Plant organ system: The roots, stem and leaves form a plant organ system for transport of substances around the plant.

The idea

A plant is not just a collection of separate parts: its roots, stem and leaves work together as an organ system that moves substances from where they are taken in or made to where they are needed. Roots absorb water and mineral ions from the soil. The stem contains vascular tissue and holds the leaves up, providing a transport route between roots and leaves. Leaves absorb light and carbon dioxide and make glucose by photosynthesis. Water and dissolved mineral ions travel up from the roots through the stem to the leaves, while sugars made in the leaves are transported to growing regions, storage organs and roots. This coordination allows the whole plant to survive, grow and reproduce.

What earns the marks

• Identifies roots, stem and leaves as organs that together form a transport system in a plant.
• States that roots absorb water and mineral ions from the soil.
• Explains that the stem supports the leaves and contains vascular tissue that connects roots to leaves.
• Describes leaves as the main site of photosynthesis, producing sugars that must be moved to other parts of the plant.
• Recognises that substances are transported in two directions: water and mineral ions upwards, and sugars to growing or storage regions.
• Uses the idea of an organ system to link the functions of roots, stem and leaves rather than treating them separately.

Common mistakes and how to put them right

• Thinking that roots only anchor the plant.

  Put it right: Roots also absorb water and mineral ions, which are essential for transport and growth.

• Believing that transport happens only upwards.

  Put it right: Water and mineral ions move upwards, but sugars can move upwards or downwards to wherever they are needed.

• Describing the stem as a dead support structure.

  Put it right: The stem contains living vascular tissue that actively transports substances.

Exam tips

• Link each organ to its role in transport: roots absorb, stem connects and supports, leaves produce sugars.
• Use the phrase 'organ system' to show that the parts work together, not in isolation.
• When describing transport, name the substances being moved and state the direction of movement.