影响紫花苜蓿叶片光合速率日变化的因素分析

Analysis of Major Effecting Factors on Diurnal Changes of Photosynthetic Rate for Leaves of Alfalfa

在夏季干热天气条件下,用LI-6400光合仪田间测定了旱作栽培的四年生紫花苜蓿品种再生草初花期的光合日变化及其影响因子,利用相关性分析和通径分析方法,考察了光合有效辐射、叶温、相对湿度、气孔导度和胞间CO2摩尔分数对光合速率的影响。结果表明,紫花苜蓿叶片净光合速率日变化为典型的"双峰"曲线,两个峰值分别出现在10:00左右和14:00左右,第一峰值大于第二峰值,正午12:00左右存在明显的光合"午休"现象。早晨6:00-10:00期间,光合速率的上升主要是光合有效辐射、温度和相对湿度造成的。10:00-14:00期间,光合速率的降低,尤其是"午休"期间的下降,气孔因素是主要限制因子。而14:00-18:00期间,光合速率的下降主要受非气孔因素的限制。

During fine weather, daily changes in photosynthetic rate （Pn） and its effecting factors were determined by Portable LI-6400 Photosynthesis System under dry farming for alfalfa species at the flowering after the first cutting in the fourth growth year. The relationships between diurnal changes of photosynthetic rate （Pn） and its factors were analyzed with correlation analysis and path analysis. The result as follows. The curves of diurnal change in photosynthetic rate （Pn） of alfalfa leaves all had two peaks, and the first peak value appearing around ten o＇clock was higher than the second around fourteen o＇clock. In addition, there was an obvious midday depression around 12：00 o＇ clock. During 6：00-10：00 o＇clock period, climbing of photosynthetic rate （Pn） was primarily caused by photosynthetic active radiation （PaR） ,leaf temperature （Ti）, relative humid （RH） . Descending photosynthetic rate （Pn） from 10：00 o＇clock to 14：00 o＇clock, especially ＂middy depression＂ was mostly caused by stomata factor. During 14 ： 00-18 ： 10 o＇clock, non-stomata factors were primary reason of descending of photosynthetic rate （Pn）.