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322158

Growing cotton in space helps identify sustainable production practices

With about 15 million bales produced in 2020, cotton is considered America’s No. 1 value-added crop. However, it requires access to natural resources such as water that are increasingly at risk.

By sending 48 cotton seeds to the International Space Station, botanists at the University of Wisconsin-Madison hope to generate ideas for sustainable cotton production.

It all starts with the plant’s root system, which is crucial to plant survival, says Simon Gilroy, a botanist at the University of Wisconsin-Madison.

“In the past, we collaborated with researcher Roberto Gaxiola at Arizona State University,” Gilroy says. “He had discovered a variety of cotton that has an enzyme that enables cotton to be stress-resistant. We compared this variety with a normal variety of cotton. Roberto discovered differences between the two varieties’ root system architecture and that gravity is actually quite important in its development.”

Funded by a grant from Target Corp. and sponsored by the International Space Station National Laboratory, the Targeting Improved Cotton Through On-Orbit Cultivation (TICTOC) is an extension of Gaxiola’s initial research.

“Target is very interested in cotton textiles and the production of the materials needed, for example, to make T-shirts and other clothing items,” says Sarah Swanson, a University of Wisconsin-Madison botanist assisting on the project. “Cotton uses a lot of inputs like water, fertilizer, and pesticides, so being able to produce cotton sustainably is a concern for the company. If Target can somehow enhance cotton production, not only does its business benefit but the environment does, too.”

Guided by Gravity

On Earth, plant roots in search of water are guided down into the soil by gravity. By removing gravity, the botanists hope to discover other factors that influence which direction roots travel. Understanding this, say Gilroy and Swanson, could help define how to create new strains of cotton with deeper roots that search and collect water more efficiently, as well as sequester carbon in the soil.

“Cotton is such a hungry, thirsty crop, which is directly related to its root system. It takes up water and nutrients through its roots, so the shape of the root system and what makes that root system develop the way it does are key to understanding why cotton behaves the way it does,” Gilroy says. “There could be elements related to gravity sensing that we could tweak on Earth to redesign the root system — from genetic engineering to selective breeding — to make it more efficient.”

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The information gathered will provide one piece of the puzzle about what the cotton plants are using to determine how their root system is exploring the soil on Earth. The experiment will also help the researchers better understand how to grow plants in space, where the lack of gravity makes it difficult to water them.

“In space, it’s very challenging for water to get where it needs to be and keep it away from where it shouldn’t be,” Swanson says. “It’s a chronic flooding situation.”

Ahead of the June 3 launch, researchers prepared the 48 cotton seeds at the Kennedy Space Center in Florida. Placed in special petri dishes filled with gel, seeds were refrigerated until loaded into a SpaceX Dragon aircraft for the nearly 40-hour journey to the space station, a state-of-the-art microgravity laboratory unlocking discoveries not possible on Earth.

“This prevents seedlings from germinating,” Swanson says. “The Jell-O-like agar substrate contains nutrients, which will keep the cotton seedlings happy while they’re growing in space.”

Once they arrived at the space station, astronauts transferred the seedlings into a 2×2-foot growth chamber called the Veggie.

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Three strains of cotton seeds had six days to germinate and grow. While the seedlings grew, astronauts photographed their roots to capture information about size, shape, and direction of growth. 

“Taking pictures of their growth may sound simple, but those images are powerful because we get to see what is happening on a day-to-day basis,” Gilroy says.

When the experiment was complete, seedlings were frozen until they could be sent back to Earth. On July 9, a spacecraft successfully splashed down off the coast of Florida, returning more than 5,300 pounds of scientific experiments and other cargo from space.

“Six days may not sound like a lot, but the seedlings will have made a significant amount of development,” Gilroy says. “The seedlings will have a root system that is 8 inches long with 10 branch roots.”

The number of days seedlings were allowed to grow is also limited by the size of the growth chamber.

“On Earth, roots reach the bottom of the chamber after six days, so it was a factor that had to be taken into consideration when growing in space,” Gilroy says. “We didn’t want the roots to hit the bottom of the chamber because we wanted a straight, unobstructed root rug.”

Analyzing the Data

In Madison, researchers will analyze the patterns of root growth and the expression of different root-related genes between space- and land-grown plants to determine how zero gravity affected the seedlings.

Gilroy says not only will they look at the images gathered in space to extract every parameter that describes how the growth went, but the researchers also will be able to dig deeper into the genetic makeup of the plant based on research previously done on Earth.

“One of the big sets of data we already have is the patterns of which genes are switched on and off under certain circumstances on Earth,” he explains. “These gene patterns are like fingerprints. We know what the fingerprint of drought looks like. We know what the fingerprint of flooding looks like.”

Like astronauts who lose muscle mass because they’re not fighting against gravity, the botanists know plants won’t be able to make as strong a root structure as they normally would on Earth. 

“Because space is such a weird environment, we don’t know what other factors are affecting growth. We can make some guesses, but we want to know if our guesses are correct,” Gilroy says. “By using genetic fingerprinting, we can try to answer what that plant thinks is going on while it’s in space.”

Improving how cotton is produced, the botanists say, has far-reaching implications. 

“Cotton is a crop with a big environmental and economic footprint. There are several benefits that can come from improving it, but it is a long-term process. The beauty of research is that it provides that base knowledge, which can serve as a building block the industry can capitalize on,” Gilroy says. “For example, a breeder can take this information and begin to think about how to feed it into their breeding program. The successful programs are the ones where there is a lot of thought about how to combine traits to get the improved varieties.”

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