旱作条件下紫花苜蓿光合蒸腾日变化与环境因子的关系

在旱作条件下测定了4年生紫花苜蓿初花期光合蒸腾特性，以及光合有效辐射(PAR)、田间CO₂浓度(C_a)、相对湿度(RH)、大气温度(T_a)等环境因子的日变化，并采用相关系数、通径系数和决策系数分析了紫花苜蓿光合蒸腾特性日变化与环境因子的关系.结果表明，对光合速率日变化直接影响最大的因子是T_a，而RH、PAR和C_a主要是通过T_a而间接地影响光合速率日变化；对蒸腾速率日变化直接影响最大的因子是PAR，而RH、T_a和C_a主要是通过PAR而间接地影响蒸腾速率日变化.对光合蒸腾特性起主要决定作用的因子是PAR，主要限制因子是T_a.

Diurnal dynamics of photosynthetic and transpiration rates of alfalfa under dry farming and their relationships with environmental factors

In this paper,the diurnal dynamics of photosynthetic rate(P_n)and transpiration rate(T_r)of four years planted alfalfa under dry farming,as well as those of photosynthetic active radiation(PAR),CO_2 concentration in field(C_a),relative humidity(RH)and air temperature(T_a)were measured,and the relationships between the diurnal dynamics of P_n,T_r and climatic factors were analyzed by correlation coefficient,path coefficient,and decision coefficient analyses.The results showed that T_a had the greatest effect on the diurnal dynamics of P_n,while RH,PAR and C_a affected P_n mainly through their acting on T_a.PAR had the greatest effect on the diurnal changes of T_r,and RH,T_a and C_a affected T_r indirectly by acting on PAR.For the characteristics of photosynthesis and transpiration,PAR was the primary determining factor,and T_a was the main limiting factor.