Carbon monoxide (CO) is a colorless, odorless, and tasteless gas produced by the incomplete burning of carbon-containing fuels. While known as a danger to humans and animals, CO is also highly toxic to plant life. Exposure to elevated levels can poison plants, leading to severe damage and death.
How Carbon Monoxide Interferes with Plant Biology
The toxicity of carbon monoxide begins at the cellular level by disrupting the plant’s ability to process energy. CO directly interferes with cellular respiration, which occurs within the plant’s mitochondria. Similar to the mechanism in animals, CO binds to and poisons the oxygen-processing components, specifically the cytochrome enzymes in the electron transport chain.
When CO binds to these critical enzymes, it prevents the final steps of aerobic respiration from completing successfully. The cells are unable to efficiently utilize oxygen to generate the necessary energy (ATP) for growth and survival. This essentially suffocates the plant’s cells internally.
CO also acts as a potent mimic of the plant hormone ethylene, which regulates growth and maturity. High concentrations of CO activate these same hormonal pathways, causing the plant to prematurely initiate processes like the shedding of leaves or the ripening of fruit.
Recognizable Signs of Carbon Monoxide Exposure
Plant owners can observe several distinct physical symptoms that signal carbon monoxide exposure. One of the most common indicators is chlorosis, the abnormal yellowing of the leaves, which often starts with the oldest foliage.
A sudden and unexplained leaf drop, known as abscission, is another frequent symptom, especially when leaves fall without browning or drying. This rapid shedding results directly from CO mimicking the ethylene hormone, signaling the plant to drop foliage prematurely.
Other signs include general wilting, stunted growth, and the failure to produce flowers or set fruit. Plants may also display epinasty, the abnormal downward curling or twisting of leaves and stems. These symptoms are often confused with common issues like overwatering or nutrient deficiencies, making CO poisoning difficult to diagnose.
Sources of Carbon Monoxide Exposure in Indoor Environments
In the home, carbon monoxide is generated by any device that relies on burning carbon-based fuel. CO becomes a problem when combustion is incomplete or ventilation is insufficient, allowing the gas to accumulate to toxic levels.
Common sources include malfunctioning furnaces or boilers, especially during colder months. Gas stoves and ovens can also release CO if their burners are dirty or improperly adjusted. Unvented appliances, such as kerosene or propane space heaters, pose a high risk because they release combustion byproducts directly indoors.
Fireplaces, wood-burning stoves, and tobacco smoke also contribute to CO levels. Operating vehicles in an attached garage is a hazard, as fumes can easily seep into the house. Combined with tightly sealed windows and doors, these sources can create a dangerous environment where CO concentrations rise rapidly.