3.1.3 Transport in plants

Question 1

What is the basic reason for the need for transport systems?

Answer 1

To move substances between leaves, stems and roots

Question 2

What is the general pressure in the phloem?

Answer 2

2000 kPa

Question 3

What sort of pressure would you compare the phloem to?

Answer 3

• The systolic blood in main arteries (humans) - 16 kPa
• Steam turbines in a power station - 4000 kPa

Question 4

What is the need for transport systems in multicellular plants?

Answer 4

• Metabolic demands/rate
• Size
• SA:V

Question 5

What is meant by metabolic demands/rate?

Answer 5

• Transport of oxygen and glucose to internal and underground parts of the plant (do not photosynthesise)
• Waste products of cell etalobism are removed
• Tranport of hormones to areas of effect
• Tranport of absorbed mineral ions for production of proteins required e.g. enzymes, structure of the cell

Question 6

What is meant by ‘size’?

Answer 6

• Plants grow throughout their lives - many perennial plants are large and some of them are enormous
• Effective transport system is needed to move substances both up ad down from the tip of the roots to the topmost leaves and stems

Perennial plants: plants that live a long time and reproduce year after

Question 7

What is meant by SA:V?

Answer 7

• Leaves are adapted to have a relatively large SA:V ratio for gas exchange
  *Multicellular plants are complex - when stems, trunks are taken into account, the SA:V is relatively small
• This means they cannot rely on diffusion alone to supply the cell with everything they need