Researchers at the University’s Carl R. Woese Institute for Genomic Biology have developed a new system for more detailed real-time observations of plant gas exchange.
Published in the journal Plant Physiology, the study details a new microscopy technique focused on stomata, or pores on the surface of leaves, that control the flow of gases in and out of the leaf.
More specifically, stomata are used to balance the loss of water from the plant with the gain of carbon dioxide from the environment. This makes them crucial aspects of the plant that can be changed to increase drought tolerance, as stomata that can reduce water loss while still obtaining carbon dioxide can lead to more efficient plant growth.
“If you want to increase water-use efficiency at the leaf level, stomata are really key for understanding that and manipulating that, or engineering that,” said Joe Crawford, a post-doctoral researcher at the IGB. “That was kind of the original rationale for the project.”
According to Crawford, he, along with Andrew Leakey, professor in LAS, initially began the project to more closely observe the plant’s anatomy and physiology. For example, measurements like how many stomata are present on a leaf didn’t necessarily correlate strongly with the amount of water lost through the stomata.
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Instead, researchers needed to see exactly how the stomata acted in relation to their environment and measure their gas exchange rates simultaneously. This allows for a better understanding of how stomata physically change to affect rates of photosynthesis and water loss. In turn, scientists gain more knowledge for developing methods to keep water-use efficiency high even under stressful conditions.
To do so, Crawford worked heavily with the IGB’s Core Facilities, which handle imaging and microscopy for researchers at the University. Much of the Core Facilities’ work involves bespoke projects created at the request of researchers, allowing for more flexibility and innovation.
“When people walk in the door and say, ‘Hey, I want to try doing this, or that,’ whatever it is, we say, ‘Yeah, we can help with that,’” said Glenn Fried, director of Core Facilities at the IGB. “It doesn’t matter what it is. We try to figure out how to make it work.”
In setting up the project, the research team needed to address various issues.
One of these issues was the microscope lenses, also known as objectives — they are what allow the user to see the image at different magnifications. In this experiment, researchers needed a long-distance objective to visualize the stomata at a fine level without blocking any gas from exiting the pores themselves.
The researchers could only observe one side of the leaf at a time, even though both sides of the leaves contain stomata that can lose water.
The Core Facilities played a major role in addressing these issues, obtaining the necessary parts and setting up the complex system.
“We knew we needed a long working distance objective,” Fried said. “Then we needed to adapt them. … We knew all those things, and we just worked through it.”
Additionally, gas exchange measurements normally use multiple fans, which can vibrate the microscope stage where the leaf sits and make it difficult to photograph the stomata. It required suspending one part of the system in the air to prevent vibrations from disrupting the image.
The team also used machine learning to speed up the process of analyzing the stomata images. This allowed them to measure how open the pores were at a much faster rate than doing it by hand.
Altogether, the project, which has been worked on for over five years, is creating new paths in researching water use in plants, both at the IGB and in labs across the field.
In Leakey’s lab specifically, researchers study how stomatal density can be genetically altered and how these stomata control water-use efficiency. However, Crawford believes many possible applications are contributing to the project’s support within the community.
“I think there’s a lot of people who are excited about this because stomata are really at the center of the control of water use,” Crawford said. “There’s a deep unknown about water use in plants right now. … This is going to hopefully contribute to answering that question.”
