Effects of shoot girdling on bud abscission, carbohydrate and nutrient concentrations in pistachio (Pistacia vera L.)

Abstract

SummaryThe effects of shoot girdling and fruit removal on bud abscission, and of shoot girdling on nutrient and carbohydrate concentrations in leaves, inflorescent buds and current wood of pistachio shoots were investigated. Girdling individual shoots at the base of the current year’s shoot (girdle I), thus separating inflorescent buds at the terminus of the current year’s shoot from the developing fruits, reduced inflorescent bud abscission by 62–66% compared to untreated controls. In contrast, girdling at the base of 1 year-old shoots (girdle II) or fruit removal treatments reduced bud abscission by 20% and 16%, respectively, in 1994; but had no effect on bud abscission in 1995. Girdle I significantly decreased N concentrations in leaves and Ca, Mg and Mn concentrations in all parts. In contrast, concentrations of P and K in inflorescent buds were significantly higher in girdled shoots. Girdle I increased the dry weight of inflorescent buds and non-structural carbohydrate concentrations in inflorescent buds and current year’s wood. Current wood and leaves on girdled shoots had higher starch accumulation, but leaves had lower fructose concentrations than control leaves. Inflorescent buds on girdled shoots had higher concentrations of starch and sugars, especially sucrose. The possibility that a reduction in sucrose movement from leaves to inflorescent buds inhibits bud growth and triggers inflorescent bud abscission is discussed.