Plants may be exposed to high temperatures and irregular or infrequent irrigation during shipping and retailing. These poor postproduction environments cause rapid substrate drying, plant wilting, and accelerated senescence. Drought stress is a major cause of postproduction decline in greenhouse crops, and plants quickly become unsalable (Armitage, 1993; Barrett and Campbell, 2006; van Iersel et al., 2009). The ABA helps plants survive drought stress by closing stomata to reduce transpirational water loss and prevent wilting (Malladi and Burns, 2007).
Antitranspirants can be used by producers to prevent wilting and extend the postproduction shelf life and marketability of floriculture crops (Goreta et al., 2007; Martin and Link, 1973). These products enhance drought tolerance by providing a physical barrier to water loss or by inducing stomatal closure. Physical antitranspirants contain resins, polymers, or waxes that coat the leaves and block the stomata. Physiological antitranspirants reduce transpiration rates by inducing the plants to close their stomata. These products may contain ABA or other chemicals that cause the plant to produce ABA. Prolonged stomatal closure and reduced transpiration can lead to heat stress under high temperatures, and antitranspirants may also cause phytotoxicity (Blanchard et al., 2007; Kim and van Iersel, 2008; Waterland et al., 2010a, 2010b). Additional research is therefore needed to evaluate antitranspirants and determine how they can be used to enhance the postproduction quality of specific greenhouse and nursery crops.
Comparative research has shown that antitranspirants containing ABA are more effective than physical antitranspirants at reducing water loss and delaying drought-induced wilting (Goreta et al., 2007). A new commercial product containing s-ABA, the biologically active form of ABA, ConTego (Valent BioSciences, Libertyville, IL), delays wilting in a variety of bedding plants under severe drought stress (Blanchard et al., 2007; Kim and van Iersel, 2008; Waterland et al., 2010a, 2010b). Little is known about the effectiveness or phytotoxicity of s-ABA on potted crops like chrysanthemum. Chrysanthemums are an important fall crop that accounts for about 20% of the total potted perennial market in the United States (U.S. Department of Agriculture, 2009). Enhancing their postproduction drought tolerance would result in considerable savings to retailers and producers.
The goal of this research was to determine if s-ABA could be used to enhance the drought tolerance of garden chrysanthemums without any phytotoxicity. Our objectives were 1) to determine if exogenous application of s-ABA delays wilting in finished chrysanthemums exposed to drought stress and 2) to identify any symptoms of phytotoxicity that would negatively affect the marketability of treated chrysanthemums.
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van Iersel, M.W., Seader, K. & Dove, S. 2009 Exogenous abscisic acid application effects on stomatal closure, water use, and shelf life of hydrangea (Hydrangea macrophylla) J. Environ. Hort. 27 234 238
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Waterland, N.L., Finer, J.J. & Jones, M.L. 2010b Benzyladenine and gibberellic acid application prevents abscisic acid-induced leaf chlorosis in pansy and viola HortScience 45 925 933