CIE iGCSE Co-ordinated Sciences-B8.2 Water uptake - Study Notes- New Syllabus
CIE iGCSE Co-ordinated Sciences-B8.2 Water uptake – Study Notes
CIE iGCSE Co-ordinated Sciences-B8.2 Water uptake – Study Notes -CIE iGCSE Co-ordinated Sciences – per latest Syllabus.
Key Concepts:
Core
- Identify in diagrams and images root hair cells and state their functions
- State that the large surface area of root hairs increases the uptake of water and mineral ions
- Outline the pathway taken by water through root, stem and leaf as: root hair cells, root cortex cells, xylem, mesophyll cells
CIE iGCSE Co-Ordinated Sciences-Concise Summary Notes- All Topics
Water Uptake – Root Hair Cells
🌱 Root Hair Cells
- Located just behind the root tip.
Appear as long, thin, tubular outgrowths of epidermal cells.- Seen as a fuzzy/white layer on roots of seedlings.
- In diagrams → drawn as finger-like projections from epidermis into the soil.
🧩 Functions of Root Hair Cells
- Increase Surface Area: Thin, elongated shape gives a very large area for absorption.
- Absorption of Water: Water moves in by osmosis (root cell sap is more concentrated than soil water).
- Absorption of Mineral Ions: Taken up by active transport (energy needed).
- Anchorage: Root hairs attach closely to soil particles, holding the plant firmly.
🚰 Pathway of Water Uptake
- Water entry: Water films around soil particles enter root hair cells by osmosis.
- Movement across root: Water passes through the root cortex → cell to cell (cytoplasm & vacuoles) or along cell walls (apoplast pathway).
- Into xylem: Water then enters the xylem vessels in the root.
- Up the plant: Xylem transports water upwards, driven by transpiration pull (tension).
- To leaves: Water finally reaches leaf mesophyll cells → used for photosynthesis or lost via transpiration.
📌 Key Adaptations of Root Hair Cells
- Thin cell wall → faster osmosis.
- Large surface area → more absorption.
- Close contact with soil water → efficient uptake.
- Concentrated sap → maintains water potential gradient.
📝 Quick Recap
Root hairs = increase surface area + absorb water & minerals.
Water uptake → soil → root hair cell → cortex → xylem → leaves.
Most water travels through/between cell walls; some through vacuoles.
Driving force = transpiration pull.
Root Hairs – Large Surface Area & Uptake
📖 Key Point
Root hairs have a large surface area, which:
- Increases the rate of water absorption (by osmosis).
- Increases the uptake of mineral ions (by active transport).
✨ Why Large Surface Area Helps
- Many tiny, finger-like root hairs grow from each root → huge total surface area.
- More surface area = more contact with soil particles and the thin film of water around them.
- This allows the plant to absorb maximum water and essential minerals quickly → supports growth and photosynthesis.
📝 Quick Recap
Root hairs = thin + long + numerous.
Their large surface area ensures efficient uptake of:
💧 Water (osmosis)
⚡ Minerals (active transport)
Pathway of Water in Plants (Root → Stem → Leaf)
📖 Introduction
Water absorbed from the soil must travel through different plant tissues to finally reach the mesophyll cells in the leaf (where photosynthesis and transpiration happen).
🚶 Step-by-Step Pathway
1. Root Hair Cells
Root hairs stick closely to soil particles.
Water enters root hair cells by osmosis (since soil water has higher water potential than cell sap).
This gives the first entry point for water into the plant.
2. Root Cortex Cells
From root hairs, water passes across the cortex (parenchyma cells) either:
– Through cell walls (apoplast pathway)
– Through cytoplasm & vacuoles (symplast pathway)
Movement continues by osmosis towards the central xylem.
3. Xylem Vessels (Stem & Root)
Water enters xylem vessels in the root.
Xylem acts like a continuous tube running up through the stem into the leaves.
Water is pulled upwards by transpiration pull + cohesion & adhesion of water molecules.
4. Mesophyll Cells (Leaf)
From the xylem in leaf veins, water diffuses into surrounding mesophyll cells.
Some water is used for photosynthesis.
Most water evaporates into the air spaces inside the leaf → then diffuses out through stomata (transpiration).
📊 Summary Table
| Step | Structure | Process | Key Point |
| 1 | Root hair cells | Osmosis | Entry from soil → root hair |
| 2 | Root cortex cells | Osmosis (apoplast & symplast pathways) | Water moves inward to xylem |
| 3 | Xylem (root + stem + leaf veins) | Mass flow (transpiration pull) | Long-distance transport |
| 4 | Mesophyll cells (leaf) | Osmosis & diffusion | Water used in photosynthesis or lost in transpiration |
📝 Quick Recap
Pathway = Root hair → Cortex → Xylem → Mesophyll
Driven by: Osmosis → Xylem transport → Transpiration pull
Final destination = mesophyll cells for photosynthesis & transpiration.