Efficiency of 1-methylcyclopropene (1-MCP) treatment after ethylene exposure of mini-Phalaenopsis

Phalaenopsis orchids are popular around the world, but sensitive to the phytohormone ethylene. Ethylene can cause flower wilting, drop of buds and flowers. 1-Methylcyclopropene (1-MCP) is an ethylene receptor inhibitor and effective when applied to plants before or at the same time as exposure to ethylene. In the current study, the timing of 1-MCP postharvest treatment in relation to ethylene exposure was investigated in two different mini Phalaenopsis cultivars. The aim was to determine how long 1-MCP treatment can be delayed (postponed) after exposure to ethylene had been initiated in order to effectively avoid critical losses in plants. Phalaenopsis cultivars ‘Allen’ and ‘Venice’ were exposed to 100nLL−1 of ethylene for a week and 200nLL−1 of 1-MCP, was applied either at the same time or at time points spanning from 6 to 51h, after ethylene treatment was initiated. After 42h of ethylene exposure followed by 1-MCP treatment, ‘Allen’ and ‘Venice’ displayed 91.4%±3.8 and 28.9%±4.3 senesced flowers, respectively, but when 1-MCP was applied 24h after ethylene exposure, the percentage of senesced flowers was similar to simultaneous start of ethylene and 1-MCP exposure. Colorimetrical assessment appeared not to be a fruitful parameter to determine senescence although loss of gloss in flowers and buds toward the advance in time after ethylene exposure started was visually noted. Furthermore, percentage of water dropped to similar levels in ‘Allen’ when 1-MCP application was delayed to 42h after initiation of ethylene exposure compared to plants solely treated with ethylene and electrolyte leakage started to increase to statistically different values compared to atmospheric air treated plants after 27h of delay of 1-MCP application after ethylene exposure commenced, thus correlating to the increased senescence exhibited by this cultivar. Collectively, 24–27h of ethylene exposure followed by 1-MCP treatment showed to be the threshold time span that 1-MCP application can be delayed to stop or even reverse the negative effects of ethylene exposure.