Below-freezing temperatures are forecasted for the Midwest, Northeast, and Great Lakes states over the next seven days. With low night temperatures, many seasonal retail establishments have fired up heaters to maintain minimum temperatures for newly arrived plants. Heaters can be a source of ethylene contamination, a challenging situation affecting the marketability of plants this season.
Ethylene is a plant hormone involved in ripening and senescence. As such, its presence in the greenhouse can cause leaf yellowing, premature leaf drop, flower bud abortion, epinasty, and stunted growth. Ethylene concentrations can build up in the greenhouse, especially when ventilation is poor due to the incomplete combustion of petroleum products in the exhaust of vehicles, equipment, and faulty heaters.
Because ethylene is odorless and colorless, sensitive plants can be used to indicate its presence. One of the best indicator plants for ethylene in the greenhouse is tomato. Tomato leaves bend downward when exposed to small ethylene concentrations, a phenomenon called epinasty.
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