Mass Transport In Plants

Question 1

How does water move into the root hair cells

Answer 1

Root hair cells within the epidermis actively transport ions from the soil into their cytoplasm using energy from ATP via carrier protiens

Lowers water potential in the root hair cells

water moves in the root hair cells via osmosis down a WP gradient

Question 2

give two ways root hair cells are adapted to their function

Answer 2

Thinner cellulose cell walls so shorter diffusion pathway

Hair like extensions to increase their surface area and increase area for channel and carrier proteins

Question 3

Give 4 structure and functions of xylem

Answer 3

End walls break down/no end walls SO continuous column of water

Xylem pits SO allows water to move laterally between xylem vessels/get around blocked xylem vessels

Cell walls are strengthened with lignin SO xylem is waterproof and rigid. withstands tension/enables adhesion of water

Dead cells form hollow tubes w/ no organelles/cytoplasm SO faster water flow and less resistance

Question 4

Explain how water enters xylem from endodermis in root and then transported in the leaves

Answer 4

ROOT TO XYLEM
1. Active transport by endodermis
2. of ions into the xylem
3. Lowers water potential in xylem
4. Water enters xylem via osmosis

XYLEM TO LEAF
1. transpiration causes water loss in leaf
2. creates cohesion/tension
3. adhesion- water molecules bind to xylem
4. creates continuous column of water

Question 5

what causes root pressure

Answer 5

1. Active transport by endodermis;
2. ions/salts into xylem;
3. Lowers water potential (in xylem);
4. (Water enters) by osmosis;

Question 6

what is cohesion and adhesion

Answer 6

Cohesion is hydrogen bonding between molecules

Adhesion is hydrogen molecules bonding w the walls of xylem

Question 7

Name 5 things that affect rate of transpiration

Answer 7

High light intensity = more stomata open

Increases temperature = increases diffusion = increases rate of transpiration

Increases humidity = higher water potential outside the leaf than inside = decrease rate of transpiration

Increase wind speed = increase transpiration = lowers WP at stomatal pores

Higher Stomatal Density = Increase in transpiration

Question 8

Give[ 8] precautions the students should have taken when setting up the potometer to obtain reliable measurements of water uptake by the plant shoot

Answer 8

1. Seal joints / ensure airtight / ensure watertight;
2. Cut shoot under water;
3. Cut shoot at a slant;
4. Dry off leaves;
5. Insert into apparatus under water;
6. Ensure no air bubbles are present;
7. Shut tap;
8. Note where bubble is at start / move bubble to the start position;

Question 9

give 6 adaptations of xerophytes that help them reduce water loss

Answer 9

1. Stomata in pits
2. reduced n.o of stomata
3. rolled leaves
4. thick waxy cuticle