Foliar Application of Arginine Improves Vegetative and Reproductive Characteristics of Bearing Pistachio Trees

Pistachio is one of the most important horticultural crops in Iran.  There is a unique role for amino acids in the plant response to stressful conditions, and special physiological role for Arginine (Arg) compared to other amino acids.  The effects of this compound were investigated on vegetative and reproductive characters of bearing pistachio trees of ‘Ahmad-Aghaei’. The experiments were done as a factorial based on RCBD with four concentrations of Arg (0, 100, 200 and 300 µM) and three spraying stages (post harvest, flower buds swollen and flowering). Based on the results, Arg improved the vegetative and reproductive characters. Arg increased length and diameter of shoot, leaf area, the number of floweringbuds, the number of nuts in cluster, fresh weight of cluster, nut splitting (%) and ounce, and decreased flower buds abscission percent and blankness. Arg also significantly increased photosynthetic pigments (chlorophyll a and b and total chlorophyll) in bearing pistachio trees. The best concentration of Arg was 200 µM applied of the flowering stage, but the strongest effect on the number of nut in cluster, fresh weight of cluster and blankness were observed when spraying at the flower bud swollen stage.