Abstract: This paper deals with the relationships between net photosynthetic rate and ligh intensity under appropriate ecolopical conditions in the shoots of Melissisus ruthenica, Artemisia frigida and Kochia prostrata from a typical steppe at different growing stages.The results and conclusions are as follows:1.Light saturation point, net photosyntheic rate and net photosynthetic rate/light intensity (P/I) in three plants decrease with growing and developing shoots; light compensation point is tending to rise from vegetative stage to flowering stage.2.At vegetative stage, nat photheynthetic rate and P/I in three plants are close under maximum natural light intensity; but decreased values of the index of M.ruthenica are markedly smaller than those of A.frigida and K.prostrata with growing and developing shoots.3.Light saturation point and light compensation point of C₃ plant M.ruthenica are usually higher than those of A.frigida (C₃ plant) and K.prostrata (C₄ plant) during full growing period;but P/I of M.ruthenica is the lower than that of other two plants at feeble light intensity.This indicates that it seems that the capacity of utilizing high light intensity of C₃ plant is higher than that of C₄ plant and the capacity of utilizing feeble light of C₃ plant is lower than that of C₄ plant at adequate irrigated soil condition.

Key words: Melissitus ruthenica, Artemisia frigida, Kochia prostrata, Photosyntheses, Light intensity

摘要： 本文作者研究了典型草原地区扁蓿豆、冷蒿和木地肤不同生育期的枝条在适宜条件下净光合速率与光强的关系。结果表明:(1)三种植物的光饱和点,净光合速率和净光合速率/光强均随着生育期的后移而下降;光补偿点刚从营养期到开花期呈升高趋势。(2)在营养期,三种植物的最大净光合速率与最大自然光强下的净光合速率/光强相近,但随着生育期的后移,扁蓿豆上述指标的降低值明显小于冷蒿和木地肤。这是扁蓿豆的一个优良光合生态特性。(3)在生长盛期,C₃植物扁蓿豆的光饱和点和光补偿点通常高于冷蒿(C₃植物)和本地肤(C₄植物),而在弱光下的净光合速率/光强则低于后者。这表明,在土壤水分充足的条件下,C₃植物对强光的利用能力可能高于C₄植物,而对弱光的利用能力则低于C₄植物。(4)依据光合作用的光生态特征分析,三种植物均属于阳性植物。

关键词: 扁蓿豆, 冷蒿, 木地肤, 光合作用, 光强