Search Results
Abstract
Broccoli (Brassica oleracea var. Italica) and Geraldton wax flower (Chamelaucium uncinatum cv. Purple Pride), two ethylene-sensitive commodities (1, 2), were used in a postharvest evaluation of a novel plastic film (BO film) claimed to sorb ethylene. BO film (Odja Shoji Co., Ltd.) is low density polyethylene (LDPE) extruded with a finely divided ceramic (crystburite). The BO film was compared with a conventional high density polyethylene film (HDPE). The 15-µm HDPE film had water vapor, O2 and CO2 transmission characteristics of 3.3 g·m−2, 4500 cm3·m−2, and 15,000 cm3·m−2 per 24 hr at 25° C (D. Jesaveluk, personal communication). Permeability values for the 50-µm BO film were not available; however, constituent 50-µm LDPE film has transmission characteristics of 2 g·m−2, 2100 cm3·m−2 and 6700 cm3·m−2 per 24 hr, respectively. Satchels of coarsely ground ceramic (Cerasutora A, ≈38g) were also tested for their ability to preserve postharvest quality.
Abstract
Abscission of flowers of Geraldton wax (Chamelaucium uncinatum Schau., Myrtaceae) exposed to ethylene was prevented by pulsing with silver thiosulfate. Both a short pulse (15 min, 4.0 mm Ag+) at 25°C and an overnight pulse (0.5 mm Ag+) at 2° were effective treatments. Silver thiosulfate did not improve the vase-life of flowers held in air. Gamma irradiation (60Co source), an insect control measure, resulted in a reduction in vase-life; even at doses as low as 0.05 kGy. Vase-life of Geraldton wax flowers was not affected by prior storage for up to 2 weeks at 0° to 2°. Iprodione pretreatment (1 g·liter−1, 30-sec dip) for Botrytis cinerea Pers. control improved the vase-life of flowers stored for 2 weeks. A preservative solution containing sucrose (1% to 3% w/v) and 8-hydroxyquinoline sulfate (200 mg·liter−1) increased the vase-life of Geraldton wax flowers. Higher sucrose levels (>5% w/v) may cause desiccation of foliage and excessive nectar secretion from floral nectaries. Chemical name used: 3-(3,5-dichlorophenyl)-N-(1-methylethyl)-2,4-dioxo-1-imidazolidinecarboxamide (iprodione).
Abstract
Flower abscission from the pedicel is a problem in postharvest handling of Geraldton wax (Chamelaucium uncinatum Schau., Myrtaceae). 1-Naphthaleneacetic acid (NAA) dips or sprays (1) and silver thiosulfate pulsing (STS) (2) have been recommended to prevent flower abscission in Geraldton wax. NAA (40 μg·liter-1) dips are commonly used in Western Australia. This work was undertaken to determine whether NAA or STS is the more effective treatment for preventing ethylene-induced flower abscission in Geraldton wax.
Perennial wildflower species are important but not well-understood elements in water-wise landscaping that anchors urban water conservation programs in arid climates. Comparative growth and physiological responses to soil substrate drying of three herbaceous Australian ornamental species from habitats of variable moisture regimes were investigated in the context of isohydric and anisohydric behavior. Clonal Orthosiphon aristatus, Dianella revoluta ‘Breeze’, and Ptilotus nobilis plants were container-grown individually and competitively together in two separate studies. In both studies, plants were water-stressed through cyclical dry downs. We measured stomatal conductance (g S), soil water content, and water potential during each study and osmotic adjustment estimated from pressure-volume data and plant biomass at the end of each study. O. aristatus, a rainforest species, fit a general anisohydric model of high water use and more negative water potential during soil drying until stomatal closure and leaf wilting. D. revolata and P. nobilis, indigenous to Australia's dry interior, fit a general isohydric, drought-tolerant model of stomatal closure from water deficits that moderates leaf water potential but through different mechanisms. P. nobilis and D. revolata moderate water use and maintain acceptable aesthetic performance under water stress, suitable for mixed low-water landscape plantings. O. aristatus would not be suitable for low-water urban landscapes, either isolated or in mixed plantings, because of high soil water depletion and wilting.
