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Anderson Machado de Mello, Nereu Augusto Streck, Erin E. Blankenship, and Ellen T. Paparozzi

Penstemon seed often shows an inconsistent or a low germination percentage. Although most select cultivars are propagated by cuttings, for export to other countries, seed is preferred. Three experiments were conducted to determine if soaking seed in gibberellic acid (GA3) would increase seed germination of Penstemon digitalis cv. Husker Red. GA3 concentrations used were 0, 10, 50, 100, 200, and 500 mg·L−1 (first experiment); 0, 500, 1000, and 1500 mg·L−1 (second experiment); and 0, 500, and 1000 mg·L−1 (third experiment). The first and second experiments were conducted in a growth chamber, whereas the third experiment was conducted in both a growth chamber and greenhouse with seeds either covered or not covered by the mix. In all experiments, GA3 increased the percentage and rate of seed germination. The 1000 mg·L−1 GA3 was the best treatment. In the third experiment, percentage and rate of seed germination were the highest for seeds grown inside of the growth chamber, probably as a result of the consistency of temperatures and darkness. In the greenhouse, the percentage of seeds that germinated and the rate of germination were similar whether or not the seeds were covered with mix and whether they received either the 500 or 1000 mg·L−1 GA3 treatment.

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Ellen T. Paparozzi, Walter W. Stroup, M. Elizabeth Conley, and Reid D. Landes

Horticulturists are often interested in evaluating the effect of several treatment factors on plant growth in order to determine optimal growing conditions. Factors could include three or more nutrient elements, or types and rates of irrigation, pesticides or growth regulators, possibly in combination with one another. Two problems with such experiments are how to characterize plant response to treatment combinations and how to design such experiments so that they are manageable. The standard statistical approach is to use linear and quadratic (a.k.a. response surface) regression to characterize treatment effects and to use response surface designs, e.g., central-composite designs. However, these often do a poor job characterizing plant response to treatments. Hence the need for more generally applicable methods. While our goal is to be able to analyze three and higher factor experiments, we started by tweaking two-factor nutrient analysis data. The result was a hybrid model which allows for a given factor to respond linearly or non-linearly. We will show how this was done and our current “in progress” model and analysis for analyzing three quantitative factors.

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Marci Spaw, Kimberly A. Williams*, Ingrid L. Mallberg, Laurie Hodges, and Ellen T. Paparozzi

Case studies promote the development of problem-solving skills, but few have been created for horticulture and related curricula. This web-based decision case presents the challenge of determining the cause of symptoms of foliar chlorosis in a crop of cut Dicentra spectabilis while forcing it for Valentine's Day sales. It provides a tool to promote the development of diagnostic skills for production dilemmas, including nutritional disorders, disease and insect problems, and evaluation of the appropriateness of cultural practices. Cut Dicentra is a minor crop and standard production practices are not well established. Therefore, solving this case requires that students research production protocol as well as nutritional and pest problems to develop a solution. In this case study, which is supported by an image-rich web-based version at www.hightunnels.org/cutflowercasestudy.htm, a grower at Flint's Flower Farm must determine the cause of foliar chlorosis that is slowly appearing on about half of the plants of her cut Dicentra crop. The condition could be related to a number of possible problems including a nutritional disorder, insect attack, disease infection, or production practices. Some resources are provided to aid students in gathering background information. Data accumulated by the grower is presented to allow students to logically eliminate unlikely solutions and predict (a) probable cause(s). The solution, which is rather unique to this crop, is provided. This case study is intended for use in upper-level undergraduate courses of floriculture production, nutrient management, plant pathology, and entomology.

