Elevated ethylene levels are a problem in closed environments, including the International Space Station. Studies at Utah State University have shown that ethylene decreases growth, yield, and height of peas at levels as low as 10 ppb. Ethylene, a natural plant hormone, binds to receptor proteins and influences development from germination to senescence. 1-methylcyclopropene (1-MCP) is a gas that is suspected to permanently bind to, and block, the sites of ethylene perception. 1-MCP has been used to delay flower senescence of ornamentals. Our objectives were to: 1) develop a rapid, reproducible bioassay for ethylene effects, 2) determine how much and how often 1-MCP should be applied to inhibit the effects of elevated atmospheric ethylene. 1-MCP significantly diminished the detrimental effects of ethylene on peas grown in the highest ethylene concentration (200 ppb). Daily dosing for up to 10 hours was important to maintaining the protective effects since 1-MCP does not appear to be mobile in the plants.