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Neil O. Anderson, Esther Gesick, Peter D. Ascher, Steven Poppe, Shengrui Yao, David Wildung, Patricia Johnson, Vincent Fritz, Charlie Rohwer, Lee Klossner, Neal Eash, Barbara E. Liedl, and Judith Reith-Rozelle

× grandiflorum Tzvelv.; = Dendranthema × grandiflora Tzvelv.), which have smaller and consistent plant sizes regardless of plant age. All Mammoth™ selections have been taxonomically designated Chrysanthemum × hybridum Anderson ( = Dendranthema × hybrida

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Joseph J. King, Lloyd A. Peterson, and Dennis P. Stimart

Ammonium and NO3 uptake from hydroponic solutions containing 1 mm each of (NH4)2SO4 and Ca(NO3)2 were measured during development of Dendranthema ×grandiflorum (Ramat.) Kitamura `Iridon', `Sequoia', and `Sequest'. Nitrogen depletion from solutions approximated a 1 NH4: 1 NO3 ratio throughout a 90-day growth cycle (r = 0.96). Although harvest date cultivar interactions were significant for both forms of N, overall patterns of N uptake were similar among cultivars. Nitrogen removal from hydroponic solutions (milligrams per plant) was greatest from days 40 to 60; however, N removal (milligrams per gram of tissue dry weight) was greatest in the first month of development and decreased steadily until day 90. From day 40 to 60, new leaf development ceased while inflorescence buds developed to ≈1.0 cm in diameter. After this time, N uptake decreased rapidly as inflorescences expanded. Correlations between morphological changes and N demand could maximize the efficiency of applied N by matching form and application timing with plant needs.

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R.A. May and R.N. Trigiano

Somatic embryogenesis from leaf midrib explants of Dendranthema grandiflora Tzvelev. `Iridon' cultured on modified Murashige and Skoog basal medium (MSB) containing 1.0 mg 2,4-D and 0.2 mg BA/liter was influenced by light and sucrose concentration. Somatic embryos formed directly from explants when cultured on medium containing 9% to 18% sucrose and incubated first in the dark for 28 days, followed by 10 days in light, and then returned to the dark for 14 days. Embryogenesis did not occur in continuous darkness and was drastically reduced when explants were incubated in light only. The most embryos were formed on medium containing either 12% or 15% sucrose; lower concentrations stimulated shoot and root development. Light also mediated embryogenesis from leaf explants of 'other cultivars. White-opaque or occasionally light-green cotyledon-stage somatic embryos germinated on MSB medium without growth regulators but containing 3% sucrose. Twelve of the 23 cultivars evaluated produced somatic embryos, but plants were recovered from only five. Regenerated plants were phenotypically similar to parent plants in growth habit, leaf morphology, and flower color. Chemical names used: N- (phenylmethyl)-1 H- purine-6-amine (BA); (2,4-dichlorophenoxy) acetic acid (2,4-D).

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Neil O. Anderson, Peter D. Ascher, Vincent Fritz, Charlie Rohwer, Steven Poppe, Shengrui Yao, Patricia Johnson, Barbara E. Liedl, Judith Reith-Rozelle, Lee Klossner, and Neal Eash

Garden chrysanthemums, Chrysanthemum × grandiflorum Tzvelv. (= Dendranthema × grandiflora Tzvelv.; = C. × morifolium Ramatuelle), are the number one herbaceous perennial in the top 15 U.S. producing states with a wholesale farm gate value of

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Neil O. Anderson, Vincent Fritz, Charlie Rohwer, Steven Poppe, Barbara E. Liedl, Shengrui Yao, Patricia Johnson, Judith Reith-Rozelle, Lee Klossner, and Neal Eash

Greenhouse and garden chrysanthemum cultivars, Chrysanthemum × grandiflorum Tzvelv. (syn. Dendranthema × grandiflora Tzvelv.; syn. C. × morifolium Ramatuelle), are grown for use as floral cuts, potted plants, and garden annuals or

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Neil O. Anderson, Steven Poppe, Peter D. Ascher, Esther Gesick, Shengrui Yao, David Wildung, Patricia Johnson, Vincent Fritz, James Hebel, Lee Klossner, Neal Eash, Barbara E. Liedl, and Judith Reith-Rozelle

