9.5 Plant Adaptations To Water Availability Flashcards
What is a xerophyte?
A plant that has adaptations to survive in an environment with little liquid water
What is a hydrophyte?
A plant that has been adapted to live in an aqueous environment
What are the adaptations that MOST plants have to conserve water?
-Waxy cuticle to reduce transpiration
-Closeable stomata
What are the adaptations that xerophytes have to conserve water?
-Thick waxy cuticle
-Sunken stomata
-Reduced numbers of stomata
-Reduced leaves
-Curled leaves
-Being succulent
-Leaf loss
-Root adaptations
-Avoiding the problem
How does having a thick waxy cuticle help conserve water?
Minimises water loss by transpiration through the cuticle
How does having sunken stomata help conserve water?
The stomata are now in pits, which reduce air movement and create a microclimate of still, moist air, reducing the water potential gradient and therefore transpiration
How does having reduced numbers of stomata help conserve water?
Because it reduces gas exchange abilities, and therefore transpiration
How does having a reduced number of leaves help conserve water?
Reduces the leaf surface area, so therefore less leaves for photosynthesis and transpiration
How does having hairy leaves help conserve water?
Creates a microclimate of still, humid air. This reduces the water potential gradient and therefore the rate of transpiration
How does having curled leaves help conserve water?
Confines all of the stomata within a microenvironment of still, humid air to reduce diffusion of water vapour from the stomata
How does a plant being succulent help conserve water?
Succulent plants store water in specialised parenchyma tissue in their stems and roots
How does leaf loss help conserve water?
Less leaves = less gas exchange
List adaptations of roots that help the plant to conserve water.
Being long, or having a mass of widespread and shallow roots
How do plants that need to conserve water avoid the problem of water loss?
-Many lose leaves and become dormant
-Some die completely and leave seeds to germinate
-Some survive as storage organs
What is the key problem for HYDROPHYTES? Why?
Water logging, because the air spaces of the plant need to be filled with air, not water, to survive
List the adaptations of hydrophytes that help them to survive.
-Very thin or no waxy cuticle
-Many always-open stomata on the upper surfaces
-Reduced structure to the plant
-Wide, flat leaves
-Small roots
-Large surface areas of stems and roots
-Air sacs
-Aerenchyma
Why do hydrophytes have a thin/no waxy cuticle?
Because they do not need to conserve water
Why do hydrophytes have always-open stomata?
Maximises gaseous exchange
Why do hydrophytes have a reduced structure?
Because the water supports the leaves and flowers, so there is no need for supporting structures
Why do hydrophytes have wide, flat leaves?
To capture as much light as possible
Why do hydrophytes have air sacs?
To enable leaves and flowers to float to the surface of the water
What are aerenchyma?
Sepcialised parenchyma tissue forming in the stems, roots and leaves of hydrophytes
What is significant about aerenchyma?
They have many large air sacs
What are the functions of the aerenchyma?
-They make the leaves and stem more buoyant
-They force a low-resistance internal pathway for the movement of oxygen to tissues below the water
