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Martin Meeks, H. Brent Pemberton, Lurline Marsh, and Garry V. McDonald

The effect of UV-B fluorescent lamp light on seedling elongation was investigated using three species: marigold (Tagetes sp.), cucumber (Cucumis sativa), and tomato (Lycopersicon esculentum). Seedlings were exposed to light supplied from two unshielded and unfiltered 40-watt UV-B fluorescent lamps. In two experiments, seedlings were placed a distance of 45 cm below the light for varying lengths of time, while seedlings were placed 60 cm below the light in a third experiment. For marigold, seedlings were shorter when germinated under the UV-B lamp than when germinated under natural light in a glasshouse. Two hours of exposure just after glasshouse germination (cotyledons unfolded) was effective in reducing height of cucumber seedlings, whereas 6 hours was required to significantly reduce the height of tomato seedlings. Treatments were still effective when the last measurements were taken 12 to 14 days after germination. Exposure of seedlings to UV-B lamp light provides a possible alternative means of preventing excessive seedling elongation instead of relying on chemical plant growth regulators.

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A.M. Armitage and P.M. Gross

A copper hydroxide formulation (0%, 3.5%, 7%, 11% Cu) was applied to plug trays before sowing seeds of Impatiens ×hybrida L. `Accent Red', Pelargonium ×hortorum Bailey `Scarlet Elite', and Petunia ×hybrida Hort.Vilm.-Andr. `Ultra White' to investigate the influence of the formulations on ease of transplant, root growth, and shoot growth. These factors also were investigated in Cu-treated seedling plugs held past optimal transplanting stage. Root spiraling and seedling height at transplant were reduced for all taxa grown in Cu-treated trays, regardless of concentration, compared to seedlings from nontreated trays. Root weight and shoot weight responses to Cu treatments at transplant and at flowering varied among taxa. Mature heights of all taxa were unaffected by Cu treatment; however, flowering date was delayed for impatiens and geraniums transplanted at optimal time from Cu-treated trays. In general, petunias displayed little response to Cu treatment. Root spiraling was reduced and plugs were removed more easily from Cu-treated than from control trays stored for 2 weeks in the greenhouse, but flowering time was delayed for 12 days for impatiens and petunias and 21 days for geraniums, regardless of Cu concentration.

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Jennifer L. Boatright and J. M. Zajicek

Hydrogel (Hydrosource™, Western Polyacrylamide, Inc.) was incorporated into 102 cm × 122 cm landscape beds at 25, 50, 75, or 100 lbs per 1000 sq ft. Weed barrier and 2 cm of pine bark mulch were added to the top of each bed. Controls consisted of 1) no hydrogel with weed barrier and mulch and 2) no hydrogel with mulch but no weed barrier. Each treatment was replicated four times with ten plants of petunia, marigold, and vinca planted per bed, for a total of forty plants of each species per treatment. Flower number of vinca and petunia increased with hydrogel incorporation, 75 lbs of hydrogel having the greatest number of flowers. Petunia also had higher visual ratings with increased hydrogel rates. Soil temperatures directly under the mulch and 10 cm below the mulch, at 1400 hr, were 49C and 40C respectively for controls, compared to 42C and 36C for beds with hydrogel.

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JinSheng Huang and Paul V. Nelson

