青藏高原几种典型高山植物的光合特性比较

 选用西宁地区人工栽培的高山植物唐古特大黄（Rheum tanguticum）、山莨菪（Anisodus tanguticus）和麻花艽（Gentiana straminea），比较了3种高山植物之间光合作用的光响应和CO₂响应特性，叶片光合色素以及UV_B 吸收物质的差异；并以低海拔植物菘蓝（Isatis indigotica）为对比，分析了高山植物与低海拔植物的差异。结果表明：与低海拔植物菘蓝相比，3种高山植物光合作用的表观量子效率（AQY）都偏低；唐古特大黄叶片的AQY、羧化效率（CE）和光呼吸速率（Rp）都很低，净光合速率（P_n）的光响应曲线在全日照光辐射范围内并没有达到完全饱和，这与单位面积叶片具有较高的光合色素以及UV_B吸收物质有关；麻花艽植物与唐古特大黄一样，具有较高的UV_B吸收物质和光合色素含量，但其Rp较高，加之P_n受气孔限制较为明显 ，故其光合作用的饱和光强很低，P_n相对于其它3种植物也较低；山莨菪与低海拔植物菘蓝的光合特性很相似，都具有较高的AQY和CE。这些结果表明，3种高山植物的光合特性有较大差异 ，但并没有一致的相对于低海拔植物的共性。4种植物P_n的胞间CO₂浓度(C_i)响应曲线 在CO₂饱和点以后都表现为无机磷（Pi）再生限制，其Rp的变化与CO₂饱和点以后的最大P_n 的变化基本一致。

COMPARATIVE STUDIES OF PHOTOSYNTHETIC CHARACTERISTICS IN TYPICAL ALPINE PLANTS OF THE QINGHAI-TIBET PLATEAU

The photosynthetic characteristics of three medicinal alpine plants, Rheum tanguticum, Anisodus tanguticus and Gentiana straminea, were studied and compared to a low land species, Isatis indigotica. The response of net photosynthesis rate (P-n) to intercellular CO-2 concentrations (C-i) and photon flux density (PFD) was determined using a LI-6400 photosynthesis system. The photosynthetic pigments and UV-B-absorbing compounds also were determined in the four species in order to evaluate differences in their photosynthetic characteristics. The results indicated that the three alpine plants had relatively low photosynthetic quantum yields (AQY) as compared to the low land species of I. indigotica, and AQY, carboxylation efficiency (CE) and photorespiratory rate (R-p) were the lowest in R. tanguticum. However, P-n did not respond strongly to changes in PFD, which may be due to the high concentration of photosynthetic pigments and UV-B-absorbing compounds in the leaves. Similar to R. tanguticum, the alpine plant G. straminea also had higher contents of UV-B-absorbing compounds, chlorophyll and carotenoids, but its R-p was higher and P-n was limited by stomatal conductance in response to PFD and P-n was lower. The photosynthetic characteristics of the alpine species, A. tanguticus, was similar to the low land species, I. indigotica, both of which had a high AQY and CE. These results indicated that although there were some differences among the three alpine species, no corresponding characteristics appeared in photosynthetic advancements. The response of P-n to C-i exhibited Pi regeneration limitations after reaching full CO-2 saturation. The changes of R-p in the four species were similar to that of maximum P-n in photosynthetic C-i response.