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Abstract
Girdling followed by reopening of the girdle (late in June and July) increased fruit size on mature trees of grapefruit (Citrus paradisi Macf.) while effects of 1 or 2 applications of 2,4-dichlorophenoxyacetic acid (2,4-D) superimposed in a factorial layout were marginal. Girdling caused some delay in fruit maturation as did the 2,4-D applications. Girdling caused no apparent damage to trees the following year.
Abstract
One early treatment (late May) with 25 ppm gibberellic acid (GA3) strongly depressed summer and fall bloom and resulting off-season fruits of ‘Temple’ orange (Citrus reticulata Blanco × C. sinensis (L.) osbeck). A late June treatment failed to repress and even tended to increase the number of off-season fruits. A repeated treatment at both dates, had a smaller effect than a single early treatment. A possible effect of a late GA application on the persistence of off-season fruitlets is suggested. Girdling of a part of scaffold branches gave a response similar to that of the early GA treatment.
Abstract
Paclobutrazol (PP333) [(2RS,3RS)-l-(4-chlorophenyl)-4, 4-dimethyl-2-(l,2,4-triazol-l-yl-)pentan-3-ol] sprays applied to ‘Minneola’ tangelo trees, at 500 or 1000 ppm, before the onset of summer flush, markedly reduced total growth, number of shoots, and internode length. Soil treatments (0.4 and 0.8 g per square meter) had only a small effect, probably because of the short time from application to flush inception. Sprays of Morphactin (an auxin transport inhibitor), at 250 and 500 ppm did not reduce growth, but rather enhanced it by increasing the number of emerging shoots. The spring flush of the same trees also showed effects of paclobutrazol soil treatments, whereas other treatments were not different from control. Paclobutrazol sprays on comparable ‘Minneola’ trees just before the spring flush also reduced this growth. Paclobutrazol may become a tool for the control of vegetative growth of mature citrus trees.