Do Plants Absorb Carbon Monoxide?

Yes, plants absorb carbon monoxide. They take it in through their leaves much as they take in other gases from the air.1Canadian Journal of Botany. Carbon monoxide fixation by plants The amounts are small, though, so a houseplant is no defense against a dangerous CO leak in your home. Plants also turn out to make tiny amounts of carbon monoxide themselves and use it as an internal chemical message.

How Leaves Take In Carbon Monoxide

Leaves of 35 different temperate and tropical plants all absorbed CO from air in light.2Canadian Journal of Botany. Carbon monoxide fixation by plants Gases enter a leaf through tiny openings, the same ones used to take in carbon dioxide. In a houseplant test, plants with more leaf pores absorbed more CO.3PubMed. Experimental study on the purification capacity of potted plants on low-concentration carbon monoxide in indoor environment How fast a leaf took up CO also varied a great deal with its age.4Canadian Journal of Botany. Carbon monoxide fixation by plants

Uptake rose in exact step with CO levels from 0 to 100 ppm, meaning parts per million of air.5Canadian Journal of Botany. Carbon monoxide fixation by plants A plant in dirtier air soaks up more CO than one in clean air. But at 1 to 10 ppm, some species absorbed almost none and the fastest only a small trickle.6Canadian Journal of Botany. Carbon monoxide uptake and metabolism by leaves

Can Houseplants Protect You From Carbon Monoxide

In a closed chamber, some common houseplants did lower CO. In order from most to least CO removed:

With each plant present, CO in the sealed chamber fell steadily over time, enough to bring average levels below some workplace exposure limits.11PubMed. Experimental study on the purification capacity of potted plants on low-concentration carbon monoxide in indoor environment But as CO levels rose, the share each plant removed dropped sharply.12PubMed. Experimental study on the purification capacity of potted plants on low-concentration carbon monoxide in indoor environment At 50 ppm or below, all four plants removed CO without visible damage to the plants.13PubMed. Experimental study on the purification capacity of potted plants on low-concentration carbon monoxide in indoor environment A sealed test chamber overstates what happens at home: a real room is larger, and air leaks in and out constantly, so a few pots handle a tiny fraction of it. Workplace limits are set for healthy adults over a working shift, not for children, older people, pregnant women or people with heart or lung disease.

Carbon monoxide has no smell or color, so a working CO alarm is the only reliable way to know it is present. Install alarms near sleeping areas and on each level, and test them regularly. Check the date printed on each unit, because the sensors wear out and the whole alarm usually needs replacing after several years, as the manufacturer states.

If an alarm sounds or people feel headache, dizziness or nausea, get everyone outside and call emergency services. A leaking furnace or running car can produce CO far faster than any room of plants can absorb it. Have gas appliances, chimneys and furnaces checked yearly, and never run engines, grills or generators indoors or in an attached garage.

What Plants Do With the Carbon Monoxide They Absorb

In light, bean leaves turned most absorbed CO into sucrose, the plant’s sugar, and into proteins.14Canadian Journal of Botany. Carbon monoxide uptake and metabolism by leaves Most of it was built into a building block of protein that was then turned into sugar.15Canadian Journal of Botany. Carbon monoxide uptake and metabolism by leaves Some CO was converted to carbon dioxide, and part of that the leaf may have used again in photosynthesis.16Canadian Journal of Botany. Carbon monoxide uptake and metabolism by leaves

In darkness, leaves absorbed CO nearly as fast as in light, but they converted almost all of it to carbon dioxide and released it.17Canadian Journal of Botany. Carbon monoxide uptake and metabolism by leaves So plants still remove CO at night, though they don’t keep the carbon.

Does Carbon Monoxide Harm Plants

At 100 to 400 ppm for two days, spider plant and pothos developed damaged leaf tips over the following two weeks.18PubMed. Experimental study on the purification capacity of potted plants on low-concentration carbon monoxide in indoor environment The higher the CO, the more leaf area was damaged, but every plant survived as a whole.19PubMed. Experimental study on the purification capacity of potted plants on low-concentration carbon monoxide in indoor environment

At an extreme 25% CO, sunflower leaf pores closed partway.20PubMed. Inhibition of stomatal opening in sunflower leaves by carbon monoxide, and reversal of inhibition by light CO blocks part of the cell’s machinery for using oxygen, and more oxygen reverses the effect.21PubMed. Inhibition of stomatal opening in sunflower leaves by carbon monoxide, and reversal of inhibition by light No home or street level comes close to this.

