Xylem and Phloem - Transport in Plants

Introduction to Plant Transport Systems

• Importance of Transport:
  • Vital substances like water, minerals, glucose, and oxygen are necessary for cellular function.
  • Plants absorb water and minerals through roots from the soil.
  • Glucose is produced in leaves via photosynthesis.
  • Vascular tissue facilitates movement of these substances within plants.
• Main Vascular Tissues: Xylem and Phloem.

Xylem

• Function: Transports water and minerals from roots to other plant parts.
• Components:
  • Tracheids: Conducting cells with pitted walls; do not allow continuous flow.
  • Vessels: Long, hollow tubes enabling continuous flow from roots to leaves.
  • Fiber Cells: Provide structural support.
  • Parenchyma: Living cells that aid in food storage.
• Strengthening:
  • Lignin strengthens xylem cells with patterns like rings, spirals, reticulate, or pitted.

Phloem

• Function: Transports manufactured food (e.g., sucrose, amino acids) from leaves to other plant parts - a process called translocation.
• Components:
  • Sieve Tubes: Elongated cells with sieve-like walls facilitating food movement.
  • Companion Cells: Support sieve tubes with abundant cytoplasm and nucleus.
  • Fiber Cells: Dead cells providing structural support.
  • Parenchyma: Stores food and other substances.

Arrangement of Vascular Tissue

• Roots (Herbaceous Dicot Plants):
  • Xylem forms an x-like shape.
  • Phloem surrounds the xylem.
• Stem:
  • Xylem and phloem are in circular clusters near the stem edge.
• Leaf:
  • Xylem is positioned above the phloem within the vascular bundles.

Summary

• Xylem and phloem are essential for the transport of water, minerals, and food within plants.
• Their structural and functional differences enable efficient distribution of resources throughout the plant.