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  • Author or Editor: Yin-Tung Wang x
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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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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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Ficus benjamina and Codiaeum variegatum ‘Gold Dust’ stem tip cuttings were rooted in a mist bed at 290 or 90 µmols·m–2 Photosynthetic photon flux (PPF) with or without 28° ± 1°C medium heating and then potted. Number of roots in C. variegatum was unaffected by either PPF or medium heating; however, both factors enhanced root elongation. Forty days after potting, cuttings rooted under 290 µmol·s–1·m–2 had more lateral shoots than those rooted under 90 µmol·s-1·m–2 PPF. Although cuttings rooted in heated medium under the lower PPF had roots more than twice as long as those on cuttings rooted in unheated medium under the high PPF, it had little effect on subsequent shoot growth. F. benjamina rooting was improved in heated medium and was not affected by PPF. Unheated cuttings rooted better under high than low PPF. Shoot growth 10 weeks after transplanting was unaffected by the initial differences in root grade.

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Removing 33% or 100% of the Easter lily (Lilium longiflorum Thunb. ‘Nellie White’) mother scales when flower buds were 1.3 cm in length, in conjunction with flower bud removal at the 3-cm stage, increased daughter bulb dry weight by 21% and 45%, respectively, when plants were harvested after 13 weeks. Size of the remaining mother scales in partially de-scaled plants was estimated to be 30% larger than their counterparts in intact bulbs. Growth of the Easter lily bulb is likely limited by source carbon supply.

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Abstract

Compared to floriculture crops, relatively little research has evaluated the effects of growth retardants on production and interior quality of foliage plant species. Ancymidol decreased intemode length in several foliage plant species (1–3), but not china green or dieffenbachia (3). Ancymidol improved interior performance of Epipremnum aureum and Pilea depressa (2). This experiment was conducted to determine the effect of ancymidol on growth of Syngonium podophyllum ‘White Butterfly’ in production and simulated interior conditions.

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Croton (Codiaeum variegatum Blume cv. Craigii) cuttings, enclosed in polyethylene bags, were placed in light (20 μmol·s−1·m−2) or darkness at 15°, 20°, or 30°C for 5, 10 or 15 days (simulated shipping) and then placed in a mist bed to root for 4 weeks. Final leaf loss in most of the treatments was <7%. Cuttings in simulated shipping for 15 days at 30° in darkness and light had 31% and 56% final leaf drop, respectively. These cuttings also produced fewer roots than controls. Root length increased with increased shipping duration and shipping temperature from 15° to 20°, without further increase at 30°. Regardless of temperature and duration in simulated shipping, cuttings shipped in darkness had roots 2.5 to 5 cm longer than those shipped in the light.

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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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Young, bare-root plants (three leaves, 15 cm in leaf spread) from a vegetatively propagated clone of Phalaenopsis Blume x Taisuco Kochdian were imported in late May and planted in a mix consisting of three parts medium-grade Douglas fir bark and one part each of perlite and coarse peat (by volume) or in pure Chilean sphagnum moss. All plants were given 221 N, 124 P, 515 K, 100 Ca, and 50 Mg (all in mg·L−1) when being irrigated. The total N varied from 0%, 25%, 50%, 75%, to 100% NO3-N with the balance being NH4-N. Plants were fertigated when the substrate became dry. For both substrates, as the percentage of NO3-N increased, plants produced slightly fewer leaves. Regardless of the NO3-N to NH4-N ratio, plants grown in moss produced one extra leaf than those planted in the bark mix during an 8-month period. There was a tendency of increasing top leaf length and width as well as the whole-plant leaf spread as NO3-N increased from 0% to 100% in either substrate. Plants receiving 50% or more NO3-N in either substrate spiked and flowered 2 weeks earlier than those given 25% or 0% NO3-N. When grown in the bark mix, flower count, flower diameter, and inflorescence length all increased as NO3-N increased from 0% to 75%. Flower stem (inflorescence, 5 cm from the base) became progressively thicker as NO3-N increased from 0% to 100%. Only two among the 24 plants grown in moss and receiving 100% NH4-N bloomed. These results suggest that Phalaenopsis does not grow well with 100% NH4-N and must be provided with NO3-N at no less than 50%, preferably 75%, of the total N for improved growth and flowering.

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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.

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Cuttings of a thornless mutation of Rosa odorata (RO) and R. multiflora (RM) were rooted in Feb., budded with Rosa `Queen Elizabeth' on 21 Apr. 1987, and planted in 2.6- or 5.2-liter containers. Five weeks after budding, over 50% of the buds on the thornless RO had developed into shoots, while only 4% of the buds on the RM were growing. After an additional 10 weeks, 80% and 60% of the buds on the thornless RO and RM, respectively, had development into shoots. Six months after budding, plants in the 5.2-liter pots produced 1 to 2 folds more flowers than those in 2.6-liter pots. Plants from all four production treatments were planted in a field with alkaline soil on 3 Nov. 1987. During the next four years, plants on RM showed severe chlorosis and had 5% and 45% survival for those produced in 2.6- and 5.2-liter pots, respectively. Those on the thornless RO had 85% and 100% survival when produced in 2.6- and 5.2-liter pots, respectively after four years. Leaves of plants on the thornless RO rootstock had higher concentrations of chlorophyll than those on the RM. However, analyses of leaves did not reveal differences in elemental concentrations among treatments.

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