不同生境条件下凤丹生长及光合特性比较
Comparison of Growth and Photosynthesis-Related Characteristics of Paeonia ostii in Different Habitat Conditions

设置林下（郁闭度0.6）和空旷地两种生境，比较不同生境下凤丹生长及光合特性，探讨凤丹优化栽培的合适生境.结果表明：林下生境的凤丹冠幅面积、一级分枝数、单株挂果量及单位冠幅面积挂果量均优于空旷生境，而前者树高略低于后者.林下生境的凤丹叶绿素a和叶绿素b分别高出空旷生境的103.53%和122.86%，差异具有统计学意义（p < 0.05）.在光合日变化规律方面，林下生境的凤丹净光合速率呈现明显的'单峰'曲线，而空旷生境下的呈不明显'双峰'曲线，总体上前者高于后者；前者胞间CO₂浓度和蒸腾速率低于后者而气孔导度无明显变化趋势；林下生境的光能利用效率和水分利用效率普遍显著高于空旷生境.林下生境因存在一定程度的遮荫，阻挡了夏季强光对凤丹的不良影响，同时也减少了林下的光合有效辐射，但凤丹自身的特性或适应性使得光能和水分利用率高，净光合速率高，有机物合成多，分枝多，植物长势好.
In order to explore the suitable habitat for optimized cultivation of Paeonia ostii, this plant species was grown under forest with a canopy density of 0.6 and in an open land, and its growth and photosynthetic characteristics under the two habitat conditions were compared. The results showed that the crown-area, primary branch number, fruit yield per plant and fruit yield per crown-area of P. ostii in the under-forest habitat were better than those in the open land, while its plant height was slightly less than in the open land. The contents of chlorophyll a and chlorophyll b of its functional leaves were significantly different between these habitats, being 103.53% and 122.86% higher in the under-forest habitat than in the open land, respectively. Daily variation of net photosynthetic rate of P. ostii presented a typical one-peak curve in the under-forest habitat and an atypical double-peak curve in the open-land habitat. In general, net photosynthetic rate, light use efficiency and water use efficiency were higher and intercellular CO₂ concentration and transpiration rate were lower in the under-forest habitat than those in the open-land habitat, while no significant difference was detected in stomatal conductance between the two habitats. In conclusion, in the under-forest habitat, appropriately shading prevented P. ostii from irradiation of strong light in summer by reducing photosynthetically active radiation, however, the characteristics of P. ostii or its physiological adjustment resulted in higher light and water use efficiency and net photosynthetic rate, better synthesis of organics, more branches and greater growth vigour