Stem cells: Meristem tissue in plants can differentiate into any type of plant cell, throughout the life of the plant.

The idea

Meristem tissue is plant stem cell tissue found in regions of active growth, such as root and shoot tips and the cambium. Its cells are unspecialised and retain the ability to divide by mitosis and then differentiate into any plant cell type, including xylem, phloem, palisade mesophyll, epidermal and root hair cells. Unlike most animal cells, which lose this potency after early development, plant meristems remain active throughout the plant's life, so growth and repair continue for years. For example, cells left behind at a shoot tip can become new leaves, while cambium cells can become xylem or phloem as the stem thickens. This lifelong potency is why gardeners can grow new plants from cuttings.

What earns the marks

• Meristem tissue is unspecialised plant stem cell tissue located in growth regions such as root tips, shoot tips and cambium.
• Meristem cells can divide by mitosis to produce more unspecialised cells before differentiation.
• Meristem cells can differentiate into any type of plant cell, for example xylem, phloem, palisade mesophyll, epidermal or root hair cells.
• Differentiation produces cells with structures suited to particular functions, such as xylem vessels for water transport.
• Lifelong meristem activity supports continued growth, replacement of damaged tissue and regrowth after cutting or grazing.

Common mistakes and how to put them right

• Thinking meristems are only in the tips of shoots.

  Put it right: , meristems also occur in root tips and in the cambium of stems and roots.

• Stating that meristem cells are already specialised.

  Put it right: , they are unspecialised stem cells that become specialised by differentiation.

• Claiming that plant cells can change into animal cells.

  Put it right: , meristem cells differentiate only into plant cell types.

Exam tips

• Name at least two specific plant cell types that meristems can become, such as xylem and phloem, to show the meaning of 'any type'.
• Use the phrase 'throughout the life of the plant' when contrasting plant meristems with animal stem cells.
• Link the location of meristem tissue to its function, for example root tip meristems allow roots to keep growing longer.