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  • Author or Editor: Yin-Tung Wang x
  • Journal of the American Society for Horticultural Science x
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Most Phalaenopsis (the moth orchid) species and hybrids start to produce flowering shoots in the fall, bloom in January or February, and become limited in supply by April when market demand is strong. Means to defer the onset of flowering were studied. Starting 15 Sept. 1994, seedlings of 2-year-old hybrid Phalaenopsis TAM Butterfly were exposed to repeated cycles of 1 d darkness/1 d light (natural photoperiod, 1D/1L); 4 d darkness/3 d light (4D/3L); 7 d darkness/7 d light (7D/7L); and the natural photoperiod control (0D/7L). The dark treatments were achieved by covering plants with black fabric or by placing them in a dark cage. Treatments were terminated on 16 Dec., and all plants were exposed to the natural photoperiod. The control plants bloomed on 20 Jan. 1995, whereas the 4D/3L plants did not reach anthesis until 14 Apr., nearly 3 months later. Flowering of the 1D/1L and 7D/7L plants was also deferred until early April. Regardless of treatments, flower count and size were unaffected. In another experiment, beginning 15 Sept. 1995, 3-year-old plants were exposed to repeated weekly cycles of 2D/5L, 3D/4L, 4D/3L, or 5D/2L until 22 Jan. 1996. The nontreated control plants bloomed on 8 Feb. 1996, whereas the 5D/2L did not reach anthesis until 6 May. The 4D/3L treatment was not as effective as it was in 1994 and resulted in anthesis only 4 weeks after the control. In the last experiment, starting on 22 Jan. 1996, plants were removed at 2-week intervals from a 5D/2L treatment that was initiated on 15 Sept. 1995 and exposed to the natural photoperiod. Staggered anthesis was achieved. However, plants that bloomed in May and June had reduced flower count but not flower size.

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Results of a series of experiments showed that the ground, noncomposted woody stem core of kenaf (Hibiscus cannabinus L.) can be used successfully as a container medium amendment for producing potted tropical foliage and woody nursery crops. The growth of Brassaia actinophylla Endl., Hibiscus rosa-sinensis L. `Jane Cowl', and Pittosporum tobira (Thunb.) Ait. `Wheeler's Dwarf' in 70% or 80% kenaf (by volume, the balance being peatmoss or perlite or vermiculite and other nutrients) was similar to or greater than growth in two popular commercial mixes. Undesirable shrinkage of certain kenaf-amended media during plant production was reduced greatly by mixing it with at least 30% peatmoss or by using a coarser kenaf grind. As the portion of peatmoss increased from 0% to 30%, noncapillary porosity and water-holding capacity per container increased. A medium consisting of 50% kenaf, 40% peatmoss, and 10% vermiculite held as much water as a commercial medium. However, plants in most kenaf-amended media required more-frequent irrigation than those in the commercial media.

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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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Research was conducted to investigate the interaction of water-soluble fertilizer and medium composition on vegetative growth and the concentration of mineral nutrients in media and in leaves of a hybrid moth orchid (Phalaenopsis Blume.). The vegetatively propagated `TSC 22' clone of the hybrid Phalaenopsis Atien Kaala plants 15 cm in leaf spread were potted in a medium consisting of either 100% fine grade douglas fir [Pseudotsuga menziesii (Mirb.) Franco] bark or a mixture of 7 fir bark: 3 sphagnum peat (by volume). Plants were fertigated at each irrigation with a soluble 10N-13.1P-16.6K, 20N-2.2P-15.8K, or 20N-8.6P-16.6K fertilizer, or a 2N-0.4P-1.7K liquid fertilizer at a common N rate of 200 mg·L-1. After 1 year in a greenhouse, plants grown in the bark-peat medium produced more leaves, greater fresh weights (FW), and larger total leaf areas than those in 100% bark. In the bark medium, the 20N-2.2P-15.8K fertilizer resulted in plants of the highest quality, despite its low P concentration (22 mg·L-1). When grown in bark-peat, the two fertilizers (20N-2.2P-15.8K and 20N-8.6P-16.6K) containing urea as part of their N source (10% and 52%, respectively) resulted in plants with 40% to 50% heavier shoot FW and 40% larger leaf area than the other fertilizers without urea. With any given fertilizer, plants had similar root FW in both media. Media and fertilizers had limited or no effect on the concentrations of mineral nutrients in the second mature acropetal leaves, except P, which nearly doubled in leaves of plants grown in 100% bark. High leaf Mg concentration was associated with low Ca. Water extracts from the bark-peat medium had lower pH, higher electrical conductivity, and much higher levels of NH4-N, Ca, Fe, Na, Cl, B, and Al than those from 100% bark. Extracts from the bark medium did not have detectable levels of NO3-N, whereas extracts from the bark-peat medium all had similar levels of NH4-N, regardless of which fertilizer was applied. Levels of P and K were not different between the two media.

