Freshly harvested unwaxed `Marsh Ruby' grapefruit (Citrus paradisi Macfad.) were obtained from Wabasso, Fla. The fruit were treated with methyl jasmonate by dipping, pressure infiltration (82.7 kPa for 3 minutes), or vapor fumigation. Control fruit were similarly treated with distilled water. All fruit were then stored at 1°C. Samples from all treatments were transferred to 20°C for 3 days after 4 and 10 weeks of storage at 1°C for evaluation of chilling injury. Symptoms of chilling injury were negligible in all treatments after 4 weeks of storage. However, after 10 weeks of storage, moderate to severe pitting occurred in the control fruit but the severity of chilling injury was significantly reduced by methyl jasmonate treatments. The most effective treatments were either pressure infiltration using a 0.1 mm emulsion or fumigation with vapor at saturation.
An inexpensive system for maintaining desired water potentials throughout seed germination was developed. During hydration, a water reservoir at the base of inclined petri dishes allowed continual saturation of filter paper on which seeds were placed. During dehydration, seeds were exposed to equilibrium vapor pressures above saturated salt solutions. Constant temperature, necessary to prevent condensation of water vapor, was achieved via a small (0.2 A) fan that furnished and circulated heat throughout an insulated chamber in which salt solutions were placed. By operating the chamber above ambient laboratory temperature, interior cooling was not required. The system allowed manipulation of the rate, degree, and frequency of dehydration episodes to which germinating seeds were exposed.
A computer simulation model was developed to be used in evaluating irrigation scheduling techniques and assisting irrigation scheduling decisions under greenhouse conditions in Colorado. The model simulates variable greenhouse conditions and shows how each of four irrigation scheduling techniques responds to these conditions. Reports from the model detail numbers of irrigation events, sensitivities to parameters, and forecasts water usage. The model was also used to determine appropriate accumulation triggers for Colorado conditions.
Four techniques evaluated here include: time clock control; accumulated radiation; accumulated vapor pressure deficit; combination method (radiation and vapor pressure deficit). The model has shown the combination method to be the most sensitive to changes in environmental conditions, while the time clock method proved to be least sensitive (and most wasteful of water).
The model may evaluate additional irrigation scheduling techniques by including additional parameters in the model, and may readily be adapted to different climatic regions.
Abstract
Antitranspirant chemicals Clear Spray (200 ml/liter) and Vapor Gard (50 ml/liter) significantly increased stomatal diffusive resistance in cineraria (Senecio cruentus DC.) on hot days. Foliar applications of the antitranspirants were effective in reducing plant water stresses for a period of 4 weeks. These chemicals did not have a significant effect on stomatal diffusive resistance when no water stress occurred in the plants. Foliage sprayed with these chemicals was more attractive and plants required less watering to maintain vigorous growth.
The repellency and toxicity of a petroleum-based proprietary horticultural oil, Sunspray 6E Plus, was tested against the greenhouse whitefly, Trialeurodes vapor-ariorum (Westwood), on greenhouse-grown chrysanthemums [Dendranthema ×grandiflorum (Ramat.) Kitamura cv. Iceberg]. A 2% (v/v) aqueous spray repelled adult whiteflies for at least 11 days after spraying and it was toxic to newly hatched and third stage larval whiteflies. No phytotoxicity was observed when four weekly sprays of 1%, 2%, and 4% oil were applied.
Abstract
Antitranspirants (Exhalt 4-10, Vapor Gard, Wilt Pruf, and Folicote) were more phyto-toxic when applied to detached florets than to detached leaves of hydrangea (Hydrangea macro-phylla Thunb. cv. Improved Merveille). Transpiration was high from hydrangea flowers as well as leaves. Folicote applied to intact flowering plants at concentrations of 1.25–5.00% was effective in reducing transpiration 10–15% compared to untreated plants.
Abstract
Two experiments were conducted to determine if one-year-old field-grown Cornus florida L. seedlings could be transplanted successfully after leafing out. Survivability was improved with 100% defoliation at the time of planting. Vapor Gard used as a shoot dip and a whole plant dip had little positive effect. Root dips of a starch-based polymer and a peat and water slurry were not beneficial.
Abstract
Early winter flowering of Alstroemeria ‘Regina’ plants was accomplished by a long-day, high-pressure sodium vapor lamp (HPS) treatment before the low 5°C temperature induction treatment. This HPS treatment predisposed the plants to respond to a subsequent long photoperiod treatment during winter. Winter generative shoot yield was increased by 35% through the use of HPS pretreatment. Stem length increased as the duration of the HPS treatment prior to cold induction increased.
Abstract
Wine grape (Vitis vinifera L.) vineyards in much of the desert Southwest are frequently exposed to intense solar radiation, high vapor pressure deficits, and high air temperatures. Although wine grape production in this region has increased during recent years, the harsh environment often results in growth conditions that may be suboptimal for photosynthesis and other plant processes, ultimately affecting fruit yield, wine color, and acidity.
Abstract
Mechanically harvested fruits of A-5344 and ‘Earlibelle’ strawberry (Fragaria × ananassa Duch.) were stored at 24°C for 72 and 120 hours in atmospheres containing acetaldehyde (Aa) with and without prior dipping in 0 to 1.5% acetaldehyde solutions. Aa atmospheres and a combination of atmospheres and dips were most effective in maintaining visual color, freedom from browning, and product acceptability of machine harvested strawberries for processing. Fruit stored in atmospheres containing Aa vapor increased in acidity by 72 hours.