Brown tips on pothos or spider plants are usually caused by dry air, fluoride in tap water, or overfertilizing. CO damage would only appear at levels already dangerous to people, so damaged houseplants are not a reliable CO warning. A plant can look fine while air is dangerous to people, so if you suspect a leak, trust an alarm, not plant symptoms.

Do Trees and Forests Reduce Carbon Monoxide Pollution

Beside a busy road, a strip of mahogany trees lowered CO by 45% about 10 meters away at head height.22IOP Conference Series: Earth and Environmental Science. Study of the Effectivity of Several Tree Canopy Types on Roadside Green Belt in Influencing The Distribution Vertically and Horizontally of CO gas Emitted from Transportation Activities to Vicinity of The Road A different tree species cut it by only 22%, and with no trees, CO rose by 2% at the same distance.23IOP Conference Series: Earth and Environmental Science. Study of the Effectivity of Several Tree Canopy Types on Roadside Green Belt in Influencing The Distribution Vertically and Horizontally of CO gas Emitted from Transportation Activities to Vicinity of The Road Dense, broad canopies between a road and homes or schools may help, though species choice matters. Leaves and canopies also slow wind and spread exhaust, so some of the measured drop may come from mixing and blocking rather than uptake.

On a larger scale, forests removed nearly ten times more CO than non-forest vegetation.24Science of Remote Sensing. Quantifying the impact of vegetation on carbon monoxide reduction using multi-source remote sensing in China Evergreen broadleaf trees contributed the most.25Science of Remote Sensing. Quantifying the impact of vegetation on carbon monoxide reduction using multi-source remote sensing in China

Plants are a small piece of the global picture. About 2,600 million tonnes of CO are released worldwide each year, around 60% from human activity like burning fuels.26Chemosphere. The global cycle of carbon monoxide: Trends and mass balance About 85% of it is removed by a natural cleaning chemical in the air, and about 10% by soils.27Chemosphere. The global cycle of carbon monoxide: Trends and mass balance For a household, a tree strip near a busy road may lower the exhaust drifting toward your home, but it does not replace a CO alarm for indoor sources like heaters or stoves.

Plants Make Their Own Carbon Monoxide

Plants make small amounts of CO when an enzyme breaks down heme, the iron-containing compound whose breakdown also produces CO in the human body.28PubMed Central. Carbon monoxide: A novel and pivotal signal molecule in plants? In plants, CO plays a part in seed sprouting and in closing leaf pores.29PubMed. The role of carbon monoxide signaling in the responses of plants to abiotic stresses It works closely with nitric oxide, another signaling gas, to close those pores.30PubMed. Carbon monoxide-induced stomatal closure in Vicia faba is dependent on nitric oxide synthesis The amounts are tiny and stay mostly inside plant tissue, so houseplants are not a source of indoor CO poisoning.

CO also helps roots form. The rooting hormone auxin triggers CO production, and CO then helps cucumber cuttings grow new roots.31PubMed Central. The heme oxygenase/carbon monoxide system is involved in the auxin-induced cucumber adventitious rooting process Small doses of CO showed the same kind of benefit in rapeseed seedlings, increasing the number and length of side roots.32Journal of Integrative Plant Biology. Carbon Monoxide Promotes Lateral Root Formation in Rapeseed

It helps plants handle stress too. Salt, drought and heavy metals like cadmium and mercury tend to raise CO production in plants.33PubMed. The role of carbon monoxide signaling in the responses of plants to abiotic stresses The extra CO helps protect cells by boosting the plant’s own antioxidant defenses.34PubMed. The role of carbon monoxide signaling in the responses of plants to abiotic stresses

Carbon Monoxide and Keeping Fruit Fresh

Low-dose CO fumigation kept stored peaches firmer, slowed rot and helped keep vitamin C and antioxidants.35PubMed Central. Carbon Monoxide Fumigation Improved the Quality, Nutrients, and Antioxidant Activities of Postharvest Peach A higher dose had the opposite, harmful effect.36PubMed Central. Carbon Monoxide Fumigation Improved the Quality, Nutrients, and Antioxidant Activities of Postharvest Peach In jujubes after 30 days, the best dose cut rot by a third and kept fruit firmer.37PubMed. Effects of carbon monoxide on quality, nutrients and antioxidant activity of post-harvest jujube This is still experimental and not a common practice for peaches. At home, keep fruit fresh with cool temperatures, not gases.