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Structure of a root

Structure of a root

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Why are the walls of epidermal cells thin?

Structure of a root

This is my costume for the school play! I’m a tree! Hm… it’s not very realistic though. Where are your roots?! You can’t be a good tree without roots!

Huh? Why does that matter? It’s easy to forget about roots, because we rarely see them; most of the time, they’re underground. But, roots are very important for plants. Roots make sure plants stay firmly in the soil.

Roots also take up water and minerals from the soil. Their structure is very well adapted for this. Let’s see how! The outermost layer of the root is the epidermis. It’s usually only one cell layer thick.

The epidermis protects the inside of the root, but also plays a role in absorbing water and minerals. Some of the cells in this layer form long, thin growths. These are the root hairs. These grow out of the main root and greatly increase the area of the root that is in contact with the soil. The cell walls of these cells are thin, so that water and minerals can be taken up by the plant more easily.

It’s the root hairs that absorb most of the water that a plant needs. At the very tip of the root is a cover, made up of specialised cells. These cells make sure the roots grow downwards and they produce a thick, gluey substance that helps roots move through the soil easily. This layer of cells is only found in the roots and is called the root cap. But what about the inside of the root?

If we cut the root across, we notice that it’s quite round, and that it has several layers of rings. The thickest layer of the root, starts just beneath the epidermis. It’s made up of cells that are loosely arranged and have thin cell walls. This thick layer is called the cortex. You can think of the cortex as a storage unit, where plants store glucose and water.

Water and minerals that are absorbed by the root hairs, pass through the cortex to get further into the root. The first layer that water and minerals reach after the cortex, is a single layer of tightly packed cells. This layer is the endodermis. The walls of cells in the endodermis are covered in a substance that doesn’t let water seep through. Because of this, the endodermis can control the amount of water and minerals that pass through this layer.

It can also prevent toxic substances from entering the rest of the plant. Further inwards after the endodermis, is another thin layer of cells. Cells in this layer produce roots that grow horizontally from the main root. This layer is the pericycle. Together, the endodermis and the pericycle form a ring around the vessels that transport water and nutrients around the plant.

These vessels can be arranged in different ways in different types of plants. In some plants, the vessels are arranged as a cross, while in others they are arranged in a ring around the centre of the root. So even though it might not matter for the school play if Philip’s costume has roots or not, roots are vitally important. Okay Kim. I guess roots are important.

Can you help me stick some onto the costume?