Example 1
Which tissue carries water from roots to leaves?
Xylem carries water and dissolved mineral ions mainly upward from the roots.
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Year 8
Plant transport and gas exchange
Connect roots, xylem, phloem, leaves and stomata to plant survival.
Method and worked examples
Root hairs increase surface area for absorbing water and mineral ions. Xylem carries these materials mainly from roots toward above-ground parts. Phloem carries sugars and other organic substances from sources, such as green leaves, to organs that use or store them. Different phloem pathways can have different transport directions.
Leaves receive light, and stomata allow gas exchange. Carbon dioxide enters for photosynthesis; water vapour can leave by transpiration. Guard cells regulate pore opening. Closing stomata reduces water loss but can limit carbon dioxide entry. Roots normally absorb water and minerals, not a green plant’s food sugar; photosynthesis makes the sugars that phloem distributes.
Example 1
Example 2
A root stores sugars made in leaves. Which transport tissue supplies them?
Phloem moves organic substances from a source leaf to the storage root.
Watch out: Green plants normally make sugars by photosynthesis. Roots absorb water and mineral ions; phloem supplies organic substances to them.