02. Plant structure and function

LEARNING TARGETS:

Annotate and describe the functions of key plant structures (roots, stem, leaves, flower, vascular tissue (xylem, phloem), sinks or storages for carbohydrates). 

A plant has organs that have specific functions, just like animals do. This section explores the structure and function of the main organs of a plant: the roots, stem, leaves and flower. The flower will be dealt with in more detail in another topic: Plant reproduction.

Us this website to find out the basics about plant organs and their functions. To help you to remember this fill in the following sheet.

The roots:

Use a microscope to look at the roots of a plant closely. You will see that they are branched and also are covered in very small 'hairs'. These are called root hairs and are actually part of the cells that form the outside layer of the root. The cells are called root hair cells and they look like this:

This video explains the role of root hairs:

Have a look at root slides under the microscope. can you see any root hairs? Also can you see the tubes in the centre that carry water? These are called xylem tubes - see below for details.

Stems:

Inside the stem of a plant are 2 types of tubes: xylem and phloem. Xylem vessels carry water from the roots up to the other parts of the plant, especially the leaves. They are woody thickened tubes.

To see xylem vessels you can use celery. 

1) Put the end of a stick of celery plant into food colouring and leave for 30 mins.

2) Slice the celery stem into slices and you should see that there are coloured dots in the slice. This is the xylem. You can examine these with a hand lens or under the microscope (if you cut a really thin piece).

Phloem are tubes that carry sugars around the plant. They carry the sugar dissolves to form sap. Aphids feed on sap by piercing the outside of the stem with their mouthpiece.

Have a look at stem slides under the microscope. Can you see the xylem and phloem tubes? They are usually in bunches around the edge of the stem.

Leaves:

The leaves are where a plant makes its own food. Plants take in the sunlight energy, Carbon dioxide gas from the air and water from soil. They use these to make sugar called glucose and oxygen gas. 

The process is called photosynthesis and can be represented by the equations below:

Look at a leaf under the microscope and see if you can find all of the parts shown on the sheet provided. Then label your copy of a leaf diagram to name all of the important parts by using the picture below.

Watch this video to see how leaves are adapted to be able to carry out their function of photosynthesis.

Now write a paragraph to explain how leaves are adapted to their function onto your sheet.

Flowers:

Flowers are used for plant reproduction. We will study these in much more detail later on in this unit.