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A numerical simulation model of a greenhouse floor heating system was developed and validated using data collected in a research greenhouse located at Cook College, Rutgers University, New Brunswick, New Jersey. The model was then modified and used to evaluate two different heat pipe diameters and spacings that are typical in the greenhouse industry today: 13 mm (0.5 in.) diameter pipe placed on 22.9 cm (9 in.) centers, and 19 mm (0.75 in.) diameter pipe placed on 30.5 cm (12 in.) centers. Two heat pipe elevations within the solid concrete floor system were also simulated, and the effects of the pipe's vertical position, diameter, and spacing on surface heat flux, surface temperature, and surface temperature uniformity were evaluated. The simulation results showed that the smaller diameter pipe placed closer together and at a lower elevation provided the best temperature uniformity without compromising other performance criteria. The model was then further modified to simulate flats with growing media placed on the floor surface. Model simulations were conducted for six different supply water temperatures ranging from 32.2°C (90°F) to 60°C (140°F), while maintaining a target ambient greenhouse air temperature of 15.6°C (60°F). The simulation outputs showed that using the smaller diameter pipe placed closer together resulted in a higher surface heat flux, a higher growing media temperature, and greater temperature uniformity within the growing media, for each supply water temperature simulated.

A silver thiosulfate (STS)-mediated increase in pathogen susceptibility was investigated using shoot cuttings from stock plants of pelargonium (Pelargonium hortorum Bailey cv. Ringo Scarlet) with and without STS treatment. Callusing and rooting were reduced in shoot cuttings from ST&treated plants. The pathogen-tolerant tissue (no STS) was shown to produce enhanced levels of phenolic esters and glycosides during wound healing. Reactivity to the histochemical stain phloroglucinol-HCL was also enhanced during wound healing in cuttings from plants that had not received a silver treatment.

Indoleacetic acid induces senescence in isolated carnation (Diandhs caryophylhu, cv. White Sum) petals, increasing the duration and amount of ethylene production. This effect is inhibited by Actinomycin D, an inhibitor of RNA synthesis, and cycloheximide, a translational inhibitor of protein synthesis. The ability of petals to respond to indoleacetic acid appears to be a function of physiological age. Indoleacetic acid is capable of enhancing ethylene evolution and senescence only in specific portions of the petal.The senescence process in the carnation flower is closely associated with a marked increase in ethylene evolution (14). The ability of auxins to enhance ethylene evolution is well documented in several plant systems (3,4,7,8). Moderate levels of the auxin 2,4-D have been shown to increase ethylene evolution and enhance senesence rates in carnation (15,17). Auxins are suggested to act by increasing the activity of ACC2 synthase, an enzyme that converts S-adenosyl-methionine to ACC (6,21). It is known that ACC is an intermediate in the biosynthesis of ethylene in some plant systems, and that the increase in ethylene synthesis during the ripening ofclimacteric fruits (1, 5) and senescence of carnation flowers (2, 18) is accompanied by increased levels of ACC in the tissues.Despite recent work (2), it is not clear whether the levels of ACC observed in carnation flower petals result from the transport of ACC to the petals or from increased synthesis of ACC by the petal in response to auxin movement into the petals from other areas.The use of isolated petals has been suggested as a useful system for studying senescence (11). If the senescence of such isolated carnation petals can be enhanced by auxin, this would suggest that petals maintain the ability to form ACC and may not rely on its transport from other flower portions. It was the purpose of this work to examine this possibility by supplying IAA to isolated carnation petals and examining its effect on senescence. Senescence in this system can be observed as petal in-rolling or measured as fresh weight loss and increased ethylene evolution. Greenhouse carnations (Dianthus caryophyllus, cv. White Sim) were grown to provide freshly cut flowers. Flowers were harvested at a stage when the outer petals became perpendicular to the longitudinal axis of the flower. Outer petals were removed by cutting at the base near the junction of the petal with the receptacle. To minimize the possible effect of variability in the physiological states among flowers sampled (10), in each experiment, four flowers were harvested and four petals from the outer whorl of each were removed. The bases of the individual petals were inserted through holes drilled in caps of 20-ml scintillation vials which held various treatment solutions. The experiments were designed so that each petal in a single treatment was from a different flower. MATERIALS AND METHODSThe protein synthesis inhibitors CHI and Act. D were used in some experiments. Petals were placed in CHI or Act. D soluti...

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