Lignin, xylem vessels and sclerenchyma fibres

Overview

Recall questions on secondary thickening, the patterns of lignin deposition, and the structure and function of xylem vessels and sclerenchyma.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   Define secondary thickening in plant cells.

   Model answer

   Secondary thickening is the deposition of additional layers of cellulose and lignin inside the primary cell wall.

2. 2

   What is lignin and what properties does it confer to cell walls during secondary thickening?

   Model answer

   Lignin is a complex polymer that provides rigidity, waterproofing, and resistance to compression.

3. 3

   In what patterns is lignin deposited in the walls of xylem vessels?

   Model answer

   Lignin is deposited in spiral, annular, or reticulate patterns.

4. 4

   Why is the pattern of lignin deposition in xylem vessels advantageous?

   Model answer

   It provides support while allowing some flexibility and lateral water movement.

5. 5

   Describe the key structural features of xylem vessels.

   Model answer

   Xylem vessels are dead, hollow, elongated cells with no end walls, forming continuous tubes.

6. 6

   What are the two main functions of xylem vessels?

   Model answer

   Water transport and providing structural support.

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