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  • Author or Editor: Nichole F. Edelman x
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The family Solanaceae, which includes both important crop and ornamental species, is generally considered to have high sensitivity to ethylene. Our objectives were to evaluate ethylene sensitivity between accessions with the family Solanaceae and to determine whether similar sensitivity was observed in seedlings and mature plants. For the seedling evaluations, seeds were germinated and grown in the dark on filter paper saturated with 0 or 100 μM 1-aminocyclopropane-1-carboxylic acid (ACC; the immediate precursor to ethylene). The relative hypocotyl length at 100 μM ACC was compared with untreated control (0 μM) seedlings. Mature plants were treated with 0 or 10 μL·L−1 ethylene in the dark for 24 hours. Ethylene responses including flower abscission, flower senescence, and epinasty were observed and quantified. Seedlings and mature plants were classified as having no response, low, medium, or high ethylene sensitivity based on the severity of the ethylene responses observed. Sensitivity differences were observed among seedling, juvenile, and mature plants, and a range of ethylene responses and symptom severity was observed between accessions within a species. The majority of the accessions were classified as medium or high ethylene sensitivity at both the seedling and mature plant stages. Solanum melongena ‘Black Beauty’ (eggplant) had a low response to ethylene at the seedling stage and a high response at the mature plant stage, whereas Petunia ×hybrida ‘Daddy Orchid’ had a high response at the seedling stage and a low response at the mature plant stage. Peppers (Capsicum annum), tomatoes (Solanum lycopersicum), and tomatillos (Physalis ixocarpa) exhibited both floral and vegetative symptoms of ethylene damage, whereas calibrachoas (Calibrachoa ×hybrida), eggplants, nicotianas, and petunias exhibited only floral symptoms. The most common floral response to ethylene treatment was flower abscission, which was observed in almost all of the Solanum, Capsicum, and Nicotiana accessions. We consistently observed ethylene-induced epinasty in the genus Capsicum and in all of the Solanum except eggplant. Our results indicated that developmental stage influenced ethylene sensitivity, and there was not a consistent correlation between seedling and mature plant responses within the Solanaceae accessions that we evaluated.

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Ethylene gas can cause extensive damage to bedding plants during production, shipping, and retailing. Seedlings exposed to ethylene exhibit the triple response, which includes an exaggerated apical hook, thickened hypocotyl, and reduced hypocotyl elongation. Our objective was to determine if the hypocotyl elongation component of the seedling triple response could be used to predict the sensitivity of mature plants at the marketable stage. Eighteen common bedding plants were evaluated. For the seedling hypocotyl elongation screen, seeds were germinated and grown in the dark on filter paper saturated with various concentrations of 1-aminocyclopropane-1-carboxylic acid (ACC; the immediate precursor to ethylene). The relative hypocotyl length at each ACC concentration was compared with untreated control (0 μM) seedlings. Mature plants, with at least four open flowers, were treated with ethylene (0, 0.01, 0.1, 1, or 10 μL·L−1) in the dark for 24 hours. Phenotypic responses to ethylene, including flower abscission, flower senescence, leaf abscission, leaf chlorosis, and epinasty, were rated on a scale of 0 to 5. Five species exhibited very little reduction in hypocotyl elongation when grown on ACC (low sensitivity). The remaining species were classified as medium or high ethylene sensitivity at the seedling stage. The most common symptoms of ethylene damage observed in mature plants were leaf epinasty, flower abscission, and flower senescence. The severity of these responses was used to identify plants with high, medium, or low sensitivity to ethylene. For six of the bedding plant species that were equally responsive at both developmental stages, the seedling hypocotyl elongation screen would provide a reliable means of predicting the ethylene sensitivity of mature plants.

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