遮荫对珙桐幼苗光合特性及生长特征的影响研究

A Study of the Effects of Shading on the Growth and Development of Davidia involucrata Seedlings

以不同遮荫条件(50%、25%和自然光)下适应生长1 a后的珙桐幼苗为研究对象,测定分析了珙桐幼苗的生理生化指标和生长的变化特征,结果表明:(1)不同的遮荫处理下,珙桐幼苗的净光合速率日变化曲线均为双峰型,有"午休"现象。但不同光强下出现峰值的大小和时间有差异。不同的光强下蒸腾速率日变化趋势也是不一致的,全天蒸腾速率大小顺序为一层遮荫(50%)>两层遮荫(25%)>全光照。(2)遮荫下珙桐的单叶面积、比叶面积和叶柄长均大于全光照下,表明珙桐利用弱光的能力很强,提高了对有限光资源的吸收。遮荫试验结果说明:适度的遮荫(50%透光率)有利于珙桐幼苗生长。

In order to investigate the effects of shading on the growth and development of Davidia involucrata seedlings, a comparative study was made of the photosynthetic characteristics and growth characteristics of D. involucrata seedlings. The one-year old D. involucrata seedlings cultivated were used as experimental materials under different light intensity （ 100% ,50% and 25% ）. The results showed that （ 1 ） the daily net photosynthetic rates of different shading treatments of D. involucrata seedlings were all bimodal curves and ＂Midday depression＂ phenomenon was observed. But under different light intensity the value and time of the peak were different. The daily variation trend of transpiration rate under different light intensity was different and in an order of one-layer shading （5%） 〉 two-layer shading （25%） 〉 full surtlight.. （2） The average leaf area, specific leaf area and leafstalk length of Davidia involucrate under shading were larger than those of Davidia involucrate under full sunlight. It indicated that Davidia involucrate had strong ability of utilizing the limited low light resource. This study showed that Davidia involucrata seedlings grew best under appropriate shading（50% Transmittance）.