Objectives By the end of the lesson, students will be able to explain how plant growth and animal growth differ.
Think about how you grow. – As your height increases, your arms and legs get longer. – As you get taller, the distance between your arms and the ground increases.
If you have lived in the same neighborhood for a long time, you have probably noticed that the trees have also grown taller.
However, as trees grow, you may have observed that their branches always remain the same distance off the ground.
This observation tells you something about how trees grow. How is it different from the way animals and humans grow?
How Plants Grow Plants, unlike humans, continue to grow larger as long as they live.
In plants, growth occurs at special growth tissue sites. The plant's root and shoots grow longer from their tips, where growth tissues are found.
Growth tissue cells are small and divide constantly, making new cells.
Growth occurs in two stages: – First, more cells are made. – Second, those cells increase in length. This process in plants is called primary growth.
In addition to increasing in length, a tree trunk or plant stem grows wider, or thicker. This process is called secondary growth.
The cambium, a layer of growth tissue in the stem, continues to divide. It makes a layer of new xylem cells toward the center of the stem and a layer of new phloem cells toward the outside of the stem.