香椿苗期几个光合特性的研究

研究结果表明，香椿品系间的光合能力和光合特性存在差异。红芽品系和红叶品系的光合能力高于绿芽品系。红芽品系的光饱和点为３０ＫＬＸ，而绿芽品系为１０～４０ＫＬＸ。红芽品系的光合适温为２０～２２℃（春季），而绿芽品系为１６～２４℃。香椿苗期的光合能力和光合特性亦存在季节性差异。净光合速率（Ｐｎ）在春季出现高峰，夏初低谷，从仲夏至秋冬变化平缓且Ｐｎ值低于春季。秋季的光合适温比春季高２℃，为２２～２４℃。在晴天，香椿苗光合日变化呈双峰型，上午大峰，下午山峰，中午低谷。综合分析表明，小气候因子中强光、高温和低湿是造成中午Ｐｎ降低的主要原因。

Studies on Several Photosynthetic Characteristics of Chinese Toon Seedlings

Several photosynthetic characteristics of Chinese Toon (Toona Sinensis Roem)seedlings were studied. The results obtained are as follows. There are different photosynthetic capacities and photosynthetic charaeteristics among the lines of Chinese Toon. Photosynthtic capacity of red buds line and red leaves line is higher than that of green buds line and red leaves line is higher than that of green buds line. The saturation point of photosynthesis of red buds line is 30klx while that of green buds line is 1040klx. The optimum temperature of photosynthesis of red buds line is 20～22℃ in the spring, while that of green buds line is 16～24℃ in this time. The seasonal variation in photosynthesis shows that the highest peak occurrs in the spring (May) but the lowest tide takes place at the beginning of summer, and there is a inobvious variation in photosynthesis from mid-summer to the beginning of winter. The optimum temperature of photosynthesis is 22～24℃ in photosynthesis shows as a double sigmoid type. There are a bigger peak in the morning and a smaller one in the afternoon, and a low tide in the midday. The major reasons which cause net photosynthetic rate becoming foul in the midday are such factors as high light intensity, excessively high ambient temperature and excessively low atmospheric relative humidity.