why do plants need oxygen to survive
Answer 1: This is a really good question and something a lot
of people usually don't think about. The answer is that all plant cells need oxygen to live, because without oxygen they can't perform aerobic respiration (respiration is the process of breaking down food to get energy). Of course you probably know that when plants perform photosynthesis, they combine water, carbon dioxide, and the sun's energy to produce sugar and oxygen. So the cells in the green parts of the plant, where photosynthesis is taking place, get all the oxygen they need from the oxygen produced by photosynthesis. So cells in the leaves and stems are okay. The trick is the cells down in the roots, where there is no photosynthesis. In most plants, these cells get their oxygen from air in the spaces between dirt particles in the soil (you'd be surprised how much empty space there is in the soil -- mostly because earthworms are always moving around, churning up the dirt).
But for plants that live in soggy environments, that's not an option, because water holds a lot less oxygen than air does (we're talking about O here, not the oxygen in H 0). So some wetlands plants have developed a tolerance for low-oxygen conditions, and a lot of them have really shallow root systems so they're as close as possible to the air. Mangroves are trees that live in saltwater lagoons, and they have evolved special roots, called pneumatophores (Greek for 'air carrier'), that act like snorkels for the roots. But most plants don't have these special tolerances and adaptations, which is why you can 'drown' your houseplants if you water them too much. Answer 3: Plants need oxygen for the same reason you and I do -- without oxygen we can't convert the carbohydrates, fats, and proteins we eat into energy. We call this process respiration, and the formula for this sort of reaction is like this: So we breathe in oxygen and eat food, and we exhale carbon dioxide and excrete water.
This exact same reaction goes on in every living cell, including all plant cells. But of course plants don't have to eat food, because they make their own food using photosynthesis. The formula for photosynthesis is basically this: You can see that this is basically the reverse of respiration, but plants convert the energy in sunlight into the chemical bonds of the sugar. When cells respire, they break those bonds and get the energy out of them. Anyway, you can see that photosynthesis produces oxygen as a waste product, so for the most part plants don't have to breathe in extra oxygen -- they can just use the oxygen that they produce during photosynthesis. However, plants only perform photosynthesis in the green parts, like leaves and stems, but all plant cells need oxygen to respire.
Cells in the leaves get plenty of oxygen from photosynthesis, but cells in the roots often need to get oxygen from the environment to stay alive. Even though roots are buried, they can absorb oxygen from the small air spaces in soil. This is why it's possible to 'drown' plants by watering them too much. If the soil is way too wet, the roots are smothered, the roots can't get any oxygen from the air, and the cells in the roots die. Without those root cells, the rest of the plant dies. Some plants have evolved adaptations to deal with extremely wet soil. Mangroves are trees that live in swampy environments along the coast in the tropics. The roots of mangroves are often entirely under saltwater, so they have special structures called pneumatophores (Greek for "air carrier") that act like snorkels, sticking up out of the water to get a oxygen for the roots. Click to return to the search form.
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