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Martin Meeks, H. Brent Pemberton, Lurline Marsh, and Garry V. McDonald

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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H. Brent Pemberton, Yin-Tung Wang, and Garry V. McDonald

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.

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William E. Roberson, H. Brent Pemberton, and George L. Philley

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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Lisa Chen Cushman, H. Brent Pemberton, and John W. Kelly

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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Ursula K. Schuch, H. Brent Pemberton, and Jack J. Kelly

Five cultivars of bare-root rose plants were exposed to increasing periods of drying and after rehydration were grown in containers until flowering in a plastic-covered greenhouse. At the start of the experiment, moisture content of well-hydrated roses was between 51% and 56%. Five or 7 h of drying resulted in moisture contents below 43% for four of the cultivars and caused up to 80% mortality, increased time to flower, and decreased the number of flowering shoots. ‘First Prize’ was most tolerant of drying conditions and all plants survived, whereas ‘Mister Lincoln’ plants were most susceptible and had poor regrowth performance. Whole-plant moisture of ‘Mister Lincoln’ was similar to that in the stem or shank, which means that aboveground components instead of the entire plant can be used for moisture determination.

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David Wm. Reed, Yin-Tung Wang, and Brent H. Pemberton

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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Shannon E. Beach*, Terri W. Starman, and H. Brent Pemberton

Bracteantha bracteata (Vent.) Anderb. & Haegi (bracteantha) is a vegetative annual produced as a 12.7-cm potted plant in 6 weeks of greenhouse production. A dense leaf canopy produced with a conventional constant-feed fertilization regime (300 mg·L-1 20N-4.4P-16.6K) caused increased disease pressure and lower leaf chlorosis during greenhouse production. During shelf life, lower leaves of plants con-tinued to become chlorotic. The objective was to decrease leaf area and prevent lower leaf chlorosis without affecting harvest time, plant quality or shelf life of two cultivars of three series of bracteantha. The first experiment was to reduce the rate of fertilizer two weeks prior to harvest. Treatments were no fertility reduction (300 mg/liter), 50% reduction (150 mg/liter), and 100% reduction (0 mg·L-1). At harvest, plants were evaluated for shelf life in a growth room at 21.1 ± 1.3 °C and 6 μmol·m-2·s-1 PPF. Five cultivars in the 100% fertility reduction treatment had decreased height and/or width index at harvest and three cultivars maintained higher postharvest quality ratings compared to the other treatments. Separately, the effect of the duration of fertilization was evaluated by terminating fertilization at weekly intervals (0-6 weeks) throughout production. Ceasing fertilization two to three weeks prior to harvest produced plants with lower leaf area without affecting flower number. In another experiment, thidiazuron (TDZ) as a foliar spray at 0, 0.1, 0.5, and 1.0 mg·L-1 was applied to decrease lower leaf yellowing. SPAD-502 chlorophyll meter readings of lower leaves were increased with 0.1 mg·L-1 TDZ treatment compared to the control. Phytotoxic symptoms occurred on plants receiving higher TDZ rates.

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José Antonio Saraiva Grossi, H. Brent Pemberton, and Harvey J. Lang

Rooted liners of pot rose (Rosa L.) cultivars Meiferjac, Meigagul, Meighivon, Meishulo, Ruijef, Ruidodo, and Ruirosora were used to study the influence of cultivar and seasonal growing environment on growth and postharvest performance. Single-shoot plants were grown in controlled environment chambers simulating summer (30 °C day/21 °C night cycle with a 14-hour photoperiod) and winter (21 °C day/16 °C night cycle with a 10-hour photoperiod) greenhouse growing conditions. At flower developmental stage 2 (showing color, calyx reflexing, no petals reflexed), the plants were placed in a continuously lighted simulated interior evaluation room at 21 ± 1 °C under 15 μmol·m-2·s-1 photosynthetic photon flux from cool-white fluorescent lamps for postharvest evaluations. Plants had quicker flowering, smaller flower diameter, more compact growth, and smaller leaf area when grown under the summer environment compared to the winter environment. Most cultivars exhibited greater flower longevity on summer-grown plants when compared to winter-grown ones. `Ruirosora' did not exhibit this difference due to exceptional longevity on winter-grown plants. Also, the use of single-shoot plants was shown to be a potentially useful way to increase replication in small growing environments such as growth chambers.

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Titus M. Kyalo, H. Brent Pemberton, and Jayne M. Zajicek

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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David G. Clark, John W. Kelly, and H. Brent Pemberton

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).