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4.2.2Unit 4: Energy, Environment, Microbiology and Immunity

Water and Inorganic Ions in Plants — IAL Edexcel Linear Revision Notes & Topical Questions

5 min read 4 parts Lesson 15 of 28 Unit quiz

📚 IAL Edexcel Linear Hub / Topical Revision
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Part 1 of 4Uptake and Transport

4.2.2 Water and Inorganic Ions in Plants

Plants need water and mineral ions to carry out their functions efficiently.

1
Water and inorganic ions are absorbed from the soil through the root hairs of the root.
2
They then travel up the stem in the xylem vessels to reach the leaves and other tissues.
3
If any one of them is in short supply, the plant shows deficiency symptoms such as yellow leaves or stunted growth.

Part 2 of 4Role of Water

Water has several jobs in a plant besides being a raw material.

Photosynthesis
  • Water is one of the reactants required for photosynthesis in the leaf.
Transport medium
  • It dissolves mineral ions and carries them from the roots to the rest of the plant.
Turgidity
  • Water in the cell vacuoles creates pressure that keeps cells firm and the plant upright.
Temperature control
  • Water helps regulate temperature so that enzymes can work at close to their optimum rate.

Part 3 of 4Inorganic Ions

Different ions are needed for different molecules.

Inorganic Ions
Magnesium ions
  • Needed to make chlorophyll, the green pigment essential for photosynthesis; lack of it causes yellowing.
Nitrate ions
  • Provide the nitrogen needed to make DNA, proteins including enzymes, and chlorophyll, and so are vital for growth, fruit and seeds.
Calcium ions
  • Form an important part of cell walls, and are needed for proper growth of the plant.
Deficiency link
  • Yellow leaves and stunted growth are symptoms that can point to a lack of a particular ion.

Part 4 of 4Exam Checklist & Tips

4.2.2 – Key Points for the Exam

  • Inorganic ion A charged mineral particle, such as Mg²⁺, NO₃⁻ or Ca²⁺, absorbed by plants.
  • Root hair A cell extension that increases the surface area of the root for absorption.
  • Turgid Firm because the vacuole is full of water and pressing on the cell wall.
  • Deficiency A shortage of a nutrient that causes visible symptoms.

Common Mistakes

  • Saying nitrate is needed to make carbohydrates; it supplies nitrogen for proteins, DNA and chlorophyll.
  • Stating that magnesium is part of cell walls, when this is the role of calcium.
  • Forgetting that water is a reactant in photosynthesis as well as a transport medium.
  • Describing ions as travelling in the phloem from the soil, when they move up the stem in the xylem.

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