Component 3.2 - Plants Adapt To Water Availability Flashcards
What is a mesosphyte?
A plant living in conditions of adequate water supplies
What happens if a mesophyte loses too much water?
It wilts and it’s leaves droop. The stomata close and the leaf surface are available for absorbing light is reduced so photosynthesis becomes less efficient.
What do mesophytes do to survive unfavourable times of the year when the ground is frozen and liquid water is not available?
1) Shed their leaves before winter, so that they do not lose water by transpiration.
2) The aerial parts of many non-Woody plants die off in winter so they are not exposed to cold winds, but their underground organs survive.
3) most annual mesophutes lay over-winter as dormant seeds, with such a low metabolic rate that almost not water is required
What are xerophytes?
They are plants that live in conditions where water is scarce e.g hot or dry deserts or cold regions where the soil water is frozen, windy locations
How are the stomata of marram grass adapted to their environment?
Stomata occurs on the upper surface, but not the outer surface of the leaf.
They are in pits and humid air is trapped in the pit, outside the stomata.
How do the adaptations of the stomata in marram grass help the plant survive?
This reduces the water potential gradient between the inside of the leaf and the outside and so reduces the rate of diffusion of water out through the stomata.
How does the adaptations of the shape of marram grass leaves help the plant survive?
This reduces the leaf area exposed to air so reduces transpiration.
How is the surface of the leaf of a marram grass plant adapted to its surroundings? And how does it help them to survive?
It has stiff, interlocking hairs trap water vapour and reduce the water potential gradient between the inside of the leaf and the outside.
How has the thickness of the layers in a marram grass plant cell adapted to their surroundings? And how does this help the plant to survive?
The plant cells have a thick cuticle and the cuticle is a waxy covering over the outer surface of the leaf. Wax is waterproof and so reduces water loss. The thicker this cuticle, the lower the rate of transpiration through the cuticle
What are hydrophytes?
They are plants which grow partially or wholly submerged in water.
What tissues do hydrophytes not have and why?
They have little or no lignified support tissues because water is a supportive medium.
There is little need for transport tissue (xylem is poorly developed) because they are surrounded by water
How are hydrophytes’ leaves and stems adapted to their surroundings?
Leaves have little or no cuticle, because there is no need to prevent water loss.
Stems and leaves have large air spaces, continue down to their leaves, forming a reservoir of o2 and co2, which provide buoyancy.
How are the stomata in hydrophytes adapted to their function?
Stomata are on the upper surface of floating leaves, because the lower surface is on the water.
