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J. Jiao, X. Wang, and M.J. Tsujita

Uniconazole was applied as a drench or spray to six hybrid lily (Liliurn sp.) cultivars. Spray application was generally more effective than drench in reducing shoot elongation rate in the first few weeks, and then the efficacy decreased and was less effective than the drench at later stages of plant development. At flowering, a uniconazole drench at 0.1 mg/pot was ineffective for height reduction in `Bravo', `Juliana', and `Sunray' lilies. At higher rates, uniconazole drench was similar to spray in reducing shoot growth in `Bravo' and 306-1 but less effective than spray in `Juliana', `Star Gazer', and `Sunray' lilies. Uniconazole spray reduced plant height at flowering in all the lilies compared to control plants. Days to flower was not affected in `Bravo', `Juliana', and `Sunray' but was increased in `Star Gazer', 306-1, and 306-2 by uniconazole spray treatments. Flowering duration was decreased only in 306-1 by uniconazole spray at 0.2 mg/pot. Chemical name used: (E)-1-(4-chlorophenyl) -4,4 -dimethyl-2-(l,2,4 -triazol-1-yl)-1-penten-3 -ol (uniconazole).

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Glenn L. Roberts and M. J. Tsujita

An experiment was conducted to determine whether the high R:FR ratio in high pressure sodium (HPS) lamps contributes to lateral bud breaking in roses. Rosa hybrida cv. `Samantha' plants were grown under HPS lamps, HPS lamps fitted with blue gel filters to reduce the R:FR ratio or metal halide lamps. Spectral graphs showed R:FR ratios of 1.05, 0.5 and 3.8 for HPS, filtered HPS and metal halide respectively. Although the R:FR ratio in metal halide was notably higher than in HPS the total energy in this range was much lower. At a 24hr supplemental PPF level of 70-75uEm-2s-1 more flowering shoots were produced under HPS and metal halide lighting than under filtered HPS. There were more dormant shoots under the filtered HPS. No differences in quality were found among flowers from any treatment.

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G.L. Roberts and M.J. Tsujita

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T.J. Blom, M.J. Tsujita, and G.L. Roberts

Potted bulbs of Lilium longiflorum Thunb. `Ace' and `Nellie White' and Lilium (Asiatic hybrid) `Enchantment' were grown in a greenhouse under ambient photoperiod (APP), 8-h photoperiod by removing twilight from ambient by blackout cloth (8PP), or 8PP extended with 1 hour of low-intensity far-red radiation (9PP). Height of `Ace', `Nellie White', and `Enchantment' increased by 24%, 18%, and 12%, respectively, under APP and by 118%, 100%, and 44%, respectively, under 9PP compared to 8PP. In a second experiment, the effects of reduced irradiance (0%, 25%, 50%, and 75% shade) were determined on the same cultivars grown under APP or 8PP. The effects of APP on height were similar in magnitude for `Ace' and `Nellie White' but were insignificant for `Enchantment' compared to 8PP. Shading increased height linearly for all cultivars. The regression was greater under APP (2.8 mm/percent shade) than under 8PP (1.8 mm/percent shade) for `Ace' and `Nellie White' combined. Plant height of `Enchantment' was less affected by reduced irradiance. For all cultivars, APP or 9PP produced higher stem dry weight compared to 8PP. Shading decreased leaf and bulb dry weight of the Easter lily cultivars.

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Theo J. Blom, M.J. Tsujita, and Glen L. Roberts

Potted plants of Lilium longiflorum Thunb. cvs. `Ace' and `Nellie White' were grown either under an ambient photoperiod (APP) or under an 8-hour photoperiod (8PP) in a greenhouse. The latter photoperiod was achieved by pulling black cloth over the plants at 1615HR and removing the cloth at 0615HR each day, from emergence to flowering. Within each photoperiod, ambient light intensity was reduced by 0, 20, 40 or 60% using various shade cloths permanently suspended above the plants. Heating was set at 20/16C for the dark/light period, respectively. Plant height, determined from the rim of pot to the top of plant, was 25% lower under 8PP compared to APP for both cultivars. Plant height of `Ace' and `Nellie White' increased by 1.5 mm and 2.5 mm, respectively, per 1% light reduction.

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G.L. Roberts, M.J. Tsujita, and J. Gerrath

Sisyrinchium bemudiana L. plants were grown in growth chambers under lo-hour short-day regimes. Scanning electron microscopy of shoot apices collected at biweekly intervals showed that the transition from vegetative to floral status occurs after 10 weeks of short days. Stamens and tepals develop first as common stamentepal primordia that then bifurcate to form outer tepals with stamens opposite. Subsequently, the inner tepals are initiated in an alternate pattern.

