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  • Author or Editor: Yin-Tung Wang x
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Foliar application of 500 or 1000 mg BA or PBA/liter to stock plants of golden pothos [Epipremnum aureum (Linden & Andre) Bunt.] induced axillary bud elongation but did not promote growth of cuttings taken from these stock plants. Cuttings from plants treated with BA + GA4+7, each at 1000 mg·liter-1, died. Plants grown under 1000 μmol·s-1·m-2 had more but smaller leaves than those under 420 μmol·s-1·m-2. Cuttings produced under the higher light level grew more rapidly. Leaf area increased while stem length decreased as Osmocote slow-release fertilizer (18N-2.6P-10K) increased from 4 to 16 kg·m-3. A 24N-3.5P-13.3K water-soluble fertilizer applied at the rate of 0.42 g/500 ml weekly produced the best plants and resulted in the best cutting growth. Cuttings taken from stock plants receiving Osmocote at 4 kg·m-3 grew slower than those produced at other rates. Placement of cuttings in a mist-propagation bed for 1 or more weeks resulted in an accelerated growth rate relative to nonmisted cuttings. Chemical names used: N-(phenylmethyl)-1H-purin-6-amine (BA); N-(phenylmethyl)-9-(tetrahydro-2H-pyran-2-yl)-9H-purin-6-amine (PBA); (1α,2β,4aα,10β) 2,4a,7-trihydroxy-l-methyl-8-methylenegibb-3-ene-1,10-dicarboxylic acid l,-4a-lactone (GA4+7).

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Viterra hydrogel at rates of 0, 1.75, or 2.50 kg·m−3 was tested for the production of three tropical ornamental plant species in two or all of the three media. These were a commercial peat-lite medium (SUN), a medium consisting of equal volumes of peatmoss, bark, and sand (PBS), and a mix containing equal volumes of peatmoss and bark (PB). Codiaeum was grown in SUN and PBS, Dieffenbachia was produced in all three media, and Hibiscus was planted in SUN and PB. Codiaeum variegatum (L.) Blume ‘Norma’ and Dieffenbachia ‘Camille’ grew more and required a longer time to reach initial wilting when grown in SUN than PBS. Hibiscus rosa-sinensis L. ‘Brilliant Red’ had similar growth in SUN and PB. In general, hydrogel had no beneficial effect on plant growth in a greenhouse. Hydrogel extended the time required to reach initial wilting of C. variegatum by 3 days (from 24 to 27 days), but had no effect on Dieffenbachia. Leachate from PBS had higher pH and lower electrical conductance (EC) than that from SUN. Hydrogel had no effect on leachate pH, but decreased EC of the leachate for C. variegatum used at the 2.5 kg·m−3 rate and for H. rosa-sinensis at both rates.

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The rate of full hydration for several hydrophilic polymers differed greatly (starch-based polymers > propenoate-propenoamid copolymer > polyacrylamide). Maximum water retention in distilled water varied from over 500 g to 57 g of water per of different dry materials. All polymers retained less water in the presence of metal ions or fertilizers, with substances releasing Fe+2 being the most detrimental. Potting media containing a polyacrylamide polymer reached maximum water retention after 6 irrigations, while those with Micromax (micronutrient source) required 10 irrigations to reach maximum hydration. The water-holding capacities of the media declined after repeated fertilization. Medium bulk density, total watet retention, and water retention per unit volume of medium were increased by the incorporation of the polymer, regardless of the presence of Micromax. Non-capillary porosity in medium amended with Micromax progressively decreased as the amount of the polymer increased, but remained unchanged in medium without Micromax. Repeated wet-dry cycles resulted in decreased water retention and increased non-capillary pore space of the media.

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Bare-root, vegetatively propagated plants (average 15-cm leaf spread) of a white-flowered Phalaenopsis Taisuco Kochdian clone were imported in late May and planted either in a mix consisting of three parts medium-grade douglas fir bark and one part each of perlite and coarse canadian sphagnum peat (by volume) or in chilean sphagnum moss. All plants were given 200 mg·L−1 each of nitrogen and phosphorus, 100 mg·L−1 calcium, and 50 mg·L−1 magnesium at each irrigation with 0, 50, 100, 200, 300, 400, or 500 mg·L−1 potassium (K). After 8 months, K concentration did not alter the number of new leaves on plants in either medium. Plants grown in moss produced four to five leaves, whereas those planted in the bark mix produced only two to three leaves. K concentration did not affect the length of the uppermost mature leaves when grown in the bark mix. However, in moss, plants had increasingly longer and wider top leaves as K concentration increased. The lower leaves on plants in the bark mix lacking or receiving 50 mg·L−1 K showed symptoms of yellowing, irregular purple spots, and necrosis after spiking and flowering, respectively. Yellowing and necrosis started from the leaf tip or margin and progressed basipetally. Symptoms became more severe during flower stem development and flowering. All of the plants lacking K were dead by the end of flowering. Leaf death originated from the lowest leaf and advanced to the upper leaves. K at 50 mg·L−1 greatly reduced and 100 mg·L−1 completely alleviated the symptoms of K deficiency at the time of flowering. However, by the end of flowering, plants receiving 50 or 100 mg·L−1 K had yellowing on one or two lower leaves. Plants grown in moss and lacking K showed limited signs of K deficiency. All plants in the bark mix bloomed, whereas none in sphagnum moss receiving 0 mg·L−1 K produced flowers. For both media, as K concentration increased, flower count and diameter increased. Flower stems on plants in either medium became longer and thicker with increasing K concentration. To obtain top-quality Phalaenopsis with the greatest leaf length, highest flower count, largest flowers, and longest inflorescences, it is recommended that 300 mg·L−1 K be applied under high N and high P conditions regardless of the medium.

