Module 3: Plant adaptations to water availability

Question 1

What are xerophytes?

Answer 1

plants living in dry habitats who have evolved a wide range of adaptations that enable them to live and reproduce in places where water availability is low

Question 2

XEROPHYTES:

Explain how a thick waxy cuticle and sunken stomata are strategies for conserving water

Answer 2

waxy cuticle-having an extra thick cuticle helps to minimise water loss by transpiration

sunken stomata-stomata located in pits which reduces air movement creating a microclimate of still humid air that reduces water vapour potential gradient and reduces transpiration

Question 3

XEROPHYTES:

Explain how having a reduced number of stomata/leaves helps to conserve water

Answer 3

stomata-reduces water loss by transpiration (this does also reduce their gas exchange capabilities)

leaves-reducing leaf area reduces area for water to be lost by transpiration

Question 4

XEROPHYTES:

Explain how having hairy or curled leaves helps to conserve water

Answer 4

hairy leaves-this creates a microclimate of still humid air which reduces water vapour potential gradient so minimises loss of water by transpiration from surface of leaf

curled leaves-confines all stomata within a microenvironment of still humid air to reduce diffusion of water vapour from stomata

Question 5

What do succulent plants do in terms of water storage?

Answer 5

they store water in specialised parenchyma tissue in their stems and roots

-water is stored when its in plentiful supply and is then used in times of drought

Question 6

XEROPHYTES:

Explain how leaf loss helps plants to conserve water

Answer 6

when water is not available , plants simply drop their leaves

Question 7

XEROPHYTES: ROOT ADAPTATIONS

Give 2 root adaptations that help plants to conserve water

Answer 7

long tap roots-grow deep into the ground and penetrate several metres so they can access water thats far from the surface

mass of widespread shallow roots- have a large surface area so are able to absorb any available water before it evaporates

Question 8

What are hydrophytes?

What is a main problem for all hydrophytes , why?

Answer 8

plants that live in water

water logging-air spaces of the plant need to be filled with air not water

Question 9

Why is it important that surface water plants leaves float?

Answer 9

so they are near the surface of the water to get the light needed for photosynthesis

Question 10

Give the first 4 adaptations of hydrophytes and explain them

Answer 10

thin/no waxy cuticle-they do not need to conserve water

many always-open stomata on upper surfaces-this maximises gas exchange , they do not need to close as there is no risk of turgor loss

reduced structure to plant-water supports leaves and flowers so no need for strong supporting structures

wide/flat leaves-spread across surface of water to capture as much light as possible

Question 11

Give the other 4 adaptations of hydrophytes and explain them

Answer 11

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

large SA of stems/roots underwater-maximises area for photosynthesis and for oxygen to diffuse into submerged plants

air sacs-enables leaves/flowers to float to surface of water

aerenchyma-specialised parenchyma tissue forms in leaves , stems and roots
-has many large air spaces which makes leaves and stems more buoyant and helps formation of a low resistance internal pathway for movement of substances such as oxygen to tissues below water