2) Transport Tissues

Question 1

How do xylem vessels form?

Answer 1

• xylem vessels develop –> LIGNIN impregnates cell walls = waterproof

= KILLS cells

End walls + contents cell decay
= long column dead cells with no contents

Question 2

What does lignin do in cell walls?

Answer 2

STRENGTH

+ prevents from COLLAPSING –> keeps open when little water

Question 3

Why does lignin form patterns in cell wall?

E.g. Spiral, annular, reticulate

Answer 3

Prevents from being too rigid –> FLEXIBILITY of stem/branch

Question 4

How + why do BORDERED PITS form

Answer 4

Incomplete lignification –> leaves gaps

• BP in 2 adjacent vessels = aligned
  
  • water leaves one vessel + pass into next vessel
  • water leaves xylem + pass to living parts of plant

Question 5

Xylem tissue contains:

Answer 5

• vessels - carry water + dissolved ions
• fibres - support
• living parenchyma cells = packing tissue to separate + support vessels