳代谢途径,试验选用典型的专性景天酸代谢植物大叶落地生根为对照。光合作用测定结果表明,报春石斛的光饱和点为700μmolphoton.m-2s-1,最大表观光合作用速率达3.826μmol.CO2m-2.s-1,光合作用日变化呈现出景天酸代谢植物的四阶段特征;鼓槌石斛的光饱和点为900μmolphoton.m-2.s-1,最大光合作用速率高达5.912μmolCO2.m-2.s-1,光合作用日变化呈单峰曲线,最大值出现在中午前后,不具备景天酸代谢植物特征;金钗石斛表现为更适合荫蔽环境,光合作用日变化呈双峰曲线,中午光照最强烈的时段表观光合作用速率出现一定程度降低。

Comparative Study on Photosynthesis between Three Dendrobia and Kalancho(e) Daigremontiana

In the family of orchidaceae,dendrobium is a big genus,and some species performed crassulacean acid metabolism（CAM） in their carbon assimilation.To testify the pathways of carbon assimilation among dendrobia,the typical obligate CAM plant named Kalanchoё daigremontiana was selected as control.The results showed that,the light saturation point of D.primulinum was 700 μmolphoton·m-2·s-1,and the maximum photosynthetic rate was 3.826 μmolCO2·m-2·s-1.The diurnal change of photosynthesis in D.primulinum was composed by four distinct phases.The light saturation point of D.chrysotoxum was 900 μmolphoton·m-2·s-1,and maximum photosynthetic rate was high and up to 5.912 μmolCO2·m-2·s-1,while the diurnal change of photosynthesis showed single summit at noon,which meant that D.chrysotoxum did not show the characteristics of CAM plant.For D.nobile,it preferred to shade environment,whose diurnal change of photosynthesis exhibited double summits with declining to some extent at noon when illumination was intensive.