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  • Author or Editor: Terril A. Nell x
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Abstract

Harmful effects on the physiology and morphology and reductions in yield resulting from water stress on horticultural crops (1) have been documented increasingly in HortScience, the Journal of the American Society, for Horticultural Science, and in review articles. The scientific accomplishments in understanding horticultural crop water stress physiology have been extensive, considering limitations in instrumentation and procedures.

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The quality and longevity of flowering potted plants and cut flowers are affected by the cultivar grown and cultural practices used during production. Preharvest factors may account for 70% of the life of flowering plants. Longevity is directly related to the cultivar grown. In potted chrysanthemums, longevity has been increased by 100% by carefully selecting a long-lasting variety. Cultural factors, such as fertilization practices, may increase longevity by 40% to 50%. Chrysanthemums grown without fertilizer during the final 3 weeks of production lasted 10 to 14 days longer than plants receiving fertilizer for the entire crop. Flower and plant quality is influenced by cultivar and cultural practices. Poinsettia bract edge burn, a marginal burn or spotting on the bracts, appears to be caused by a calcium deficiency that may be triggered by use of cool day temperatures or warm night temperatures and use of cultivars sensitive to this disorder. Light compensation point and carbohydrate status of the plant at flowering have not been related to differences observed in flower longevity and quality.

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Several pulse solutions were tested for their effectiveness in preventing leaf senescence on four cut oriental lily cultivars (Lilium sp. `Acapulco', `Kissproof', `Noblesse' and `Star Gazer'). Stems were pulsed 24 hours after harvest for 1 hour, stored in boxes in the dark for 5 days at 3 °C (37.4 °F) then evaluated in postharvest conditions. A new commercial product called Chrysal BVB, a proprietary mixture manufactured by Pokon & Chrysal (Miami) containing cytokinine and gibberellic acids, was the most effective product tested. Chrysal BVB [1 mL·L–1 (0.1%)] prevented leaf chlorosis and abscission on `Acapulco' and `Noblesse' and significantly reduced it by 82% on `Star Gazer' and by 69% on `Kissproof'. Stems pulsed in Fascination, a commercial mixture containing 1.8% gibberellins (GA4+7) and 1.8% benzyladenine [5.4 mg·L–1 (ppm) each], virtually prevented leaf chlorosis on `Noblesse', reduced it by 50% or more on `Acapulco' and `Star Gazer', and significantly delayed it 8 days on `Kissproof'. A 10 μm (2 ppm) pulse in thidiazuron, a substituted phenylurea with cytokinin-like properties, delayed leaf chlorosis on `Star Gazer' but to a lesser extent compared to BVB and Fascination. Chrysal SVB, a propri-etary mixture manufactured by Pokon & Chrysal containing gibberellic acid, had no effect on reducing leaf chlorosis on `Star Gazer'. None of the pulse solutions had adverse effects on bud opening, flower quality or vase life. Maintaining stems in a bulb flower preservative significantly reduced leaf chlorosis and abscission in all cultivars when stems were not pretreated with a pulse solution or when a pulse solution was ineffective.

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Abstract

Pressure chamber and thermocouple psychrometer measurements of leaf water potentials in vegetative Euphorbia pulcherrima Willd. cv. Eckespoint C-l Red were evaluated. The 2 methods agreed within 0.2 MPa between −0.3 and −1.8 MPa and were equal at −1.1 MPa. Minimum daily water potential for nonstressed plants reached −0.67 MPa by 1230 hr. Abaxial water vapor conductance and water potential varied little between 1230 and 1630 hr. When drought was imposed, incipient stomatal closure occurred at −0.8 MPa with full closure observed at −1.2 MPa. Complete loss of turgor pressure occurred at water potentials between −1.2 and −1.4 MPa. The linear correlation coefficient for conductance and leaf-air temperature differential was 0.96, with leaf and air temperature equal when conductance was 0.6 cm·s−1. Xylem pressure potentials of upper leaves on drought-stressed plants declined to −1.7 MPa in 8 days and abscission of proximal leaves began. There was little change in xylem pressure potentials of upper leaves after leaf abscission began.

Open Access

Abstract

Bract necrosis of Euphorbia pulcherrima Willd. ‘Gutbier V-14 Glory’ was most frequently observed on transitional bracts (red leaf-shaped organs attached to the stem in the same alternate phyllotaxy as leaves and subtending the inflorescence). Transitional bracts lacked a palisade layer and their stomatal density was lower than on leaves. Necrosis was prevalent at the transitional bract tips in areas with a brochidodidmous-semicraspedodromous veination pattern. Plant growth was not affected when either fertilization was terminated at bract coloration or when plants were watered at wilt during the period from bract color to anthesis. Necrosis was greatest, however, on plants grown with high fertilizer and water levels. Necrosis may be associated with a toxicity of elements transported through pitted vein endings at the tip of the bract.

Open Access

Abstract

‘Gutbier V-14 Glory’ poinsettia was introduced to the commercial industry in the late 1970s and has been shown to be sensitive to bract necrosis (3). Necrotic spots occasionally develop on the intermediate bracts during the latter parts of the crop cycle. Nell and Barrett (2) found this problem to be worse when plants were provided 300–400 mg/liter Ν at every irrigation and well watered during bract coloration. Symptoms resembled injury due to elemental toxicity or desiccation. Observations in commercial operations suggested that necrosis may be related to fertilizer source or formulation.

