Here's a breakdown of each:

* Parenchyma: These are the most common type of plant cell. They are thin-walled and have a variety of functions, including photosynthesis, storage, and secretion.

* Collenchyma: These cells have thicker cell walls than parenchyma cells, and they provide support for growing plant parts. They are often found in stems and leaves.

* Sclerenchyma: These cells have very thick, rigid cell walls and are often dead at maturity. They provide structural support for the plant. There are two types of sclerenchyma cells: fibers and sclereids.

So, while all three cell types make up the ground tissue system, it's important to note the differences in their structure and functions.