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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

Irradiation of, ferric ethylenediaminetetraacetic acid (FeEDTA, iron chelate)-containing commercial fertilizer solutions by fluorescent plus incandescent lamps resulted in the loss of both FeEDTA and soluble iron (Fe), and the formation of a yellow-tan precipitate that was mostly composed of Fe. The ratio of soluble Fe:manganese (Mn) was altered due to FeEDTA photodegradation from 2:1 in the nonirradiated solutions to 1:4 in the irradiated solutions, respectively. Storing fertilizer solutions in containers that were impervious to light prevented FeEDTA photodegradation.

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Yao-Chien Chang and William B. Miller

A necrotic disorder occurs on upper leaves of many oriental hybrid lily (Lilium L.) cultivars, including the most-widely-grown `Star Gazer'. We term this disorder “upper leaf necrosis” (ULN) and hypothesize that it is a calcium (Ca) deficiency. We demonstrated that Ca concentration in necrosed tissues was nearly six-fold below that of normal leaves (0.10% vs. 0.57% dry weight), and that Ca concentration was negatively associated with percentage necrosed leaf area. It was concluded that ULN is a Ca deficiency disorder. When the symptoms were slight, early ULN symptoms appeared as tiny depressed spots on the lower surface of the leaf, or as water-soaked areas when the disorder was severe. Most commonly, ULN began on the leaf margin. The injured areas turned brown, leading to leaf curling, distortion, or tip death. ULN occurred on leaves associated with flower buds and leaves immediately below the flower buds. For the plants grown from 16-18 cm circumference bulbs, the five leaves directly below the flower buds and larger leaves associated with the 1st and the 2nd flower buds were most susceptible. In general, flower buds were not affected by ULN, and continued to develop and flower normally, even though they were associated with subtending, highly distorted leaves. Eighty-five percent of plants began to exhibit ULN symptoms 30-40 days after planting (i.e., 24-34 days after shoot emergence). This was the stage when the 6th or 7th leaf under the bottom flower bud was just unfolded. Light was not the main factor that initiated ULN, however, ULN severity was greatly increased by light reduction, as leaf transpiration was reduced.

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Joseph P. Albano and William B. Miller

Our objective was to assess the susceptibility of seven marigold varieties to Fe toxicity. Marigold varieties included were one hedge type, `Orange Jubilee'; five semi-dwarf types, `First Lady', `Gold Lady', `Orange Lady', `Marvel Gold', and `Yellow Galore'; and one dwarf type, `Discovery Orange'. Plants were grown in a greenhouse in a soilless medium and treatments consisted of 0.018 mm (low) and 0.36 mm (high) Fe-DTPA incorporated into a nutrient solution. Plant height was not affected by Fe treatment and ranged from 32 cm in `Orange Jubilee', 13 to 14 cm in the semi-dwarf varieties, and 7.0 cm in `Discovery Orange'. Leaf dry weight per plant was not affected by Fe treatment and ranged from 1.15 g in `Orange Jubilee', 0.68 to 0.95 g in the semi-dwarf varieties, and 0.56 g in `Discovery Orange'. Symptoms of Fe toxicity only developed in the high Fe treatment, and the percent leaf dry weight separated at harvest as symptomatic ranged from 97% in `Orange Jubilee', 55% to 85% in the semidwarf varieties, and 15% in `Discovery Orange'. The Fe concentration in leaves in the high Fe treatment was 5.7-times greater in `Orange Jubilee', 2 to 3-times greater in the semi-dwarf varieties, and 1.6-times greater in `Discovery Orange' than in the low Fe treatment. Based on these findings, `Orange Jubilee' and `Discovery Orange' were the most and least susceptible varieties, respectively, to Fe toxicity of the seven marigold varieties evaluated in this study.