Mango (Mangifera indica L.) fruit can be injured by heat disinfestation protocols imposed to kill insects. We determined if mango fruit have the capacity to acclimate, thereby becoming more tolerant of heat disinfestation treatments. Conditioned `Kensington Pride' mango fruit (7-hour heating-up period to a 37C core temperature maintained for ≤12 hours) showed less pulp injury on ripening following hot water treatment (1.5 hours for previously conditioned fruit to 2 hours for fruit not previously conditioned) than fruit not conditioned before hot water treatment. During treatment, the core reached 47C and was maintained for 25 minutes. Extending the conditioning period by ≤12 hours beyond the 7-hour heating-up period (total of 19 hours) gave no additional benefit. Conditioning did not consistently reduce peel injury that was hot water treatment-induced as indicated by irreversible loss of chlorophyll variable fluorescence.
Better maintenance of firmness and suppression of ethylene production in 'Queen Cox' and 'Bramley' apple [Malus ×sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] fruit was achieved by prestorage applications of 1-MCP. 1-MCP concentration, exposure time and exposure temperature ranges of 0.1 to 10.0 μL·L-1 1-MCP, 6 to 48 h, and 0 to 20 °C, respectively, were effective on fruit subsequently stored for 2 ('Cox') and 3 ('Bramley') months in air at 3 to 4 °C. However, 1-MCP had little effect on either firmness or ethylene production after 4 ('Cox') or 6 ('Bramley') months storage. Nonetheless, 1-MCP treated 'Bramley' fruit had reduced rot and superficial scald incidences compared with untreated control fruit. Chemical name used: 1-methylcyclopropene (1-MCP).
Abstract
The cut-flower and potted plant industries in Australia have traditionally been based on exotic species. However, native Australian plants have gradually assumed greater importance—particularly in the expanding export trade, but also on local markets. Floriculture is practiced in all Australian states, with the major production areas for exotic cut-flowers (e.g., roses, carnations) and potted plants being close to the state capital cities. The cultivation of native Australian flowers and of South African Proteaceae tends to be somewhat more decentralized.
Low concentrations of ethylene induced abscission of leaves and berries from cut branchlets of English holly (Ilex aquifolium L.) and American mistletoe [Phoradendron tomentosum (DC.) Engelm. ex Gray ssp. macrophyllum (Engelm.) Wiens]. Application of 1 μmol of Ag+ per branchlet (as the anionic silver thiosulfate complex, STS) via the transpiration stream was found to retard this abscission. A higher application rate (4 μmol Ag+ per branchlet) stimulated leaf abscission in mistletoe. There were marked differences in sensitivity to ethylene among various types of holly.
In studying the postharvest water relations of cut flowers, researchers aim to determine rates of water uptake and water loss along with changes in fresh weight. An automatic apparatus was devised for continuous monitoring of these indices. The novel apparatus consists of two balances automatically recording mass at a relatively high data acquisition rate (min−1), a personal computer, two containers, and plastic tubing. The apparatus is accurate, labor-saving, and real-time. It enabled dynamic synchronous recording of water uptake as well as fresh weight of the cut flower stem, from which precise water uptake loss rates during vase life can be accurately determined. Rates of water uptake and water loss of individual cut rose (Rosa hybrida cv. Movie Star) stems were measured using the apparatus under alternating 12-h light and dark periods. Both water uptake and water loss rates fluctuated with the light to dark shift over 120 h of observation. Stem fresh weight increased rapidly over the first 40 h of vase period and decreased gradually thereafter. Cut lily (Lilium hybrida cv. Yellow Overlord) stems showed similar trends in water uptake and water loss rate to cut rose stems. The accuracy and sensitivity of the new apparatus was validated by comparison with manual weighing using a balance at 2-h intervals under alternating 12-h light and dark periods over 108 h. The apparatus described here constitutes a suitable method for direct measurement of water uptake and fresh weight, including capturing relatively rapid water balance responses to changes in the postharvest environment.