Stem cells

Stem cells are cells that have not undergone differentiation. A cell which has not yet become specialised is called undifferentiated.

An embryo develops from a fertilised egg. Cells at early stages in the development of the embryo are stem cells.

If embryonic stem cells are removed from the embryo they will differentiate into any cell type.

Some adult stem cells remain in the bodies of adults. These are found in limited numbers at certain locations in the body. Adult stem cells can be found in:

Adult stem cells can differentiate into related cell types only. So bone marrow cells can differentiate into blood cells and cells of the immune system, but not other cell types.

Stem cells in plants

Cell division in plants occurs in regions called meristems. Cells of the meristem can differentiate to produce all types of plant cells at any time during the life of the plant. The main meristems are close to the tip of the shoot, and the tip of the root.

Cells of the meristem can differentiate to produce all types of plant cells at any time during the life of the plant.  The main meristems are close to the tip of the shoot, and the tip of the root.The growth of cells by mitosis in the meristem and differentiation in other parts of the plant

In a growing shoot, new cells are being produced continuously near the tip. As the cells become older, further away from the tip, they become differentiated. They enlarge and develop a vacuole.