Xylem and Phloem - Structure of Plants

Overview

• Plants are adapted to efficiently collect raw materials for photosynthesis.
• Transport of these materials is crucial and is facilitated by specialized structures.

Key Plant Structures

Xylem

• Function: Transports water and mineral salts from roots to other parts of the plant.
• Structure:
  • Narrow, hollow, dead tubes
  • Contains lignin for structural support
  • Impermeable to water
  • Formed of elongated dead cells arranged end-to-end to create continuous vessels

Phloem

• Function: Transports the products of photosynthesis, including sucrose and amino acids, throughout the plant.
• Structure:
  • Consists of living cells arranged end-to-end
  • Contains cytoplasm, allowing for the movement of substances through sieve plates
  • Facilitates translocation (movement of substances) from sources (production areas) to sinks (areas of use or storage)

Transport Processes

Transpiration Stream

• Associated with Xylem
• Involves the upward movement of water and minerals from roots to leaves

Translocation

• Associated with Phloem
• Involves the movement of sucrose and amino acids, can go in both directions:
  • From roots to leaves in spring
  • From leaves to roots in summer
• Enables transport of chemicals like pesticides through the plant

Importance

• Efficient transport systems are vital for plant health and growth.
• Understanding xylem and phloem functions is essential for grasping plant biology and ecosystems.

Visual Aid

• Image depicting a cross-section of a plant root showing xylem and phloem positioned centrally in the root.

These notes provide an overview of the functions and structures of xylem and phloem in plants, crucial for the GCSE Biology curriculum as per WJEC standards.