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  • Author or Editor: Elodie B. Ho-a x
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Uniconazole (0.2 g a.i. per cm trunk diameter) was applied as a soil drench to 2-year-old potted macadamia (Macadamia integrifolia Maiden & Betche) trees, and reapplied yearly for 4 additional years. Uniconazole significantly reduced tree height and trunk diameter 1 year after initial treatment, and suppressed shoot extension for the duration of the study. It significantly increased flowering the second year after initial treatment, the first year that both the control and treated trees flowered. Subsequently, no differences in flowering were observed until the fifth year, when flowering was significantly less in treated trees, probably due to reduced shoot and trunk growth and tip dieback. Chemical name used: E-1-(p-chlorophenyl)-4,-4-dimethyl-2-(1,2,4-triazole-1-penten-3-ol) (uniconazole).

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Flowering of Macadamia integrifolia trees was monitored following application of 220 mg/liter gibberellic acid (GA3) at various times preceding the onset of the flowering season. In untreated trees, flowering extended over a 4-5 month period. When GA3 was applied at 2, 3 and 4 months before the onset of anthesis, raceme production during the entire flowering season was inhibited. A slight reduction in raceme production was observed when GA3 was applied at 1 month preceding anthesis. This application coincided with appearance of the earliest infloresceuces. GA3 application after the onset of anthesis did not alter the flowering pattern of trees during the remaining 4 months of the flowering season. Results suggest that GA3 inhibits flower initiation, but has no effect on raceme emergence after flower bud differentiation has occurred. The relationship between flower initiation and raceme emergence will be discussed.

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Flowering of Macadamia integrifolia trees was monitored following application of 220 mg/liter gibberellic acid (GA3) at various times preceding the onset of the flowering season. In untreated trees, flowering extended over a 4-5 month period. When GA3 was applied at 2, 3 and 4 months before the onset of anthesis, raceme production during the entire flowering season was inhibited. A slight reduction in raceme production was observed when GA3 was applied at 1 month preceding anthesis. This application coincided with appearance of the earliest infloresceuces. GA3 application after the onset of anthesis did not alter the flowering pattern of trees during the remaining 4 months of the flowering season. Results suggest that GA3 inhibits flower initiation, but has no effect on raceme emergence after flower bud differentiation has occurred. The relationship between flower initiation and raceme emergence will be discussed.

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Uniconazole at 0.20 g-ram of a.i./cm of trunk diameter was applied as a drench to potted 2 year-old M. integrifolia cv. Kau trees in July 1990, and reapplied in August 1991, August 1992 and August 1993. Observations between December 1991 to December 1993 showed that elongation of newly emerging vegetative flushes was inhibitedwithin 6 months after the initial treatment. Shoots had a compact appearance, and the overall height of the trees was shorter than in untreated trees. By December 1993, diameters of the treated trees were also signficantly smaller than the controls. Uniconazole increased the number of racemes, number of racemes with mature fruit set and fruit production in young trees during the 1992 and 1993 seasons. The effect was more pronounced in 1992 compared to 1993. Results from this study show that young macadamia trees can be brought into heavier bearing at an early age with uniconazole treatments.

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