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This is the first report on how leaf harvest techniques and sulfur may affect leaf initiation and yield of Aloe barbadensis Miller (syn. Aloe vera L.). Two long-term experiments were conducted to determine the effects of supplemental mineral nutrients, severity of harvest, and sulfur application on leaf yield of this species. Plants were each grown in a 38-L pot with or without monthly applications of a 20N–8.6P–16.6K water-soluble fertilizer. In the first experiment, beginning in June 1994 (7 months after initiation), the lower leaves were harvested every 3 months with 12, 15, or 18 leaves remaining per plant. All plants were harvested to 12 leaves at the final harvest in Mar. 1997. Fertilized plants that were harvested to 12 leaves produced 81 leaves each during the 3-year period, whereas those harvested to 15 or 18 leaves each produced 76 leaves. In contrast, each of the nonfertilized plants produced 36 leaves. Fertilization tripled the cumulative weight of harvested leaves over a 3-year period. The initial quarterly and cumulative leaf weights were higher in plants harvested to 12 leaves than those harvested to 15 or 18 leaves. However, this difference diminished and disappeared over time. Fertilized plants harvested to 18 or 15 leaves yielded over 10.8 kg annually, whereas nonfertilized plants with 12 leaves produced an average of 3.5 kg leaves per plant. In the second experiment (with or without fertilizer and micronutrient and 0, 25, 50, or 100 g/pot of powdered sulfur per year), plants responded similarly to fertilization as they did in the first experiment. The added micronutrients (25 g/pot per year) had no effect on plant growth. The highest rate of sulfur resulted in few leaves being harvested and reduced cumulative leaf weight in fertilized plants, but did not affect the number of harvestable leaves or their total weight in nonfertilized plants. Soil pH declined from 7.6 to 4.6 as a result of fertilization regardless of the amount of sulfur being applied. In both experiments, plants that received fertilizer had slight cold injury on the abaxial side of some south-facing leaves. The results suggest the importance of fertilizer application to enhance leaf initiation rate. Plants should be harvested to leave no fewer than 15 leaves, preferably 18, on the plant to maintain high leaf yield.

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It was unknown how prolonged periods of cool days and warm nights affect Phalaenopsis Blume hybrids, which perform crassulacean acid metabolism and absorb CO2 primarily at night. The ‘Lava Glow’ plants vegetatively propagated from a hybrid Doritaenopsis (Phalaenopsis Buddha's Treasure × Doritis pulcherrima Lindley*), 15 cm in leaf span, were grown at day/night (12 hours each daily) temperatures of 30/25, 25/30, 25/20, or 20/25 °C under 170 μmol·m−2·s−1 PPF. After 37 weeks, plants at the higher average daily temperature of 27.5 °C (ADT, 30/25 and 25/30 °C) produced more leaves than the lower 22.5 °C ADT. Those grown at 30/25 °C had the largest leaf span and combined length of the new leaves. Plants at 30/25, 25/30, 25/20, or 20/25 °C had 5.0, 4.7, 3.6, and 2.8 new leaves that were 72, 61, 44, and 29 cm in total length, respectively. Warmer nights than days resulted in a small leaf span, reduced leaf growth, and shorter leaves that were particularly noticeable at the 22.5 °C compared with 27.5 °C ADT. Leaves that emerged and grew at the lower ADT had a reduced length to width ratio and a more oval shape. The most striking effect of the 20/25 °C treatment was that 14 of 15 plants bloomed, whereas only five plants at 25/20 °C and none at 30/25 or 25/30 °C produced flowers. Similar results were obtained in a second experiment using 30/20, 20/30, 25/15, or 15/25 °C. After 29 weeks, all plants at 15/25 °C bloomed, whereas none in the other treatments had flowers. Long-term exposure to 15/25 °C resulted in slow leaf production and undesirable small leaves. These results suggest that day and night temperature may both affect growth and flowering of this orchid.

