The mineral nitrogen fertilizer effects on photosynthetic index of alfalfa (Medicago sativa) under salinity stress condition

Abstract:A greenhouse study was conducted to evaluate the effects of mineral nitrogen fertilizer effects on some physiological characteristics of alfalfa (Medicago sativa) under salinity stress conditions at Mohaghegh Ardabili University experimental greenhouse in 2010. The experimental design was randomized complete design as factorial with three replications. Alfalfa seeds were planted in five kg pots after disinfecting. The mineral nitrogen fertilizer was applied after the emergency level as Urea at four different levels (0, 30, 60, 90 kg.ha-1). The salinity was applied at three different levels (0, 100, 200 mM). The evaluated factors in this study were stomata resistance, amount of chlorophyll and chlorophyll fluorescence, respectively. The result of experiment demonstrated that the increase of salinity reduced both the stability of chlorophyll and quantum yield of photosystem II, while the stomata resistance increased significantly. The mineral nitrogen fertilizer consumption did not have significant effects on the regarded features. The process of stomata resistance variability displayed that the increase of salinity improved the stomata resistance at first but it reduced later because the plant was adapted to the condition as well.