Ethylene (C2H4) is a colorless, flammable gas usually obtained from natural gas or petroleum. It is a plant hormone that controls plant growth and development in areas such as seed germination, fruit ripening, rooting and flower initiation. Defective heaters, faulty gas lines, engine exhaust and rotting plants are common sources of ethylene pollution in the greenhouse. Ethylene contamination can occur when the gas builds up to harmful levels, which can cause considerable crop damage that ranges from moderate to severe. Plants aren’t the only ones in danger from gas pollutants. Carbon monoxide poisoning from malfunctioning heaters can cause problems for workers, as well, prompting headaches, dizziness, vomiting, and in worst case scenarios, loss of consciousness and death.
In an online article titled “Prevent Ethylene And Carbon Monoxide From Occurring In Your Greenhouse,” Michigan State University Extension and Department of Horticulture educators Tom Dudek and Randy Beaudry say knowing the symptoms of ethylene damage for plants and the human symptoms of carbon monoxide poisoning due to faulty greenhouse heating symptoms can help avoid crop losses and worker illness concerns. Here are some highlights.
Ethylene Damage To Plants
Plants are very susceptible to ethylene injury at levels from 0.01 to 1 ppm or more. No other air pollutant causes a greater range of symptoms than ethylene gas. Symptoms range from shedding or shattering of flower petals, misshapen or malformed leaves and flowers, thickened stems, leaf yellowing or chlorosis, stunted plant growth, flower bud and leaf abortion to epinasty or twisting.
A great indicator plant to use for the presence of ethylene is a tomato plant. They are highly sensitive and will twist or wilt when exposed to ethylene. Tomatoes will exhibit injury within 24 hours if ethylene is present. Thus, many growers will put a young potted tomato transplant into every new growing area they open up each season to test for low levels of the damaging gas.
To avoid ethylene injury, greenhouse heaters need proper ventilation and intake of fresh air from the outside. One square inch of vent cross section of outside air for every 2,500 BTUs of heater output is recommended.
If you suspect ethylene injury is occurring, contact your local Extension floriculture educator to look at the crop and obtain air samples to verify if ethylene is the problem. Using gas chromatography, the air samples can be assessed for ethylene levels and other hydrocarbons such as methane and propane, which is helpful in discovery of leaks in gas supply lines and leaks in the heat exchangers. Also, call your furnace maintenance firm to inspect the unit in question.
Carbon Monoxide Poisoning
An early symptom of CO poisoning is headaches, but can be accompanied by dizziness, weakness, upset stomach, vomiting, chest pain and confusion as poisoning becomes more extreme. CO symptoms are often described as “flu-like.” If you breathe in a lot of CO, it can make you pass out or kill you.
The Center for Disease Control and Prevention has some excellent information on carbon monoxide poisoning at its website, including fact sheets and other useful leaflets. There are also CO detectors that are available, often from local hardware stores, for just a few dollars. These detectors are small badges or tags that can be worn or placed in the greenhouse environment.
Heating Unit Checklist
Also, greenhouse heaters need to be maintained so that the heater itself is running properly and the distribution tube, vent stack, ventilation louvers and fuel line are all functioning correctly.Try this checklist for proper maintenance to avoid problems.
- Inspect heat exchanger for cracks by inspecting for light penetration while the furnace is running
- Test furnace for leaks by placing a smoke bomb or furnace candle within the firebox
- Check gas lines for leaks by painting soapy water on the joints and seams
- Examine exhaust chimney for leaks and obstructions
- Clean pilot light and orifice
- Observe flame to see if it is clear blue — yellow or orange flames represent impurities or a wrong setting
Read the full Michigan State University Extension article, “Prevent Ethylene and Carbon Monoxide From Occurring In Your Greenhouse,” by Tom Dudek and Randy Beaudry, to further understand how to recognize and deal with ethylene damage and carbon monoxide poisoning in your greenhouse. For more information, visit the Michigan State University Extension website.