Effect of Foliar Application of Amino Acids on Grain Yield and Physiological Traits of Chickpea under Drought Stress

This study aimed to investigate the effects of foliar application of proline, valine, alanine and commercial amino acids on physiological traits and yield of chickpea under irrigation regimes. The experiment was conducted as split plots in a randomized complete block design with three replications in two consecutive growing seasons in years, 2019 and 2020 in the Research Farm of the Faculty of Agriculture, Tarbiat Modares University, Iran. Experimental treatments composed of irrigation regimes at three levels including optimal irrigation, moderate and severe water deficit stress as main plot units, and foliar application regimes including proline + valine, proline + alanine, alanine + valine with two controls of distilled water and without foliar application as subplot. The results revealed that in addition to reducing the physiological traits of chickpea, the water deficit stress decreased the grain yield. Under water deficit stress, the amount of chlorophyll, flavonoid and anthocyanin decreased sharply. Moreover, foliar application of amino acids significantly affected grain yield, chlorophyll a, b and total, carotenoids, anthocyanins and flavonoids, photosynthesis rate, water vapor stomata conductance, CO₂ stomata condutance, proline and ratio of intracellular CO₂ concentration to air CO₂ concentration. Although foliar application of all amino acids could improve plant yield in the face of low irrigation stress, proline + alanine treatment outperformed rather than others and improved most plant traits. In other words, foliar application of proline + alanine, proline + valine, and commercial amino acids, respectively, affected the measured plant traits by providing tolerance mechanisms in the plant under water stress. Consequently, plant oxidative response induced by water deficit decreased and plant growth and yield improved. Therefore, according to the results obtained under low water stress conditions, the combined treatment of amino acids proline + alanine, proline + valine and amino acids of commercial composition is recommended to ameliorate the adverse effects of drought stress on chickpea.