Tulip (Tulipa gesneriana L.) is an ornamental geophyte prized for centuries as a cut flower, potted plant, and garden favorite. Tulip bulbs are grown in fields and sold to specialized producers who “force” the plants into flower after a cold treatment of 12 or more weeks. In cut flower tulip production, bulbs are often forced in hydroponic systems that facilitate flower harvesting. With hydroponic forcing, tulip bulbs are given ≈80% to 85% of their required cold duration before “planting” in water or a dilute nutrient solution and then further cooled 1 to 3 weeks to complete the cold requirement (De Hertogh, 1996). This process allows a minimal level of root establishment before forcing at warmer temperatures.
During tulip bulb development and storage before cooling, ethylene can cause a number of physiological and morphological disorders, including gummosis (excretion of polysaccharides), flower bud abortion, shortened leaves or flowers, reduced or eliminated roots, deformed anthers, abnormal growth habit, loss of fresh weight during storage, and excessive growth of daughter bulbs (splitting) (Kamerbeek and de Munk, 1976). The degree of ethylene damage depends on a number of factors, including concentration, duration (De Munk, 1972), temperature during exposure (De Munk, 1973), and tulip cultivar (Miller et al., 2004; De Wild et al., 2002). A significant source of ethylene in the tulip industry is the fungal pathogen fusarium (Fusarium oxysporum Schlecht f. sp. tulipae), which produces ethylene when colonizing tulip bulbs (Kamerbeek and de Munk, 1976). These fungal infections therefore create a unique production challenge for cut flower tulip growers given the potential for ethylene exposure to actively growing roots and shoots.
1-Methylcyclopropene (1-MCP) is widely used in postharvest horticulture, gaining popularity for ornamental plants as an ethylene perception inhibitor that blocks ethylene binding sites in plant tissue (Blankenship and Dole, 2003; Watkins, 2006), thus protecting the tissue against ethylene damage for variable periods (Sisler and Serek, 1997). Gude and Dijkema (2005) demonstrated protection from ethylene damage in tulip storage by 24 h 1-MCP applications (0.2 μL·L−1) at 12-d intervals. The potential for 1-MCP application immediately before planting has not been investigated and is the subject of this research.
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