Plant Root Structure

# Learning objectives

1. Describe the Structure of Plant Roots.{.info}
2. Describe how Water is absorbed at the Roots.{.info}

**Key Elements and scene Summary**

Plants' extensive root system is adapted for the absorption of water and mineral ions. The active transport of minerals into the root hair cells ensures that the concentration gradient favours diffusion of water towards the roots by osmosis. This continues throughout the root tissue all the way to the vascular bundle through the cortex.

In this scene, the detailed structure of the roots can be explored, and by interacting with the different parts - epidermis, root hair cells, cortex, xylem and phloem - the organisation of plant roots can be observed. Links to adaptations such as a large surface area and a short diffusion pathway can be observed to understand how plants absorb water quickly and in large quantities.

# Root Organisation{.objective .objective1}

Plants have a degree of organisation to ensure processes or jobs can be completed effectively. This includes absorbing water. The roots in plants are made up of specific tissues, each designed to carry out a specific job for the transport of water. These include: the epidermis, where the root hair cells are located for the absorption of water from soil; the cortex, responsible for transporting water to the vascular bundle; and the vascular bundle itself, where the xylem is located.

Students will be able to interact with the roots and identify specific tissues within the root. They should be asked to identify and move the different parts based on their knowledge developed by exploring the scene.

# Absorbing Water{.objective .objective2}

Roots are adapted to absorbing water. The concentration gradient of water across the cell membrane, from outside to inside the root hair cell, determines the diffusion of water by osmosis. Active transport of mineral ions from the soil into the cells ensures that the concentration gradient always leads to water diffusing into the root hair cells. Minerals continue to be transported towards the vascular bundle through the cortex, causing water to follow by osmosis until it reaches the xylem within the vascular bundle.

Students should observe the movement of mineral ions and water to see the pathway water takes to reach the xylem. They should identify which part of the cells the water travels through and draw a conclusion that water moves through the cell walls and cytoplasm of the cells within the cortex.

# The Vascular Bundle{.objective .objective3}

The central region of the root structure, made up of two types of transport systems - xylem and phloem - can be described as being made up of two types of specialised cells. Xylem, made up of xylem cells - dead, lignified cells stacked end to end making up hollow channels that transports water to the leaves by a process called the transpiration stream. Phloem, made up of phloem cells, also stacked end to end creating a series of channels responsible for transporting nutrients such as glucose throughout the plant. Unlike xylem, phloem is made up of living cells, and neighbouring phloem cells share cytoplasm, which is the means of distributing nutrients along the phloem.

Students should be asked to observe the vascular bundle and identify the xylem and phloem based on their specific structure. They should be able to describe their observations to draw their conclusion.

# Teacher Resources

### Download Teacher Notes

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### Student Quiz Answers Document

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