Effects of Sinorhizobium meliloti Bacterium and Phosphorus on Leaf Chlorophyll Index, Nitrogen and Phosphorus Concentrations in Alfalfa Shoot and Root under Drought Stress Conditions

Soil water and nutrients are important factors controlling plants growth. Legumes inoculation with nitrogen fixing bacteria and phosphorus (P) fertilization can improve plants growth in drought stress conditions. The effects of Sinorhizobium meliloti inoculation, soil water and P levels on leaf chlorophyll index, nitrogen (N) and P concentrations in alfalfa (Medicago sativa cv. Ghareyonjeh) shoot and root were studied by conducting an experiment under greenhouse conditions in a clay loam soil. The study was performed as a factorial experiment based on a randomized complete blocks design including soil water conditions at three levels (0.5FC-0.6FC, 0.7FC-0.8FC and 0.9FC-FC), P at three levels (0, 30 and 60 mg P kg-1 soil equal to 0, 60 and 120 kg P ha-1 as Ca (H2PO4)2.H2O, respectively) and bacterium inoculation at two levels (with and without S. melilotiinoculation), with three replications. The leaf chlorophyll index was measured during the growth period. After harvesting, concentrations of N and P in the alfalfa shoot and root were measured. The results indicated that the leaf chlorophyll index and shoot N concentration were significantly increased by decreasing soil moisture content from 0.9FC-FC to 0.5FC-0.6FC (water deficit stress) and shoot and root P concentrations were significantly decreased (p