Module 3: Transport of water and features of the leaf

Question 1

What are the 2 routes in which water can travel to the xylem through?
State how they differ

Answer 1

symplast route-between the cytoplasms of cells through plasmodesmata
apoplast route-between cells via their cell walls

Question 2

Name the 3 main functions of the casparian strip

Answer 2

-prevents harmful substances entering the xylem
-prevents leakage of water from xylem vessels
-aids development of root pressure

Question 3

How does the casparian strip prevent harmful substances entering the xylem?

2 points

Answer 3

it forces water moving through the apoplast pathway to diffuse into the cytoplasm of cells and enter the symplast pathway

-in the symplast pathway water passes over membranes which won’t let harmful substances cross due to their selective permeability

Question 4

Describe the first two steps of the transport of water from roots to xylem

Answer 4

1)mineral ions from the soil enter the root hairs by active transport which lowers the water potential in the root hairs
2)creates a water potential gradient between inside and outside the root hair so water moves into root by osmosis down its water potential gradient

Question 5

Describe the next two steps of the transport of water from roots to xylem

Answer 5

3)water continues to move through the root , the epidermis and cortex via either the symplast or apoplast route
4)water flowing through the apoplast route will reach the endodermis and be stopped by the casparian strip

Question 6

Describe the final 2 steps of the transport of water from the roots to the xylem

Answer 6

5)water in the apoplast route diffuses into the cytoplasm of endodermis cells and enters the symplast route
6)water moves into the xylem by osmosis as the water potential inside the xylem is smaller than in the endodermis

Question 7

How is the waxy cuticle involved in photosynthesis?
How is the upper epidermis involved in photosynthesis?

Answer 7

its waterproof to prevent water evaporating out of cells
its transparent to allow light required for photosynthesis to pass through

Question 8

How is the palisade mesophyll involved in photosynthesis?
How is the spongy mesophyll involved in photosynthesis?

Answer 8

contains lots of chloroplasts that are required for photosynthesis
has many air gaps/pockets for gas exchange and diffusion of oxygen and carbon dioxde

Question 9

How is the lower epidermis involved in photosynthesis?

Answer 9

contains stomata and guard cells that control gas exchange

Question 10

How are the xylem and phloem involved in photosynthesis?

Answer 10

xylem-made of dead cells to allow an uninterrupted flow of water flow to the leaves
phloem-transports amino acids and sucrose(assimilates) from the leaf to other parts of the plant where they are required