Effect of various nitrogen sources on physiological and biochemical changes of beans under waterstress conditions.

Nitrogen has an important role for supplying carbon skeletons which needs for producing compatible solutes and stress tolerance enzymes. Water deficit affects nitrogen fixation in legums. So we studied the effect of various nitrogen sources on physiological، and biochemical features of bean under water stress. This experiment was conducted as factorial based on completely randomized design with three replications in the greenhouse of university of Mohaghegh Ardabili in 2012. The treatments irrigation included three levels (30، 55، and 80% of field capacity) and nitrogen sources (control، N source as ammonium، nitrate، and nitrate + ammonium). In this experiment lysine and methionine amino acids، catalase and polyphenol oxidase enzymes activity، soluble sugars، proline and proteins content measured in 3، 5 and 7 days after the stress induction. Water stress increased leaf proline and soluble sugars content. Using of nitrate and nitrate + ammonium caused the highest proline and total soluble sugars content، while enhancing stress intensity decreased protein content. Nitrate showed remarkable impact on protein content under water stress conditions. The highest lysine produced by severe stress، whereas methionine decreased by enhancing stress. Supplying mineral nitrogen significantly affected lysine content، compared to the control and increased and nitrate was the most effective nitrogen source for increasing methionine. Catalase and polyphenol oxidase activities were elevated under stress conditions، compared to the non-stress ones. Combined application of ammonium and nitrate showed the highest activities of these enzymes.