OrganisationDefinitions

Key Definitions

Part of Plant Transport Systems · GCSE GCSE Biology revision

This definitions covers Key Definitions within Plant Transport Systems for GCSE Biology. Xylem and phloem structure, water and sugar transport, root hair adaptations, translocation, and practical investigations It is section 11 of 18 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.

Topic position

Section 11 of 18

Practice

25 questions

Recall

24 flashcards

Key Definitions

Xylem: A plant tissue made of dead, hollow, lignified cells that transports water and dissolved mineral salts from the roots upwards to the leaves. Flow is one-directional (upward only).

Phloem: A plant tissue made of living cells (sieve tube elements and companion cells) that transports dissolved sugars and amino acids from leaves (sources) to all other parts of the plant (sinks). Flow can be in both directions.

Translocation: The movement of dissolved organic substances (mainly sucrose) through phloem from a source (e.g. leaf) to a sink (e.g. root or growing tip).

Transpiration: The evaporation of water from the surfaces of plant cells, followed by diffusion of water vapour out through the stomata.

Lignin: A tough, waterproof polymer deposited in xylem cell walls. It strengthens the vessel and prevents it collapsing under the negative pressure created by transpiration.

Sieve tube element: A living phloem cell with a perforated end wall (sieve plate) allowing dissolved substances to flow through. Lacks a nucleus in maturity.

Companion cell: A nucleated cell adjacent to a sieve tube element. It provides ATP for the active loading and unloading of sugars into the phloem.

Root hair cell: A specialised epidermal cell with a long projection that greatly increases the surface area of the root for absorption of water (by osmosis) and mineral ions (by active transport).

Keep building this topic

Read this section alongside the surrounding pages in Plant Transport Systems. That gives you the full topic sequence instead of a single isolated revision point.

How It Works: The Transpiration-Cohesion-Tension Theory Common Misconceptions The Plant Highway System Key Facts: Plant Transport Systems

Practice Questions for Plant Transport Systems

Which substance does xylem tissue transport?

A. Sugars and amino acids
B. Oxygen and carbon dioxide
C. Water and dissolved mineral ions
D. Proteins and lipids

1 markfoundation

Explain how root hair cells are adapted for their function.

3 marksstandard

Quick Recall Flashcards

What is xylem tissue?

A plant tissue that transports water and mineral salts from the roots to the leaves.

What is phloem tissue?

A plant tissue that transports sugars and amino acids from the leaves to other parts of the plant.

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How It Works: The Transpiration-Cohesion-Tension Theory

Common Misconceptions