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Presently, there are no standards for producing Phalaenopsis Blume (the moth orchids) as a flowering, potted crop. Determining optimal irradiance for in vitro and greenhouse production will help optimize growth and flowering. Four-month-old, aseptically propagated Phalaenopsis Atien Kaala seedlings with 1.0 cm leaf spread were transferred to a sterile agar medium in November 1995. They were placed under 10, 20, 40, or 80 μmol·m-2·s-1 photosynthetic photon flux (PPF) from cool-white fluorescent lamps. In June 1996, plants grown under 40 or 80 μmol·m-2·s-1 in vitro PPF had 38% greater fresh weight (FW), wider leaves, and more roots than those under the two lower PPF levels. Plants from each in vitro PPF were then transplanted and grown ex vitro in a greenhouse (GH) under high, medium, or low PPF, representing 12.0%, 5.4%, or 2.6% of full sunlight, respectively. Full sunlight at this location was 2300 and 1700 μmol·m-2·s-1 in August 1996 and January 1997, respectively. In November 1996 and June 1997, plants that had received 40 μmol·m-2·s-1 in vitro PPF and then grown under the high or medium GH PPF had the greatest FWs. Overall, plants under the high, medium, or low GH PPF had average FWs of 61, 36, or 17 g, respectively, in June 1997. By mid-September 1997, plants had increasingly larger leaves and higher concentrations of malic acid, sucrose, and starch as GH PPF increased. Leaf glucose and fructose concentrations remained constant as GH PPF increased; however, sucrose level doubled and malic acid concentration increased by nearly 50% from the low to high GH PPF. Each doubling in GH PPF more than doubled plant FW. Plants grown under the high, medium, or low GH PPF had 98%, 77%, or 2% flowering, respectively, in Spring 1998. Anthesis occurred 2 weeks earlier under the high GH PPF. Plants grown under the high GH PPF had twice as many flowers and larger flowers than those grown under the medium PPF.

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Abstract

Eight-month-old ‘Jane Cowl’ hibiscus (Hibiscus rosa-sinensis L.) in 2.8-liter pots received 0, 0.1, 0.2, or 0.4 mg of uniconazole/pot as a soil drench. Plants were pruned 35 days after treatment and then grown for an additional 65 days. Plant height, number of leaves and flower buds per shoot, shoot length, stem diameter, and leaf size decreased with increasing rates of uniconazole. Flower number was greater at the two low rates; however, days to first bloom and leaf dark respiration rate were unaffected. Leaf chlorophyll concentration increased with increasing rates of uniconazole. Development of secondary xylem tissue, transverse diameter of vessels, and number and size of phloem fibers were suppressed by uniconazole, resulting in a cascading growth habit. Plants grown from cuttings taken from plants 35 days after treatment were shorter, with fewer lateral shoots and total leaves than cuttings from untreated plants. Uniconazole had no effect on growth of shoot tip cuttings taken from the new lateral shoots of treated plants 110 days after pruning. Soil drenches of uniconazole at 0.025 to 0.2 mg/pot to young plants in 1.5-liter pots resulted in shorter plants, delayed flowering, and fewer flowers with smaller diameter and shorter pedicels. Results from foliar application of uniconazole at 0.05 to 0.2 mg/plant (10 to 40 mg·liter−1) were similar to the soil drench, except that the reduction in shoot growth was less at low rates than with drench application. Chemical name used: (E)-1-(p-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-ol (uniconazole).

Open Access

Abstract

Whole shoots of Easter lily (Lilium longiflorum Thunb. cv. Nellie White) were exposed to 14CO2 at 25, 37, and 51 days after full bloom of the commercial crop. Seven days after each exposure, 20% of the total recovered 14C remained in the shoot, which included stem roots, 10-25% in stem bulblets, 11-20% in mother scales, and 34-44% in daughter scales. Sink activity increased sharply from the outer mother scales to the inner daughter scales. The fraction of total 14C in the main bulb decreased, while that in the stem bulblets increased at successive exposures. Another group of plants was labeled repeatedly by dosing with 14CO2 on the three previous occasions and, also, at 65 days after full bloom. Bulbs were harvested 7 days after the final exposure, stored at 18°C for 14 weeks, and then replanted, At bulb digging, 50%, 30%, and 20% of the total 14C recovered were in the main bulb, stem bulblets, and shoot, respectively. Mother scales lost dry weight and 14C during storage and were nearly depleted when flower buds were visible the next season. Specific 14C activity in the emerging flowering shoot was high but decreased dramatically as the leaf number rapidly increased. The shoot and new daughter scales were the principal recipients of mobilized scale reserves, although only 28% of the 14C lost from mother scales were recovered in other plant parts. A majority of the carbon originally in mother scales was likely lost in respiration between fall harvest and 3 weeks after anthesis the following year. The daughter bulb contained 64% of the 14C in the bulb at fall harvest, and lost very little 14C during regrowth the following year.

Open Access

Abstract

Buds or open flowers are often removed in the production of Easter lily (Lilium longiflorum Thunb.) bulbs. To determine if time of flower removal affects bulb size or plant growth, flower buds of container-grown ‘Nellie White’ plants were removed when the length of the largest flower bud was 1.0 cm (early) or 3.5 cm (late). Net photosynthesis of the 5th (upper) and 25th (mid-shoot) leaves was monitored and plants were harvested 2 months after full bloom of intact controls. Early disbudding stopped pedicel growth, inhibited stem elongation, and reduced total leaf area 12%, but did not affect bulb weight. Stem elongation was inhibited less by late disbudding; leaf area and plant weight were unaffected. Both fresh and dry bulb weights of late disbudded plants increased by 15%. Early disbudding reduced the rate of net photosynthesis of leaf 5 (particularly during the 3 weeks following full bloom), whereas late disbudding had less effect. Treatments did not affect photosynthesis of leaf 25. Reduced stem growth under late disbudding, without a severe reduction in photosynthesis, may have increased the availability of assimilate for bulb growth. Early disbudding caused 81% of the daughter bulbs to sprout prematurely, compared to 27% for late disbudding and 9% for controls. In a field study, removing flower buds at 1.5 cm or 4.0 cm in length increased bulb fresh weight over intact controls by 12% and 30%, respectively. Disbudding did not increase sprouting of field-grown plants. Delaying removal until the first flower bud is 3.5–4.0 cm long reduces deleterious effects on shoot growth while significantly improving bulb size.

Open Access