遮阴对4种豆科牧草光合特性的影响

摘要：研究豆科牧草的耐阴特性，以期为林下种草提供耐阴草种，在不同遮阴处理条件下对紫花苜蓿(Medicago sativa)、草木樨(Melilotus suaveolens)、白三叶(Trifolium repens)和沙打旺(Astragalus adsurgens)4种豆科牧草的光合特性指标进行了测定。结果表明，紫花苜蓿的气孔导度(Gs)、蒸腾速率(Tr)在透光率为60％处理下受影响较小，随着光强减弱，光饱和点（LSP）、光补偿点(LCP)和表观量子效率（AQY）降低，CO2补偿点(CCP)和饱和点(CSP)均呈增加趋势，羧化效率（CE）逐渐减小；白三叶的Gs和Tr在透光率较低的23％处理下下降明显，LSP和LCP很低，AQY较高，CSP与对照（不遮阴）基本一致，CCP较小，CE逐渐减小；草木樨的各光合指标在不同程度的遮阴下均变化较小；沙打旺随着光强的减弱LSP和LCP减小，AQY仅在透光率60％处理下高于对照，CSP 和CCP值较低，CE减小。4种豆科牧草中白三叶具有较强的耐阴性，草木樨在一定程度的遮阴下具有较强的适应性，紫花苜蓿耐阴性一般，而沙打旺则仅在透光率为60％的处理下长势较好。

Effects of shading on photosynthetic characteristics of four legumes

We measured the photosynthetic characteristics of Medicago sativa, Trifolium repens, Melilotus suaveolens, and Astragalus adsurgens to analyze shade tolerance mechanism of leguminous forage, and provide undergrowth plant germplasm. The results of this study showed that when the light transmission rate was 60%, Gs and Tr of M.sativa were less affected, as the light intensity decreased, LSP, LCP and AQY decreased, CCP and CSP increased, CE decreased gradually. Gs and Tr of T.repens decreased obviously when the light transmission rate was 23%, LSP and LCP were very low, AQY comparatively high and CSP were basically consistent, CCP were smaller, CE gradually decreased. The changes of photosynthetic indexes of M.suaveolen in different degree of shade were slight. When the light intensity decreased, LSP and LCP of A.adsurgens decreased. While under transmittance 60% treatment, AQY were higher than 100%, CSP and CCP were lower, CE decreased. T.repens in 4 legume forages had strong resistance to shading, M.suaveolens had strong adaptability in the degree of shading, negative general tolerance in M.sativa, A.adsurgens grew better only under the light transmittance of 60% treatment.