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The effect of UV-B fluorescent lamp light on seedling elongation was investigated using three species: marigold (Tagetes sp.), cucumber (Cucumis sativa), and tomato (Lycopersicon esculentum). Seedlings were exposed to light supplied from two unshielded and unfiltered 40-watt UV-B fluorescent lamps. In two experiments, seedlings were placed a distance of 45 cm below the light for varying lengths of time, while seedlings were placed 60 cm below the light in a third experiment. For marigold, seedlings were shorter when germinated under the UV-B lamp than when germinated under natural light in a glasshouse. Two hours of exposure just after glasshouse germination (cotyledons unfolded) was effective in reducing height of cucumber seedlings, whereas 6 hours was required to significantly reduce the height of tomato seedlings. Treatments were still effective when the last measurements were taken 12 to 14 days after germination. Exposure of seedlings to UV-B lamp light provides a possible alternative means of preventing excessive seedling elongation instead of relying on chemical plant growth regulators.

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The effect of exogenous ethylene was investigated on single-stemmed plants of Rosa L. `RUIdodo', `RUIrosora', `RUIjef', `MEIferjac', `MEIshulo', `MEIghivon' and `MEIgagul' grown in controlled environment growth chambers simulating summer-like and winter-like conditions. When the flower on each plant reached developmental stage 2 (showing color, calyx reflexing, no petals reflexed), the plants were placed for 18 h in plexiglass chambers with ethylene at 0, 0.1, 0.5, 1.0 and 5.0 μL·L-1 under a simulated interior environment at 21 °C with 14 μmol·m-2·s-1 fluorescent light. Under the same interior environment, the plants were kept for postharvest evaluation. Response to ethylene of all cultivars was not affected by the difference in growing conditions. As shown previously by other authors, however, the ethylene reduced flower longevity. Treatment with 0.1 μL·L-1 of ethylene reduced flower longevity by 1 day in comparison to the control (0 μL·L-1). The ethylene concentrations of 1.0 μL·L-1 and 5.0 μL·L-1 reduced flower longevity by 3 days. Regardless of ethylene concentration or growing conditions, `RUIjef' and `MEIferjac' exhibited the longest flower longevity and `MEIghivon' and `MEIgagul' the shortest flower longevity. All cultivars, except `RUIrosora', exhibited the longest flower longevity under summer-like vs. winter-like conditions, with the difference ranging from 1.5 to 5 days. `RUIrosora' exhibited similar flower longevity regardless of growing conditions. Differences in flower longevity in response to seasonal growing conditions have been found by us and other authors, but the cultivars used in this study have not been previously studied. This difference in flower longevity as a response to growing conditions cannot be explained by differences in response to ethylene so that other factors must be involved.

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Research with the Basye Rose Breeding and Genetic Program at Texas A&M University has developed rose populations to use to study the genetic nature of leaf, stem, and several other rose traits. The rose populations are from the backcross of Rosachinensis`Old Blush' to WOB (interspecific hybridization of the diploid parents Rosawichuariana `Basye's Thornless' and `Old Blush'). The qualitative trait of presence of stem prickles and the quantitative traits of stem prickle density and leaflet number were observed in three field locations. Two locations are in College Station, Texas, and one location in Overton, Texas. The qualitative trait of presence of stem prickles supports the reported monogenic modes of inheritance. The presence of stem prickles (dominant) had a segregation ratio of 1:1 for prickles: no prickles. Prickle density and leaflet number demonstrated a quantitative mode of inheritance. For prickle density the genotype was significant and environment was nonsignificant. For leaflet number the genotype/generation was significant and environment was nonsignificant. This shows that genotype influences prickle density and leaflet number expression. The genotype by environment interaction was nonsignificant for all traits.

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Pelargonium × hortorum ‘Tango Dark Red’, ‘Tango Pink’, ‘Americana Red’, and ‘Rocky Mountain Lavender’ unrooted cuttings were subjected to Electron beam (E-beam) irradiation at 0 (control, no treatment), 0.61 ± 0.04, 0.83 ± 0.07, or 1.02 ± 0.01 kGy (mean ± se, n = 4) in Expt. 1 and 0 (control, no treatment), 0.08 ± 0.00, 0.16 ± 0.00, 0.31 ± 0.00, or 0.57 ± 0.02 kGy (mean ± se, n = 4) in Expt. 2. Cuttings exposed to E-beam irradiation other than the control treatment did not root or form callus and exhibited a change in leaf color from green to red and eventually yellow. Our results suggest that the use of ionizing irradiation for preventing the accidental importation of biothreat agents through unrooted Pelargonium cuttings is not feasible.

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To determine the efficacy of cyproconazole for control of black spot [Marssonina rosae (Lib.) Lind] when applied as a drench, treatments of 0, 32.5, 65, 97.5 and 130 g a.i./ha were initiated 9 May 1994 on individual Rosa `Peace' plants in a randomized complete-block design. Treatments were applied once per month until 18 Oct. 1994. Data were taken in July, Sept., and Nov. 1994 when separate disease and defoliation ratings were assigned. By July, the controls were heavily infected; the higher treatment rates resulted in significant control. By September, the disease and defoliation ratings exhibited a linear response with cyproconazole rate, with the highest treatment rate giving the best control. The relationship between disease and defoliation ratings and treatment rate remained the same in November, although there was increased disease incidence overall. No phytotoxicity was observed. These results indicate that soil applied treatments of cyproconazole can control black spot effectively on roses.

