苜蓿光合速率日变化及其与环境因子的关系

利用LI-6400光合仪测定苜蓿叶片净光合速率,研究其日变化及与环境因子的关系。结果表明: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;净光合速率峰值出现在10:00和13:00,分别为33.55和27.88μmol CO₂·m^-2·s^-1,第1峰值大于第2峰值;蒸腾速率的峰值出现在11:00和14:00,比光合速率滞后1小时;相关分析表明,苜蓿净光合速率与光合有效辐射、气孔导度呈极显著正相关(r=0.8433^**、0.8223^**),与田间CO₂浓度呈极显著负相关(r=-0.8125^**);在光照强度、CO₂浓度、气温和空气湿度4个环境因子中,影响净光合速率日变化的主要因子是田间CO₂浓度。

Relationship between Diurnal Changes of Alfalfa Net Photosynthetic Rate and Environmental Factors

In order to identify the relationship between diurnal changes of photosynthetic rate and environmental factors of Alfalfa(Medicago sativa L.cv.Zhenyuan),photosynthetic characteristics were monitored using portable LI-6400 photosynthesis system.The results show that the curves of diurnal variation in Pn(net photosynthetic rate) and Tr(transpiration rate) had two peaks and an obvious midday depression at 12:00 O′clock.The Pn peaks were detected at 10:00 am and 13:00 pm and reached to 33.55 μmol CO₂·m^-2·s^-1 and 27.88 μmol CO₂·m^-2·s^-1,respectively;the first peak was higher than the second.The Tr peaks were detected at 11:00 am and 14:00 pm and 1 hour behind those of Pn.Pn was significantly positively correlated with PAR(photosynthetically available radiation;r=0.8433^**) and Gs(stomatal conductance;r=0.8223^**) and significantly negatively correlated with Ci(intercellular CO₂ concentration;r=-0.8125 ^**).Ci was the major environmental factor influencing diurnal changes of the Pn of alfalfa.