A Comparison of Putrescine and Arginine Effects on Yield Components and Growth Parameters in Pistachio Trees

Introduction: Improving the growth characteristics of pistachio trees has always been of great importance. The present study aims to evaluate the effects of different levels of putrescine and its precursor arginine on some nut characteristics and physiological parameters of pistachio trees in ‘Owhadi’ cultivar. Materials and Methods: Pistachio trees were treated with putrescine 0, 0.1, and 0.2 mM as well as arginine 0, 300, and 600μM at two stages (the green tip and the tight cluster of the bud) in a factorial experiment based on a randomized complete block design (RCBD) with 4 replications. Results: According to the results, putrescine and its precursor arginine decreased the physiological disorders of pistachios and increased the crop yield. In addition, putrescine and arginine decreased the percentage of inflorescence bud abscission, fruit abscission, fruit deformation, as well as early splitting and indehiscent shells compared to the control treatment. In both ‘on’ and ‘off’ years, the effects of putrescine and arginine were greatly dependent on both the time of application and the concentrations used. According to the results, the exogenous application of these compounds, especially at the tight cluster stage of buds, increased indehiscent shells and the crop yield in both ‘on’ and ‘off’ years. The exogenous application of arginine at the tight cluster stage of buds decreased the abscission of inflorescence buds and other physiological disorders, but it increased indehiscent shells and the crop yield, especially arginine 600μM at the tight cluster stage of buds. Conclusion: It seems that arginine plays a key role in the growth and development of vegetative and reproductive characteristics in pistachios.