Q: Dear Dr. Mao,
I thought plants gave off oxygen not carbon dioxide. I’ve always been under the impression that plants use the carbon dioxide we exhale & we benefit from plants in a room because of the oxygenation they provide. Please explain.
A: I am glad that so many people are interested in plants and oxygen, judging from the overwhelming responses to my article. The beauty of nature is that energy is either stored, transformed or transferred but cannot be destroyed. This principle is illustrated in the life of plants. The light initiates a process of photosynthesis whereby green plants convert energy from the sun to transform carbon dioxide and water into glucose and oxygen. Plants rely on this process for growth and propagation. Animals and humans take advantage of the energy that plants store in their tissues by consuming the carbohydrates found in plant as their main source of energy. In a way, when you and I eat vegetables, fruits and grains and take herbs, we are getting the sun’s energy indirectly.
However, plants can’t produce glucose, carbohydrates and oxygen without light. To get through the night, most plants reverse the process of photosynthesis and breathe, like you and I, by burning carbohydrates and oxygen while producing carbon dioxide and water. So surround yourself with plants during the day but remove them from your bedroom at night when you sleep. Consider putting plants in the living and working space, especially in the kitchen and near machines where the cooking fumes and emissions can be absorbed readily by the plants. Mother Nature to the rescue: plants are our best air purifiers. They produce oxygen and eliminate volatile organic compounds–VOCs at the same time. Most effective are indoor palms, English ivy, ficuses, peace lilies, and chrysanthemums. But certainly most leafy indoor plants are fine.
While we are on the subject of light, humans also benefit from light, just as plants do but in different ways. For example, in my past articles, I have talked about SAD or seasonally affective disorders characterized by depression and melancholy that afflicts millions of Americans each year during the winter months when day is short and the night is long. So besides mood altering, how else does light affect our lives? Light makes your bones stronger. Light stimulates the manufacture of Vitamin D in our body, which is a critical micronutrient for healthy bones. Additionally, light also helps our immune system, waking up the activities of the natural killer cells that patrol our borders looking for intruders and cancer cells.
In short, there are many other benefits that we derive from light. So when you can, get outdoors daily and let the sun bathe you with its life-giving and spirit-lifting properties early and late in the day to avoid the harmful UV rays and spend time among one of nature’s best gifts–plants.