Transport in Plants

8. Transport in Plants — Cambridge IGCSE Biology 0610 Revision Notes & Topical Questions

5 min read 10 parts Lesson 1 of 9 2 quizzes

📚 Cambridge IGCSE Biology 0610 Hub / Topical Revision

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Lesson summary

8. Transport in Plants — IGCSE BIOLOGY notes: Describe how plants take up and move water, mineral ions and sugars through xylem and phloem, and how this links to transpiration.Size — a large plant has a small surface area to volume ratio and cannot rely on diffusion alone.Water a…

Water and ions
Vascular tissues
Root hairs
Absorption of water
Absorption of ions
Photosynthesis

Part 1 of 8Why plants need transport systems

Why plants need transport systems

Size

Size a large plant has a small surface area to volume ratio and cannot rely on diffusion alone.

Water and ions

Water and ions absorbed by the roots and must reach the leaves.

Sugars

Sugars made in the leaves and must reach roots, shoots and fruit.

Vascular tissues

Vascular tissues xylem and phloem, grouped together in vascular bundles throughout the root, stem and leaves.

Part 2 of 8Xylem compared with phloem

Feature	Xylem	Phloem
Transports	Water and mineral ions	Sucrose and amino acids
Direction	One way, upwards from roots to leaves	Both up and down, from sources to sinks
Cells	Dead, hollow, no end walls	Living sieve tubes with companion cells; sieve plates in the end walls
Strengthening	Lignin gives strength and support	No lignin
Process	Transpiration stream	Translocation (needs energy)

Part 3 of 8Water uptake by root hair cells

Root hairs

Root hairs single-celled extensions of root epidermis cells that grow between soil particles.

Absorption of water

Absorption of water by osmosis, because soil water has a higher water potential than the cytoplasm of the cell.

Absorption of ions

Absorption of ions mineral ions such as nitrate and magnesium are taken up by active transport.

Surface area

Surface area the root hair greatly increases the surface area, which speeds up absorption.

Part 4 of 8Pathway and transpiration stream

Water enters the root hair cells from the soil by osmosis.

Water moves across the root cortex cells into the xylem by osmosis.

Water rises through the xylem to the leaves and enters the mesophyll cells.

Water evaporates from the surfaces of mesophyll cells into the air spaces.

Water vapour diffuses out through the open stomata (transpiration).

Part 5 of 8Functions of transpiration

Functions of transpiration

Transport

Transport carries mineral ions up the plant.

Support

Support supplies water to keep cells turgid.

Photosynthesis

Photosynthesis provides water to leaf cells.

Cooling

Cooling evaporation uses heat energy, which cools the leaf.

Part 6 of 8Translocation in the phloem

Translocation

Translocation movement of sucrose and amino acids in phloem from sources (where they are made or released, e.g. leaves) to sinks (where they are used or stored, e.g. roots, growing tips and fruit).

Energy

Energy the process needs energy, supplied by companion cells.

Winter

Winter storage organs are the source, supplying sucrose and amino acids to the rest of the plant.
Spring — roots are the source and growing regions are the sinks.

Summer

Summer leaves are the source and roots are the sink, where sucrose is converted to glucose and stored as starch.

Part 7 of 8Water loss, wilting and support

Water loss

Water loss the waxy cuticle waterproofs the upper surface, most stomata are on the lower surface, and guard cells close stomata when water is scarce.
Xerophytes (desert plants) have extra adaptations such as fleshy water-storing stems, spines instead of leaves and sunken stomata in hair-lined pits.

Turgor

Turgor turgid cells press against their walls and keep non-woody stems upright.
If water loss exceeds uptake the cells become flaccid and the plant wilts;
- wilting is reversible when water is supplied.

Woody plants

Woody plants gain extra support from xylem walls strengthened with lignin.

Part 8 of 8Investigations of plant transport

Dye in a stem

Dye in a stem stand celery or a white carnation in dyed water for a few hours.
Cut a cross sectiononly the xylem is stained, showing it carries water.

Potometer

Potometer measures the rate of water uptake as a bubble moves along a capillary tube.
Compare still and moving air, light and dark, or humid and dry conditions.

Ringing

Ringing removing a ring of bark including the phloem makes sugars accumulate above the ring.

Key terms

Term	Meaning
Xylem	Tissue that transports water and mineral ions up the plant.
Phloem	Tissue that transports sucrose and amino acids.
Translocation	Movement of sucrose and amino acids in phloem.
Transpiration	Loss of water vapour from leaves through stomata.
Source	Part of the plant that makes or releases sugars.
Sink	Part of the plant that uses or stores sugars.
Cohesion	Attraction between water molecules.

Avoid these mistakes

Saying phloem carries water up the plant — that is xylem.

Saying the plant sucks water — it is pulled by evaporation from the leaves.

Saying translocation only goes upward — it goes to wherever sugars are needed.

Writing that xylem cells are living — they are dead and hollow.

Last updated: 13 October 2026