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3.9 describe adaptations of a range of terrestrial Australian plants that assist in minimising water loss
Describe adaptations of a range of terrestrial Australian plants that assist in minimising water loss
- You will recall from the Preliminary course that the leaves of plants contain stomates or small pores that allow the exchange of gases essential for respiration and photosynthesis. These gases include water vapour, as well as oxygen and carbon dioxide. If stomates are open, there will be a loss of water by transpiration and evaporation. Plants in arid areas have to balance the need for CO2 with the need to conserve water.
- Adaptations of Australian xerophytes (plants adapted to dry conditions) include:
- hard leathery, needle-shaped leaves with reduced surface areas such as in Hakea sericea (needlebush) and coastal tea trees
- use of phyllodes for photosynthesis rather than leaves that would lose water by transpiration, as in many acacias
- some salt bushes, e.g. Atriplex, change the reflectiveness of their leaves during leaf development so that they have highly reflective leaves during summer
- Eucalypts avoid high radiation in the middle of the day by hanging their leaves vertically to present less surface area to sun
- heat loss is greater for small leaves or highly dissected leaves than it is for larger leaves and many Acacias have fronds of bipinnate leaves
- waxy cuticle prevents evaporation in many Eucalypts.