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Experiments were conducted to study the interaction of cultivar, flower stage, silver thiosulfate (STS), and BA on flower senescence and leaf abscission in greenhouse-grown potted miniature roses. Plants of Rosa L. `Meijikatar' (Orange Sunblaze) and `Meirutral' (Red Sunblaze) were sprayed with several concentrations of STS and BA in factorial combination. In winter, plants were sprayed with STS at 0 or 2 mm and BA at 0, 0.02,0.04,0.11,0.22, or 0.44 mm In spring, flowers at three stages of development were sprayed with STS at 0,2, or 3 mm, and BA at 0, 0.02, 0.04, 0.22, or 0.44 mm One day after treatment in both experiments, plants were placed in darkness at 16C for 4 days to simulate shipping, and then they were evaluated in a controlled environment at 21C. Poststorage floral longevity (PSFL) was longer for `Meirutral' than for `Meijikatar' plants, regardless of chemical treatment or flower stage. Flowers that were in the bud stage (stage 1) before simulated shipping lasted longer than flowers showing color (stages 2 and 3), regardless of cultivar or chemical treatment. Combinations of STS and BA did not increase PSFL compared to STS alone. Plants treated with 2 or 3 mm STS exhibited longer PSFL than nontreated plants; however, 2 and 3 mm were about equally effective. STS at 4 mm was phytotoxic in a preliminary experiment. Applying BA alone did not affect PSFL, but did improve postharvest flower opening on `Meijikatar' plants about the same as STS applied alone. The large flowering cultivars represented by `Meijikatar' and `Meirutral' appear to be nonresponsive to BA. A star-shaped malformation was induced on `Meijikatar' and `Meirutral' plants by simulated shipping and was not prevented by STS or BA. Chemical name used: N-(phenylmethyl) -1H-purin-6-amine (BA).

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Six cultivars of potted rose (Rosa ×hybrida L.) plants were evaluated for shipping stress-induced leaf chlorosis during holding at 8, 16, or 28C for 2, 4, or 6 days. `Meijikatar' showed more leaf chlorosis than the similar `Meirutral' at the higher simulated shipping temperatures and longer durations. Plants of `Meijikatar' were treated before simulated shipping with BA, TZ, or Promalin at 0, 25, 50, or 100 mg cytokinin/liter each, then paper-sleeved and stored in the dark in fiberboard boxes at 16C for 5 days. Plant quality 5 days after removal from storage was better with BA at 50 or 100 than at 0 mg·liter–1. All cytokinin-treated plants showed less leaf chlorosis than controls. Benzyladenine at 50 or 100 mg·liter–1 reduced leaf chlorosis when compared to all TZ treatments. There were no differences among treatments in the number of etiolated shoots per plant. Chemical names used: N-(phenylmethyl)-1H-purin-6-amine (benzyladenine, BA); trans-zeatin (TZ); gibberellic acid (GA4+7) + BA (Promalin).

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To assess the effects of summer-like [high-temperature long-day (HTLD)] vs. winter-like [low-temperature short-day (LTSD)] growing conditions on production quality and postproduction longevity of potted miniature roses, plants of Rosa L. `Meirutral' and `Meijikatar' were grown in growth chambers using a short-cycle production schedule (potted liners grown until root establishment, pinched, and flowered). Plants grown under the HTLD environment [30C day/21C night plus 725 μmol·m–2·s–1 photosynthetic photon flux (PPF) for 14 hours per day] had more flowering shoots than those grown under the LTSD environment (21C day/16C night plus 725 μmol·m–2·s–1 PPF for 10 hours per day). The difference is attributable to fewer blind shoots (shoots with aborted growing terminals) under HTLD, because plants in both environments had the same total number of shoots at flowering. Plants in the HTLD chamber also flowered faster, were shorter, and had smaller and lighter-colored flowers than plants in the LTSD chamber. In addition, plants under HTLD exhibited greater poststorage floral longevity and whole-plant shelf life than plants grown under LTSD conditions, regardless of cultivar, simulated shipping (storage) treatment (4 days at 16C), or stage of floral development at harvest. These results suggest benefits from summer production of potted miniature rose plants and the possibility of using a higher-temperature forcing regimen than is normally recommended for winter production.

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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.

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Abstract

Lily plants were exposed to natural daylight (ND), 50% ND (50% saran), ND plus 16 hours of incandescent (Inc) or ND plus 16 hours of high pressure sodium discharge (HID) lamp light at both University of Minnesota and Michigan State University. Light intensity had no significant horticultural effect on plant development rate that could not be readily explained by temperature. The Inc or HID light source hastened flowering by 5 to 8 days over the ND plants when given from emergence to flower. However, the rate of development from visible bud to flower was not influenced by light intensity. Plant heights were increased by all light treatments when compared to the ND plants. These increases appeared due to photoperiod for the HID treated plants, photoperiod and light quality for the Inc treated plants, and light quantity for the 50% saran-treated plants. The number of flower buds initiated was not affected by light treatment but Inc lighting increased flower bud abortion. Final plant height was highly correlated with height at visible bud; final height being about double the height at visible bud when plants were grown continuously under ND, HID, or 50% saran.

Open Access