From U Arizona: “Biosphere 2 as You’ve Never Seen It Before”
April 12, 2017
U Arizona Biosphere 2
UA researcher Tyeen Taylor goes high into Biosphere 2 in his study of plant volatiles, the molecular compounds that are small enough to become a gas. (Photo: Bob Demers/UANews)
Inside the iconic structure far from the UA’s main campus, climate change researcher Tyeen Taylor uses the simulation rainforest to study botanical volatiles, looking for clues to how those plants manage high temperatures and drought.
Tyeen Taylor moves catlike along a narrow path fashioned from wooden planks. The path, tucked inside a simulation Brazilian rainforest, is man-made. The air is warm and thick. The scent of damp earth and assorted greenery predominates.
This living lab is part of the University of Arizona’s Biosphere 2, which this month is celebrating its 10th anniversary of UA research. And this is where Taylor conducts much of his study of climate change — specifically volatiles, the molecular compounds that are small enough to become a gas.
“My work is about what you smell as you walk into the rainforest, which is plant volatiles,” says Taylor, a researcher at Biosphere 2. “I’m studying the volatiles that help plants deal with stress like the stress that comes from high temperatures and drought. With some plants’ leaves, if you crush them up, you smell all of this good-smelling stuff. Those are oils, and they’re stored as oils, but once you break them free, just like a perfume, the oil is gradually released into the air.”
But other volatiles are produced on demand in response to environmental conditions that can shift at any given moment. Those are the ones Taylor is focused on. He explains that once the temperature of a leaf climbs, enzymes start modifying particular molecules inside the leaf, which turns those molecules into gas, which is then released.
Although plants that inhabit rainforests exchange massive amounts of carbon dioxide and oxygen, it’s this process of volatile production, says Taylor, that mitigates damage and helps plants cope with climatic change — and, in turn, affects the world’s climate. For example, volatiles affect the length of time methane, a greenhouse gas, stays in the atmosphere, he says.
“The volatiles also form aerosol particles after reacting with other chemicals in the atmosphere, and those aerosol particles are required for water to condense around,” Taylor says. “That’s what makes clouds, and the clouds, of course, make rain, and they reflect sunlight, which cools the planet.”
Taylor, who grew up in Alaska, says his love for tropical forests started early, when he traveled as a child with his parents to Costa Rica on Christmas breaks. Now one of his favorite things to do when visiting tropical rainforests is to identify the plants by scent.
“Oftentimes the leaves are so high up you can’t get a sample, but you can put a little cut in the trunk, and from the smell from that cut, you can work your way through the evolutionary structure of different plant groups because particular plant groups have particular types of volatiles,” Taylor says. “Once you calibrate your nose, you can get to the order and family and genus of a plant — maybe even the species, if it’s a peculiar enough smell.”
While working on his doctorate at UA, Taylor built the first-ever instrument designed for the precise measurements of leaf-volatile emissions in the field. He is now attempting to merge the instrument with one that measures photosynthesis, so he can see these two processes simultaneiously.
“I’ll be able to see how much carbon is entering the leaf in terms of carbon dioxide and how much of that carbon is leaving the leaf in terms of volatiles,” Taylor says.
Taylor says carbon is like money in the bank for the leaf, and the leaf has to spend that money wisely. Too high a cost, and plant growth and leaf processes could be reduced, which could become an unsound evolutionary strategy for some species, he says.
“I want to see what the carbon expense of these volatiles is because we know they help leaves deal with stress, but we also know not all species do it,” Taylor says. “The important question is why, and the answer may be that it costs too much carbon. If it turns out it doesn’t cost enough carbon to be a selective disadvantage, then there has to be another answer.
“We know that different species will respond to climate change differently, but we want to know if some of them will be able to handle the warmer temperatures and droughts. By understanding the evolutionary controls on plant stress responses, we can better predict which species will be tolerant and which will not. If we know that, we’ll know a little more about the response of the rainforest and a little more about how the forest controls the climate.”
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