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New limitations to photosynthesis discovered by observing plants in the real world

Using innovative methodologies that combine biology and statistics, researchers from the David Kramer lab in the Michigan State University-Department of Energy (DOE) Plant Research Laboratory (PRL) observe the ways plants respond to their natural environments.

Atsuko Kanazawa, lead author of the study and research assistant professor in the Kramer lab, brought together a team of researchers, engineers and statisticians to use innovative open science platform and instruments developed at MSU called PhotosynQ and MultispeQ to reveal how photosynthesis in one species (mint) responds to complex environmental changes. The study is published in Royal Society Open Science.

Traffic along the highway

In the field, the sunlight shining on a plant can change rapidly with clouds. Excess energy from the sunlight could cause damage, and therefore, plants must regulate photosynthesis to avoid photodamage by adjusting to this rapidly changing light. These processes are similar to the brakes on a car: They protect the car from crashes, but also lose energy. Ideally, the brakes on photosynthesis are only applied when needed. When they see the traffic going too fast or are sensing the crash, they put on the several different brakes in combination.

Screenshot of Atsuko Kanazawa and David Karmer
Atsuko Kanawaza and David Kramer. Courtesy of David Kramer

Previously, one of the big problems was that it was difficult to study these processes in the real world, partly because probing photosynthesis at this level of detail required cumbersome, expensive and slow scientific instruments. Seeing as plants behave very differently in laboratories compared to the real world, where many variables are changing rapidly and at the same time, the researchers needed a new solution.

PhotosynQ simplifies field measurements

In 2015, David Kramer, Hannah Distinguished Professor of Photosynthesis and Bioenergetics, who is also a faculty member in the MSU Department of Biochemistry and Molecular Biology in the College of Natural Science, developed the MultispeQ with Prabode Weebadde and Sebastian Kuhlgert, a handheld device that allows researchers to easily take field measurements. It clamps onto a plant’s leaf and takes measurements of its photosynthetic activity and surrounding environmental data such as light intensity, temperature and GPS coordinates.

The device is linked through a smart phone app to PhotosynQ, the cloud-based open science platform where data taken from every MultispeQ device across the world are uploaded and permanently stored. To date, there are over two million data points that have been taken and shared in the PhotosynQ website.

“What’s cool about the MultispeQ instrument is that it allows sophisticated and detailed measurements of photosynthesis under the conditions of the real world,” Dave said. “It can capture phenomena that simply do not happen under the artificial conditions of the lab, and that is how we made the discoveries described in this paper.

Image of paper co authors Abhijnan Chattopadhyay, Sebastian Kuhlgert, Hainite Tuitupou and Tapabrata Maiti.
Co-authors on the paper: Abhijnan Chattopadhyay, Sebastian Kuhlgert, Hainite Tuitupou and Tapabrata Maiti. Image 1: Sneha Banerjee. Image 2-3: David Kramer. Image 4: courtesy photo

“But simply being able to measure these phenomena in the field is not enough,” Dave continued. “To understand them, we need to collect ‘metadata’ – location, species, weather, environmental conditions and so on. To bring all the data together, we need a platform like PhotosynQ.”

Combining statistics with biology

Analyzing a data pool of this size and interpreting the information in a meaningful way proved to be a challenge. Atsuko and Dave teamed up with a graduate student Abhijnan Chattopadhyay and Professor Tapabrata Maiti – statisticians from MSU – for the project.

“The future of science is in integrating data,” Dave said. “This requires that we communicate with people trained with different disciplines, who speak different scientific languages. Statistics and data science can be very abstract and involve a lot of math background. Understanding photosynthesis requires a lot of background knowledge on physics, biochemistry and genetics. Once we learned each other’s lingo, we made huge progress. For the first time, we can turn field data like that we obtained on photosynthesis into scientific models.”

“We cannot control the environment in the field,” Atsuko said. “Developing MultispeQ and PhotosynQ platform helped us conduct experiments all over the world without losing any data. The new analytical method enables us to process large data without bias. It identified the connection between plant behaviors and environmental factors.”

Working together, the researchers found that plants in the field do indeed behave differently than lab-grown plants. Field plants were able to adjust to environmental changes in a ways lab plants were not.

“The most exciting things is that, by going out in the real world, we found new biology: Photosynthetic behaviors that were completely unexpected,” Dave said. “We were thinking that one system was the limiting factor, but instead we found something new. Even under fairly mild changes in weather, the most effective ‘brakes’ of photosynthesis fail because something in the chloroplasts ‘freezes.’ The plants use a secondary backup system that is less effective. Intriguingly, this brake freezing phenomenon is different in various species or varieties of plants, making it possible to breed or engineer new crops that overcome this limitation. It will help developing more efficient, climate-ready crops.”

This work was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) under award number DE-FG02-91ER20021. The setup and collection of field data was funded by the U.S. National Science Foundation (1847193). David Kramer received partial salary support from Michigan AgBioResearch


Banner image: Atsuko Kanazawa uses a handheld MultispeQ device to measure a plant's photosynthetic activity and surrounding environment. Credit: Kara Headley