- Which plants grow on the river shores?
- How do plants tolerate the water level fluctuating?
- What are the leaves of river plants like?
Fewer plants can grow in fast-flowing water than in lakes
The water in the fast-flowing parts of the river is enriched with atmospheric oxygen, but no sediments remain on the bottom of the river in these places. Only a few plant species can grow permanently on these sandy and gravelly sections of the river. There is also very little plankton in these places, because the water carries it away. Therefore, fast-flowing river sections have less aquatic vegetation than slow-flowing river sections and lakes.
The vegetation growing on the river banks is quite similar to the vegetation on the shores of the lakes. However, on river banks, there are more plant species that can tolerate high water because the water level fluctuates more than in lakes. In early spring, when the flood-meadows are underwater, the marsh-marigold blooms. Its flowers and leaves then stretch out of the water. Subsequently, drying does not stop its growth. Common trees that grow by rivers are willows and alders. Their roots fortify the river bank, so the river often carves long passages under the tree roots, where many aquatic animals find hiding places.
Almost all plant species that grow in the lake can also be found in rivers. However, they usually grow in the slow-flowing sections of rivers. There are no large aquatic plants in the fast-flowing parts of the river; only algae and water mosses that are firmly attached to rocks can grow here.
Think!
- Why are the fast-flowing river sections poor in vegetation?
- What can happen if the trees growing on the river bank are cut down?
- Living conditions in the river are the same all year round.
- Sediments accumulate at the bottom of the river in slow-flowing parts of the river.
- The fast-flowing sections of the river have a lot of plankton and the flow brings in more and more of it.
- Many species of plants growing in lakes also grow in rivers.
- Many river plants grow leaves of different shapes according to the flow rate.
Different leaves help to cope with the changing water levels
Aquatic plants often have different leaves. It is particularly characteristic of plants growing in rivers. Where the flow is fast, they usually have long and narrow submerged leaves that float freely in the flow. For example, the arrowhead has such leaves. In slow-flowing water, it can also grow wider leaves that float on the water's surface.
Small white-flowered water-crowfoot can tolerate the often changing water level. Like the arrowhead, it also has different types of leaves: fine, branching, submerged leaves resembling dill leaves, and floating leaves with wider lobes. There are several types of crowfoots. It isn't easy to distinguish them because the same species may look very different depending on the water level and flow. When the current is fast and the water level is high, the roots of the crowfoots can grow more than a meter long, and they grow only thin submerged leaves. As the water level drops and the current weakens, more and more floating leaves will grow on it. The thread-leaved water-crowfoot, which most often grows in running water, has no floating leaves at all.
The water horsetail can also grow in lakes and bogs, but in rivers it can occupy habitats where other plants cannot grow. The narrow, strong and tubular stems of the water horsetail are resistant to even strong currents, and the whole plant withstands water level fluctuations well. The stem of the water horsetail is much smoother than other parts - it reduces the flow resistance.
- Round and wide
- Long and thin
- Submerged
- Floating
Think!
- Which conditions affect the number and diversity of river plants?
- Why doesn't the water flow carry the plants growing in the river away?
I now know that…
Due to the flow, fewer plants grow in rivers than in lakes. It is characteristic of river plants to have different leaves depending on their growing conditions. Where the flow is fast, the leaves are long and narrow, and where the flow is slow, the leaves are wider. The most common river plants are, for example, the arrowhead, water-crowfoot, and water horsetail.
