Home / iGCSE / Coordinated Sciences / CIE iGCSE Co-ordinated Sciences-B8.1 Xylem and phloem- Study Notes

CIE iGCSE Co-ordinated Sciences-B8.1 Xylem and phloem- Study Notes- New Syllabus

CIE iGCSE Co-ordinated Sciences-B8.1 Xylem and phloem – Study Notes

CIE iGCSE Co-ordinated Sciences-B8.1 Xylem and phloem – Study Notes -CIE iGCSE Co-ordinated Sciences – per latest Syllabus.

Key Concepts:

Core

  • State the functions of xylem and phloem:
    (a) xylem – transport of water and mineral ions, and support
    (b) phloem – transport of sucrose and amino acids
  • Identify in diagrams and images the position of xylem and phloem as seen in sections of roots, stems and leaves of non-woody dicotyledonous plants

CIE iGCSE Co-Ordinated Sciences-Concise Summary Notes- All Topics

Transport in Plants: Xylem and Phloem

📌 Vascular bundles

  • Found in roots, stems, leaf stalks, and leaf veins.
  • Connect throughout the plant to form a transport system.
  • Made up of xylem and phloem, surrounded by supporting cells.

1. Xylem

  • Functions:
    • Transport of water from roots → stem → leaves.
    • Transport of mineral ions (dissolved salts) absorbed from the soil.
    • Support: Thickened walls of xylem vessels provide mechanical strength to the plant.
  • Key features:
    • Made of elongated vessels.
    • Lignified walls help in support and prevent collapse under tension.
  • Pathway: Water enters root hairs → passes through root cortex → enters xylem → moves up to stem and leaves.
  • Example: Water moves by transpiration pull and cohesion-tension.

2. Phloem

  • Functions:
    • Transport of sucrose (from leaves, where photosynthesis occurs) to other parts of the plant.
    • Transport of amino acids (for growth and protein synthesis).
  • Key features: Made of sieve tube elements with companion cells.
  • Flow: Can be upwards or downwards (source → sink).
  • Pathway: Sugars produced in leaves → transported via phloem → delivered to roots, stems, growing regions, or storage organs.
  • Example: Food stored in roots (like carrots or turnips) comes from leaf phloem transport.

🔹 Quick Comparison

TissueMain FunctionDirectionStructure Feature
XylemWater & mineral transport + supportRoots → leavesLignified vessels
PhloemSugar & amino acid transportUp & downSieve tubes + companion cells

💡 Memory Tip:
Xylem → X = eXits from roots (upwards), carries water/minerals.
Phloem → Phood = carries food (sugars/amino acids) to all parts.

Xylem & Phloem in Non-Woody Dicot Plants

In non-woody dicotyledons, xylem and phloem are part of vascular bundles, which are arranged differently in roots, stems, and leaves.

1. Root (Transverse Section)

  • Xylem: Central star-shaped or cross-shaped in the middle.
  • Phloem: Found in between the arms of the xylem star.
  • Vascular bundle: Xylem + Phloem together.
  • Function: Xylem carries water/minerals upward; phloem carries food downward.

2. Stem (Transverse Section)

  • Vascular bundles: Arranged in a ring around the central pith.
  • Xylem: Faces toward the center of the stem.
  • Phloem: Faces toward the outside of the stem.
  • Cambium: Lies between xylem and phloem for secondary growth.
  • Position: Outside → Phloem → Cambium → Xylem → Pith ← Center

3. Leaf (Transverse Section through Vein / Midrib)

  • Xylem: Located on the upper side of the vascular bundle (closer to the upper epidermis).
  • Phloem: Located on the lower side (closer to the lower epidermis).
  • Vein structure: Ensures water reaches mesophyll for photosynthesis; sugar moves to phloem.

🔹 Quick Tip:
Root: Xylem in center, phloem between xylem arms.
Stem: Vascular bundles in a ring; xylem inner, phloem outer.
Leaf: Xylem on top, phloem on bottom.

Scroll to Top