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Douglas A. Bailey and William B. Miller

Plants of Euphorbia pulcherrima Wind. `Glory' were grown under 13.4, 8.5, or 4.0 mol·m-2·day-1 and sprayed with water (control); 2500 mg·liter-1 daminozide + 1500 mg·liter-1 chlormequat chloride (D+C); 62.5 mg·liter-1 paclobutrazol; or 4, 8, 12 or 16 mg·liter-1 uniconazole to ascertain plant developmental and pest-production responses to the treatment combinations. Days to anthesis increased as irradiance was decreased. Anthesis was delayed by the D+C treatment, while other growth retardant (GR) treatments had no effect on anthesis. Irradiance did not affect plant height at anthesis, but all GR treatments decreased height over control plants. Bract display and bract canopy display diameters declined as irradiance was decreased. Growth retardants did not affect individual bract display diameters, but all GR treatments except paclobutrazol reduced bract canopy display diameter. Plants grown under lower irradiance had fewer axillary buds develop, fewer bract displays per plant, and fewer cyathia per bract display. Cyathia abscission during a 30 day post-anthesis evaluation was not affected by treatment; however, plant leaf drop was linearly proportional to irradiance. All GR treatments increased leaf drop over controls, and the D+C treated plants had the highest leaf loss. Results indicate the irradiance and GR treatments during production can affect poinsettia crop timing, plant quality at maturity, and subsequent post-production performance.

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Susan E. Trusty and William B. Miller

Exudation of phloem sap into EDTA (ethylenediaminetetraacetic acid) solutions has been found to be a successful technique for qualitatively determining translocated assimilates in many plants. Mature Chysanthemum leaves were excised under a solution of 10 mM EDTA (pH 7.0). The petioles of these leaves were placed in EDTA, and leaf exudate was collected at intervals for 24 h. Soluble carbohydrates were determined with HPLC. While numerous sugars were present in the leaf, sucrose was the only sugar found in the EDTA solutions. The greatest rate of sucrose exudation occurred in the first two h after excision. Diurnal fluctuations of soluble sugars in Chrysanthemum leaves were also monitored in greenhouse-grown plants (late winter in Arizona). Sucrose exhibited a clear diurnal fluctuation, and nearly doubled in concentration (to appx. 25 mg/g DWT) in the afternoon relative to the low in the morning. Other leaf carbohydrates, including glucose, starch, and fructans showed diurnal variations as well.

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Michael R. Mason and William B. Miller

Interactions of ethephon and irradiance reduction were investigated in terms of flower bud blasting in Easter lily (Lilium longiflorum Thunb. `Nellie White'). Silver thiosulfate (STS) was investigated as an inhibitor of ethylene-induced bud abortion. Fourteen days of 92% irradiance reduction significantly increased bud abortion when plants were exposed to 2.1 mm ethephon. Bud abortion was 39% and 60% for plants grown in ambient and reduced irradiance, respectively. Silver thiosulfate was applied to plants 2 or 3 weeks after the date of the first visible bud, followed by ethephon treatment 2 days later. Bud abortion was significantly reduced by 1 or 2 mm STS, without phytotoxicity. Pretreatment with 1 or 2 mm STS as early as 4 weeks before ethephon exposure significantly reduced ethephon-induced bud abortion. Silver thiosulfate application could inexpensively reduce flower bud abortion during latter stages of greenhouse forcing of Easter lilies.

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Douglas A. Bailey and William B. Miller

Plants of Euphorbia pulcherrima Wind. `Glory' were grown under 13.4, 8.5, or 4.0 mol·m-2·day-1 and sprayed with water (control); 2500 mg·liter-1 daminozide + 1500 mg·liter-1 chlormequat chloride (D+C); 62.5 mg·liter-1 paclobutrazol; or 4, 8, 12 or 16 mg·liter-1 uniconazole to ascertain plant developmental and pest-production responses to the treatment combinations. Days to anthesis increased as irradiance was decreased. Anthesis was delayed by the D+C treatment, while other growth retardant (GR) treatments had no effect on anthesis. Irradiance did not affect plant height at anthesis, but all GR treatments decreased height over control plants. Bract display and bract canopy display diameters declined as irradiance was decreased. Growth retardants did not affect individual bract display diameters, but all GR treatments except paclobutrazol reduced bract canopy display diameter. Plants grown under lower irradiance had fewer axillary buds develop, fewer bract displays per plant, and fewer cyathia per bract display. Cyathia abscission during a 30 day post-anthesis evaluation was not affected by treatment; however, plant leaf drop was linearly proportional to irradiance. All GR treatments increased leaf drop over controls, and the D+C treated plants had the highest leaf loss. Results indicate the irradiance and GR treatments during production can affect poinsettia crop timing, plant quality at maturity, and subsequent post-production performance.

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Ted Whitwell, John Kelly, and William B. Miller

In 1993, Carolina Nurseries and the Department of Horticulture at Clemson Univ. entered into a partnership to create a research and development program to solve short and long term nursery production problems. Research is conducted on site at Carolina Nurseries in a specially designed 0.6-ha area built by the nursery. Faculty from the Depts. of Horticulture, Agricultural and Biological Engineering, Plant Pathology and Entomology have worked with graduate and undergraduate students located on site. The nursery staff is involved in overall planning and stay current with results so that research can be immediately implemented on the nursery. Yearly funding for the graduate student is provided by the nursery and grant funds are obtained from various companies for labor and supplies. Carolina Nurseries has committed to funding research to improve their production and also sharing the results with the rest of the nursery industry. Research findings are presented in peered reviewed articles, conference proceedings, abstracts, and oral presentations. Outstanding training opportunities for students and staff are available to also improve career development for future nursery managers. Faculty interaction with companies and the nursery industry are enhanced.

