Plant tissues: meristem tissue found at the growing tips of shoots and roots.

The idea

Meristem tissue is a plant tissue made of unspecialised, actively dividing cells. It is found at the growing tips of shoots and roots, where it allows the plant to grow in length. The cells divide by mitosis and then elongate and become specialised to form new tissues such as xylem, phloem, epidermis and palisade mesophyll. Because meristem cells can divide repeatedly and can develop into different cell types, they are described as undifferentiated and are important for growth and repair. A useful method is to observe a stained root tip squash under a microscope: cells near the tip are small, tightly packed and often seen at different stages of mitosis, showing that this is a region of active cell division.

What earns the marks

• Meristem tissue is found at the growing tips of shoots and roots.
• Meristem cells are unspecialised and divide by mitosis to produce new cells.
• Cell division at the meristem allows the plant to grow in length and to replace damaged tissues.
• New cells produced by the meristem elongate and become specialised to form tissues such as xylem, phloem and epidermis.
• Meristem cells are undifferentiated, meaning they can develop into more than one type of plant cell.

Common mistakes and how to put them right

• Saying that meristem tissue is found throughout the whole plant.

  Put it right by stating that it is mainly at the growing tips of shoots and roots.

• Confusing meristem cells with specialised cells such as xylem vessels.

  Put it right by stating that meristem cells are unspecialised and can divide and differentiate.

• Stating that meristem cells divide by meiosis.

  Put it right by stating that they divide by mitosis to produce genetically identical cells for growth.

Exam tips

• Link the position of meristem tissue at shoot and root tips directly to its role in growth in length.
• Use the terms unspecialised, undifferentiated, mitosis and differentiate accurately when explaining meristem function.
• When describing a root tip squash, refer to cells at different stages of the cell cycle as evidence of active division.