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David C. Percival, J.T.A. Proctor, and M.J. Tsujita

The influence of irradiance, CO2, and temperature on whole-plant net CO2 exchange rate (NCER) of Rubus idaeus L. `Heritage' micropropagated raspberries was examined. Within the set of environmental conditions examined, irradiation was the most important factor, accounting for 58% of the whole-plant irradiance/CO2 concentration/temperature NCER model variation, followed by CO2 concentration (28%) and temperature (2.5%). Net photosynthesis (Pn) required irradiance levels >600 μmol·m-2·s-1 PPF for saturation, greatly increased under CO2 enrichment (up to 1500 μL·L-1), and was optimum at a whole-plant temperature of 20 °C. Temperature effects were partitioned in an experiment using varying air and root-zone temperatures (15, 20, 25, 30, and 35 °C) under saturated light and ambient CO2 levels (350 μL·L-1). Air and root-zone temperature influenced Pn, with maximum rates occurring at an air × root-zone temperature of 17/25 °C. The contribution of air and root-zone temperature to the NCER model varied, with air and root-zone temperature contributing 75% and 24%, respectively, to the total model variation (R 2 = 0.96). Shoot dark respiration increased with air and root-zone temperature, and root respiration rates depended on air and root-zone temperature and shoot assimilation rate. Humidity also influenced Pn with a saturated vapor pressure deficit threshold >0.25 kPa resulting in a Pn decrease. Quantifying the physiological response of raspberries to these environmental parameters provides further support to recent findings that cool shoot/warm root conditions are optimum for raspberry plant growth.

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G.L. Roberts, M.J. Tsujita, and B. Dansereau

Rosa ×hybrida `Samantha' plants were grown under high-pressure sodium (HPS) lamps, HPS lamps fitted with blue gel filters to reduce the red to far-red (R:FR) ratio, or metal halide lamps. R: FR ratios were 1:0.95, 1:2, and 1:0.26 for HPS; filtered HPS, and metal halide, respectively. Although the R: FR ratio for metal halide was 3.5 times higher than for HPS, the total energy from 630 to 750 nm was 2.8 times lower. At a nighttime supplemental photosynthetic photon flux of 70 to 75 μmol·m-2.s-1, plants under HPS and metal halide lamps produced 49 % and 64% more flowering shoots, respectively, than those under filtered HPS (averaged over two crop cycles). The quality index for flowers under HPS, metal halide, and filtered HPS was 25.0, 23.3, and 18.5, respectively. Vase life was 10 to 11 days, regardless of treatment.

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Glenn L. Roberts, M.J. Tsujita, and T. Blom

Lilium hybrid `Enchantment' bulbs were grown at a -4C or +4C DIF in growth chambers set at 100 μmolm-2s-1 PPF, with or without one hour red or far-red light extensions to each end of an eight hour photoperiod. Far-red light extensions completely reversed the growth regulating effect of negative DIF temperatures. Negative DIF treated plants given far-red extensions were 43% taller than plants with no light extensions and 15% taller than plants given red light extensions. Prephotoperiod red or far-red extensions did not increase stem elongation over similar plants given no light extension, but postphotoperiod far-red extension stimulated stem elongation up to 52%. Red light extensions caused a less dramatic increase than far-red in some cases. The phenomenon is not photoperiodic since lengthening the photoperiod to ten hours caused no appreciable increase in stem elongation. Total 24 hour accumulated energy also proved not to be involved in the process.

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David C. Percival, John T.A. Proctor, and M.J. Tsujita

The influence of irradiance, CO2, and temperature on whole-plant net C exchange rate (NCER) of micropropagated raspberries (Rubus idaeus L. cv. `Heritage') was examined in 1994. Irradiances >1000 μmolm–2–s–1 PAR were required for light saturation, and net photosynthesis (Pn) greatly increased under CO2 enrichment (up to 2000 μlliter–1) and was optimum at 17C. Temperature effects were separated in another experiment using varying air and soil temperatures (15, 20, 25, 30, and 35C) under saturated light and ambient CO2 levels (350 μlliter–1). Both air and soil temperature influenced net Pn, with maximum rates occurring at an air/soil temperature of 17/25C and each contributing 71.2% and 26.7%, respectively, to the total variation explained by a polynomial model (R 2 = 0.96). Dark respiration and root respiration rates also increased significantly with elevated air and soil temperatures. Therefore, results from this study indicate that maximum net Pn occurred at an air/soil temperature of 17/25C and that irradiance, CO2 levels, and shoot and root temperatures are all important factors in examining NCER in raspberries.