Open Access

Abstract

‘Gutbier V-10 Amy’ (‘Amy’) poinsettia lost more leaves and cyathia after simulated shipping at different temperatures (4°, 16°, or 24°C) and 30 days under interior conditions than ‘Annette Hegg Dark Red’ (‘AHDR’) plants. ‘Amy’ and ‘AHDR’ plants lost a large number of leaves when shipped for more than 4 days at 24°. ‘Amy’ quality was reduced when shipped at 4° due to chilling injury (white lesions on bracts). Bracts less than 2.5 cm long were most sensitive to this injury.

Open Access

Three simulated transport temperatures (5, 11, or 17C) and durations. (3, 6, or 9 days) were used to evaluate the postproduction flowering patterns of miniature potted rose (Rosa sp) `Orange Rosamini'. The postproduction environment was maintained at 20 ± lC, 60% ± 5% relative humidity (RI-I), and an irradiance level, from cool-white fluorescent lamps, of 4.5 W·m-2 photosynthetically active radiation (PAR) for 12 hours daily to simulate conditions at the retail or consumer level. At 3 weeks postproduction, plants held for 9 days at 17C had the fewest buds showing color per plant. As temperature increased, there were fewer flowers per plant at weeks 2 and 3 of postproduction. In a second study, the effect of simulated transport (3 days at 5C vs. no transport) and postproduction irradiance level (1, 2, or 4 W·m-2 PAR) were evaluated over a 7-week postproduction period for `Orange Rosamini'. A three-way interaction was observed between simulated transport treatment, postproduction irradiance level, and time in postproduction for the number of open flowers per plant. Plants responded similarly at 1 and 2 W·m2 throughout the postproduction period, regardless of transport treatment; however, at 4 W·m-2 the plants of the no transport treatment had two to three open flowers each week up to week 6 of postproduction, while plants subjected to simulated transport followed the pattern of one and two open flowers for 0 to 3 weeks. Flowering then increased to three to four open flowers for the duration of the postproduction period. A third study involved two simulated transport treatments (3 days at SC vs. no transport), three postproduction irradiance levels (1, 2, and 4 W·m-2 PAR), and six miniature rose cultivars (`Orange Rosamini', `Red Minimo' `Sweet Rosamini', `Golden Rosamini', `Favorite Rosamini', and `White Rosamini'). Plants held at 1 or 2 W·m-2 for 3 weeks had no open flowers, while those held at 4 W·m-2 for 3 weeks had one to four open flowers, except `Sweet Rosamini', which had no open flowers with simulated transport.

Free access

Impatiens L. wallerana Hook., Salvia splendens Sello ex Nees, Tagetes erecta L., and Petunia hybrida Vilm. plants in 610-cm3 pots were sprayed with either uniconazole or paclobutrazol at concentrations from 10 to 160 mg·liter-1. For all species, both chemicals reduced plant size compared with untreated control plants, and the effect increased with higher concentrations. Uniconazole produced smaller plants than did paclobutrazol at similar concentrations. For impatiens, salvia, and marigold, there was an interaction between chemical and concentration; the degree of difference between the effects of the chemicals was greater at higher concentrations. For these three species, uniconazole elicited a quadratic response and reached saturation within the concentrations used; however, these concentrations were still in the linear portion of the dose response curve for paclobutrazol. Chemical names used: (2RS,3RS)-1-(4-chlorophenyl)-2-(1,1-dimethylethyl)-(1H-1,2,4-triazol-1-yl)pentan-3-ol (paclobutrazol); (E)-(+)-(S)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-pent-1-ene-3-ol (uniconazole).

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Miniature flowering potted `Orange Rosamini' rose plants (Rosa × hybrida) were placed directly from production into simulated transport (STR) for 3 days at 5C and then into a retail handling treatment for 0, 1, 2, or 4 days. In the retail handling treatment, plants placed at 1 W·m-2 were then moved into a final postproduction irradiance level of 4 W·m-2; plants placed at 4 W·m-2 were then moved into a final postproduction irradiance level of 1 W·m-2. Also, a no-STR control treatment, plants placed directly into final postproduction environment (no transport or retail handling treatment), was included. All plants were placed into a final postproduction irradiance level (1 or 4 W·m-2) for 3 weeks to evaluate the effects of postproduction irradiance. The retail handling and postproduction environments were maintained at 20 ± 1C, 1 or 4 W·m-2 of irradiance (12 hours daily) from cool-white fluorescent lamps, and relative humidity (RR) of 60% ± 5% to simulate retail and/or consumer home conditions. Little difference was observed due to retail handling treatment or postproduction irradiance after 1 week. At weeks 2 and 3 of postproduction, there were 40% to 50% more open flowers on the no-STR plants maintained at 4 W·m-2 than on those maintained at 1 W·m-2 or on STR plants maintained at 1 or 4 W·m-2 postproduction irradiance. At week 3 of postproduction, plants with STR maintained at 1 W·m-2 had no buds showing color, while those maintained at 4 W·m-2 had three to five buds showing color. However, the no-STR control plants had one bud showing color at week 3, regardless of postproduction irradiance level. These results indicate that the detrimental effects of transport, i.e., bud drop, likely can be minimized by high postproduction irradiance levels following transport.

Free access