A new NASA video explores the science of space gardening and what researchers are learning about plants in space.

In 2015, astronauts aboard the International Space Station ate the first produce ever grown in space. During Expedition 44, NASA astronauts Scott Kelly and Kjell Lindgren, as well as the Japan Aerospace Exploration Agency's Kimiya Yui, chomped down on red romaine lettuce that was grown in the station's Veggie plant growth system in August of that year.

It was a big moment, and a necessary step toward NASA's goal to travel to Mars someday. [Plants in Space: Photos by Gardening Astronauts]

As the new video from the agency's video series "Science at NASA"explains, the ability to grow both edible and nonedible plants in space is essential for deep-space travel and the establishment of dwellings. Plants provide both a food source and the ability to recycle air and water, Anna-Lisa Paul, a University of Florida professor who researches how plants grow in extreme environments, said in the video.

While it was a major step toward someday being able to grow gardens on Mars, the lettuce taste test was nowhere near the end of this endeavor. Scientists aboard the space station and here on Earth continue to test how plants adapt to harsh environments.

Paul and her colleague Robert Ferl, also at the University of Florida, first launched plants into space in 1999, on space shuttle Columbia, and have been studying plant growth in space ever since.

The roots of plants grown on tilted soil on Earth grow in a slanted direction, which scientists call "skewing," according to the video.

Through their research, Paul and Ferl discovered that gravity doesn't actually affect the direction in which roots grow, as Charles Darwin had previously hypothesized. Darwin believed that skewing was partially due to gravity's effect on the roots, but Paul and Ferl discovered that plants grown in microgravity exhibit the same behavior, meaning that roots don't need gravity to seek out necessary nutrients.

Growing in microgravity did, however, change the plants' genetic response, according to the video.

"When living organisms are faced with environmental change, their response almost always involves a change in genetic expression," Paul said in the video. "To cope, they switch on and off certain genes."

The genes that changed are associated with the cell walls of plants, according to the video, though Paul and Ferl aren't yet sure what purpose this serves. They plan to conduct experiments to study this effect as well as other ways plants adapt to microgravity, and scientists aboard the space station will also continue to study plant growth in an effort to help people survive on Mars and beyond.

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