4个紫花苜蓿品种分枝期光合速率、蒸腾速率日变化及其影响因子分析

Analysis on Diurnal Changes of Photosynthesis and Transpiration Rate and Effecting Factors of Four Alfalfa at Branching Stage

在自然条件下,利用CIRAS-Ⅱ型便携式光合仪对分枝期的阿尔冈金、WL323高品质、WL414、大富豪4个紫花苜蓿品种(3龄1茬)的叶片净光合速率(Pn)、蒸腾速率(Tr)及相关的生理因子和生态因子的日变化进行测定,分析了4个紫花苜蓿品种的光合、蒸腾速率以及各影响因子对光合、蒸腾速率日变化的影响。结果表明,Pn、Tr及相关生理、生态因子的日变化趋势都呈单峰曲线或U型曲线,WL323高品质是高光合、高水分利用率和低蒸腾品种;4个苜蓿品种Pn的下降是由非气孔因素所致,Tr日变化与气温(Ta)、光合有效辐射(PAR)相关性最密切,且变化趋势一致;而Pn则主要受PAR和胞间CO2浓度(Ci)及气孔导度(Gs)的影响,其日变化趋势与PAR变化趋势相同,与Ci的变化趋势相反;生态因子PAR和Ta是4个紫花苜蓿品种Tr的主要决定因子,Ca是主要的限制因子,PAR是Pn的主要决定因子;生理因子Gs是Pn和Tr的主要决定因子,Ci是主要限制因子。

Under natural conditions,the diurnal changes of photosynthesis and transpiration rate of four alfalfa varieties （Algonquin, WL323HQ, WL414, Millionaire） and related physiological and ecological factors at branching stage were measured with CIRAS-II portable photosynthesis system. The physiological factors included leaf temperature （T1） , stomatal conductance （Gs） and internal CO2 concentration（Ci）. The ecological factors included photosyn thetic available radiation （PAR）, air temperature（Ta ）,CO2 concentration in field （Ca）. Relative analysis was used to discuss how related factors influenced diurnal changes of photosynthesis and transpiration rate. The results showed that the net photosynthesis rate of the four varieties varied in a single-peak curve or a U-shape curve; WL323HQ had high photosynthetic rate, high water utilization rate and low transpiration rate. The depression of the four alfalfa varieties＇ photosynthesis rate mainly resulted from non stomatal factors; Coefficient analysis showed that Ta and PAR were primary determining factors for the characteristics of transpiration, the tendency of variation were similar; simultaneously, PAR,Ci and Gs were primary determining factors for the characteristics of photosynthesis, the diurnal changes were similar to PAR and opposite to Ci; PAR and Ta were primary ecological determining factors for the characteristics of transpiration, Ca was the main limiting factor for the characteristic of transpiration; PAR was the primary ecological determining factor for the characteris tics of photosynthesis, Gs was the primary physiological determining factor for the characteristics of photosynthesis and transpiration, Ci was the main limiting factor.