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Root System Growth: The Root Cap, Primary Roots & Lateral Roots

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  • 0:05 Root System Growth
  • 0:22 The Root Cap
  • 0:59 Primary Roots
  • 3:17 Lateral Root Growth
  • 4:24 Lesson Summary
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Lesson Transcript
Instructor: Danielle Weber

Danielle teaches high school science and has an master's degree in science education.

It is easy to see some plants get taller, but it is important to know that plants must also have a strong support that we cannot always see. Root growth helps plants survive and can happen in two ways.

Root System Growth

As plants grow above the surface, there is also growth that occurs within the soil. Roots need to grow in order to better support the plant and to better absorb both water and nutrients for the growing plant. We will review some structures of the root in addition to looking at how roots grow.

The Root Cap

You can think of root growth as a construction site. The root is creating new cells in order to expand and help the plant further develop. When at a construction site, people are required to wear hardhats in order to protect their heads. In roots, the root cap serves a similar purpose. This outer area of the bottom of the root protects other root tissues as the root continues to grow into the soil.

The cells in the root cap are specialized for several different things. First, they can sense gravity, which is why roots grow down. Second, they secrete a slimy substance that helps roots move through the soil. We can see the root cap in the diagram below.

Diagram of root cap

Primary Roots

Directly behind the root cap is the root meristem, which is where cell division occurs. This means that when the root grows, the new cells come from the root meristem. Remember that the root cap serves to protect the root, and therefore protects this area of new growth.

There are three main areas involved in the growth of primary roots. The new cells start in the meristematic region, which is the location of cell division. This is the first area right behind the root cap and kind of looks like an inverted cone. We can see the meristematic region below on our diagram. This is a very active region of the root, and the cells in this area divide about every 12-36 hours.

diagram of meristematic region

The cells formed here eventually create the three tissues needed for primary root growth: protoderm, procambium and ground meristem. The protoderm will eventually become the epidermis, or skin of the root. The procambium will eventually become the vascular tissue.

Remember that there are two types of vascular tissue: xylem to move water and phloem to move food. The procambium will produce cells that make both types of tissues. The third type of cell created in the meristematic region is the ground meristem, which will become ground tissue and help with storage of water and nutrients for the plant.

The next region involved in primary root growth is the elongation region. This is the area of root lengthening. The cells that were produced in the meristematic region grow in the elongation region. No new cells are produced here, but this is the area that actually creates the growth of the root. We can see in this diagram that the cells in this area actually do look longer than those in the meristematic region.

diagram of elongation region

The third region involved in primary root growth is the maturation region. As the name implies, this is the area of cell maturation. It is also where the cells that grew in the elongation region fully develop and become adult cells. The three different primary cells that were created in the meristematic region fully develop into the cells they were designed to become.

The protoderm cells become the epidermis, which is like the root skin. The epidermis cells move to the outer layers of the root in order to provide protection. The procambium cells either become xylem - to carry water - or phloem - to carry food. Lastly, the ground meristem cells become the ground tissue of the root, which is basically all the other cells, such as those found in the cortex of the root.

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