黄土高原半湿润区不同生长年限苜蓿叶片光合性能研究

A study on photosynthetic characteristics of alfalfas grown for different lengths of time in the semi-humid region of the Loess Plateau

利用Li-6400型光合作用测定系统,测定了不同生长年限苜蓿叶片的光合参数。结果表明,1)生长年限对苜蓿光合特性有较大的影响,对气孔导度的影响最大,其次是蒸腾速率和叶绿素相对含量。2)苜蓿叶片净光合速率、蒸腾速率日变化均呈现"双峰"曲线,有明显的光合"午休"现象。3)净光合速率与光合有效辐射、气孔导度、叶绿素相对含量呈极显著正相关,与蒸腾速率呈显著正相关,与田间CO2浓度呈极显著负相关。蒸腾速率与叶绿素相对含量、光合有效辐射呈极显著或显著正相关,与田间CO2浓度呈极显著负相关。4)从苜蓿的光合特性综合分析,苜蓿的最佳利用期为6年。

The daily dynamics of photosynthetic characteristics of alfalfas grown for different lengths of time in the Loess Plateau were monitored using a Portable LI-6400 Photosynthesis System. The results showed： 1） Alfalfas grown for different lengths of time had considerable influence on photosynthetic characteristics of which the most important was stomatal conductance followed by transpiration rate and the chlorophyll relative content. 2） Diurnal variation in Pn and Tr had two peaks, and an obvious midday depression. 3） The net photosynthetic rate was significantly positively correlated with photosynthetic radiation, stomatal conductance, the relative chlorophyll content, and transpiration rate. The net photosynthetic rate was significantly negatively correlated with intercellular CO2 concentration. The transpiration rate was significantly positively correlated with the relative content of chlorophyll and photosynthetic radiation but significantly negatively correlated with intercellular CO2 concentration. Analysis of the photosynthetic characteristics showed the best length of time to grow alfalfa was six years.