9.5 Plant Adaptations to Water Availibility

Question 1

Define xerophyte

Answer 1

Plants in dry habitats that have adaptations to help retain water

Question 2

List and explain the way xerophytes conserve water

Answer 2

Thick waxy cuticle

Sunken stomata - reduces air movement and creates climate of still, humid air that reduces water vapour potential gradient ( and reduces transpiration )

Reduced number of stomata

Reduced leaves - reduces leaf area and therefore water loss

Hairy leaves - create climate of still humid air.

Curled leaves - creates climate of still humid air

Succulents - store water in specialised parenchyma tissue in stems and roots.

Leaf loss

Root adaptations - long tap roots can penetrate several metres. Widespread, shallow roots can absorb rainfall before it evaporates.

Question 3

You need to know adaptations for specific plants

Answer 3

look at the notes you made

Question 4

Define hydrophyte

Answer 4

Plants that exist in aquatic habitats

Question 5

Give examples of xerophytes

Answer 5

Cacti
Marram grass
Conifers

Question 6

Give examples of hydrophytes

Answer 6

Water lilies 
Water cress
Duckweed
Bulrushes 
Yellow iris

Question 7

List and explain some hydrophytic adaptations

Answer 7

Thin or no waxy cuticle

Many always - open stomata on the upper surfaces - maximises gaseous exchange

Reduced structure to the plant - water supports the leaves and flowers

Wide, flat leaves - capture as much light as possible

Small roots - water can diffuse directly into stem and leaf tissue so less need for uptake by roots

Large surface area of stem and roots under water - maximises area for photosynthesis and o2 to diffuse in

Air sacs - enables leaves and flowers to float

Aerenchyma - specialised parenchyma tissue that has many large air spaces. Makes leaves and stems more buoyant. Forms low - resistance internal pathway for movement of substances like o2 to tissues.