Why do plants need roots?

Roots are not pretty and bright like leaves and flowers but most plants could not survive without them. Anchored in the soil they hold plants upright against wind and weather.

Roots also grow out and down in search of water and minerals which are drawn all the way up to the leaves. Because trees grow to such enormous heights, their roots need to grow outwards to balance the spread of the branches above. Most roots grow in the top 30cm of soil. This part contains most of the important minerals the tree needs to survive. Every single root grows a mass of tiny hairs near its tip to enable it to absorb water from the soil. There are little pockets of air in the soil. Without these, roots would simply wither and die.

Which plants have no true roots?

Liverworts, hornworts and mosses do not have true roots. Instead they are anchored to the ground by hair-like structures called rhizoids that resemble roots. A liverwort absorbs water over its entire surface and dries out quickly.

Consequently, liverworts grow extremely close to the ground and often measure less than 1.4cm high. Most liverworts grow only in damp, shady environments, such as rotten logs, stream banks and moist cliffs.

Moss has a short stem which grows from the rhizoids. It is covered by tiny leaves in a spiral pattern. The leaves contain chlorophyll, a green substance that the plant uses to make food. In many cases, a vein runs the length of the leaf from the stem to the tip. This vein, called the costa or midrib strengthens the leaf and transports food and water. Many mosses grow in moist or aquatic environments.

However, some mosses can survive in very dry conditions. Their need for water changes with the amount of water available in the environment.

Fact file

Lichens have no roots. They have an outer layer of fungal cells that are pigmented green, brown or yellow. This protective layer, called the upper cortex, covers a zone of green or blue-green algal cells.