Efectul combinat al fertilizării cu fosfor şi deficitului de apă din sol asupra dezvoltării frunzelor şi concentraţiei de aminoacizi la două cultivare de soia (Glycine Max l. Merr)

The effects of phosphorus application (KH2PO4) levels 0 mg P/kg (P0), 10 mg (P10), 20 mg (P20) and 100 mg P/kg (P100)on leaves development and amino acids concentrations in two cultivars of soybean under two soil moisture regimes: control as normal irrigation, 70% of water holding capacity (WHC) and moderate stress (35% WHC) were studied. Plants were subjected to water deficit conditions at flowering stage for two weeks. Leaves area and amino acids concentrations in leaves were measured in relation to P nutrition. Plant performance of Licurici was better than Zodiac under P deficiency (P0) and low P (P10) supply. Leaves growth of both soybean cultivars was significantly reduced when the soil moisture content was decreased from 70% to 35% WHC. The highest leaf area and dry matter accumulation by leaves was found in the treatment with 100 mg kg-1 of P application. The same trend of P supplementation influence was denoted in plants subjected to drought stress, but to a lesser extent than in well-watered plants. Total soluble amino acids concentrations in leaves rose under temporary drought irrespective of P nutrition levels. Cultivar Zodiac displayed higher response in amino acids accumulation at suboptimal moisture regime. Hence, the adequate P fertilization improved the ability of soybean plants to tolerate drought stress