内蒙古高原甘蒙锦鸡儿光合作用和水分代谢的生态适应性研究

 对分布于内蒙古高原和林格尔和阿拉善的甘蒙锦鸡儿（Caragana opulens）种群的光合特性和水分代谢特性进行了比较研究。结果发现：和林格尔种群的光补偿点（500 μmol proton·m-2·s-1以下）、光饱和点（1 200 μmol proton·m-2·s-1）、光合最适温度（26 ℃）均低于阿拉善种群（光补偿点为700～800 μmol proton·m-2·s－1之间；光饱和点为1 500 μmol proton·m－2·s－1；光合最适温度为28～29 ℃），在低温、低光强下表现出更高的光合速率；和林格尔种群比阿拉善种群需要更高的空气湿度来维持其光合速率；和林格尔种群表现高蒸腾、高光合和低水分利用效率的代谢特点，阿拉善种群采取低蒸腾、低光合和高水分利用效率的节水对策。这些生理特性与它们分布区的光、温、湿条件相适应。阿拉善种群的净光合速率、蒸腾速率和光能利用效率远低于和林格尔种群，而水分利用效率和叶水分亏缺明显高于和林格尔种群。这主要是由于两地区水分状况差异引起的。

ECOLOGICAL ADAPTATION OF CARAGANA OPULENS ON THE INNER MONGOLIA PLATEAU:PHOTOSYNTHESIS AND WATER METABOLISM

Caragana opulens belongs to the Caragana genus of legume, and it is found across a vast area of the Inner Mongolian Plateau from Daqing Mountain and Erlianhaote (112° E) in the east to Alashan (105° E) in the west. There have been many reports about its distribution, floristic composition, growth habits, anatomy and morphology. However, there have not been any reports about its physiological and biochemical characteristics. The adaptation of plants to their environment is determined by their genetic potential, but light energy and water metabolism are ready measurable indicators. The characteristics of photosynthesis and water metabolism of C. opulens populations which are found in Helinger (a semi-arid/partial humid region with lower temperature, lower light intensity and shorter day length) and Alashan (a very droughty region with higher temperature, higher light intensity and longer day length) were compared in this paper in order to understand the adaptative mechanisms of the species to its habitat. The results indicated that the light compensation point (<500 μmol proton·m－2·s－1), light saturation point (1 200 μmol proton·m－2·s－1) and optimum temperature for photosynthesis (26 ℃) in the Helinger population were all lower than those in the Alashan population (700-800 μmol proton·m－2·s－1, 1 500 μmol proton·m－2·s－1 and 28－29 ℃, respectively). The Helinger population exhibited a higher photosynthetic rate at lower temperature and light intensity; i.e. the Helinger population exhibited better adaptations to lower temperature and light radiation, while the Alashan population was better adapted to higher temperature and more intensive light radiation. The Helinger population needed higher relative humidity to maintain its higher net photosynthesis rate than the Alashan population. The Helinger population was characterized by higher transpiration rates, higher photosynthetic rates and lower WUE, whereas the Alashan population exhibited water-saving strategies with lower photosynthetic rates and lower transpiration rates. These results suggest that the different populations have adapted physiologically to local conditions of light, temperature and humidity allowing them to photosynthesize most efficiently in their native habitats. Considering that water is a key factor for plant growth and development in the Inner Mongolia Plateau and that there is a difference in annual precipitation, soil water content and plant water status between the Helinger and Alashan regions, it is suggested that water shortage was the key driving factor responsible for the physiological differences in the net photosynthetic rate, transpiration rate, light use efficiency, and water use efficiency between the two populations.