Seven ways the International Space Station is helping us study the growth of plants in space

While NASA is planning long-term missions to the Moon and Mars, a key factor is figuring out how the crews will eat during their weeks, months, and even years in space.

The food for the crews on the International Space Station is primarily pre-packaged, requires regular deliveries of cargo spacecraft supplies, and the quality and nutrition deteriorates after approximately 18 months. But what if astronauts can grow their own food in microgravity? Earth researchers and crews on the International Space Station are exploring the idea by testing different crops and equipment to determine if the plan can succeed.

NASA hopes to successfully grow fresh crops that are easy to harvest and that do not require a lot of additional equipment or valuable electricity.

“Crews seem to really enjoy growing that food,” Howard Levine, chief scientist for NASA’s International Space Station Research Office at the Kennedy Space Center in Florida, said. “It’s a nice break from the usual activities at the station, and astronauts often volunteer their free time to do so.”

To date, NASA has grown a variety of plants, including lettuce, mustard and radish varieties – and learned a lot about how to do it successfully.

Here are seven aspects of plant growth that we study on the space station:

1) Picking real plants

What grows well on Earth may or may not go so well in space. Before sending crops to space, scientists must determine which plants should be tested on the space station. To improve that process, NASA launched a project in 2015 with the Fairchild Botanical Garden in Miami called “Growing Beyond Earth”. The program has recruited more than 230 high school and science high schools across the U.S. to grow a variety of seeds using special equipment. The seed, which thrives well in classrooms, is then tested in a Kennedy chamber that is very reminiscent of space station equipment. Selected seeds that do well in Kennedy are sent to the station. How they grow in orbit can inform the selection of plants for long-term missions, with minimal crew attention.

2) Learning to garden in space

Plants need a place to grow, and NASA has tested a number of microgravity garden household facilities. One way is to experiment with a vegetable production system or “Veggie”, which is a simple low-power garden chamber that can accommodate six plants. The seeds are grown in small “pads” of fabric placed in Veggie. The crews then take care of the plants and water them by hand, much like when they take care of a window garden on Earth.

NASA is developing another system, called the Passive Nutrient Delivery System, or PONDS, to work with the Veggie platform. PONDS replaces the seed cushions with a new plant holder that automatically feeds and waters the product, but still requires the crew to perform some breeding tasks. The research also uses a hand removal system called Advanced Plant Habitat. This fully automated device is designed to study the physiology of how plants grow in space in ways that require only minimal crew attention.

3) Real light

The composition of the light that shines on plants can affect their size, nutritional content, microbial growth and taste. Plants especially rely on red and blue light for growth. Researchers conducted experiments on the space station to see how different ratios of red and blue light affect the development of plants in space. Experiments have shown that plants in space grow well under the same light conditions that plants on Earth prefer. Although green lights are not needed for plant growth, they are included in plant growth systems, so plants appear to be similar to those grown on Earth.

4) Influence of gravity

Changes in gravity can affect how plants grow and how many crops they produce. Plants can sense gravity using a mechanism that involves changes in calcium within their cells. Astronauts recently launched experiments on the space station to measure how microgravity affects these calcium levels, which could offer clues to designing improved ways to grow food crops in space.

In the PESTO experiment, crews grew wheat plants to see how microgravity could change some of their key characteristics. They found that microgravity alters the development of leaves, plant cells and chloroplasts used in photosynthesis, but does not harm plants as a whole – in fact, wheat plants have grown 10% more than those on Earth.

Cell teams also successfully cultivated two generations of mustard using the Advanced Astroculture Chamber for an experiment that showed that a change in gravity caused the seed to be smaller and the secondary branches and seeds of the pod to grow differently. In addition, the experiment grew soy from seed to seed in space, which yielded larger plants and seeds.

5) Water delivery

One of the significant challenges for growing plants in microgravity is providing enough water to their roots to keep them healthy without drowning the plants in too much water. Numerous experiments have tried various methods to achieve this, including the aforementioned new PONDS plant and a plant water management experiment. A water management study demonstrated a hydroponic method to provide water and air in the root zone to help them grow. Researchers are growing plants both on board the space station and on Earth to compare how well they grow.

6) How old is too old?

Future space missions could take years, meaning the seeds that astronauts take with them can be far from fresh by the time they need to be planted. On Earth, seeds decline in viability and germination over time. But how do the age of seeds and long-term exposure to space flight affect their ability to germinate and grow? To find out, in January 2021, NASA grew lettuce and seeds from the cabbage family (kale, mustard and bok choi), which were at the station for almost three years. The results showed that although lettuce seeds did not thrive well compared to seeds that were in space for a shorter time, mustard seeds responded better than expected at the time of storage in space.

7) Human effect

Gardens, of course, need to be nurtured, which means astronauts or robots have to guard the plants that grow. NASA has studied how space gardening can contribute to the behavior and well-being of astronauts. Many astronauts have reported that caring for plants is a fun and relaxing activity for them.

“Caring for plants can also help astronauts stay in touch with life cycles on Earth,” said Gioia Massa, a scientist from the Kennedy Science Project. Mass research has focused on growing plants on the space station.

Moreover, astronauts say that time spent in the garden excites them to eat fresh produce when they are ready. Excitement motivates astronauts to creatively use products as ingredients in their meals, increasing the quality of life in space and raising their morale.

The Department of Biological and Physical Sciences (BPS) of NASA’s Directorate for Scientific Mission at NASA’s Washington headquarters provides funding for Veggie, APH, and related investigations.

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