Section 3: The Basic Parts of a Plant

Glossary

Lesson 3: The Stems



Just above the ground, next to the root, is the stem of the plant. A stem can be a very small part of the plant, or it can be extremely large, in which case we refer to it as a trunk.  Think of the stems (trunks) of giant cedar trees, which are known to be the largest trees on earth.

Plant stems are very important to man; lumber for our houses comes from this part of the plant.

A man is standing by the trunk (stem) of a redwood
tree near Felton, California.
 

The stem is an organ of the plant that is, for most plants, vertical and above the ground. It functions primarily for the following purposes:

The stem supports the leaves, flowers, and buds; the stems keep the leaves in the light and provide a place for the plant to keep its flowers and fruits.
The stem carries the water and nutrients, from the root, to the leaves of the plant.
The stem helps to transport sugars, produced through photosynthesis, from the leaves to the rest of the plant.

The three major internal parts of a stem are the following:
 The xylem tubes are located toward the inside of the stem. They conduct water and minerals upward from the roots to the leaves, where plant food, a type of sugar, is produced.


 

The phloem tubes are just inside the bark of stems. They carry the sugars from the leaves downward to other parts of the plant. Thus, the xylem and phloem tubes form a plant's vascular system, like the arteries and veins of humans and animals.
 

The cambium is the site of cell division that produces new growth. It is located between the xylem and the phloem, and it is the tissue responsible for a stem's increase in circumference as it produces both the xylem and phloem tissues. This gives rise to the annual tree rings that you see in the trunk of a tree.










Courtesy of www.boundless.com

 An area of the stem where leaves are located is called a node . Nodes are areas of great cellular activity and growth, where buds develop into leaves or flowers. The area between nodes is called the internode .