I am sure the very first thing we learned about living things, including plants, is that “all living things breathe!”
What do living things do when they breathe?
They inhale or take in oxygen inside their body, and exhale or give out carbon dioxide.
As we progressed into higher classes, we learned another important fact about plants, and that is, plants prepare their own food. To do this, all they need is water & carbon dioxide, and the whole process takes place only in the presence of sunlight. This complete process is termed as photosynthesis wherein, the word “photo” indicates “light” and “synthesis” means “to prepare”.
You might say, yaa! This is what plants do! They take in carbon dioxide, cook food inside their very own kitchen, that’s leaf, and give out oxygen. So does this indicate that plants don’t breathe? Can we say that plants breathe in only carbon dioxide and not oxygen? Of course not!
Let me elaborate! All living things need oxygen. They use oxygen to break down the food, present inside their cells, and release energy trapped inside the food.
Do I need to mention all the things we do with the help of energy? You’re able to read and gulp down all this information itself is a proof that oxygen inside you has already hammered few food molecules.
Once the food is broken, and energy is released, the carbon present in the food combines with oxygen molecules and forms carbon dioxide. This carbon dioxide then do the same journey as oxygen does but in reverse.
This whole process of taking in oxygen, utilising it to release energy, and giving out carbon dioxide is called as respiration.
Respiration is different from breathing. In breathing, living things such as humans, inhale air into the lung and then exhale it out of the bodies afterwards. Thus, it is simply a physical process of exchange of gas molecules i.e. oxygen is taken in and carbon dioxide is given out, between the living beings and the environment, whereas respiration is a more complex chemical process where the oxygen is taken inside the body and is used to breakdown the food molecule and release energy along with carbon dioxide and water.
What makes green plants different from other living beings?
Plants, like every other living being, respire all the time, day and night. So yes! Plants need oxygen. But along with respiration plants also carry out photosynthesis, a process that occurs only during the day when there is sunlight.
Now you must have heard many saying that you shouldn’t sleep under a tree during the night. It’s because the tree gives out carbon dioxide during the night. Of course, they are right, but what they missed is that plants give out carbon dioxide all the time, because they respire all the time. It’s just that during day time, plants give out more oxygen during photosynthesis than they take in during respiration. During the night, there is no sunlight. Thus the only process in action inside plant cells is respiration.