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Christine Meyer, Ellen T. Paparozzi*, Scott J. Josiah, and Erin M. Blankenship

Woody floral stems are an emerging specialty crop within the floral industry, and stem color is a key to marketability. This study was conducted to assess stem color change over time in order to determine the optimum window for stem harvest. Plants of `Scarlet curls', `Flame' willow, `Bailey', `Cardinal' and `Yellow twig' dogwood were planted in a randomized complete block design in rows parallel to a windbreak.. Each experimental unit consisted of a group of five plants, each of the same cultivar. Plants were initially tagged at a set height and stem diameter and measured for color. Each stem was also tagged with one of three colored tapes, according to initial color: green for green colored stems, red for stems already showing color change, and pink for intermediate colored stems. Color was assessed initially and on a weekly basis for 10 weeks, starting at the end of September, using the Royal Horticultural Society color chart. Data were analyzed using a repeated measures procedure. `Scarlet curls' and `Flame' stems, already displaying color, attained the darkest color value for their cultivar at an early stage and were at the point of harvest in early November, while stems that were initially green never attained a similar dark color value. `Yellow twig' dogwood stems already displaying color and those beginning to color attained the darkest color value in late November. `Cardinal' stems attained a darker color value more quickly than other dogwood stems. In most cases, stems of `Cardinal' dogwood could be harvested from early October until early December, while early November was the optimum time to harvest `Bailey' dogwood stems. Woody florals planted closest to the windbreak were more variable in color development and, in some cases, appeared to be more vigorous.

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Ellen T. Paparozzi, Melinda McVey McCluskey, M. Elizabeth Conley, and Walter W. Stroup

Previous hydroponic studies have shown that nitrogen rates applied to roses can be cut in half as long as known quantities of sulfur are added. A two-year study began in February, 1991, to determine if roses potted in a 2:1:1 mix (soil:peat:perlite) would respond similarly. Six cultivars and three treatments (300 ppm N 20-30-10, N:S at 2:1 and N:S at 4:1 with N being approx. 155 ppm) were replicated three times in a split-plot design. Data included number of flowers and length of stems cut daily. Plants were allowed to grow for 4 months, were cut back, then allowed to grow for 7 months and cut back again. After the second pruning, shoots were harvested for N and S analysis. Soil samples were also taken. Initial data, analyzed through September, indicates that across cultivars the total number of flowers produced was not influenced by the N:S treatments. Certain cultivars, however, were more productive than others. Champagne and Bridal White consistently produced more flowers than Samantha and Amorous, regardless of fertilizer treatment. Certain treatment cultivar combinations were also significant indicating that cultivar response may limit N:S recommendations.

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Ellen T. Paparozzi, Neil Mattson, Mara Grossman, Stephanie Burnett, and Roberto Lopez

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Marci Spaw, Kimberly A. Williams, Laurie Hodges, Ellen T. Paparozzi, and Ingrid L. Mallberg

This universally accessible, Web-based decision case presents the challenge of determining the cause of foliar chlorosis in a crop of dicentra (Dicentra spectabilis) being forced as a cut flower for Valentine's Day sales. The case study serves as a tool to promote the development of diagnostic skills for production dilemmas, including nutritional disorders, disease problems, and evaluation of the appropriateness of cultural practices. Cut dicentra is a minor crop and standard production practices are not well established. Solving this case requires that students research production protocol, as well as nutritional and pest problems, and determine whether they have enough information to recommend a solution. In this case study, a grower at Flint's Flower Farm must determine the cause of foliar chlorosis that is slowly appearing on about half the plants of her cut dicentra crop. The condition could be related to a number of possible problems, including a nutritional disorder, disease infection, or production practices. Resources are provided to aid students in gathering background information. Data accumulated by the grower are presented to allow students to eliminate unlikely solutions logically. The solution, which is unique to this crop, is provided along with detailed objectives and discussion points in teaching notes. This case study is complex in nature and is intended for use with advanced students in upper-level undergraduate courses of floriculture production, nutrient management, and plant pathology who have been previously exposed to the diagnostic process.

