Plants are famous for photosynthesis. Most of us learn early on that plants make oxygen. We also understand that all living things use oxygen to produce energy. So it’s a really natural question to end up with – Do plants breathe? I’m going to do my best to give you an answer about exactly what’s going on with plants and breathing.
If you’re after a quick answer, though, here’s the summary. Plants don’t breathe, but they do respire. This means they take in oxygen and use it to make energy.
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Respiration vs Breathing
The first thing to talk about is the difference between breathing and respiration. In science, we use words in precise ways. But, non-scientists (and scientists at home) often use words in more general ways. Breathing is an excellent example of this.
To a non-scientist, breathing often refers to getting oxygen from the air, using it, and breathing out carbon dioxide. To a scientist, breathing is only a tiny part of that big process. Breathing is the act of inhaling and exhaling.
Respiration is the process of using oxygen inside your cells to release energy from your food.
In other words, breathing is something that happens on a big scale. It uses organs and muscles. Repatriation is something that occurs on a much smaller scale. It’s a reaction that happens inside cells.
So Do Plants Breathe or Do They Respire?
For us, breathing is an integral part of respiration as it’s how we get our oxygen.
Plants need to respire the same as all living things. But, they don’t have lungs. They don’t have an active biomechanical system to inhale and exhale. So plants don’t breathe. They get their oxygen in a much slower process. They can do this because their needs are smaller than ours.
What this means is the plants don’t breathe, but they do respire.
How Do Plants ‘Breathe’?
For simplicity, let’s consider that breathing is the process a living creature uses to get oxygen. So, since plants need oxygen, but they don’t have lungs, let’s talk about what they do instead.
Every cell in a plant needs oxygen. But plants don’t have a transport system quite like ours. We use our circulatory system to carry oxygen around our body in our bloodstream. While plants do have a transport system, it’s for moving water and food. This means that every part of a plant needs to be close to a source of oxygen.
For the parts of the plant above the ground, most of the oxygen is collected through the leaves. Even though different plant leaves look very different, their basic structure is the same. On the underside of most leaves, you can find small structures called stomata. Even with a beginner microscope, you can easily look at these structures.
Stomata are like doorways into the leaf’s cells. They are shaped a bit like a donut with two guard cells on either side of the hole. The guard cells can open and close the hole as needed. This means they can open to let oxygen in and carbon dioxide out. But, they can also close to keep water in when the air is too dry.
The oxygen is taken out of the air by diffusion. This means it moves from a higher concentration area to a lower concentration one. It’s a passive system. So the plant can’t decide to take a ‘big breath’, it just has to let the oxygen come to it.
The rest of the plant will also take in oxygen by diffusion, but this has to happen through the cell walls, so it’s a much slower process. But it’s important to know that this is happening on every surface of a plant, including its roots.
If you’re anything like me, then you might have killed a houseplant or two in your time. One of the ways you can do this is by overwatering them. The water fills all the air holes in the soil. So the roots can no longer take in oxygen, and the plant essentially drowns.
Do Plants Make More Oxygen Than They Use?
We all know that plants are excellent sources of oxygen. So it can seem confusing that they use oxygen too. A logical thought is to consider if they make more oxygen than they use. Because if they don’t, then maybe there’s no benefit to planting more trees.
As will all things, the answer isn’t completely simple. It depends on the time of day and the weather. A plant’s respiration rate, the rate at which oxygen is used, is reasonably stable. So it’s always taking in a relatively constant amount of oxygen.
The rate at which it photosynthesizes depends on the amount of light that’s shining on its leaves. If there is no light, there is no oxygen being made. In dim light, there is a small amount of oxygen produced. In bright light, there is a large amount of oxygen production happening.
So to summarise…
|Respiration||Photosynthesis||Change in Oxygen levels|
|No light||yes||no||Small decrease|
|Dim light||yes||some||No change|
|Bright Light||yes||lots||Big increase|
If you average out the amount of oxygen that plants make versus the amount they use, you find that they make much more than they use. That’s why plants’ appearance on the planet is what caused the atmosphere to change to the relatively high oxygen composition it does now.
So it is absolutely worth planting more trees!
Frequently Asked Questions
Do plants breathe at night?
You might have learned about stomata when you learned about photosynthesis. One of the things you find out is that they close at night to stop water from escaping from the cells. So at night, it’s true that the leaves aren’t taking in oxygen through the stomata. But, the whole plant is still slowly absorbing oxygen through all of its surfaces, so it is still getting oxygen at night time.
What do plants breathe?
Plants need oxygen the same as us. All living things need to take in oxygen to release energy from their food. This reaction is called respiration.