Xylem Tissue: Structure and Introduction

Overview

• Focus on the structure of xylem tissue
• Introduction to its function (detailed function discussed later)
• Common student issue: difficulty visualizing xylem tissue

Xylem as Vascular Tissue

• Vascular Tissues: Involved in the transport of substances
• Xylem: Specifically transports water and minerals

Location of Xylem

• Found in roots, stem, and leaves
• Highlighted in blue in cross-sections

Composition of Xylem Tissue

• Made of tube-like structures
• Contains parenchyma tissues (not the focus)
• Xylem Vessels: Key structures, comprised of dead cells

Formation of Xylem Vessels

• Young plant cells in the stem contain live cells
• Cells are connected by plasmodesmata
• Lignification Process:
  • Lignin forms around cells, making them rigid and waterproof
  • Cells die due to lack of minerals and nutrients
  • Dead cells form hollow, rigid tube-like structures (xylem vessels)

Xylem Vessel Elements

• Xylem Vessel Element: The basic unit of xylem vessels
• Surrounded by lignin
• Lacks end walls, allowing continuous space
• Pits: Unlignified spaces where plasmodesmata were

Characteristics of Xylem Vessels

• Longitudinal Section: Shows continuous appearance from the side
• Transverse Section (TS): Hexagonal, thick-walled structures
• 3D Structure: Hollow inside, made of dead cells, pits present

Key Points

• Xylem vessels are made of dead cells (xylem vessel elements)
• Interior is hollow
• Walls are lignified, providing rigidity and waterproofing
• Pits interspersed within vessels

Conclusion

• Understanding the structure is essential before discussing function
• Function in transporting water and minerals will be covered in detail later