Plant tissues: Plant tissues include:

The idea

Plants are multicellular organisms whose organs, such as leaves, stems and roots, are built from several tissues working together. A tissue is a group of similar cells that share a structure suited to a particular job. In this topic you learn to recognise the main plant tissues and relate each one's cell structure to its function. Epidermal tissue forms a protective outer layer and often carries stomata and a waxy cuticle. Palisade mesophyll is packed with chloroplasts for photosynthesis. Spongy mesophyll has air spaces for gas diffusion. Xylem transports water and mineral ions upward and supports the stem. Phloem transports dissolved sugars. Meristem tissue at shoot and root tips provides new growth. Naming each tissue and linking structure to function is the core skill.

What earns the marks

• A tissue is a group of similar cells working together to carry out a shared function; plant organs contain several tissues.
• Epidermal tissue covers plant surfaces, protects against water loss and pathogens, and contains stomata and guard cells in leaves.
• Palisade mesophyll cells contain many chloroplasts and are positioned near the upper leaf surface to absorb light for photosynthesis.
• Spongy mesophyll cells are loosely packed with air spaces that allow carbon dioxide and oxygen to diffuse through the leaf.
• Xylem tissue contains dead, hollow cells strengthened with lignin; it transports water and mineral ions from roots to leaves and helps support the plant.
• Phloem tissue contains living cells that transport dissolved sugars and amino acids around the plant in translocation.
• Meristem tissue at shoot and root tips contains unspecialised cells that divide to produce new growth.
• The waxy cuticle on the upper epidermis reduces water loss by evaporation.

Common mistakes and how to put them right

• Confusing xylem and phloem.

  Put it right: Xylem carries water and mineral ions upward while phloem carries dissolved sugars; use the phrase 'xylem up, phloem around' to correct this.

• Thinking all leaf cells photosynthesise equally.

  Put it right: Palisade mesophyll is the main photosynthetic tissue because it has the most chloroplasts, whereas epidermal cells lack chloroplasts in most plants.

• Describing stomata as cells.

  Put it right: Stomata are pores or gaps in the epidermis, and the guard cells either side of each pore control its opening and closing.

Exam tips

• When asked to name plant tissues, give the tissue name and one function, for example 'xylem transports water and mineral ions'.
• Link each tissue to its location: epidermis on the surface, palisade near the top of the leaf, xylem and phloem in vascular bundles.
• Use comparative language such as 'more chloroplasts' or 'air spaces' to show how structure relates to function rather than just listing parts.