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- Author or Editor: Terril Nell x
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.
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.
‘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.
‘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.
Bedding plant seedlings were obtained as plugs from commercial sources, transplanted into 10-cm pots, and grown using standard commercial procedures. When plants reached a marketable stage, they were treated with Hydretain, moved to a heavy shaded bench in the greenhouse, and time to first wilt was determined. At wilt, plants were given 180 ml of water, and time to second wilt was observed. Hydretain was applied directly to the media in a volume of 90 ml per pot. Hydretain dilutions in water were 1:4, 1:9, 1:14, 1:19, and 0:1 (controls). Time to first wilt in 'Red Elite' geraniums was 11, 10, 9, 10, and 5 days, respectively. For 'Little Bright Eyes' vinca, first wilt was in 7, 8, 5, 5, and 4 days; and time from treatment to second wilt was 18, 14, 11, 10, and 8 days, respectively. For 'Super Elfin Red' impatiens, first wilt was in 5, 4, 4, 3, and 3 days; and the water absorbed was 121, 167, 172, 132, and 148 ml, respectively. Second wilt was in 7, 7, 8, 5, and 5 days, respectively.
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.
`V-14 Glory' poinsettias in 15-cm pots were pinched on 24 Sept. and given long days until 8 Oct. Chemical treatments were paclobutrazol drench, paclobutrazol spray, or daminozide/chlormequat (D/C) spray. Time of application was between 8 Oct. and 12 Nov. Heights ranged between 27 and 31 cm. D/C reduced bract size more than paclobutrazol spray, and for both, later treatments had greater affect. Paclobutrazol drench did not have a significant affect.
A second experiment had two cultivars, `Freedom' and `V-14'; three paclobutrazol concentrations, 0.2, 0.3 or 0.4 mg per pot; and three application times, 30 Sept., 14 Oct. or 28 Oct. Treatment on 30 Sept. produced the smallest bracts. The cultivar × concentration interaction was significant with 0.4 mg reducing bract size for `Freedom' but not `V-14'. Treatments on 28 Oct. had less effect on height than the other two dates. `Freedom' were shorter than `V-14'. and higher concentrations had more effect on `Freedom' than `V-14'.
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.
Euphorbia pulcherrima cvs. Freedom, SUPJIBI, and Celebrate 2 were sprayed with paclobutrazol or a tank mix of daminozide and chlormequat at week 40, 41, 42, 43, or 44. Application time had little effect on plant size. The tank mix had greater efficacy on `Freedom' but not on the other cultivars. Interactions for bract size indicated: 1) time of application had less effect on `Freedom', 2) there was little difference between the chemicals on `SUPJIBI', but the tank mix had greater efficacy on the other cultivars, and 3) the tank mix had greater efficacy than paclobutrazol during weeks 41, 42, and 43.
`Freedom', `Celebrate 2', `SUPJIBI', and `V-14 Glory' were planted on 8 or 15 Aug. and placed under short days on 12, 19, or 26 Sept. `Freedom' reached anthesis between 30 Oct. and 6 Nov., about 5 days before `SUPJIBI' and `Celebrate 2' and 7-10 days ahead of `V-14 Glory'. `Freedom' planted in Aug. and given short days 14 days apart flowered only 7 days apart (40 to 47 days from start of short days), but when planted in Sept. flowering was in 54 days and each long day resulted in 1 day delay in flowering.
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).