October 2026 - Plant Biology Study Guide

Core ideas to know

Learn the relationships, not a string of isolated definitions. These are the facts that let you reason through unfamiliar wording.

• Plant cells have cellulose cell walls, chloroplasts and a large central vacuole in addition to structures shared with animal cells.
• Xylem moves water and dissolved minerals mainly from roots upward and adds structural support.
• Phloem transports sugars from sources, such as mature leaves, to sinks that use or store them.
• Stomata are adjustable epidermal pores; guard cells regulate carbon dioxide entry and water-vapour loss.
• Roots absorb water and minerals, stems support and transport, and leaves provide a broad surface for photosynthesis and exchange.

A reliable way to answer

Use the same short process every time so the wording of the question does not decide your method for you.

1. Identify the material being followed: water, mineral ion, sugar, gas or growth signal.
2. Locate its entry or production site and its destination.
3. Choose the responsible tissue or structure: xylem, phloem, stomata, root hair or meristem.
4. Predict how changing light, water availability or pore opening affects both photosynthesis and water balance.

Distinctions that earn marks

Terms to know

Transpiration

Loss of water vapour from a plant, chiefly through stomata.

Meristem

Region of actively dividing plant cells responsible for growth.

Tropism

Directional growth response to a stimulus such as light or gravity.

Key points

• Xylem carries water and minerals; phloem carries sugars.
• Opening stomata supports carbon dioxide uptake but also increases water loss.
• Structure and function differ across roots, stems and leaves but depend on continuous transport.