目的 探明铁皮石斛、广东石斛和重唇石斛光合速率的日变化特性及与光强和温度的关系,明确各种石斛叶片中叶绿素含量。方法 测定一天中不同时段(7:30～ 16:30每隔 1.5 h测定一次)、不同光合有效辐射(0～ 14 0 0μm ol· m- 2· s- 1和温度(2 9.6～ 38.2℃)下的净光合速率,测定叶片中叶绿素 a和 b的含量。结果 3种石斛光合作用的净光合速率、光饱和点和光补偿点均较低;净光合速率于早晨 8:0 0～ 10 :0 0处于高峰,此后随温度升高、光照增强而迅速下降;石斛叶片中叶绿素 b的含量较高。结论 石斛的光合作用特性体现了其作为一种阴生植物对生长环境的高度适应性。

Object To determ ine the diumal changes of photosynthesis,its relationships with light intensities and temperatures,and the contents of chloroophyll in leaves of Dend robium candidum W all.ex.Lindl.,D.wilsonii Rolfe and D.hercoglossum Reichb.f.Methods The net photosynthetic rate (NPR )was measured at intervals of 1.5 h during daytimes 7: 30 — 16: 30,under the photosynthetic affective rates 0—140 mmol/(m²· s ),and under the temperatures 29.6—38.2℃ ; contents of chlorophyll a and b inleaves were measured.Results NPR,light saturation point and compensation point were low in each of the three Dendrobium L.species.The NPR peaked during 8: 00 and 10: 00 am,and thereafter decreased rapidly as the temperature and light intensity increased.Content of chlorophyll b was high in the leaves.Conclusion These Results indicated that the Dendrobium L.species,which are sciophyte plants,have great adaptations to their grow ing habitats.