Like all living creatures, plants need five things to be able to survive, and one of those things is air. But plants don’t have lungs like we do, so my 6-year-old wants to know: do they breathe?
For humans, breathing is part of a process called ‘respiration’. Respiration is the name for the chemical reactions our bodies use to release energy from the food we eat. Here is a really good description of respiration, if you want to find out more.
All living things respire but not all living things breathe. Breathing is the way that we move air in and out of our lungs in order to get the oxygen we need for respiration.
Oxygen (chemical symbol O2) is one of the gases in the air. It is needed to make the chemical reactions in respiration work: Oxygen reacts with glucose (a kind of sugar found in food), through a chain of chemical reactions, to make carbon dioxide and water and an energy molecule called ATP (or adenosine triphosphate).
The chemical reaction for aerobic respiration can be written in words like this:
oxygen + glucose → carbon dioxide + water + energy
In order to get the energy they need to stay alive, humans eat food and breathe air. Oxygen and glucose are passed into the blood and carried around to all the cells in the body, where respiration can happen.
But plants don’t eat or breathe like us! Plants make glucose in a chemical process called photosynthesis. (I talked about this when I explained why trees are green) And photosynthesis also produces oxyxgen, which they use for respiration.