青藏高原东部不同海拔高度裂叶沙参气体交换与水分利用效率

GAS EXCHANGE AND WATER USE EFFICIENCY OF ADENO PHORA LOBOPHYLLA (CAMPANULACEAE) AT DIFFERENT ALTITUDES ON THE EAST BOUNDARY OF THE QING ZANG PLATEAU 

裂叶沙参（ＡｄｅｎｏｐｈｏｒａｌｏｂｏｐｈｙｌａＨｏｎｇ）主要分布在四川省青藏高原东部边缘海拔２３００～３４００ｍ区域范围内，比较了不同海拔高度的裂叶沙参的气体交换、水分利用效率和塑性，评价了裂叶沙参在各种生境条件下的适应性和环境因子间可能的相互作用。低海拔的裂叶沙参的净光合速率（Ｐｎ）和表观量子效率（ＡＱＹ）比高海拔地区低，并与相对土壤水分含量（ＳＷＣ）和空气温度（Ｔａ）紧密相关。相反，由于空气温度高，低海拔的暗呼吸速率（Ｒｄ）比高海拔地区高。低海拔的裂叶沙参的蒸腾速率与Ｒｄ增加和较低的Ｐｎ相关联。在这些生境下，气孔对叶面蒸汽压饱和亏缺（Ｖｐｄｌ）和叶面温度（Ｔｌ）的反应是非常明显的。在低海拔区域内，在较高的Ｔｌ、Ｖｐｄｌ和较低土壤水分的利用效率的条件下，裂叶沙参的光合速率（Ｐｎ）降低。在海拔２３００ｍ，由于极端土壤水分亏缺、很高的Ｔｌ和Ｖｐｄｌ，非气孔限制也出现。在不同海拔高度，蒸腾速率与气孔导度（Ｇｓ）关系密切，并受叶面温度（Ｔｌ）和叶面蒸汽压饱和亏缺（Ｖｐｄｌ）影响。水分利用效率随着海拔上升而升高。气孔密度随海拔上升而升高，呈现不同的塑性。在低海拔地区，通过影响气孔开放，ＳＷＣ和Ｔａ是裂叶沙参的碳同?

Field measurements were made of leaf net photosynthetic rate (Pn), apparent quantum yield (AQY), dark respiration (Rd), transpiration (Tr), water use efficiency (WUE), stomatal conductance (Gs), intercellular CO 2 concentration (Ci), leaf temperature (Tl), stomatal density, air temperature (Ta) and relative soil water content (SWC) for Adenophora lobophylla Hong in August, 1996. The species grows in the region from an altitude of 2300 m to 3400 m on the eastern boundary of the Qing Zang Plateau in Sichuan Province, China. Leaf gas exchange, water use efficiency and plasticity of populations in field were compared among different altitudes to evaluate the possible interactions between adaptation of A. lobophylla and environmental factors in these habitats. Pn and AQY at low altitudes were lower than those at high altitudes. They strongly responded to SWC and Ta. On the other hand, Rd at low altitudes was higher than that at high altitudes because of the higher air temperature there. The growth rates at low altitudes were associated with the increases in Rd and a relevant less Pn. Stomata showed strong responses to leaf to air vapor pressure deficit at the leaf surface (Vpdl) and Tl in these habitats. Increasing stomatal limitations to photosynthesis appeared to be responsible for the reduction in Pn at high Tl, Vpdl and low available soil water for A. lobophylla at low altitudes. Nonstomatal limitation to photosynthesis also happened at extreme soil water deficits and high Tl and Vpdl at an altitude of 2300 m. Tr had a close relationship with stomatal conductance and was also affected by leaf temperature and leaf to air vapor pressure deficit at the leaf surface among habitats grown in different altitudes. WUE increased with altitude. Increasing stomatal densities showed different plasticity of A.lobophylla as altitude increased. SWC and Ta appeared to be important factors to limit carbon assimilation in A.lobophylla at low altitudes, primarily through the process of stomatal closure. The overall results are in consistence with the hypothesis that strong pressure from unfavorable environmental factors to gas exchange and water use of A. lobophylla may prevent their population expansion at low altitudes, which indicate that the above mentioned restrictions might lead to the endangerment of A. lobophylla.