Going to extremes to help save vulnerable native plants

Researchers are exposing tiny leaves to temperatures from as high as 65C to below -10C to measure how their photosynthetic systems respond to help protect threatened Australian plant species from climate change impacts.

Philippa Alvarez is a University of Technology Sydney (UTS) PhD candidate at the Australian Institute of Botanical Science (Institute) and is based at the Australian Botanic Garden Mount Annan. Her research will lead the way to a better understanding of our iconic Banksia, Acacia, and Eucalyptus species’ capacity and could lead to enhanced management and conservation strategies for a variety of other native trees and shrubs. Unfortunately, Philippa’s studies are already identifying serious vulnerabilities in the young stages of a plant’s life cycle from extreme temperatures.

Saturday 11 February 2023 marks the United Nations’ International Day of Women and Girls in Science and Philippa’s research reflects the transformative impact women are having at the Institute in helping to build more resilient ecosystems for future generations.

Testing for plant vulnerabilities

Philippa’s work is part of a wider study - Living on the Edge: how do Australian plants cope with extreme temperature – looking at the effects of thermal tolerance in plants from three distinct biomes (Desert, Temperate, Alpine).

One aspect of her work was to find “the happy place” of seed germination across these three biomes to see where they would be most harmed by extreme temperatures.

Although extreme temperature events are increasing in frequency and intensity, little is known about the thermal tolerance breadth of plants from extreme environments, where both heat and cold extremes are common. This information is crucial to understand species distribution and survival under future climate regimes.

Philippa is examining the lifecycle of a plant from a seed to a freshly sprouted plant, to the late seedling stage. She has tested about 30 types of species from a pool of 70 species included in The Living on the Edge project and compared the differences between desert, temperate, and alpine species.
 

Measuring the proverbial “canary in the coal mine” of a leaf

When sunlight hits the chloroplasts inside a leaf, one of three things happens: 1) it can be absorbed and used for photosynthesis, 2) it can be dispersed as heat or 3) it will bounce back out again. A key part of Philippa’s research is measuring the light bouncing out of photosynthetic systems within the chloroplasts of germinating seeds and seedlings.

“I measure the light coming back out those photosynthetic systems to see if there is a point where the plant is like, ‘Yep, I'm quite happy with these temperatures. I'm still good. I'm still absorbing your sunlight and photosynthesising’,” Philippa said.

“And then there'll be a point where they're like, ‘no, I can't do this anymore, no more temperature stress please. That point is what I'm trying to determine, and that point is the canary in the coal mine. It’s an early warning system of plant functional breakdown under extreme temperatures,” she said

Philippa is comparing whether seedlings from an extreme biome, such as a desert system, will respond differently to those temperatures compared to temperate ones, which had been assumed to be a more benign environment.

“The differences between the three biomes aren’t that big, possibly as a result of how they grew up. What I am finding though, is these seedlings are responding quite strongly to a heatwave event – one which an adult plant would probably be OK with. They’re also showing signs of damage after a repeated heatwave event,” Philippa explains.

Better understanding the respiration rate of germinating seeds

When seeds are dry, they are strong and hardy, but as soon as they are exposed to water, their germinating processes start to kick in. However, what will happen if there is a big heat wave at that point and a large, intense amount of heat?

Philippa is going to Kings Park in Perth to measure seed respiration and the impact of increased temperatures on the very first stages of a plant’s life cycle, specifically in Acacias, using cutting-edge technology that has potential to revolutionise seed banking in the future.

“One thing that seeds do is respire, it's kind of like breathing, so I'm able to measure how much carbon dioxide and oxygen the seed is releasing and absorbing in this process before they've even started to produce leaves,” Philippa said.

“This process has been used in agriculture, but it's only just starting to come into the seed banking and conservation world. There's been some research done at Kings Park with this so I'm going over there to understand how.”

Increasing temperature could change the way these seeds are respiring, and if the seed’s respiration slows down or stops, they may be dead. If there is an increase in temperature because of climate change, there could be a shift in the composition of a plant species because the seeds will not be able to germinate and there may be implications for this on their population due to climate change.

Women researchers a ‘force to be reckoned with’

Phillipa said her project is part of a very collaborative effort, led by extraordinary women. “I'm one of many people involved in The Living on the Edge project. It is led by two women researchers – Associate Professor Andy Leigh at UTS and Professor Adrienne Nicotra at ANU – and most of the researchers are women, so we’re a force to be reckoned with. It has been such a great project to be a part of,” Philippa said.   

“In this field, my research has never been done before and addresses some big gaps in our understanding, which is what a PhD should be.  I’m hoping it'll give me the right platform to build my career from.”

Philippa will be submitting her research soon and is hoping to have it published sometime this year.

The project is a collaboration between researchers at the Australian National University Research School of Biology, UTS Life Sciences, the Save our Species program of the Department of Planning and Environment, the Australian National Botanic Garden, the Australian Institute of Botanical Science (the Institute) and the Universidad la Frontera, Chile. 

The Australian Institute of Botanical Science consists of the physical and virtual scientific collections, research, services, and facilities, and of course, staff at the Royal Botanic Garden Sydney, Australian Botanic Garden Mount Annan and the Blue Mountains Botanic Garden Mount Tomah. The Institute is one of the nation’s premier botanical research organisations and helps ensure the survival of plants.