روند تغییرات نیتروژن و تأثیر اسیدهای آمینه در گلدهی و تشکیل میوه مرکبات

Background and Objectives: Amino acids are a large group of biological compounds that contain an amino group and a carboxyl group. Amino acids used in foliar nutrition are usually mixtures of different amino acids and short-chain peptides. These amino acids are plant growth stimulants that can be used by foliar spraying and fertigation. Plants may consume amino acids as a source of nitrogen, and in some cases, the amino acid may also be a plant stimulant. On the other hand, the flowering and fruiting period in citrus trees is the most important and critical stage of fruit development in fruit trees. The maintenance of reproductive organs and fruits during this period is directly related to the final yield of the trees. There is a high demand for nitrogen during the flowering and fruiting period. For this purpose, the trend of leaf nitrogen changes during the flowering stage of citrus trees and the effect of amino acids on nitrogen concentration, flower drop, and fruit formation of citrus trees were investigated in two separate experiments.
 

 



Materials and Methods: In the first experiment, trends of nitrogen changes in the leaves of Satsuma mandarin (C. unshiu cv. Miyagawa) trees on Carrizo citrange (Citrus sinensis Osb. × Poncirus trifoliata L. Raf.), rootstock, and on Thomson Navel oranges on Sour Orange (C. aurantium L.) rootstock were measured in the eastern Mazandaran region. In the second experiment, the effect of foliar spraying of amino acids (combined amino acids) was carried out in a randomized complete block design with three treatments and three replications for three years with Satsuma mandarin (C. unshiu cv. Miyagawa) trees on Carrizo citrange (Citrus sinensis Osb. × Poncirus trifoliata L. Raf.), rootstock. The treatments included: T₁. Control; T₂. amino acid 1 g L^-1; T₃. amino acid 3 g L^-1. The amino acid mixture used contained 8% aspartic acid, 12% glutamic acid, 14% serine, 8% glycine, 2% histidine, 6% arginine, 6% alanine, 6% threonine, 12% proline, 6% valine, 7% leucine, 5% phenylalanine, and about 1% methionine, cysteine, lysine, isoleucine, and tyrosine, and 13% total nitrogen.
 
Results: The results of the first experiment showed that the nitrogen concentration of leaves in Satsuma gradually began to decrease from the time of bud break and the beginning of spring shoot growth, and reached a minimum at the flower opening stage, from 2.65% at the beginning of sampling to 1.84% at full bloom. From full bloom, the amount of nitrogen in the leaves gradually increased again, from 1.84% to 2.66% at the physiological fruit drop (June drop) stage. In the case of Thomson Navel orange trees, the results showed that the nitrogen concentration decreased from 2.57% at the time of sampling to 1.85% at full bloom. After flowering, the nitrogen in the leaves gradually increased and reached from 1.85% to 2.56% at the physiological fruit drop (June drop) stage. The results of the second experiment showed that foliar spraying of amino acids at concentrations of one and three parts per thousand (W/V) showed that foliar spraying treatments had no significant effect on reducing flower and fruit drop, increasing fruit set, leaf nitrogen concentration, and increasing the yield of Satsuma mandarin trees.
 

 



Conclusion: According to the results of this study, the flowering time in citrus trees coincides with the minimum nitrogen concentration in the leaves. This indicates the limitation and need for nitrogen in this sensitive stage of phenology, but foliar spraying of amino acids did not have a significant effect on increasing nitrogen concentration and fruit set. Therefore, foliar application of amino acids for citrus trees during the flowering and fruit set stages in the climatic conditions of the north of the country is not recommended for citrus orchards