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  • Author or Editor: Yin-Tung Wang x
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The effects of water salinity [0.05, 0.40, 0.75, 1.10, and 1.40 dS·m-1 of electrical conductivity (EC)] on Phalaenopsis orchids grown in 100% fine-grade fir bark or a combination of 80% bark and 20% sphagnum peat were studied. In both media, flower diameter decreased slightly as salinity increased. Plants in bark had more flowers as salinity increased, but had fewer flowers than those grown in bark/peat. In either medium, salinity had no effect on the number of new leaves produced. As salinity increased, plants in bark had increasingly larger total leaf area, with a maximum at EC = 1.10 dS·m-1. Leaf area of plants in bark/peat was greater than that of those in bark, but was unaffected by salinity. Root fresh mass was lower with increasing salinity in both media. Media had no effect on mineral concentration in the leaf. In bark, increasing salinity increased the Ca and Na concentrations but had no effect on the concentration of other minerals in leaves. As salinity increased in the bark/peat medium, leaf concentrations of P, Fe, and Cu decreased and those of K, Ca, Mg, Na, and Zn increased, but the concentration of N was unaffected by salinity. Leachate from bark/peat had twice the EC and lower pH (4.9) than bark (5.7).

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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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Potted mature Phalaenopsis `Joseph Hampton' orchid (clone Diane) plants were placed in each of four growth chambers with 0, 8, 60, or 160 μmol·m–2·s–1 photosynthetic photon flux (PPF) for 12 hours daily and at 20C day/15C night air. Plants under 160 or 60 μmol·m–2·s–1 PPF began spiking (an elongating reproductive bud protruding through the base of its subtending leaf) in an average of 28 or 34 days, respectively. None of the plants placed under 0 or 8 μmol·m–2·s–1 PPF started spiking within 6 weeks. These plants, following return to a greenhouse, spiked and flowered 8 weeks later than those receiving 160 μmol·m–2·s–1. In a second experiment, plants were placed in each of three growth chambers and kept in complete darkness at 20C day/15C night for 2, 4, or 6 weeks before exposure to 160 μmol·m–2·s–1 PPF. Air was maintained at 20C day/15C night for an additional 6 weeks and then raised to 25C day/20C night to accelerate flowering. Plants exposed to 2, 4, or 6 weeks of darkness required 45, 60, or 77 days, respectively, to reach spiking. However, all plants spiked at similar times (31 to 35 days) after lighting began. Anthesis occurred at progressively later dates for plants placed in darkness for increasing durations, but plants in all treatments required 123 days to reach anthesis following their exposure to light. Flower count and size were not affected in both experiments.

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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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Vegetatively propagated liners of six hybrid anthurium cultivars (Anthurium Schott), `Pink Aristocrat', `Patty Anne', `Purple Viking', `Royal Pink', Royal Orange', and `Royal Red', were planted in pots and grown under warm [maximum 30 °C (86 °F)] or hot [maximum 35 °C or (95 °F)] conditions with or without a single foliar application of 500 mg·L-1 (ppm) GA3 and evaluated after 7, 9, and 13 months. GA3, when applied 7 months after planting, did not promote flower production or result in taller plants. Plants in warm and hot areas, except for `Pink Aristocrat', had similar degrees of foliage injury in April, but those in the warm environment had better quality in July than those in the hothouse. Yellow leaves and necrosis on leaf margins were apparent on plants in the hot area. `Pink Aristocrat' was the most (>20 flowers) and `Royal Red' was the least (2 flowers) floriferous after 1 year. Flower color of `Royal Red' was unaffected by high temperature, whereas flowers of the other cultivars faded under heat. Growing these anthurium cultivars at maximum 30 °C (86 °F) air temperatures is recommended for good quality and high flower count.

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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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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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Hibiscus rosa-sinensis `Jane Cowl' were pruned several weeks after receiving 0.1 mg/pot uniconazole soil drenches to retard the growth. Plants then received foliar sprays of GA3 (50 ppm), KIBA (200 ppm), or PBA (200 ppm) immediately after pruning or when the lateral shoots had three leaves. Application of the above growth regulators immediately after pruning had no effect on plant growth. When treatments were delayed until the three-leaf stage, GA3 completely restored leaf production rate and partially restored shoot elongation and pedicel length. GA3 also increased leaf area, and the leaf specific weight was similar to leaves on plants not receiving uniconazole. GA3 increased flower production 175% and 65% more than plants treated with uniconazole and the untreated plants, respectively. KIBA and PBA had no effect on altering the growth of uniconazole-treated plants. Foliar application of a combination of GA3, KIBA and PBA at the three-leaf stage had an effect similar to that of GA3 alone. However, the effect of GA3 on growth appeared to be transient and repeated application may be required to maintain the restored growth of uniconazole-treated plants.

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Since Phalaenopsis orchids are CAM plants, learning how they respond to night temperature warmer than the day would help regulate their production. On 1 Apr. 2003, P. amabilis plants were subjected to day/night temperatures at 30/25, 25/30, 25/20, 20/25, 20/15, or 15/20 °C under 140 μmol·m-2·s-1 PPF. After 4 months, the total length of new leaves was shorter as a result of fewer and shorter new leaves when nights were cooler than the days and as the average daily temperature declined. More spikes were produced at 25/20 and 20/25 °C than at 20/15 or 15/20 °C. In another experiment, P. amabilis plants were moved to the above conditions on 12 Aug. Plants exposed to 30/25 or 25/30 °C had more leaf growth than at lower temperatures, but no flowering. Plants that were exposed to 25/20 or 20/25 °C spiked in 2 weeks; but plants took 20 and 18 d to spike under 20/15 or 15/20 °C, respectively. Again, as average daily temperature decreased, there was less leaf growth. Cooler day than the night reduced vegetative growth, regardless of temperature. Plants at 25/20 or 20/25 °C had higher flower count (12) than those at 20/15 or 15/20 °C (8). In a third experiment, plants of a large-flowered Doritaenopsis hybrid spiked at 22–24 d when exposed to 25/20 or 20/25 °C, whereas 30-33 d were needed to spike under 20/15 or 15/20 °C. In a fourth experiment, a Doritaenopsis hybrid spiked after 22, 21, or 25 d under 25/25, 25/20, or 20/20 °C. However, 37 d was required to spike under 20/15 °C. These results suggest that the best temperature range for spiking these orchids is 25 to 20 °C and a day/night temperature differential is not needed for spiking when temperature is at or below 25 °C.

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