Abstract
The effect of hydrogen cyanamide (Dormex) at different concentrations for reaching early break dormancy in buds of "Astrachan" apple (Malus sylvestris, Mill) trees and their effects on metabolic changes in the content of buds from promoter and inhibitor substances during their release from dormancy was investigated. The efficiency of early bud break was noticed in varying degrees with Dormex at different concentrations. All applied concentrations led to early bud break, short flowering duration, high percentages of bud break and fruit-set, high contents of total indoles, indole-3-acetic acid, gibberellic acid, total and conjugated phenols and low content of abscisic acid and free phenols. These results were positively reflected in the final yield. Accordingly, we recommend using Dormex at 3% for reaching the early break dormancy in buds of "Astrachan" apple trees under Egyptian winter conditions and maximizing the yield by regulating the hormonal and phenolic content in buds.
Highlights
Dormancy is "the inability to initiate growth from meristems or other organs and cells with the capacity to resume growth under favorable conditions" (Rohade and Bhalerao 2007)
The foliar application with hydrogen cyanamide (Dormex) at three concentrations for "Astrachan" apple trees was hastened the floral bud break as compared to the control in which trees were sprayed with tap water (Table 1)
Foliar-applied Dormex at 1, 2 and 3% increased the contents of total soluble phenols and conjugated phenols and decreased free phenols in the floral buds of "Astrachan" apple trees when compared to the control in which trees were sprayed with tap water (Table 5)
Summary
Dormancy is "the inability to initiate growth from meristems or other organs and cells with the capacity to resume growth under favorable conditions" (Rohade and Bhalerao 2007). The main physiological stages of dormancy have been recently termed paradormancy, endodormancy, and ecodormancy. It was demonstrated that cyanamide calcium salt, when applied to soil, may be hydrolyzed into active CA after contact with water molecules and is converted into urea inter alia by cyanamide hydratase (Cah) produced by the fungus Myrothecium verrucaria (Maier-Greiner et al 1991). It may be considered as a source of inorganic nitrogen. Except of its fertilizing role, its more recent applications are mainly breaking dormancy of fruits (e.g. grape, apricot, apple), buds (Ben Mohamed et al 2012 a &b; El-Sabagh et al 2012; Vergara et al 2012; Bill 2012 and Eshghi et al 2012; Seif El-Yazal and Rady 2012&2013; Seif El-Yazal et al 2012&2014; Ahmed et al.2014; Leonel et al.2015; İmrak et al.2016 and Mohamed and Gouda 2017)
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