This talk ‘Research on the adaptations of Australian plants in desert and alpine landscapes’ – an informal slide show by A/Prof Andy Leigh, UTS (also a member of APS HGR) on the 4th of April 2024
Notes by Liz Cameron & Peter Geelan-Small
Andy Leigh is a plant ecologist with a particular interest in extreme environments, which are not uncommon in Australia. She argues that temperature is the most important climate factor affecting how different plant (and animal) species are distributed on Earth. Different plant species have developed particular mechanisms to deal with the level of heat stress caused by the characteristic temperature and amount of water available in their environment.
Temperature and rainfall (climate) and geology shape biomes, which are major types of environment that exist on a large scale. The diagram below shows the major terrestrial biomes and how they are related to annual rainfall and average annual temperature. As each biome is related to a particular combination of climatic factors, the same biome can occur wherever that particular climate prevails. See diagram
To understand the responses of plants to their environment, Andy and her team study leaf function and survival, using a range of techniques in both glasshouse and field research; these include electronic sensors to measure the transpiration, heating and other properties of leaves.
The main strategies employed by plants are regulation of water loss (transpiration) and reflection of the sun’s radiation. Water loss is regulated by pores (stomata) on the undersurface of leaves which can open and close; these are illustrated in the following diagram:
Photosynthesis, which occurs primarily within leaves, is a really important process. Heat stress mainly harms photosynthetic machinery and that’s what Andy and her team really care about.
Plants can cool down by transpiring (or ‘sweating’) – losing water vapour out of their stomata – but in arid areas where water is scarce, loss of water through the stomates could lead to extreme dehydration and leaf death.
In low rainfall areas, therefore, many plants adopt different strategies to stay cool. The leaves are often small (which reduces the surface area over which water loss can occur) and tend to have tiny hairs; surface hairs reduce water loss and, as Andy pointed out, also reflect the sun’s radiation. Another adaptation to reflect radiation is waxy coating on the leaf’s surface. The combination of hairs and wax gives leaves a paler and greyer appearance – typical of Australian desert plants such as Mulga (Acacia aneura) and many species of Eremophila.
Another strategy to reduce high levels of radiation and water loss, is for the leaves to hang vertically to reduce the surface area exposed to the sun, for example the pendulous adult leaves of eucalypts.
The issue with climate change is not only increasing heat; the extremes of weather are increasing, so cold climate plants are affected too. In alpine areas the temperature range is widening and causing earlier snow melt. The snow acts as an insulating blanket, so some alpine plants that are exposed prematurely are suffering cold stress.
Some of Andy & her team’s research is conducted around Uluru, where their results obtained from electronic sensors inserted in leaves, differ markedly from results obtained in Europe (where the sensors were developed).
They are working with the local Indigenous people to learn which plants are culturally important and merit further attention in their research. For example, Mulga (Acacia aneura or Warranee) is not only important for fixing carbon but also as a food source – the Anangu roast and grind mulga seeds into an edible paste, eat the gum of the tree and also the ‘mulga apples’ (galls caused by wasp larvae) and dig up witchetty grubs from around the roots. It is a two-way exchange, with the local people keen to learn more about the internal structure and function of plants.
So far, there has not been much work done on selective breeding of native plants to better survive climate change. The Australian Arid Lands Botanic Garden in Port Augusta is doing some work and Greening Australia has commenced research in this field, too.
We look forward to hearing of improvements in land management coming from this most important area of research.
For further information, see a talk Andy gave at the Australian Arid Lands Botanic Gardens on 12 May 2015: