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  • Author or Editor: Yin-Tung Wang x
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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

Case-cooled bulbs of Lilium longiflorum `Nellie White' were potted on 4 Dec. 1995 and forced to flowering using standard growing procedures. Plants were illuminated from shoot emergence to visible bud with supplemental high-intensity-discharge sodium vapor light at 70 μmol·m–2·s–1 from 1700 to 2200 HR each day. When the first primary flower bud (first initiated flower bud most proximal on the shoot) was 5 to 7 cm long, each plant was treated with 3 ml of either de-ionized water or 500 mg·liter–1 6-(benzylamino)-9-(2-tetrahydropyranyl)-9H-purine (PBA). Sprays were directed at the flower buds and associated bracts. When the tepals on the first primary flower bud split, plants were placed at 2°C in the dark for 0, 4, or 21 days. After storage, plants were placed in a postharvest evaluation room with constant 21°C temperature and 18 μmol·m–2·s–1 cool-white fluorescent light. The first three primary flowers on PBA-treated plants lasted significantly longer than corresponding flowers on control plants, but there was no difference between flowers at the fourth and fifth positions. Also, the total postharvest life of the five primary flowers on PBA treated plants was 3 days longer than those on control plants. Storage time inversely affected the postharvest longevity of the first three primary flowers, but had no effect on the longevity of the fourth or fifth primary flowers or total postharvest life of the five primary flowers. There were no significant interaction effects between PBA treatment and storage duration on primary flower longevity.

Free access

The effect of drought on the growth and gas exchange of six bedding plant species—agastache [Agastache urticifolia (Benth.) O. Kuntze `Honeybee Blue'], dusty miller (Cineraria maritima L. `Silverdusty'), petunia (Petunia ×hybrida `Wave Purple'), plumbago (Plumbago auriculata Lam. `Escapade'), ornamental pepper (Capsicum annuum L. `Black Pearl'), and vinca [Catharanthus roseus (L.) G. Don `Titan']—was quantified under greenhouse conditions. Seeds were sown in January and seedlings were grown in the greenhouse until 18 Apr., when two irrigation treatments—drought (D, ≈18% volumetric moisture content at reirrigation) and control (C, ≈25% volumetric moisture content at reirrigation)—were initiated. Leaf net photosynthetic rate (Pn), stomatal conductance (gs), and transpiration (E) were determined in response to a range of substrate moisture content (from ≈5% to 30% by volume) and temperature (from 20 °C to 40 °C). Dry weight of agastache, ornamental pepper, and vinca was unaffected by drought, whereas that of other species was reduced. Leaf area of plumbago and height of plumbago and vinca were reduced by drought. As substrate moisture content decreased from 25% to 10%, Pn, E, and gs decreased linearly in all species except petunia and plumbago. Leaf net photosynthetic rate of all species declined as leaf temperature increased from 20 °C to 40 °C. In contrast, E of all species, except petunia, increased as temperature increased. Transpiration rate of petunia increased as temperature increased from 20 °C to 30 °C, and then decreased between 30 °C and 40 °C. Although petunia had the highest Pn among the tested species, its Pn and gs declined more rapidly compared with the other species as temperature increased from 20 °C to 40 °C or as substrate moisture content decreased, indicating that petunia was most sensitive to high temperature and drought.

Free access

Three experiments were conducted to determine how nitrogen (N), phosphorus (P), and potassium (K) rate and nutrient termination date would affect the growth of Dendrobium nobile Red Emperor `Prince'. For each experiment, 150 one-year-old liner plugs, each with a single psuedobulb, were potted on 4 Feb. 2005. Each of the factorial experiments had five rates of the nutrient and three termination dates. The rates for N and K were 0, 50, 100, 200, and 400 mg·L-1. P rates were 0, 25, 50, 100, and 200 mg·L-1. Termination dates for all experiments were 1 Sept., 1 Oct., and 1 Nov. 2005. Ten months after planting when plants had ceased growing, data were collected for plant height, node number, number of leaves remaining, chlorophyll readings for the lower, middle, and upper leaves, and pseudobulb width and thickness. With one exception, interactions between fertilizer rate and termination date were nonsignificant for the variables measured. For all nutrients, terminating fertilization on 1 Oct. or 1 Nov. resulted in decreased pseudobulb thickness compared to 1 Sept. Prolonged fertilization with N resulted in slightly thinner pseudobulbs. Pseudobulbs grew taller as N rate increased, reaching its peak at 100 and 200 mg·L-1, and declined as N further increased to 400 mg·L-1. Plants had increasing chlorophyll readings in the middle leaves with increasing N rate. All P rates resulted in taller plants with equally more nodes compared to 0 mg·L-1. As K rate increased from 0 to 100 mg·L-1, height and node number increased, but there were no further increases in height at high rates. Number and percentage of leaves remaining increased as N and K rates increased.

