Defect found in plants could alter their role in climate change fight
A recent study revealed that plants are starting to lose more water under high temperatures. A phenomenon known as 'leaky plants' is increasing because of climate change, potentially converting them from a carbon sink to a carbon source
Plants have a lot of burden to bear with how much they're relied on––from providing the oxygen we breathe and the food we eat to absorbing carbon.
But a new study reveals some trouble is afoot with plants losing more water than previously believed through their waxy cuticle under high temperatures, a phenomenon termed "leaky plants."
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With a rise in global temperatures, the issue is exacerbated by climate change, and can intensify droughts and reduce photosynthesis, potentially turning plants from carbon sinks to sources.
Climate change is already having an effect on plants in many areas, especially in the Arctic where some species are declining because of warmer temperatures, while others are thriving.
Plants. (Paul H. Joseph/University of British Columbia/Submitted to The Weather Network)
According to Sean Michaletz, assistant professor at the University of British Columbia (UBC), plants will normally close the pores to conserve moisture under extreme heat conditions so they don't dry out.
But what researchers discovered is that water will still seep through on the waxy layer on the leaves, causing them to lose a lot more of the liquid they previously thought, he said.
"What we think is happening is that the waxy layer is kind of softening and starting to break down under high temperatures, kind of like [what] a candle wax would do. But we're not sure about that, and we're actually starting some followup work to look at the exact mechanism there. So, that's what we mean by the the leaky plants concept," said Michaletz, in a recent interview with The Weather Network.
Water loss could cause 'feedback,' worsen climate change
Since plants are losing more water than what scientists previously thought, that can lead to the drying of vegetation or the soil. As a result, we could possibly see the intensification of drought conditions for the entire ecosystem that they’re growing in, Michaletz said.
(Maryna Terletska/ Moment/ Getty Images)
“These drought conditions can reduce photosynthesis or it can lead to the death of leaves or entire plants. That's really important because plants are basically the foundation of the entire biosphere,” said Michaletz. “They capture energy from the sun and they store it in their biomass as sugars. That's what photosynthesis does.”
“Ultimately," Michaletz said, plants provide all of the energy that fuels all life on Earth.
“All of the other living organisms on Earth...that's the energy source for all of the other living organisms. Other organisms eat that biomass for food,” said Michaletz.
Another key reason is that plants, and photosynthesis, in particular, remove carbon dioxide from the atmosphere, he noted.
“It's actually the largest, single component in the Earth's carbon budget. Because carbon dioxide is driving global warming, if we start to see increased loss of leaves or plants, that could have really big effects on how much carbon dioxide plants are basically inhaling from the air,” said Michaletz.
Leaky plants. (Paul H. Joseph/University of British Columba/Submitted to The Weather Network)
The result is a “feedback” that can amplify climate change, causing faster rates of global warming, Michaletz added.
“I personally think these are some of the most important issues that humans will be facing over the next few hundred years. [So], over the next few 100 years, I think these are going to be some of the most important questions we have to deal with,” said Michaletz.
"our fossil fuels that we use for energy...all of that is a product of photosynthesis. All of that was photosynthesized by plants and then became biomass. Then it is incompletely decomposed and became our the fuel that we're drawing upon now."
Irrigation is key to mitigating the leaks
Plant leaves are coated in a waxy layer called a cuticle, intended to prevent water loss, but it also stops carbon dioxide from entering the leaf, something that is needed for photosynthesis, Michaletz said.
"As a way to deal with that, plants have evolved tiny, little pores in their leaves called stomata, and they can open and close those pores to regulate the amount of water loss," said Michaletz.
Plants. (Paul H. Joseph/University of British Columbia/Submitted to The Weather Network)
So, he said one of the ways of dealing with the leaky problem is to start irrigating more, especially during "really hot" periods.
The evaporation of water, when it occurs, requires energy, which gives off a cooling effect––another reason why irrigation is "really important."
"[It is] kind of like how humans sweat. When plants lose water, it's a way for them to cool themselves. Under extreme heat, if we can irrigate, it not only prevents plants from drying out, but it can also help them cool themselves, as well. I think irrigation is key," said Michaletz.
Chemical reactions in plants
While the assistant UBC professor believes all plants are susceptible to the "leaky" phenomenon, two of the species he worked with in the study were broadleaf and maple, among others.
He said there are two different types of chemical reactions in plants, a series of responses, actually, but the main one is photosynthesis.
Plants. (Getty Image/Megakunstfoto/1571993866-170667a)
"It takes carbon dioxide from the atmosphere and it combines it with light. It uses light, energy and combines it with water to produce sugars for the plant. And those sugars then are broken apart, basically by doing photosynthesis in reverse. That process is called respiration," said Michaletz.
Respiration then takes sugar and gives off energy, but it also then releases carbon dioxide (CO2) into the air--making plants a carbon sink and a source, Michaletz explained.
"Those reactions are temperature dependent, and at very high temperatures, we tend to see more respiration than photosynthesis, so there's more carbon dioxide being released at high temperatures," said Michaletz.
Leaky plants. (Paul H. Joseph/UBC/Submitted to The Weather Network)
With respect to heat and its effect on plants, researchers found that photosynthesis tends to start breaking down at temperatures ranging from 40 C to 50 C, depending on the plant, he noted.
"Some plants differ. How they're sort of acclimatized to their local environment also makes a difference. But somewhere between 40 C and 50 C, photosynthesis stops working. In some other work, we've actually been looking at how proteins degrade under high temperatures," said Michaletz.
The work of Michaletz and his colleagues seems to indicate that a temperature of around 60 C seems to be the highest temperature that plants can withstand, and that's due to their proteins breaking down at that value, according to Michaletz.
(Nathan Coleman/The Weather Network)
"We've actually looked at data from across the entire world and there's actually only a few observations, mainly from deserts and tropical areas, where plants have been seen to survive temperatures of 60 C. So that seems to kind of be an upper limit for plant survival," said Michaletz.
"Actually, during the B.C. 2021 heat dome, there were a lot of observations of plant leaves actually getting scorched from the heat. They just heated up so much that they died, probably because they were hotter than 60 C or so."
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Thumbnail courtesy of Getty Images/Megakunstfoto/1329527410-170667a.