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Susan E. Trusty and William B. Miller

Postproduction changes in carbohydrate types and quantities in the leaves, stems, and inflorescences of pot chyrsanthemums [Dendranthema × gramfiflorum (Ramat.) Kitamura `Favor'] placed in interior conditions were investigated. Fructans, sucrose, glucose, and fructose were present in all plant parts. In inflorescences and leaves, an additional unidentified substance was present. All plant parts decreased in dry weight during the postproduction evaluation. This decrease was accompanied by overall reductions in total soluble carbohydrates (TSC) and starch. The appearance of leaves and stems was acceptable throughout the experiment. Leaves lost significant amounts of TSC during the first 4 days postproduction (DPP), due primarily to a 76% decrease in sucrose concentration. After 4 DPP, leaf and stem TSC remained relatively unchanged. In inflorescences, petal expansion continued through 12 DPP. Visible signs of senescence, including loss of turgor, color changes, and inrolling of petal edges were observed at 20 DPP, and by 28 DPP, the plants were determined unacceptable for consumer use. Inflorescences increased in fresh weight, but not dry weight, during petal expansion, then each decreased. Inflorescence TSC fell from 146 mg.g-1 dry weight at O DPP to 11 mg.g-1 at 28 DPP. Reducing sugars accounted for 84% of the inflorescence TSC at 4 DPP, dropping to 48% at 28 DPP. Fructan concentration decreased through 16 DPP and then remained unchanged, while starch levels rose from 25 to 34 mg·g -1 dry weight through 12 DPP, then decreased. Fractans decreased in polymerization during petal expansion. This result suggests an alternate use of fructans and starch as pools of available reserve carbohydrate during petal expansion in chrysanthemum.

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Susan S.C. Liou and William B. Miller

During transportation and storage of Dutch tulip bulbs, potential ethylene exposure could lead to flowering abnormalities, including accelerated flowering, shortened plant heights, and in the most extreme case, flower abortion. Sources of ethylene include Fusarium-infected bulbs, deteriorating tissues, and combustion engines. Treatment with 1-MCP (1-methylcyclopropene) may prevent ethylene action as 1-MCP occupies ethylene specific receptors on target tissue. Two aspects of this problem were quantified using four tulip cultivars: duration of ethylene exposure necessary to induce damage as well as the effective period of protection by 1-MCP against ethylene. Flower abortion appeared in susceptible cultivars after ≥9 days of ethylene exposure (10 ppm) and was only found in mature bulbs (late November). The effective protection period of 1-MCP against ethylene (2-week exposure of 10 ppm) was determined, using flowering percentages, to be as long as 4–7 days in young bulbs and 28 days for older bulbs. Effects of ethylene on other flower attributes and implications of these findings in industry practices will be discussed.

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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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Chad T. Miller, Neil S. Mattson, and William B. Miller

Oxalis regnellii, the shamrock plant, and O. triangularis are niche ornamental greenhouse crops produced and marketed primarily for their foliage; thus, it is imperative to produce the fullest, most colorful, and blemish-free plants as possible. An experiment was conducted using O. regnellii, comparing two irrigation methods, overhead (drip) irrigation versus subirrigation, in addition to varying 20N–2.2P–16.6K fertilizer concentrations, 50, 100, 200, 300, and 500 mg·L−1 nitrogen (N). Overhead irrigation produced larger plants with increased root mass as compared with subirrigation. Low or high fertilizer concentration (50 mg·L−1 N and 500 mg·L−1 N, respectively) led to reductions in the fresh and dry weight of overhead-irrigated plants compared with intermediate fertilizer rates. At the highest fertilizer treatment, plant height was decreased. Chlorophyll index (based on SPAD readings) increased linearly and quadratically for subirrigated and overhead-irrigated plants, respectively. A second study analyzed the effects of seven different fertilizer formulations on growth of O. regnellii and O. triangularis. The fertilizers used in this study were Jack's LX All Purpose (21N–2.2P–16.6K), Peter's Professional (20N–8.8P–16.6K), Jacks Poinsettia FeED Ca-Mg (15N–1.7P–12.5K), Jack's Petunia FeED Mg (20N–1.3P–15.7K), Peter's Professional Peat-Lite Dark Weather Feed (15N–0P–12.5K), Peter's Excel Cal-Mag (15N–2.2P–12.5K), and the slow-release fertilizer Osmocote® (14N–4.2P–11.6K). Growth of both species was significantly reduced by fertilizers that contained little or no phosphorus (P). Current water-soluble fertilizer recommendations of 21N–2.2P–16.6K or slow-release granule fertilizer of 14N–4.2P–11.6K (Osmocote®) produced acceptable, marketable plants, whereas the best O. regnellii and O. triangularis plants were produced using 15N–2.2P–12.5K and 20N–1.3P–15.7K formulations, likely as a result of the additional calcium (Ca), magnesium (Mg), and iron (Fe) in the mixtures.

