Postproduction Studies Of A Sprayable Formulation Of 1-Methylcyclopropene In Bedding Plants

Abstract

Studies were conducted with a sprayable formulation of 1-methylcyclopropene (1-MCP), formulation AFxRD-038 (Rohm and Hass, Philadelphia, PA), to determine the sensitivity to exogenous ethylene and efficacy of 1-methylcyclopropene (1-MCP) on bedding plants. Effects of ethylene concentration, plastic bag enclosure, 1-MCP concentration and volume, water quality, solution age, timing and length of irrigation, delay of ethylene challenge, surfactants, extended darkness and high postproduction storage temperatures on efficacy of 1-MCP in protecting Impatiens walleriana and I. hawkeri from premature floral senescence were evaluated. The sensitivity to exogenous ethylene and efficacy of sprayable formulation of 1-MCP of seventy-three cultivars from twenty species of annual bedding plants was investigated. Impatiens walleriana and I. hawkeri exposure to 1.0 [MICRO SIGN]l⋅liter-1 ethylene for 18 hours caused complete senescence of open flowers, 1-MCP at 2.5 mg ai⋅liter-1 protected plants from ethylene exposure. Placing plants in unsealed High Density Polyethylene (HDPE) produce bags had no effect on flower abscission in the presence or absence of ethylene or 1-MCP. At 5 and 10 mg ai⋅liter-2, the efficacy of 1-MCP increased as spray volume increased from 102 ml⋅meter-2 to 306 ml⋅meter-2. 1-MCP appeared to be effective within 1 minute after application with no decrease in efficacy regardless of irrigation water applied after 1-MCP pretreatment. There was no significant effect of surfactant concentration (Capsil, Aquatrols, Paulsboro, NJ) on 1-MCP activity though some plants exhibited phytotoxicity symptoms on flower petals with Capsil rates above 1.0 ml⋅liter-1. Increasing pH of the 1-MCP solution from 6 to 9 resulted in slightly reduced efficacy but not enough to reduce marketability of plants. Prepared 1-MCP solutions (10 mg ai⋅liter-1) remained effective up to two weeks after mixing if held in airtight containers. With Impatiens, 1-MCP provided protection against exogenous ethylene for a maximum of four days. 1-MCP provided protection against darkness and high temperature stress related abscission for at least three days of extended darkness in the absence of ethylene and two days at high temperatures (28 °C). In the second study, 73 cultivars from twenty species of annual bedding plants were grown from seed or vegetative cuttings under optimum greenhouse production until mature at which time they were sprayed with 0 or 25 mg ai⋅liter-1 1-MCP and then exposed to 0 or 1.0 [MICRO SIGN]l⋅liter-1 for 18 hours in darkness at 21°C to simulate postproduction stress. Immediately after postproduction stress, plants were assessed for senescence symptoms including flower abscission, wilting or discoloration, leaf epinasty and abscission. There were three groups of ethylene sensitivity: no response to ethylene (Bidens ferulifolia, Heliotropium arborescens, Osteospermum ecklonis, Scaevola aemula), transient ethylene symptoms (Solenostemon scutellarioides), and permanent ethylene damage. Plants showing ethylene damage were split into two groups, those that were completely protected by 1-MCP (Angelonia angustifolia, Begonia x benariensis, Calibrachoa x hybrida, Catharanthus rosea, Cleome hassleriana, Diascia barberae, Euphorbia hypericifolia, Impatiens x hawkeri, I. walleriana, Lantana camara, Lobelia erinus, Petunia hybrida, Vebena hybrida) and those for which 1-MCP provided incomplete protection (Cuphea ramosissima, Pelargonium x hortorum [Interspecific and Zonal hybrids], P. peltatum)