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Sabrina J. Ruis, Humberto Blanco-Canqui, Ellen T. Paparozzi, and Russ Zeeck

Processed corn (Zea mays L.) stover (PCS), defined as finely ground stover with or without additions, could be a potential alternative to peat in greenhouse mixes. However, this option has not yet been examined. We performed two split-plot experiments (1 and 2) with tomatoes (Solanum lycopersicum L.) and marigolds (Tagetes patula L.) as main plots. Expt. 1 involved five stover rates (0%, 25%, 50%, 75%, and 100% by volume) mixed with peat as subplots. Expt. 2 involved 0% stover mixed with peat, 25% distillers grain, and 50% quick compost (mechanically processed to accelerate compost process) stover with and without CaO, and 75% quick compost stover without CaO, as subplots. We measured growth parameters (height, dry weight, and flower number) and properties of the mixes. During Expt. 1, across both species, the addition of stover at rates >50% reduced relative greenness by 40%, vegetative biomass yield by 74%, and reproductive biomass yield by 73% compared to mixes with 0% and 25% stover. As the stover rate increased, available water content in the mixes decreased (r = −0.34; P < 0.001). Mixes with 0% and 25% stover had 34% more available water than mixes with 100% stover, which probably reduced plant growth in the 100% stover treatment. As the stover rate increased, plant tissue N and P concentrations decreased. Mixes with 0% stover generally had greater N and P concentrations than mixes with stover. During Expt. 2, for marigolds, the addition of 50% quick compost stover+CaO and 75% quick compost stover-CaO reduced relative greenness by 19% and vegetative biomass by 66% compared to mixes with 25% distillers grain or 0% stover. For tomatoes, the addition of 50% quick compost stover+CaO and 75% quick compost stover-CaO reduced biomass yield by 64%, which may be due to the higher pH and electrical conductivity (EC) of both treatments. Plant tissue N and P concentrations were greater in the mix with 25% distillers grain compared to most treatments, but N and P concentrations in the other mixes varied. Overall, the 25% distillers grain (3 peat: 1 distiller grain: 4 perlite) and 25% stover (3 peat: 1 stover: 4 perlite) treatments showed the most promise as additives in a peat-based mix.

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Ellen T. Paparozzi, Jazbaat K. Chahal, Petre Dobrev, Elizabeth A. Claassen, Walter W. Stroup, and Radomira Vankova

Nitrogen response was compared in two Plectranthus species, Plectranthus parviflorus and Plectranthus ambiguus, which differ substantially in their phenotypic reaction to nitrogen limitation. The leaves of the former species gradually yellow during the nitrogen stress but are retained on the plant. This species copes with nitrogen deficiency also by gradual hydrolysis of starch grains. The latter species, P. ambiguus, responds by abscission of lower leaves. As plant hormones cytokinins are involved in nitrogen response as well as in regulation of the chlorophyll content, their dynamics were followed to explore the fast responses as well as the impact of nitrogen treatment. Both plant species responded to nitrogen deficiency/supplementation in similar ways, by downregulation and upregulation, respectively, of active cytokinins. However, the different phenotypic reactions imposed by nitrogen limitation were associated with specific regulation of cytokinin pool accompanying the stress response by the two species. The increase of the active cytokinins on nitrogen resupply was faster and stronger in the regreening species, P. parviflorus than in P. ambiguus. However, the P. ambiguus plants maintained higher basal levels of all cytokinin metabolites as well as chlorophyll content when compared with P. parviflorus. Nitrogen deficiency was associated in this species with accumulation of cis-zeatin-type cytokinins, which preceded abscission of lower and later on of middle leaves. The achieved results indicate that phenotypic variations in the response to nitrogen deficiency/supplementation are associated with significant quantitative and qualitative differences in the cytokinin pool.

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Ellen T. Paparozzi, Kimberly A. Williams, Robert Geneve, Harlene Hatterman-Valenti, Cynthia Haynes, Helen Kraus, Cynthia McKenney, and Joelle Pitts