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  • Author or Editor: Ian J. Warrington x
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Abstract

A survey experiment was carried out to examine the effect of five growth regulators on the vegetative growth of Boronia megastigma. Promalin, daminozide, and chlormequat chloride were shown to have potential for modifying plant growth in the development of a commercial pot plant. Promalin restricted plant height and promoted lateral branch formation; concentrations of 0.5 and 1.0 g·liter–1 restricted height by ≈40% while branch number doubled. Daminozide significantly restricted plant height at concentrations of 5 and 10 g·liter–1. Plants that received a single application of daminozide also showed an increase in branch number. Dikegulac-sodium completely inhibited vegetative growth even at the lowest concentration used (2.5 g·liter–1) while chlormequat chloride, applied as a foliar spray (3 and 6 g·liter–1), restricted both height growth and plant dry weight. Chlormequat chloride and paclobutrazol, applied as root drenches, were ineffective. Chemical names used: butanedioic acid mono(2,2-dimethylhydrazide)(daminozide); N-(phenyImethyl)-1H-purine-6-amine and GA4+7 (Promalin); Na 2,3:4,6-bis-O-(1-methylethylidene)-α-l-xylo-2-hexulofuranosonic acid (dikegulac-sodium); 2-chloro-N,N,N-trimethylethanaminium chloride (chlormequat chloride); (2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-l-yl) pentan-3-ol (paclobutrazol).

Open Access

In New Zealand, harvest maturity for kiwifruit is determined by the soluble solids concentration (SSC) of juice (minimum 6.2%). Commercial maturity differs in various regions of the country within each season and between years and may be due to differences in temperatures during growth.

Mature `Hayward' kiwifruit vines were grown in controlled environment temperature treatments of 14/8, 18/8, 22/8, 26/8, 14/12 and 22/12C to determine whether the increase in SSC at low night temperatures recorded in a related study was a result of the mean temperature, the min. daily temperature, or the magnitude of the max./min. temperature difference. Measurement was made of fruit size, firmness, starch and total sugar concentrations in the fruit at 10 day intervals.

SSC increased fastest with the coolest mean temperature irrespective of the min. temperature or max./min. difference. In the coolest treatment the concentration of starch decreased rapidly with a rise in total sugar, in the warmest treatment the change in the carbohydrate components was slower. Data will be used to predict harvest date at commercial orchard sites based on field temperature measurements.

Free access

The early growth responses of apple fruit to temperature were studied under controlled environment conditions. Growth of fruit on young trees of `Fuji'/M.9 `Golden Delicious'/M.9, and `Harold Red Delicious'/M.9 was frequently measured, over a 30-day period commencing 10 days after full bloom, under daily maximum/minimum temperatures of 22/12, 19/9, 16/6 and 13/3C. All other environmental conditions were maintained constant across all temperature treatments. Fruitlet diameter growth rate was approximately constant over the treatment period within each temperature regime and ranged from 0.24 mm day-1 at 13/3C to 0.85 mm day-1 at 22/12C. The growth responses to temperature were similar among cultivars but expansion rates were highest for `Fuji' and lowest for `Golden Delicious'. Cell division rates and durations, using flow cytometry, were measured over the treatment period and could be related to diameter growth rates. The impacts of temperature-induced differences in early fruit growth rates on final fruit sire will be described.

Free access