中文摘要：

测定了高光照和低光照2种光环境下美洲商陆的光合性能指标以及比叶面积、热值、碳素、氮素利用效率等，以分析其对光环境的适应性。结果表明：低光照下美洲商陆的光饱和点、光补偿点、暗呼吸速率都显著低于高光照下的值，但表观量子效率、最大净光合速率和光合系统性能指数却与高光照下无明显差异；低光照下比叶面积远大于高光照下，叶绿素a／b值则显著低于后者。另外，低光照下美洲商陆的光合氮利用效率、矿质元素利用效率和光能利用效率显著高于高光照下的植株，而热值及碳素和水分利用效率则显著低于后者。研究表明，美洲商陆可以根据光环境的变化来调整形态和生理适应性，使其在不同环境下均能够充分利用丰富资源且最大可能地利用限制性资源。

英文摘要：

In this study, the adaptability of Phytolacca americana to light environment was ana- lyzed based on the investigation of the photosynthetic performance indices, specific leaf area, cal- orific value, carbon and nitrogen use efficiency in P. americana under both shaded and unshaded environments. The results showed that the light saturation point, light compensation point and respiration rate all decreased significantly in the shaded P. americana, but the apparent quantum yield, maximum net photosynthetic rate and photosynthetic performance index showed no signifi- cant difference between the shaded and unshaded plants. In addition, the specific leaf area of the shaded P. americana was much larger, while the chlorophyll a/b ratio, the calorific value, car- bon use efficiency and water use efficiency were significantly lower than those of the unshaded plants. Furthermore, the photosynthetic nitrogen use efficiency, mineral element use efficiency and light use efficiency in the shaded plants were significantly higher than those in the unshaded plants. The results suggest that P. americana can adjust its adaptability morphologically and physiologically to varied light environments, so as to make an efficient use of available radiation.