9.5 Xerophytes and Hydrophytes

Question 1

What are the 6 adaptations xerophytes have to living in dry environments?

Answer 1

1. Thick waxy cuticle
2. Sunken stomata
3. Reduced number of stomata
4. Reduced leaves
5. Succulents
6. Root adaptations

Question 2

How is a thick waxy cuticle an adaptation in xerophytes?

Answer 2

Minimizes water loss

Question 3

How are sunken stomata an adaptation in xerophytes?

Answer 3

Stomata located in pits - reduces air movement - produces microclimate of still, moist air which reduces water vapour potential gradient - so less water lost by transpiration

Question 4

How are reduced number of stomata an adaptation in xerophytes?

Answer 4

Less stomata = less water loss by transpiration

Question 5

How are reduced leaves an adaptation in xerophytes?

Answer 5

Reduced SA:V ratio = less SA for transpiration to occur

Question 6

How are hairy leaves an adaptation in xerophytes?

Answer 6

Create a microclimate of still, humid air, reducing water vapour potential gradient, minimising water loss by transpiration

Question 7

How are curled leaves an adaptation in xerophytes?

Answer 7

Confines stomata within a microclimate of still, humid air, reducing diffusion of water vapour from stomata

Question 8

How are succulents an adaptation in xerophytes?

Answer 8

Succulents have specialised parenchyma in stems + roots - when water is enough, it’s stored for times of drought

Question 9

How is leaf loss an adaptation in xerophytes?

Answer 9

If water is unavailable, water loss is prevented by shedding leaves

Question 10

What 2 root adaptations do xerophytes have?

Answer 10

• Tap roots several metres long access underground water

* Mass of shallow roots w/ large SA to absorb any available water from rainfall

Question 11

How are hydrophytes adapted to living in wet environments?

Answer 11

1. Thin/no waxy cuticle
2. Many constantly open stomata
3. Reduced plant structure
4. Wide, flat leaves
5. Small roots
6. Large SA of stems + roots underwater
7. Air sacs
8. Aerenchyma

Question 12

How are thin/no waxy cuticles an adaptation for hydrophytes?

Answer 12

Hydrophytes don’t need to conserve water as water loss by transpiration isn’t an issue

Question 13

How are multiple open stomata an adaptation in hydrophytes?

Answer 13

Maximising stomata = maximises gas exchange

No risk of turgor loss as water is readily available

Question 14

How is a reduced plant structure an adaptation in hydrophytes?

Answer 14

Water supports plant so no need for strong supporting structures

Question 15

How are wide, flat leaves an adaptation in hydrophytes?

Answer 15

Maximises SA for photosynthesis

Question 16

How are small roots an adaptation in hydrophytes?

Answer 16

Water can directly diffuse into stem + leaf tissue, so less need for water uptake by roots

Question 17

How is a large SA of underwater roots and stems an adaptation in hydrophytes?

Answer 17

Maximises SA for photosynthesis + oxygen diffusion

Question 18

How are air sacs an adaptation in hydrophytes?

Answer 18

Enable leaves to float to water surface

Question 19

What are aerenchyma?

Answer 19

Specialised parenchyma - forms in leaves, stems + roots of hydrophytes

Question 20

What is the structure of aerenchyma?

Answer 20

Many large air spaces

Question 21

What is the function of aerenchyma in hydrophytes?

Answer 21

• Make leaves + stems more buoyant

* Form low-resistance internal pathway - allows movement of substances to tissues below water e.g. oxygen