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Yin-Tung Wang

Blooming Phalaenopsis orchids have become a popular pot plant in recent years. Plants start producing spikes after experiencing cool air in early fall, bloom in early spring, and become limited in supply after April when market demand is strong. Deferring spiking and flowering by maintaining the greenhouse air constantly above 28°C is cost prohibitive. Previous research has discovered that plants must be given light while being exposed to cool air to induce spiking. In Fall 1994, 2-year old Phalaenopsis TAM Butterfly plants were exposed to repeated cycles of 1 day in darkness and another day in light (1D/1L), 4D/3L, 7D/7L, or 0D/7L (continuous lighted control) between 15 Sept. and 16 Dec. Each plant was removed from the treatment once it had started spiking. The control plants bloomed on 20 Jan. 1995, whereas the 4D/3L plants did not reach anthesis until April 17, nearly three months later. Flowering of the 1D/1L and 7D/7L plants was also deferred until early April. The treatments had no adverse effect on flower count or size. In 1995, 3-year old plants were exposed to 0D/7L (control), 2D/5L, 3D/4L, 4D/3L, or 5D/2L from 15 Sept. to 22 Jan. 1996. The control plants spiked on 17 Oct. and bloomed on 8 Feb. 1996 when spikes had just emerged from plants in the 5D/2L treatment. The 5D/2L plants are expected to bloom in late May or early June. The other treatments were not as effective as that in 1994 and resulted in blooming only 2–3 weeks after the untreated control. The results of this research will help producers to stagger or precisely program the time of flowering to meet the market demand.

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Yin-Tung Wang

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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Yin-Tung Wang*

It not clear how a prolonged period of cool days and warm nights affect Phalaenopsis hybrids which take up CO2 mainly at night. The `Lava Glow' clone of the hybrid Doritaenopsis (Phal. Buddha's Treasure × Doritis pulcherrima) 15 cm in leaf span were subjected to day/night (12 h each daily) temperatures of 30/25, 25/30, 25/20, or 20/25 °C at 170 umol.m-2 .s-1 PPF. After nine months, plants under the higher average daily temperature (ADT) produced more leaves. Those grown at 30/25 °C had the largest leaf span and total length of the new leaves. Plants under 30/25, 25/30, 25/20, or 20/25 °C had 5.0, 4.7, 3.6, and 2.8 new leaves and 72, 61, 42, and 28 cm in total new leaf length, respectively. Cool days and warm nights resulted in smaller leaf span and reduced leaf growth, particularly at 20/25 than at 25/30 °C. Within a given ADT, cooler days resulted in shorter leaves. Leaves produced by plants at the lower ADT had a smaller length to width ratio and the more desirable oval shape. The most striking effect of 20/25 °C was that 14 out of 15 plants bloomed, whereas only 5 plants under 25/20 °C and none in the 30/25 or 25/30 °C treatment flowered. In a second experiment, 18-22 cm plants were subjected to 30/20, 20/30, 25/15, or 15/25 °C. After 29 weeks, similar results were obtained. All plants under 15/25 °C bloomed, whereas none in the other treatments produced flowers. Long-term exposure to 15/25 °C resulted in slow leaf production and undesirable small leaves. These results suggest that, with day temperatures in the 20-15 °C range, nights 10-5 °C warmer are not desirable for rapid vegetative growth. However, cool days and warm nights may be used to effectively induce the flowering process.

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Yin-Tung Wang

Dendrobium Linnapa `No. 3' plants were potted one per 1.75-liter pot with large or small fir bark with or without 30% peatmoss (by volume before mixing). Plants in each medium were fertilized at each or every third irrigation with 1 g·liter−1 of 20N-8.6P-16.6K fertilizer. Neither medium nor fertilization frequency affected flowering date of the first pseudobulb. Adding peatmoss to both types of bark resulted in taller first pseudobulbs. Peatmoss in the large bark promoted the production of more inflorescences and flowers (20) compared to the bark alone (11). Constant fertilization promoted the early emergence and development of the second pseudobulb and resulted in more inflorescences and flowers (21) than intermittent fertilization (12). Vegetatively propagated Phalaenopsis Taisuco Kochdian were planted in 0.5-liter pots with 1) equal volumes of no. 3 perlite, Metro Mix 700, and charcoal (PMC); 2) 100% large fir bark; or 3) 40% medium fir bark, 20% peatmoss, 10% each of no. 3 and no. 2 perlite, 10% vermiculite, and 10% ParGro rockwool (RM). Plants in PMC produced twice the number of new leaves and 1.5 -fold more leaf area than those in the large bark. PMC and RM resulted in similar shoot weights, but the latter enhanced flower count due to more lateral inflorescences. Most (80%) of the roots on plants in the bark were hanging out of the pots, whereas nearly all the roots remained in the pots with PMC. Although medium had no effect on flowering date, flowers on plants produced in PMC and RM were 10% larger than in those on plants produced in bark.

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Yin-Tung Wang

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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Yin-Tung Wang

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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Yin-tung Wang

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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Yin-Tung Wang

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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Yin-Tung Wang

Aloe barbadensis (Aloe vera) plants remain in production fields for several years, with their lower leaves harvested periodically. A long-term experiment was initiated in November 1993 to determine the effects of fertilization and severeness of harvest on leaf yield. Plants were grown in large pots with or without monthly applications of a 20N–8.6P–16.6K soluble fertilizer from March to October. Beginning in June 1994, the lower leaves were harvested quarterly to have 18, 15, or 12 leaves remaining. Fertilization doubled the number of leaves harvested and tripled the total yield over a 2-year period. The lower leaves on the nonfertilized plants, particularly on plants with 18 leaves remaining, sometimes became dry or partially dry at harvest. The initial quarterly yield and cumulated yield were higher in plants with 12 leaves remaining; however, this trend disappeared over time. The fertilized plants produced an average of 10 kg per plant, while the nonfertilized plants produced only 3.2 kg per plant annually. At several harvests, plants with 18 leaves remaining had higher % dry mass in the inner semi-translucent tissue than those having 12 leaves. Leaves of nonfertilized plants had high % dry mass in the inner leaf tissue when harvested in June and September 1995. Plants with 12 leaves remaining can become unstable and the tops break off in gusty wind.