Fish have gills which enables them to live in water. What does aquatic plants have as compared to trees?
In: Biology
Plants don’t need to actively breathe like animals do. Instead, CO2 and oxygen can just trickle through their skin.
However, there is an important difference between how that works with land and underwater plants: The cell membranes that let through those gases can also let out water vapor and dry the plant out unless it’s submerged. For that reason, land plants have evolved a thicker type of membrane that blocks off gases and instead use small holes called “[stoma](https://upload.wikimedia.org/wikipedia/commons/9/92/Tomato_leaf_stomate_1.jpg)”. Plants can open and close these holes in order to regulate gas exchange: If it’s wet and humid, they open so the plants can breathe as much as possible. If it’s dry, they can close to minimize the loss of water.
You technically don’t need gills to live in the water, just look at any marine mammal. Aquatic plants are no different from other plants save for certain adaptations to allow them to not get ripped apart by water pressure.
Both use photosynthesis, there really isn’t much difference. One essential part of that process is chlorophyl, which also makes plants look green.
So no, there’s nothing like gills for plants. Water plants just make due with more water and less light and carbon dioxide, that’s all.
Unlike animals, plants need to take up CO2 and emit O2 (Animals do the opposite). However they still face some challenges underwater. Getting rid of excess O2 is easy (and sometimes looks really cool). Under normal circumstances the leaf cells produce O2 and it diffuses into the water. But if the plant is producing O2 fast enough, it does what is called “pearling”. Basically the excess gas bubbles out of pores in the leaves and produces a fine stream of tiny bubbles.
video https://www.youtube.com/watch?v=bd6b906XcJ4
But plants underwater also need carbon dioxide. They are at a bit of an advantage here compared to animals….carbon dioxide dissolves _much_ more easily in water than oxygen does. Like 200x easier. Because the concentration of CO2 is higher underwater, plants don’t have to have specialized structures to extract it. However, underwater plants are still operating off of limited CO2 compared to plants with leaves in the air. People keeping aquatic aquarium plants often provide them with CO2 in order to make them grow more lushly, and plants that send up leaves out of the water almost always grow more quickly than totally submerged plants.
Mangroves grow breathing tubes that can reach lengths of up to 3m (10ft) for some species. They are like a diving snorkel but for plants!
What do aquatic plants have?
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