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Joseph P. Albano and William B. Miller

Our objective was to determine the effects on plant growth and physiology that a photodegraded Fe-chelate containing lab-prepared nutrient solution would have when used in plant culture. Plants grown hydroponically in the irradiated Fe-DTPA containing nutrient solution had ferric reductase activity 2.2 times greater, foliar Fe level 0.77 times less, and foliar Mn level 1.9 times greater than in plants grown in an identical but non-irradiated solution, indicating that plants growing in the irradiated solution were responding to Fe deficiency stress with physiological reactions associated with Fe efficiency. The youngest leaves of plants that were grown in the irradiated solution had symptoms of Mn toxicity. Restoration of the irradiated solution by removing the precipitated Fe by centrifugation and adding fresh Fe-chelate resulted in plants that were, in general, not different from those grown in the non-irradiated solution (control).

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William B. Miller and Robert W. Langhans

Easter liliy (Lilium longiflorum Thunb. `Nellie White') bulbs were stored in moist peatmoss for up to 85 days at – 1.0 or 4.5C. Bulbs were periodically removed from storage and analyzed to determine levels of soluble carbohydrates and starch. Storage at – 1.0C induced large accumulations of sucrose, mannose, fructose, and oligosaccharide in both mother and daughter scales. Starch concentration declined substantially during this period. Storage at 4.5C resulted in less dramatic alterations in bulb carbohydrates, although trends toward increased soluble carbohydrates and reduced starch levels were seen. The accumulation of mannose suggests that glucomannan, a secondary storage carbohydrate, was also degraded during – 1.0C storage.

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Joseph P. Albano and William B. Miller

Excised roots of `First Lady' marigold (Tagetes erecta L.) grown in an aerated 0 Fe nutrient solution had Fe(III)-DTPA reductase activity 14-fold greater, and an enhanced ability to acidify the rhizosphere than plants grown in a solution containing 0.018 mm (1 ppm) Fe-DTPA. Reductase activity and rhizosphere acidification of plants grown in 0.018 and 0.09 mm Fe-DTPA were similar. Manganese concentration in leaves of plants grown in the 0 Fe treatment was 2-fold greater than in leaves of plants grown in the 0.018 mm Fe-DTPA treatment. These results indicated that `First Lady' marigold is an Fe-efficient plant that possesses both an inducible or adaptive reductase system and the ability to acidify the rhizosphere, and that these Fe-efficiency reactions do not occur when Fe is sufficient. Chemical name used: ferric diethylenetriaminepentaacetic acid, monosodium salt (Fe-DTPA).

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Anil P. Ranwala and William B. Miller

Three soluble invertase isoforms from Lilium longiflorum flower buds that had been separated by DEAE-Sephacel chromatography were purified to near homogeneity by further chromatography on hydroxylapetite, Con-A sepharose, phenyl agarose, and Sephacryl S-200 gel filtration. Nondenaturing polyacrylamide gel electrophoresis (PAGE) gave a single band in all three invertases that corresponded to a band of invertase activity in a duplicate gel. The SDS-PAGE of the purified invertase I resulted in a single band with apparent relative molecular mass of 78 kDa. Invertase II and III were resolved to a similar polypeptide pattern by SDS-PAGE with three bands of 54, 52, and 24 kDa. Antiserum of tomato acid invertase cross-reacted with all three invertase protein bands. Antiserum of wheat coleoptile acid invertase cross-reacted only with 54 and 52 kDa bands of invertase II and III but did not recognize invertase I protein. Con-A peroxidase was bound to invertase I protein and all three protein bands of invertase II and III, suggesting that all proteins were glycosylated. Invertase I protein could be completely deglycosylated by incubating with peptide-N-glycosidase F to result in a peptide of 75 kDa. Invertase II and III were partially deglycosylated by peptide-N-glycosidase F resulting proteins bands of 53, 51, 50, and 22 kDa.

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Anil P. Ranwala and William B. Miller

Amylolytic activities extracted from scales of tulip (Tulipa gesneriana L. cv. Apeldoorn) bulbs stored at 4 °C for 6 weeks under moist conditions were characterized. Anion exchange chromatography of enzyme extract on DEAE-Sephacel revealed three peaks of amylolytic activity. Three enzymes showed different electrophoretic mobilties on nondenaturing polyacrylamide gels. The most abundant amylase activity was purified extensively with phenyl-agarose chromatography, gel filtration on Sephacryl S-200, and chromatofocusing on polybuffer exchanger PBE 94. The purified amylase was determined to be an endoamylase based on substrate specificity and end product analysis. The enzyme had a pH optimum of 6.0 and a temperature optimum of 55 °C when soluble starch was used as the substrate. The apparent Km value for soluble starch was 1.28 mg/ml. The inclusion of 2 mM CaCl2 in the reaction mixture resulted in a 1.4-fold increase in the enzyme activity. The presence of calcium ions also enhanced the thermo-stability of the enzyme at higher temperatures. The enzyme was able to hydrolyze soluble starch, amylose, amylopectin, and beta-limit dextrin, but it had no activity against pullulan, inulin, maltose, or p-nitrophenyl alpha-glucopyranoside. Only maltooligosaccharides, having a degree of polymerization of 7 or more, were hydrolyzed to a significant extent by the enzyme. Exhaustive hydrolysis of soluble starch with the enzyme yielded a mixture of maltose and matlooligosaccharides. This amylase activity was not inhibited by alpha- or beta-cyclodextrin upto a concentration of 10 mM. Maltose at a 50 mM concentration partially inhibited the enzyme activity, whereas glucose had no effect at that concentration.