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Yin-Tung Wang and Lori L. Gregg

Lilium longiflorum Thunb. `Nellie White' plants grown under 1300 μmol·m-2·s-1 maximum photosynthetic photon flux (PPF) in a greenhouse deliberately were completely defoliated when the oldest flower bud was 2, 4, or 7 cm long. Plants were then placed in growth chambers in darkness or in the light (250 μmol·m -2·s-1 PPF, 10 hours) with 25C air, along with intact plants as controls; all were harvested at the completion of flowering. Defoliation at the 2- and 4-cm bud stages resulted in complete flower abortion, with or without light. Plants defoliated at the 7-cm stage and kept in light had 60% of the flower buds develop to anthesis but depleted more scale reserves. Those defoliated at the 7-cm stage and kept in darkness had complete flower abortion; however, bulb weights remained similar to those of the intact plants kept in the light.

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Yin-Tung Wang and Lori L. Gregg

The levels of hydration of several hydrophilic polymers (hydrogels) varied greatly. Starch-based polymers had the fastest rate of hydration (<2 hours), followed by a propenoate-propenamide copolymer. Polyacrylamide materials required 4 to 8 hours to become fully hydrated. Maximum water retention in distilled water varied from 400 to 57 g of water per gram of dry material. All hydrogels retained less water in the presence of metal ions or fertilizers in the soaking solution, with substances releasing Fe+2 being the most detrimental. After exposure to fertilizers and ions, the water-holding capacity of a polyacrylamide with a high degree of cross linkage, but not that of hydrogels of the other structures, was fully recovered by subsequently soaking in distilled water. Pots amended with a polyacrylamide polymer but without Micromax (a micronutrient source) reached maximum water retention after six irrigations, while those with Micromax required 10 irrigations to reach peak water retention. The amounts of water being held in pots decreased after repeated fertilization. Medium volume increased with increasing levels of the polyacrylamide Supersorb C (0, 2, 4, or 6 g/pot). Micromax incorporated in medium amended with Supersorb C caused a depression in volume. Medium bulk density, total water retention, and water retention per unit volume of medium were increased by the incorporation of the hydrogel, regardless of the presence of Micromax. Noncapillary porosity measured at container capacity in medium amended with Micromax progressively decreased as the amount of hydrogel increased, but remained unchanged in medium without Micromax. Repeated drying and dehydration of the medium resulted in reduced water retention and increased noncapillary pore space.

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Yin-Tung Wang and Lori L. Gregg

Drench paclobutrazol or uniconazole applications (0.1-1.0 mg/0.5-liter pot or 0.05-0.2 mg/pot, respectively) were effective in suppressing stem elongation of golden pothos [Epipremnum aureum (Linden & Andrè) Bunt.]. Although the leaf production rate was reduced by both retardants, treated plants produced larger leaves than the controls, resulting in greater total leaf areas. Response to foliar paclobutrazol or uniconazole applications (0-200 and 0-100 mg·liter-1, respectively) was similar to the soil drench patterns, except that the leaf production rate was unaffected. Following 10 weeks in an interior environment, plants previously treated with either retardant produced shorter stems, fewer but larger leaves, and lower fresh weights than the nontreated plants. Cuttings collected from stock plants previously treated with a paclobutrazol or uniconazole soil drench (0.1 or 0.05 mg/0.5-liter pot, respectively) produced longer stemmed shoots, more and larger leaves, and heavier shoot fresh weights than cuttings from the nontreated plants. Foliar paclobutrazol application (0-200 mg·liter-1) to stock plants resulted in cuttings producing larger leaves and heavier shoot fresh weights than controls. Chemical names used: (2RS,3RS)-1-(4-chlorophenyl)-4,-4-dlmethyl-2-(l,2,4-trizol-l-yl)pentin-3-ol (paclobutrazol);(E)-1-(4-chlorophenyl)-4,-4-timethyl-2-(1,2,4-trizol-l-yl)l-penten-3-ol (uniconazole).

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Yin-Tung Wang and Lori L. Gregg

Bare-root seedling plants of a white-flowered Phalaenopsis hybrid [P. arnabilis (L.) Blume × P. Mount Kaala `Elegance'] were grown in five potting media under three fertility levels (0.25, 0.5, and 1.0 g·liter-1) from a 20N-8.6P-16.6K soluble fertilizer applied at every irrigation. The five media included 1) 1 perlite:1 Metro Mix 250:1 charcoal (by volume); 2)2 perlite:2 composted pine bark:1 vermiculite; 3) composted pine bark; 4) 3 perlite:3 Metro Mix 250:1 charcoal; and 5) 1 perlite:1 rockwool. During the first flowering season, plants in the 1 perlite: 1 Metro Mix 250:1 charcoal medium had slightly fewer but larger flowers and thicker stalks (section of the inflorescence between the base and oldest flower) than those in the 1 perlite:1 rockwool medium. Medium had no effect on stalk length. Two media (3 perlite: 3 Metro Mix 250: 1 charcoal and 1 perlite: 1 rockwool) resulted in root systems that were inferior to those in the others. Fertilizer level had no effect on bloom date or flower size. Regardless of medium, increasing the fertility from 0.25 to 1.0 g·liter-1 increased flower count, stalk diameter and length, and leaf production following flowering. During the second flowering season, media had limited effect on plant performance. Increased fertility promoted earlier inflorescence emergence and blooming. Higher fertilizer rates also caused a linear increase in the number of flowers and inflorescences per plant, and in stalk diameter, total leaf count, and leaf size.

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Yin-Tung Wang, Kuo-Hsiun Hsiao and Lori L. Gregg

Cuttings of Epipremnum aureum (Linden & André) Bunt. were soaked for 5 seconds in 5% Folicote or Stressguard antitranspirant solution, planted immediately or after 6 hours, and misted or not misted during the daylight hours for 2 weeks. Neither antitranspirant affected the growth of misted cuttings. However, in nonmisted cuttings, Folicote resulted in delayed first leaf unfolding and small plants. Misting improved shoot growth relative to not misting. In a second experiment, Stressguard sprayed on leaves of stock plants resulted in slow growth of cuttings taken from them, while Folicote had no effect. Water stress induced by delayed planting resulted in water loss and slow lateral shoot growth in both experiments. Application of uniconazole at the four-leaf stage at 0.05 to 0.4 mg/0.5-liter pot reduced stem elongation, leaf count, and the length of nodal roots. Uniconazole increased individual leaf size on the main shoot and promoted the growth of basal lateral shoots. While stem and total plant dry weights were reduced, total leaf dry weight was not affected by uniconazole. Uniconazole continued to provide good control on the elongation of newly emerged lateral shoots and promoted the production of more and larger leaves when evaluated 4 weeks after the main shoot was severed above the fourth basal node. Chemical name used: (E)-1-(p-chlorophenyl)-4,4-dimethyl-2-(1,2,4-trizol-1-yl)-1-penten-3-ol (uniconazole).