The roots, stem and leaves form a plant organ system for transport of…

The idea

A plant organ system is a group of organs working together to transport substances. Roots absorb water and mineral ions from the soil. The stem contains xylem and phloem and holds the leaves in a position to absorb light. Leaves absorb light and carbon dioxide and carry out photosynthesis, producing sugars that are transported to other parts of the plant. Xylem transports water and dissolved mineral ions from the roots upwards to the stem and leaves. Phloem transports dissolved sugars and other products of photosynthesis from the leaves to growing regions and storage organs. Together these organs form a continuous transport system that connects sources and sinks throughout the plant.

What earns the marks

• Identify roots, stem and leaves as the main organs of the plant transport system and state that they work together.
• Describe the role of roots in absorbing water and mineral ions from the soil.
• Describe the role of the stem in supporting the plant and containing xylem and phloem vessels that carry substances.
• Describe the role of leaves in absorbing light and carbon dioxide for photosynthesis and in producing sugars for transport.
• State that xylem transports water and dissolved mineral ions upwards from roots to leaves.
• State that phloem transports dissolved sugars from leaves to other parts of the plant, including growing regions and storage organs.

Common mistakes and how to put them right

• Confusing xylem and phloem.

  Put it right: Remember that xylem carries water and mineral ions while phloem carries dissolved sugars.

• Thinking that transport occurs only in one direction in all vessels.

  Put it right: State that xylem transport is mainly upwards while phloem transport can move substances to different parts of the plant.

• Describing the stem as only a support and omitting its transport role.

  Put it right: Include the xylem and phloem vessels within the stem.

• Stating that leaves absorb water from the soil.

  Put it right: State that roots absorb water and leaves absorb light and carbon dioxide.

Exam tips

• Use the phrase 'organ system' and name all three organs when describing transport in a plant.
• Link each organ to its function in one clear sentence, for example roots absorb water, stem transports it, leaves use it.
• When comparing xylem and phloem, state the substance carried and the direction of movement for each.