It is desirable to have a large root mass and compact shoot in the final stage of plug seedling production. Marigold `Discovery Orange' was grown for six weeks from sowing in a hydroponic system. Hoagland's all nitrate solution was used at 0.25X for the first three weeks and 0.5X for the final three weeks. P was applied continuously in the control and was eliminated for the first one or three weeks in the two stress treatments. Weekly mot and shoot dry weights indicated: a.) P stress caused an increase in root/shoot ratio with roots larger than in the control plants and b.) restoration of P after a P stress resulted in a rapid shift of root/shoot ratio back to the control level with final root and shoot weights less than in the control plants. A continuous marginal P stress or a stress near the end of seedling production is suggested. Tomato `Marglobe' was grown for five weeks and impatiens `Super Elfin White' for six weeks in a 3 sphagnum peat moss: 1 perlite substrate in 288 cell plug trays. Fertilizer was applied at every third watering at a zero leaching percentage. The control nutrient ratio (mM) was 5.4 NH4+ NO3: 0.5 PO4: 1.6 K while the low P treatments contained 0.15, 0.1, and 0.05 mM PO4 throughout the experiment. The root/shoot dry weight ratios increased in the low P treatments. Tomato plants at 0.15 and 0.1 mM P and impatiens plants at 0.15 mM P had larger roots than the control plants. A continuous stress at 0.15 mM PO4 appears promising.

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Jonathan M. Frantz, James C. Locke, Dharmalingam S. Pitchay, and Charles R. Krause

We thank Tera McDowell, Sarah Lancianese, Stephen Ohene-Larbi, Douglas Sturtz, and Leona Horst for their technical assistance throughout the studies, the Paul Ecke Ranch, Ball Seed Co., and GreenCircle Greenhouses for donating plant material

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J.B. Million, J.E. Barrett, T.A. Nell, and D.G. Clark

Experiments were conducted with four kinds of flowering plants to compare one-time vs. continuous application of paclobutrazol in subirrigation water. When a crop reached the stage at which it required growth regulator treatment, four concentrations of paclobutrazol were applied via subirrigation either one-time or continuously until the crop was terminated. Based upon regression equations, concentrations resulting in 30% size reduction for one-time applications of paclobutrazol were 0.01 mg·L-1 for Begonia ×semperflorens-cultorum `Cocktail Gin', 0.09 mg·L-1 for Impatiens wallerana Hook. `Super Elfin White', 0.2 mg·L-1 for Dendranthema ×grandiflorum (Ramat.) Kitamura `Tara', and 2.4 mg·L-1 for Petunia ×hybrida Vilm.-Andr. `Plum Crazy'. Respective optimal values for continuous application were 0.005, 0.02, 0.06, and 0.4 mg·L-1. Increasing the concentration for continuous application had a greater effect on paclobutrazol efficacy than did increasing the concentration for a single application. In a trial with impatiens `Super Elfin Salmon Blush', the paclobutrazol concentration was reduced 0%, 25%, 50%, 75%, or 100% (single application) for each successive subirrigation event following an initial application of 0.1 mg·L-1 of paclobutrazol. The 50%, 75%, and 100% reduction treatments provided similar levels of size control. Dilution was more important when the reduction rate was less than 50%. Chemical name used: (±)-(R*,R*)-β-[(4-chlorophenyl)methyl]-α-(1,1-dimethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).

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Thomas M. Contrisciano and E. Jay Holcomb

The objective of this research was to develop a mineral wool based growing medium for the horticultural industry. Two types of hydrophilic mineral wool, clean wool (CW) and unclean wool (UC) were used unamended, as well as both types in combinations with 25, 50, and 75 percent peat moss (PM). A control of 100 percent (PM) was also used. Unamended CW had a low bulk density, excellent water holding capacity, good aeration, but high pH. Once PM was added to CW, bulk density still remained low, water holding capacity and aeration remained good, and the pH dropped to a more suitable level. Unamended UW had a high bulk density, good water holding capacity, poor aeration, and high pH. Once PM was added to UW, bulk density decreased, water holding capacity remained good, aeration increased, and pH decreased to a more optimal level. Impatiens `Violet' and Begonia `Whiskey' were grown in the nine treatments for six and nine weeks respectively. At harvest, plant growth was evaluated by height, diameter, fresh weight, dry weight, and tissue analysis. Plant growth response showed plants grown in unamended CW, UW, and PM were smaller in size and lighter in fresh and dry weights than those in 50 percent wool/50 percent PM. The plants grown in 25 and 75 percent PM were similar to the 50 percent wool/50 percent PM in size and weight.