Free access

Sphagnum moss has been used as the major substrate for cultivating Phalaenopsis spp. in China, Japan, and Taiwan. With a lengthened duration of cultivation, the pH of the moss gradually declines. It is not understood what causes this decline in substrate pH. Using the vegetatively propagated Phal. Sogo Yukidian ‘V3’, this study investigated if substrate, fertilization, light, and plant roots could be the cause of pH decline in the substrate. The results showed that, although increasing fertilizer concentration resulted in a low initial pH (pH measured by the pour-through technique at first fertilization), fertilization itself was not the primary cause of the long-term pH decline. Regardless of whether the sphagnum moss was fertilized, the pH of the substrate without plants increased as time progressed, whereas the pH of the substrate in which living Phalaenopsis plants were growing declined with time. Although the magnitude and course of pH decline were different in various substrates, the pH of sphagnum moss, artificial textile fiber, and pine bark substrates in which living plants were growing declined with time. Whether the substrate was exposed to light (clear pots) or not (opaque pots) had no effect on substrate pH, indicating that algae were not a factor in pH decline. Therefore, the roots of Phalaenopsis may be the major contributor to substrate pH decline during production.

Free access

Cuttings of Epipremnum aureum (Linden & André) Bunt. were soaked for 5 seconds in 5% Folicote or Stressguard antitranspirant solution, planted immediately or after 6 hours, and misted or not misted during the daylight hours for 2 weeks. Neither antitranspirant affected the growth of misted cuttings. However, in nonmisted cuttings, Folicote resulted in delayed first leaf unfolding and small plants. Misting improved shoot growth relative to not misting. In a second experiment, Stressguard sprayed on leaves of stock plants resulted in slow growth of cuttings taken from them, while Folicote had no effect. Water stress induced by delayed planting resulted in water loss and slow lateral shoot growth in both experiments. Application of uniconazole at the four-leaf stage at 0.05 to 0.4 mg/0.5-liter pot reduced stem elongation, leaf count, and the length of nodal roots. Uniconazole increased individual leaf size on the main shoot and promoted the growth of basal lateral shoots. While stem and total plant dry weights were reduced, total leaf dry weight was not affected by uniconazole. Uniconazole continued to provide good control on the elongation of newly emerged lateral shoots and promoted the production of more and larger leaves when evaluated 4 weeks after the main shoot was severed above the fourth basal node. Chemical name used: (E)-1-(p-chlorophenyl)-4,4-dimethyl-2-(1,2,4-trizol-1-yl)-1-penten-3-ol (uniconazole).

Free access

Roses are adapted for growth and production on acid to slightly acid soil. When grown on alkaline soil sites, without extensive soil modification and acid forming and/or iron chelate fertilization, growth is reduced and severe iron chlorosis is prevalent. This study screened 24 Rosa rootstock species and selections on one acid and two alkaline soil sites for 2 consecutive years. Plants were observed for chlorosis, chlorophyll content, fresh and dry weight production and overall quality. A final reciprocal grafting study using susceptible and tolerant selections was conducted to assure the scion could realize the adaptability of the rootstock. Overall, the following five selections consistently exhibited greater growth and decreased chlorosis on the alkaline sites: R. odorata, R. canina, R. manetii, R. sp. “Mexican”, R. fortuniana, and R. multiflora selection K-l. All other R. multiflora selections performed poorly. On the acid soil site, all rootstocks grew well. When susceptible selections were budded onto tolerant rootstocks, the scions exhibited a higher degree of tolerance. Tolerant selections budded onto susceptible rootstocks exhibited increased chlorosis and decreased growth.

Free access

Seedling transplants produced for early fall and spring establishment of commercial vegetable crops in the Texas Lower Rio Grande Valley rapidly develop excessive shoot growth if field plantings are delayed. Therefore, several varieties of pepper, watermelon, muskmelon, and tomato transplants were treated at the 2-3 leaf stage by foliar spray with 0, 4, 8, or 12 ppm of the triazole growth retardant, uniconazole. The seedlings were field transplanted 3 weeks later. Total heights taken at the time of transplanting indicated significant varietal differences in responses to the treatments. After 60 days in the field, one of the 5 pepper varieties continued to express retarded growth. However, the uniconazole treatment stimulated early fruiting in 2 of the varieties. Tomato seedlings appeared to overcome the stunting within the first 60 days after transplanting while muskmelon and watermelon remained slightly dwarfed. Additional data on total growth and yield in response to the growth retarding treatments will be presented for each of the vegetable varieties.

Free access