The Incredible Short History of Plants in Space

Can we eat space plants? Would they survive long enough to feed a colony on Mars? These are questions that we're still trying to answer after more than 30 years of plant-growth work in space.

Seeds have flown to the moon and back, and others have sprouted and flowered on space stations near Earth. Here are some of the many plant experiments in space during the next generation.

Ten years ago on July 4, space shuttle Discovery carried a neat European greenhouse to investigate plant growth in orbit. It's called the European Modular Cultivation System and has been active in space ever since. The experiment bank has four slots available and the capability to regulate all aspects of the environment, including factors such as temperature, water, light and the atmosphere. It even has a centrifuge to spin and simulate gravities up to twice of what we experience on Earth.

The various experiments inside this bay have come up with several interesting results. It appears, for example, that lentil seedlings can "sense" gravity and send out roots using calcium ( Gravi-2 experiment). A separate set of Tropi experiments with Arabidopsis thaliana (a small flowering plant) showed that the planets grow differently under red and blue light in moon and Mars conditions, sparking questions for further study.

And in a quote that makes us think of The Martian's potatoes, the European Space Agency said this sort of work is an urgent need for colonization. "We need to know how plants will grow on neighbouring planets," they wrote. "Will they still know which way to send their roots in reduced gravity or will they go haywire?"

Image: These are arabidopsis seedlings grown in space in the European Modular Cultivation System, a small greenhouse on the space station that looks at how plants behave in different gravities (ESA)

NASA's big foray into plant growth is an experiment called Veggie (Vegetable Production System), which is intended to provide edible food for the astronauts. The first type of crop it grew was lettuce, to great success. After a precursor crop was sent to Earth to look for any potential problems, astronauts were able to munch on the harvest in space a few months later.

The follow-up zinnia growth, however, proved more troublesome. NASA controllers saw mold on the flowers around the holiday season in December 2015, and had difficulty relaying up timely instructions to care for them. Astronaut Scott Kelly then, with permission from the ground, took on full responsibility for saving the plants. While some died from the mold, zinnias successfully bloomed in space in January 2016.

While Veggie is one of the newer experiments on station, its advantage is sheer size: according to NASA, it has the largest volume available to grow plants on the orbiting complex. In other words, bigger plants can grow up in space. The bonus for astronauts, NASA stated, is they can have a "tool for relaxation and recreation" in between their experiments.

Image: A zinnia flower blooms on the International Space Station in January 2016, weeks after mold was found in the experiment and removed (NASA)

Skylab was NASA's first foray into long-duration space missions. The space station orbited the Earth for six years before de-orbiting, with some pieces crashing into western Australia. There were three crewed expeditions to Skylab, with each one stretching the limit for human spaeflight duration: 28 days on Skylab 2, 56 days on Skylab 3, and 84 days on Skylab 4. This unprecedented amount of time in space allowed the astronauts to do hundreds of hours of experiments.

Skylab also had student proposals for experiments, and received two very similar ones from Donald Schlack of Downey High School in California, and Joel Wordekemper of Central Catholic High School in Nebraska. The students combined forces and did a study of rice seeds that were planted and grown on Skylab. The plants were seeded by Skylab astronaut Edward Gibson, making him (as described by one NASA history of the day) " the first space farmer." It also was the first time plants were studied in space in an experiment that lasted longer than three days.

The rice grew pretty weirdly, first taking longer than usual to get started, and then the stems growing and stretching into odd directions -- sometimes away from the light, and sometimes curling. At the time, it was proposed the rice grew this way because plants need gravity to stimulate their auxin distribution system, which are hormones that regulate plant growth.

Image: An exterior shot of the Skylab space station, which required a jury-rigged sunshield to regulate the interior temperatures after part of its structure accidentally ripped away during launch (NASA)

A lesser-known fact about the Apollo 14 crew was Stuart Roosa, the command module pilot, used to be a U.S. Forest Service smoke jumper. So in his personal kit he carried hundreds of tree seeds as part of a NASA/USFS project. While the seeds were not activated in space, they returned to Earth safely and were planted all over the United States, particularly to celebrate the bicentennial in 1976. These are called Moon Trees.

At first it didn't look like such a rosy end for the 400 to 500 seeds that flew to the moon and back. The douglas fir, lobollly pine, redwood, sweetgum and sycamore seeds were subject to decontamination procedures upon returning to Earth. Their canister broke open, and initially investigators thought they wouldn't be able to grow trees. Luckily, most of the seeds succeeded in producing trees.

Because there was no central repository at NASA tracking where all the trees went, some of the locations are unknown. The agency does, however, have a partial list of first-generation Moon Trees and second-generation Moon Trees. Probably one of the more famous ones grows in the Kennedy Space Center's courtyard near Orlando, Fla., making this one of the easier sites for space enthusiasts to get to (while enjoying other activities on site).

Image: A second-generation Moon Tree is planted at United States National Arboretum grounds in Washington, D.C. in 2009 (NASA/Bill Ingalls)

Salyut-7 set a space milestone in 1982 when the crew grew Arabidopsis on the station, making these plants the first to flower and produce seeds, according to the Guinness Book of World Records. Scientists noted that the plants appeared to grow and develop differently in space, but that 42 percent of the seeds appeared to "valuable biologically", according to a 1984 Advances in Space Research abstract.

The abstract added that cosmonauts on Salyut 7 not only grew flowers, but also lettuce. The lettuce was studied in different gravities in a centrifuge, and also in microgravity. The hypocotyl on these plants (the stem above the root) was 17 percent shorter at 0.01 g (gravity of Earth) than control plants at 1 g. But at 0.1 g, the growth was pretty similar to the 1 g plants.

Image: The Salyut-7 space station in 1985 (Soyuz T-13 crew)

In 2011-2012, space station followers were treated to a frequent blog from NASA astronaut Don Pettit, who enjoyed talking about space from different points of view. One post included a "diary of a zucchini" that was published in June 2012, shortly before Pettit returned to Earth. Pettit's post took the point of view from the zucchini itself, who referred to an astronaut (assumedly Pettit) as "Gardener."

"Our part of the mission is nearly complete and the new crew will take over for us," the diary read. "I am a bit worried about Broccoli, Sunflower, and me. If Gardener leaves, who will take care of us? And what about little Zuc? He is now a big sprout and ready to branch out on his own. Gardener talked about pressing us. I am not sure what that means; this does not sound good."

After making a joke about the Russian Soyuz spacecraft ("It must be their version of a seed pod"), the zucchini "reported" on June 24 that the sunflower had flowered. But there were some strange features: the blossom was browner and the seeds appeared to be packed "lopsided." But the zucchini reassured itself: "We are living on the frontier and things are different here." The plants were returned in a SpaceX Dragon spacecraft for analysis.

Image: A sunflower flowers on the International Space Station in 2012 (NASA/Don Pettit)