Edexcel iGCSE Biology-3.3 & 3.4 Role of the Xylem & Phloem- Study Notes- New Syllabus
Edexcel iGCSE Biology-3.3 & 3.4 Role of the Xylem & Phloem- Study Notes- New syllabus
Edexcel iGCSE Biology-3.3 & 3.4 Role of the Xylem & Phloem- Study Notes -Edexcel iGCSE Biology – per latest Syllabus.
Key Concepts:
3.3 describe the role of phloem in transporting sucrose and amino acids between the leaves and other parts of the plant
3.4 describe the role of xylem in transporting water and mineral ions from the roots to other parts of the plant
Transport in Flowering Plants: Phloem & Xylem
📝 Introduction
Plants have two main transport tissues:
Phloem → transports food (sucrose & amino acids).
Xylem → transports water & mineral ions.
Together, they form the vascular bundles that keep plants alive and growing.
🍬 Phloem – Transport of Sucrose & Amino Acids
- Structure: Made of living cells arranged in tubes; have sieve plates and companion cells.
- Direction: Transport is bidirectional (up and down).
- What is carried:
• Sucrose → main form of sugar for transport.
• Amino acids → for protein synthesis. - Role:
Moves food substances from leaves (where made in photosynthesis) to other parts:
• Growing tissues (buds, roots, flowers, fruits).
• Storage organs (like roots and seeds).
This movement is called translocation.
💧 Xylem – Transport of Water & Mineral Ions
- Structure: Made of dead, hollow, lignified cells → strong, waterproof tubes.
- Direction: Transport is only upwards.
- What is carried:
• Water → used in photosynthesis, maintaining turgidity, cooling by transpiration.
• Mineral ions →
– Nitrates → amino acids/proteins.
– Magnesium → chlorophyll.
– Calcium → cell walls. - Role:
Carries water + minerals from roots → stems → leaves.
Also provides mechanical support to plant (because of lignin).
📊 Comparison Table
| Feature | Phloem | Xylem |
|---|---|---|
| Substances carried | Sucrose + amino acids (food) | Water + mineral ions |
| Cell type | Living cells with sieve plates | Dead cells with lignin |
| Direction | Both up & down (bidirectional) | Only upwards |
| Energy use | Active (needs energy for loading sucrose) | Passive (no energy needed) |
| Extra role | Translocation of food | Mechanical support |
⚡ Quick Recap
Phloem = food (sugars + amino acids), bidirectional, living cells.
Xylem = water + minerals, upwards only, dead lignified cells.
Both work together to keep plants alive, growing, and strong.