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Bougainvillea cuttings propagated in fall and winter often bloom profusely before putting out adequate shoot growth. These large flowers shade the small leaves, resulting in slow growth. In an attempt to solve this problem, rooted `Juanita Hatten' cuttings were planted in 11.5-cm pots, clipped to 5 cm, and placed under natural short day or a 4-hour night interruption on 7 Dec. Plants were sprayed on 8 Dec. and again on 2 Jan. with 0, 50, 100, or 200 mg GA3/L or a combination of GA3 and PBA at 200 mg·L–1. Data were taken on the uppermost new shoot of each plant. Under long-day conditions, the first inflorescence was produced on the first node of all control plants, whereas plants treated with GA3 at 100 or 200 mg·L–1 produced the first inflorescences on higher nodes. The number of inflorescences on this shoot was unaffected by any treatment. GA3 treatment resulted in longer shoots (6.7–10.2 cm vs. 2.4 cm) and more leaves (13.4–l6.2 vs. 7.5), with greater effects at higher concentrations. These shoots had several inflorescences at the base, followed by many nonflowering nodes and additional flowers near the tip. The GA3 + PBA treatment had no effect on the position of the first inflorescence. However, shoots had twice as many nodes and fewer inflorescences than the controls and were shorter than those treated with GA3 alone. Plants under short day responded similarly to respective treatments under the long-day conditions. Tests will be conducted to determine if stock plants need to be treated in early fall and cuttings collected from the new growth to prevent early flowering.

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Lilium longiflorum Thunb. `Nellie White' plants were selected when their first flower buds reached 2 or 5 cm in length, sprayed with 2 mL of PBA at 0 or 500 mg·L–1, and then placed under 1440 or 60 μmol·m–2·s–1 photosynthetic photon flux (PPF) during flowering. PBA resulted in delayed anthesis and increased dry matter accumulation in flowers under the high PPF but had no effect under the low PPF. PBA did not decrease the severity of flower bud abortion under the low PPF. Application of PBA induced the formation of numerous bulbils in the leaf axils. Regardless of PPF, PBA-treated plants had less dry weight in the main bulbs than the control plants. Chemical name used: N-(phenylmethyl)-9-(tetra-hydro-2H-pyran-2-yl)-9H-purin-6-amine (PBA).

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On 6 Sept. 1996, container-grown vegetatively propagated Phalaenopsis Atien Kaala `TSC22' plants were harvested and individually weighed. The bare-root plants were packed in cartons with shredded newspaper and placed in incubators at 15, 20, 25, or 30°C air temperature. Control plants were undisturbed. After 4, 7, or 14 days, one-third of the plants were removed from each temperature treatment, weighed, planted in pots, and then placed in a greenhouse. Mass loss (primarily water) increased with increasing air temperature and duration in storage. Symptoms of chilling injury (yellow blotches on leaves) were inversely related to 15 and 20°C storage temperatures. Chilling injury became more severe as storage duration increased. Plants had little or no chilling injury at 25 and 30°C, regardless of storage duration. Leaf loss was most severe on plants stored at 15°C for 7 or 14 days or at 30°C for 14 days. Increased storage duration up to 14 days did not affect the time of spiking (appearance of the flowering shoot) for plants stored between 15 and 25°C. Those kept at 30°C, regardless of the duration, spiked 5 to 8 days after the control. The results suggest that vegetative Phalaenopsis plants harvested in late summer should be stored and shipped at 25°C. Under such conditions, plants could lose 20% of the fresh mass between harvesting and planting without adversely affecting subsequent performance.

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Leaf blades, axillary buds, shoot tips, green bark, suberized bark, or the whole plant of container-grown Hibiscus rosa-sinensis L. cv. Jane Cowl were treated with uniconazole. Applying uniconazole (50 mg·liter-1) to axillary buds or the green bark below a bud immediately after pruning limited elongation of the first three internodes. Length of the fourth internode was unaffected, regardless of the site of uniconazole application. When used on plants with 24-day-old shoots, uniconazole (40 mg·liter -1) applied to the whole plant provided the only satisfactory height control. Leaf size was reduced by nearly 50%, with a concomitant increase (12%) in fresh weight per unit area. GA3 (50 mg·liter-1, was more effective in promoting elongation of shoots previously retarded with a drench application of uniconazole (0.1 mg/2.6-liter pot) when applied to the whole shoot, leaf blades, or shoot tip. Application of GA, only to the stein surface, whether old or young, did not effectively encourage the growth of shoots of plants previously treated with uniconazole. Chemical names used: (E)-1-(p-chlorophenyl) -4,4-dimethyl-2-(1,2,4-triazole-1-yl)-1-penton-3-ol (uniconazole); analogue of (1α,2β,4 α,4bβ,10β)-2,4a,7-trihydroxy-1-methyl-8-methylenegibb-3-ene-1,10 dicarboxylic acid 1,4a-lactone (GA3).

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