Effect of mineral nitrogen on fluorescence changes of photosynthetic pigments of alfalfa under drought tension conditions

In order to investigate the effect of organic nitrogen on fluorescence changes of photosynthetic pigments of Hamedani alfalfa under drought conditions, this experiment as factorial was conducted in a completely randomized design with three replications. The treatments of experiment consisted of drought tension in three levels of 35, 60 and 85 percentage of field capacity and nitrogen fertilizer at four levels of without fertilizer, 30, 60 and 90 kilogram nitrogen per hectare. The results showed, the interaction of nitrogen at drought at one percent level on chlorophyll a concentration, total chlorophyll and at the level of 5 percent on chlorophyll b concentration, the ratio of chlorophyll a to b and carotenoids was significant. With increasing levels of dryness the amount of chlorophyll a concentration, b, total and carotenoids was reduced but ratio chlorophyll a to b was increased. Nitrogen consumption improved photosynthetic pigments so that chlorophyll a concentration, chlorophyll b, total chlorophyll increased with nitrogen consumption and the ratio of chlorophylls and the amount of carotenoids were reduced. Nitrogen fertilizer on the maximum fluorescence (Fm), quantum yield (Fv / Fm) in pre-tension and on the minimum fluorescence (Fo) and (Fv / Fm) in after three days tension and on (Fv / Fm) in a week after tension had a significant effect. Drought tension had a significant effect only on (Fo) and (Fm) in three days after tension and on (Fo) and (Fv / Fm) in a week after tension. The minimum and maximum amount of protein was obtained in the conditions of without using nitrogen (4.79 milligram on gram wet weight) and consumption of 90 kilogram nitrogen per hectare (10/06 milligram on gram wet weight) was obtained. Nitrogen interaction in dryness, on stem height and plant dry weight was also significant. In tension conditions, stem height and plant dry weight reduced.