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Susan S. Liou, Chris B. Watkins, and William B. Miller

During transport and the subsequent storage of tulip bulbs, inadvertent failure in ventilation and/or high contamination of Fusarium-infected bulbs may expose healthy bulbs to high concentrations of ethylene. Ethylene is known to cause many detrimental effects on forcing quality, including gummosis, increased respiration, flower bud abortion, bulb splitting and poor rooting. In this work, exposure duration and timing as well as the post-stress storage temperatures were evaluated for their potential effects on ethylene sensitivity in bulbs of four tulip cultivars. Degree of damage in sensitive cultivars `Apeldoorn' and `World's Favourite' increased with days at about 10 ppm ethylene starting at 9 and 16 days respectively. This effect strongly depended on timing of ethylene stress, as late treated bulbs showed more severe responses to ethylene treatment than early treated bulbs. Additionally, bulbs that were cooled immediately after ethylene stress, compared with those stored at 17 °C after stress, have significantly higher flowering quality in all attributes measured. This response was also strongly dependent on timing of ethylene stress and cultivar. Implications of the potential cold reversal of ethylene damage as well as effects of ethylene exposure duration and timing of stress on shipping and storage recommendations will be discussed.

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Paul D. Curtis, Gwen B. Curtis, and William B. Miller

Many plants have mechanisms of physical or chemical resistance that protect them from herbivores in their environment. Vertebrates such as meadow voles (Microtus pennsylvanicus) cause significant damage to ornamental plantings and home gardens. Our goal was to identify flowering bulbs that could be used to design more herbivore-resistant home landscapes. Single-choice feeding trials with captive prairie voles (Microtus ochrogaster) were used to assess the relative resistance of 30 bulb varieties to deter rodents from consuming fresh plant material and freeze-dried, powdered bulb mixed with a preferred food (applesauce). Each fresh bulb and dried-bulb/applesauce mix was offered twice to 12 to 15 pairs of adult prairie voles. Bulb varieties that resulted in the lowest mean consumption were assumed to be the most resistant to feeding activity. With fresh bulbs, only tulips (Tulipa spp.) exhibited no resistance to prairie vole feeding. Dried-bulb/applesauce mixes containing hyacinth (Hyacinth spp.), crocus (Crocus spp.), corn leaf iris (Iris bucharica), dutch and dwarf iris (Iris reticulata), onion (Allium spp.), and squill (Scilla siberica) were also readily consumed, and thus, these bulbs could be damaged at sites with high rodent activity. Daffodil (Narcissus spp.), painted arum (Arum italicum), camass (Camassia leichtlinii), glory-of-the-snow (Chinodoxa forbesii), autumn crocus (Colchicum spp.), crown imperial (Fritillaria imperialis), persian fritillaria (Fritillaria persica), snowdrop (Galanthus nivalis), and grape hyacinth (Muscari armeniacum) bulbs were resistant to prairie vole feeding in both forms (fresh bulbs and dried-bulb/applesauce mixes). Consequently, all of the specialty flower bulbs tested, except tulip, exhibited some resistance to prairie vole feeding in their fresh form, and could be suitable for designing herbivore-resistant landscapes.