9.1 Transport Systems In Dictyledonous Plants

Question 1

Why do plants need transport systems?

Answer 1

Relying in diffusion alone would fail to meet the demands of the plant
They have small SA:V ratios

Question 2

What is the arrangement of the vascular tissues in roots?

Answer 2

Xylem in middle (+ shaped)
Phloem in circular tubes around outside 
Endodermis surrounding xylem and phloem
Cortex
Epidermis
Exodermis
Root hair

Question 3

What is the arrangement of the vascular tissues in stem?

Answer 3

Parenchyma (packaging and supporting tissue) in centre
Vascular bundles in a ring around the edge
Xylem=inner, phloem = outer
Cortex
Epidermis

Question 4

What is the arrangement of the vascular tissues in leaves?

Answer 4

Vascular bundle in midrib of leaf

Xylem ontop, phloem underneath

Question 5

What are the key features of the xylem?

Answer 5

Dead cells which have been fused to form hollow vessels, which are strengthened by lignin
Pits in the xylem wall which enable water to move out into adjacent xylem vessels or other cells
Xylem fibres add strength, and parenchyma cells store food

Question 6

What are the functions of the xylem?

Answer 6

Transport water and mineral ions up a plant

Provide structural support for the plant

Question 7

What are the key features of the phloem?

Answer 7

Sieve tube elements which are loving cells joined end-to-end, forming a tube with internal pores
Companion cells which carry out all the metabolic functions of the phloem tissue (as the tube lacks nuclei). Material pass into the sieve tube elements via plasmodesmaya

Question 8

What is the function of the phloem?

Answer 8

Transport of solutes (e.g. sugars and amino acids) up and down a plant

Question 9

What is the function of lignin in the xylem walls?

Answer 9

1. Strengthens xylem wall: prevents collapse of xylem
2. Waterproofing: water is under tension and low pressure
3. Improves adhesion of water molecules: reduces lateral loss of water through wall
4. Spiral patterns allow flexibility/strengthens movement: prevents stem breaking
5. Increases capillarity

Question 10

What is the function of the pits?

Answer 10

1. To allow water to move between vessels
2. To bypass blockage
3. Supply water to other tissues cells part of plants