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- Author or Editor: John J. Finer x
- HortScience x
Abstract
Morphogenically regenerable callus was induced from young leaf and meristem tissues of garlic (Allium sativum L. cv. Howaito-Roppen). Five auxins were compared for their ability to induce morphogenic callus. In order of decreasing effectiveness, 2,4-D (0.1–3.0 mg·liter−1), 2,4,5-T (0.3–10 mg·liter−1), dicamba (10–30 mg·liter−1), and picloram (10–30 mg·liter−1) were capable of morphogenic callus induction, while NAA did not induce morphogenic callus formation over a wide range of concentrations. The morphogenic callus was nodular and gave rise to plantlets following transfer to medium containing BA. Chemical names used: (2,4-dichlorophenoxy)acetic acid (2,4-D): (2,4,5-trichIorophenoxy)acetic acid (2,4,5-T); 3,6-dichloro-2-methoxybenzoic acid (dicamba); 4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid (picloram); 1-naphthaleneacetic acid (NAA); and N-(phenylmethyl)-1H-purin-6-amine (BA).
Drought stress during the shipping and retailing of floriculture crops can reduce postproduction shelf life and marketability. The plant hormone abscisic acid (ABA) mediates drought stress responses by closing stomata and reducing water loss. Applications of exogenous s-ABA effectively reduce water loss and allow a variety of species to survive temporary periods of drought stress. Unfortunately, s-ABA application can also lead to leaf chlorosis, which reduces the overall quality of economically important bedding plant species, including Viola ×wittrockiana (pansy). The goal of this research was to determine how to prevent s-ABA-induced leaf chlorosis in pansy and a closely related species, Viola cornuta (viola). All concentrations of both spray (250 or 500 mg·L−1) and drench (125 or 250 mg·L−1) s-ABA applications induced leaf yellowing. Young plants at the plug stage and 11-cm finished plants with one to two open flowers were further evaluated to determine if the developmental stage of the plants influenced s-ABA effectiveness or the development of negative side effects. Both plugs and finished pansies and violas developed leaf chlorosis after s-ABA applications, but symptoms were generally more severe in finished plants. The individual application of benzyladenine (BA), gibberellic acid (GA4+7), or the ethylene perception inhibitor, 1-methylcyclopropene, before s-ABA application had no effect on the development of s-ABA-induced leaf chlorosis. However, applications of 5 or 10 mg·L−1 BA and GA4+7 as a mixture (BA + GA4+7) before a drench or spray application of s-ABA prevented leaf chlorosis. The application of s-ABA and BA + GA4+7 would allow floriculture crops to tolerate temporary periods of drought stress without any loss of postproduction quality.
Drought stress is a major cause of postproduction decline in bedding plants. The plant hormone abscisic acid (ABA) regulates drought stress responses by mediating stomatal closure, thereby reducing transpirational water loss. Exogenous ABA applications delay wilting and allow plants to survive short periods of severe drought. The effectiveness of the ABA biochemical, s-ABA (ConTego™; Valent BioSciences Corp., Libertyville, IL), at delaying wilting and extending shelf life during drought stress was evaluated in six bedding plant species. Spray and drench applications of 0 or 500 mg·L−1 s-ABA were applied to Impatiens walleriana (impatiens), Pelargonium ×hortorum (seed geranium), Petunia ×hybrida (petunia), Tagetes patula (marigold), Salvia splendens (salvia), and Viola ×wittrockiana (pansy). Water was subsequently withheld and wilting symptoms were compared between treated and control plants. s-ABA applications delayed wilting in all crops by 1.7 to 4.3 days. Leaf chlorosis was observed after s-ABA application in drought-stressed seed geraniums, marigolds, and pansies. In seed geraniums and marigolds, the drought stress itself resulted in leaf chlorosis that was equivalent to or more severe than the s-ABA application alone. In pansies, s-ABA applications induced leaf chlorosis that was more severe than the drought treatment. Overall, s-ABA was consistently effective at reducing water loss and extending shelf life for all species treated. Applications of s-ABA to bedding plants before shipping and retailing would allow plants to maintain marketability even under severe drought stress conditions.