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Seenivasan Natarajan, Jeff S. Kuehny, and James E. Board

One of the greatest impediments to production of marketable ornamental herbaceous plants in southern U.S. is high temperature stress. Exposure of plants to sub-lethal temperature (heat preconditioning) before sustained heat stress helps some plants to tolerate subsequent heat stress a phenomenon often referred as acquired thermotolerance. The objective of this research was to examine various morphological, physiological and anatomical responses of `Vista red' (heat tolerant) and `Sizzler red'(heat sensitive) cultivars of Salvia splendens to heat preconditioning (HC) and subsequent heat stress treatments (challenging temperatures, CT). Cultivars of Salvia were subjected to short duration HC of 35 °C for 3 hours every third day until 5 weeks after germination and subsequent exposure to two CT treatments 30/23 °C and 35/28 °C (D/N) cycles in growth chambers for the next five weeks. Plant growth, marketable quality, stomatal conductance and net photosynthesis declined for Sizzler Red without HC treatment. Compared with nonpreconditioned plants, heat preconditioned Sizzler Red had 38.28% higher root dry weight, 95% greater leaf thickness, 50% higher marketable quality at 35/28 °C heat stress condition. Heat preconditioning helped both Vista Red and Sizzler to survive in both the heat stress treatments. Vista Red had greater heat tolerant traits than Sizzler Red, these traits exacerbated with heat preconditioning treatment. The results demonstrated that heat preconditioning enhanced heat tolerance in cultivars of Salvia, which could be related to maintenance of dense plant growth with shorter internodes, thicker stems, greater stomatal conductance, extensive root growth that compensated the transpirational water loss and overall cooling of plants.

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Joyce G. Latimer and Ronald D. Oetting

During greenhouse production in Spring 1995, conditioning treatments were applied to columbine (Aquilegia×hybrida Sims `McKana Giants'), New Guinea impatiens (Impatiens hawkeri Bull. `Antares'), marigold (Tagetes erecta L. `Little Devil Mix') and ageratum (Ageratum houstonianum Mill. `Blue Puffs') plants. Treatments included: mechanical conditioning (brushing 40 strokes twice daily); moisture stress conditioning (MSC) (wilting for ≈2 hours per day); undisturbed ebb-and-flow irrigation; overhead irrigation; high (500 mg·L-1 N) or low (50 mg·L-1 N) 3×/week N fertilizer regimes; daminozide (5000 mg·L-1); or paclobutrazol (30, 45, or 180 mg·L-1). One week after initiation of treatments, individual plants in separate greenhouses were inoculated with two adult green peach aphids (Myzus persicae Sulzer) or five two-spotted spider mites (Tetranychus urticae Koch). A natural infestation of western flower thrips (Frankliniella occidentalis Pergande) in the mite-inoculated greenhouse provided an additional insect treatment. Brushing was the only treatment that consistently reduced thrips and mite populations. Aphid populations were lower on low-N than on high-N plants, but thrips and mite populations were not consistently affected by plant fertilization. Moisture stress conditioning tended to increase aphid populations on New Guinea impatiens and marigold, but had little effect on spider mite or thrips populations. Ebb-and-flow irrigation reduced the mite population on ageratum relative to that on overhead irrigated (control) plants. Plant growth regulators did not consistently affect pest populations. Chemical names used: butane-dioic acid mono(2,2-dimethylhydrazide) (daminozide); β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-1-ethanol (paclobutrazol).

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Janice M. Smith and Marihelen Kamp-Glass

The effects of ORC and different commercial plant fertilizers on Marigolds, Salvias, and Begonias were determined by height, flower number, fresh weight, dry weight, root length and tissue analysis. The treatments included controls, regular fertigations, and an over fertigation schedule. The experiment was set in a randomized block design with 5 reps per treatment which included 9 ORC and commercial plant fertilizer combinations, 4 commercial plant fertilizers, and controls. The plants with the ORC were more vigorous, had more flowers, and better overall color than the controls.