Mammoth™ ‘Yellow Quill’ (U.S. Plant Patent 15,027; Canadian Plant Breeders’ Rights Certificate No. 2951) is a new interspecific garden chrysanthemum cultivar, Chrysanthemum × hybridum Anderson (=Dendranthema × hybrida Anderson) with common

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Jason R. Tutty, Peter R. Hicklenton, David N. Kristie, and Kenneth B. McRae

Stem elongation rate (SER) in Dendranthema grandiflorum (Ramat.) Kitamura was determined in light and in darkness under various temperature regimes. Stem growth as measured with linear voltage displacement transducers on plants in growth chambers. Under alternating 11-hour days and 13-hour nights, SER was strongly temperature dependent and showed patterns that were characteristic of the particular photoperiod-temperature regime under which the plants were grown. Total daily elongation was similar at constant 18.3C and at 11.5C days and 24C nights, but was much greater at 25.7C days and 12C nights. SER was rhythmic in continuous light with a period of slightly less than 24 hours. In continuous darkness, however, SER declined rapidly and the rhythm disappeared within 11 hours. Low-temperature pulses (a rapid decline from 18.3C to 8.3C) applied for 2, 4, 6, 8, or 11 hours during the day induced an immediate decline in SER followed by a slow recovery and peak shortly after the end of the pulse. Total diurnal stem growth declined with increasing pulse length, although short (2-hour) duration pulses apparently had little effect on growth. The results are discussed in relation to the influence of day and night temperature differentials (DIF) on stem growth in Dendranthema.

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Richard K. Schoellhorn, James E. Barrett, Carolyn A. Bartuska, and Terril Nell

Effects of heat stress on viable and nonviable axillary meristem development and subsequent lateral branching in 'Improved Mefo' chrysanthemum [Dendranthema ×grandiflorum Ramat. (Kitamura)] were studied. Plants grown at 33 °C day/27 °C night produced more nonviable buds than did plants grown at 23 °C day/18 °C night. A negative linear relationship {y = 28.7 + [-0.66 (x days)], r 2 = 0.70} between timing of exposure to high temperatures and the number of nonviable buds was observed. Histological examination 28 days after exposure to 33 °C/27 °C revealed that plants showed both normal and abnormal bud development. Abnormal bud development occurred as a consequence of premature differentiation of axillary meristematic tissue into nonmeristematic parenchyma tissue immediately after separation of axillary from apical meristems.

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Nihal C. Rajapakse, David Wm. Reed, and John W. Kelly

Experiments were conducted to evaluate Dendranthema × grandiflorum (Ramat.) Kitamura cv. Bright Golden Anne quality and post-storage growth following storage in the range of 5 to 35C, initial soil water levels (60%, 80%, 100%), and durations (0 to 8 days). Transpiration rate showed a quadratic relationship with storage temperature. Initial soil water content had little effect on transpiration rate in dark storage environments. The lowest transpiration rate was observed in plants stored at 15 or 20C. Amino acid (AA) leakage and post-storage growth were well-correlated. Plants stored at or above 25C became etiolated during storage, while storage at 15C or below did not cause etiolation. Temperatures at or below 15C did not affect subsequent growth rate of chrysanthemum plants. Storage at 20C and above caused a reduction in post-storage growth rate following 2 days of storage.

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Philip A. Stack and Francis A. Drummond

Orius is an effective predatory bug of western flower thrips on chrysanthemum. However, long days are required to prevent reproductive diapause in Orius, which is counter to the short-day flowering response in Dendranthema. Two cut flower cultivars (`Manatee Iceberg' and `Naples') and a pot cultivar (`Boaldi') were given short days, long days with broad spectrum light, and long days with supplemental blue light (430–480 nm) at critical threshold levels. Blue light at intensities of 2 to 5 μmol·m–2·s–1 had no effect on flower induction, size, or dry weight or leaf dry weight compared to the short-day control. Increasing intensity and blue light exposure reduced flowering in the cut mum cultivars. At 25C, 77% of Orius females were reproductive in blue light compared to 75% in broad spectrum and 46% in short days. Spectral quality had no effect on fecundity, survival, or insect development rate. At least 90% of Orius reproduced with blue light at 19, 22, 25, and 28C. These results indicate possibilities for providing favorable conditions for biocontrol of arthropod pests on short-day crops.