脐橙光合特性及树冠光能分布对叶片光合速率的影响

Influences of photosynthetic characters and light distribution on photosynthetic rate in the canopy of Navel orange leaves

以清家脐橙为材料,研究其光合特性及树冠不同层间叶片光合速率(Pn)的差异。结果表明,脐橙叶片的光补偿点为18.0~27.0μmol.m-2.s-1,光饱和点为853.2~887.6μmol.m-2.s-1。晴天脐橙叶片的光合速率日变化呈双峰曲线,上午7:00~9:00叶片的光合速率随光照强度的增强而急剧增高,至9:00左右达最高峰,而后开始下降,至13:00左右跌入低谷,此后又缓慢上升,至17:00形成次高峰,到19:00降至最低点,有明显的“午休”现象。树冠不同部位光合有效辐射(PAR)有差异,光合有效辐射树冠顶层>树冠外层>树冠内层>树冠中心,在树冠外层和内层不同的方位PAR南部>西部>东部>北部。树冠各部位叶片的光合速率变化趋势:树冠顶层>树冠外层>树冠内层>树冠中心,在树冠外层和内层不同的方位Pn南部>西部>东部>北部。

The photosynthetic characters and the light distribution and its influences on photosynthetic rate in the canopy of Seike Navel leaves were studied. The results shewed that the light compensation point was 18.0- 27.0μmol·m^-2·s^-1, and the light saturation point was 853.2 -887.6μmol·m^-2·s^-1. Daily variation of photosynthetic rate was double peaks curve in Seike Navel leaves on clear days, Pn increased significantly with increasing intensity of illumination in Seike Navel leaves,Pn reached a maximum at 9：00a. m. ,then declined gradually,Pn reached a minimum at 13：00p. m. ,hereafter increased slowly, the min-poak occurred at 17：00 p.m. and the lowest point at 19：00p. m., ＂midday-rest＂ phenomenon was very obvious. Phot^ynthetically active radiation （PAR） was different in canopy layers, top layers 〉 outer layers 〉 inner layers 〉 center ,in different directions the change tendency of PAR was south 〉 west 〉 east 〉 north in outer layers and inner layers of the canopy. The change tendency of photosynthetic rate of Seike Navel leaves was top layers 〉 outer layers 〉 inner layers 〉 center in different positions, in different directions the change tendency of Pn was south 〉 west 〉 east 〉 north in outer layers and inner layers of the canopy.