9.5 - Xerophytes & Hydrophytes

Question 1

What are mesophytes ?

Answer 1

Able to take up sufficient water to replace transpiration

Question 2

What are hydrophytes ?

Answer 2

Live either partially or completely submerged in water - problems with O2 uptake

Question 3

What are xerophytes ?

Answer 3

• Live in areas where water lost via transpiration is greater than taken up by roots
• plants with structural and physiological adaptations that enable them to survive in hot,dry conditions

Question 4

What happens when water is abundant in xerophytes ?

Answer 4

Their rate of transpiration is about the same as other plants

Question 5

What are some adaptations of xerophytes ?

Answer 5

• smaller leaves which reduce the surface area for water loss
• both densely packed mesophyll and thick waxy cubicles prevent water loss via evaporation
• xerophytes respond to low water availability by closing the stomata to prevent water loss
• contain hairs and pits which serve as a means of trapping moist air thus reducing the water vapour potential
• roll the leave to reduce the exposure of lower epidermis to the atmosphere thus trapping air

Question 6

What is the effect of the adaptation of the stomata being closed during light and open In the dark ?

Answer 6

• CAM metabolism to minimise photorespiration
• CO2 fixed at night
• day time water loss is minimised

Question 7

What is the effect of the adaptation of when hinge cells shrink when flaccid ?

Answer 7

• Causes leaves to roll exposing the think waterproof cuticle to the air
• creates a humid space in the middle of the rolled leaf

Question 8

What do spines do ?

Answer 8

protect the plant from small mammals which otherwise remove water from the plant

Question 9

What are some adaptations of marram grass ?

Answer 9

• stomata In pits to trap air with moisture close to the openings
• outer epidermis , small thick walled cells
• hinge cells lose their turgidity and collapse in dry conditions causing the leaf to roll up
• hair trap water vapour reducing the water potential gradient between the leaf and the air

Question 10

What are hydrophytes ?

Answer 10

They’re plants that actually live in water such as water Lillies

Question 11

What are some adaptations of hydrophytes ?

Answer 11

• very thin or absent waxy cuticle as they don’t need to conserve water
• many constantly open stomata are found on the upper surfaces of leaves to maximise gas exchange
• wide flat leaves give a large surface area for light absorption
• air sacs to enable leaves to stay afloat
• many large air spaces to make leaves and stems more buoyant
• reduced root systems - they can also extract nutrients from the surrounding water through their tissues