3.1.3 Transport In Plants

Question 1

Why do multicellular plants need transport systems

Answer 1

Metabolic demands: internal/undergound parts of plant don’t photosynthesise, need exchange of substances, hormones and mineral ions need transporting
Size: need effective transport systems to move substances up and down from roots to leaves
SA: small SA:V, can’t rely on diffusion alone to supply cells

Question 2

Function of xylem

Answer 2

Transport of water and mineral ions
Support

Question 3

Structure of xylem

Answer 3

Non-living tissue
Long, hollow structures made by several columns of cell fusing end to end
Lignified walls to provide mechanical strength (rings, spirals or bordered pits)

Question 4

Function of phloem

Answer 4

Transports food in form of organic solutes

Question 5

Structure of phloem

Answer 5

Living tissue
Can be transported up/ down
Sieve tubes elements are cells joined end to end to form long, hollow structure
Not lignified
Between cells, sieve plates which let contents flow through
No nucleus
Companion cells, linked to sieve tube elements by plasmodesmata, have organelles

Question 6

How are root hairs adapted to be exchange surfaces

Answer 6

Large SA:V due to hairs
Has thin surface layer, diffusion and osmosis can take place quickly
Concentration of solutes in cytoplasm maintains water potential gradient between soil and cell

Question 7

What is the symplast

Answer 7

Cytoplasm of cells connected through plasmodesmata