Some trees can acclimate to changing temperatures

Researchers from the Walker lab at the Michigan State University-U.S. Department of Energy Plant Research Laboratory, or PRL, are looking at how paper birch trees adapt to changing environments based on how they manage a vital plant process called photorespiration.

"If plant metabolism was a freeway system, photorespiration would be the second-highest trafficked road," said Berkley Walker, associate professor in the Department of Plant Biology and at the PRL. "We are interested in understanding if the roads of this important pathway are large enough to handle all this traffic under present and future climate conditions."

In humans, acclimation happens when we become accustomed to new conditions. We do this when we adjust to the cold weather of winter or while learning the ropes at a new job.

Plants must acclimate to new conditions as well. This is complicated by the fact that the increase of atmospheric carbon dioxide, or CO₂, and global warming have the opposite effects on photosynthesis and photorespiration. When temperature increases, so does photorespiration, but when CO₂ increases, photorespiration decreases. This tradeoff may alter the efficiency of photorespiration.

In a study published in Scientific Reports, researchers assessed whether paper birch trees adjust the activity of photorespiratory enzymes under different environmental conditions. Paper birch was selected because they live in boreal forest biomes, which are located in the northernmost parts of the planet and are expected to be among the ecosystems hit hardest by climate change.

The growth conditions were designed to mimic current, moderate and extreme climate change scenarios for the boreal forest regions, as simulated by the Intergovernmental Panel on Climate Change. In each of these scenarios, the researchers altered the CO₂ concentration in the surrounding atmosphere and increased air temperatures in different combinations.

"This study explored whether plants fine-tuned their enzyme capacity based on demand or whether they keep a buffer, so they have extra capacity in reserve to handle unpredictable changes," said Luke Gregory, former graduate student in the Walker lab and first author on the study.

Into the Biotron

Trees were grown from seeds by researchers from Professor Danielle Way's lab at the University of Western Ontario. Way grew paper birch trees under six environmental conditions using the university's Biotron, a research facility that can simulate nearly any climate on earth.

Way's lab took measurements of the trees after four months of growth and sent leaf clippings to MSU. Gregory and his team looked at nine enzymes involved in the photorespiratory pathway in these leaves and their activities.

They found that the trees do not, in fact, increase their enzyme capacity depending on the climate they are grown in and instead maintained similar capacities across all six future climate scenarios. However, all the enzyme capacities measured in the study were more than was needed for the photorespiratory pathway -- meaning the trees were prepared to grow, even under changing conditions.

"It was really interesting to find that there's this safety factor that these plants have and it's across all of these different environments that they're able to have this buffer capacity," Gregory said. "At first, we thought there was going to be this specific change to demand, but what we found is that across all of these different plants, they do maintain a buffer. They're able to deal with these different changes whether under current, moderate or extreme conditions."

This is good news: the trees have a built-in mechanism that will help them survive despite the changing climate, at least when it comes to photorespiration.

However, this is just one piece of the puzzle in understanding how photorespiration is and will continue to be affected by human-caused climate change.

"It's important that we understand how plants are responding to current conditions and future conditions because we need them in our lives," Gregory said. "Understanding if plants can acclimate or whether, over generations, they can adapt to these certain environments is important to understand because they provide a lot of fuel, food and fiber for us."