Plants in Space: ISS Microgravity Gardening
- Sylvia Rose
- Apr 6
- 4 min read
Updated: Apr 7
Experiments on the International Space Station (ISS) achieve success when astronauts cultivate and eat lettuce in space. With environmental controls seeds sprout, seedlings grow, and plants flower and fruit in microgravity.
ISS experiments demonstrate plant growth in microgravity, including the basic processes of plant life, from seed germination to fruit production. Space gardening requires a carefully controlled environment.
Plant life is adapted to Earth. In space, gravity is nearly absent, radiation levels are much higher and the atmosphere is drastically different. Growing plants in space needs a closed-loop system to replicate optimal conditions for plant growth.
The Veggie Program
Begun on ISS in 2014, the Vegetable Production System (Veggie) is a plant growth unit capable of producing salad-type crops. This provides the crew with a safe, palatable, and nutritious source of food, and extra oxygen too.
Plants grown in space include cucumbers, arugula, bok choy, rice, tulips, zinnias, flax, dill, dwarf wheat and red romaine. The romaine is the first lettuce cultivated and eaten by the astronauts.
Science of Space Gardens
Gravity
Microgravity is a problem. On Earth, gravity dictates how roots grow and how water and nutrients are distributed. In space, instead of growing roots down and stems up, plants show an altered response or gravitropism.
Without gravity, plant roots align themselves toward or away from a light source above, causing them to skew. This light-related phenomenon is known as phototropism.
With gravity's influence diminished, their growth patterns change. Scientists use aeroponics, or nutrient-rich mist sprayed directly onto roots; and hydroponics, plants cultivated in water with nutrients.
Arabidopsis thaliana, or thale cress, a small flowering plant of the mustard family, produces roots 20% longer in microgravity compared to Earth. A "model" organism, it's also successfully grown in lunar soil on Earth.
On the ISS the flora reside in specially designed growth chambers. These mimic the effects of gravity through air circulation or artificial substrates.
Light
Plants need light for photosynthesis. The ISS uses LED lights, a controlled spectrum of light.
It can be configured to the specific needs of different plant species. The lights can simulate Earth-like day and night cycles, promoting optimal plant growth.
Water and Nutrients
Delivering water and nutrients in microgravity is also difficult. Traditional irrigation systems don't work. Scientists have developed systems to manage water distribution and prevent issues like root rot.
Plants are irrigated using the "Veggie" system named after the project. Astronauts inject water into small fabric plant pillows containing seeds and fertilizer. These are placed in the Veggie growth chamber.
Hydroponic systems enable plants to absorb nutrients from a nutrient-rich water solution instead of soil. This method ensures that crops receive essential elements directly.
Atmosphere
The ISS environment is carefully controlled for temperature, humidity, and CO2 levels. The plants contribute to space health by absorbing CO2 and releasing oxygen.
Radiation
Space radiation damage plant DNA. The ISS offers protection to plants and astronauts. Future space habitats will have to use radiation shielding materials.
Benefits of Space Botany
Food Security: Needed for long-duration space missions and potential off-world settlements.
Oxygen Production: Plants convert CO2 into breathable oxygen, helping create a self-sustaining environment.
Water Recycling: Plants transpire water, which can be collected and purified for reuse.
Waste Management: Some plants process waste materials, reducing burden on recycling systems.
Psychological Well-being: Interacting with plants improves mental health and reduces stress, important for astronauts isolated in space.
Besides the Veggie project, other "space gardens" are cultivated by Russian, Chinese and other cosmonauts. China successfully breeds silkworms in a biosphere on the far side of the moon.
One plant used is thale cress. The silkworms, dine on mulberry leaves and excrete carbon dioxide, which is used by the cress to produce oxygen for the worms. Potatoes are also grown.
Other systems are also in place, such as lighting, water, soil and air. Overall 5/6 silkworms advance to form silk cocoons.
The Future of Space Agriculture
Automated Systems: Developing robots and AI to manage plant growth, reducing the need for astronaut interference.
Closed-Loop Systems: Creating self-sustaining ecosystems to recycle water, nutrients, and waste.
Crop Optimization: Identifying and breeding plant varieties well-suited to space environments and producing high yields.
Lunar and Martian Greenhouses: Designing greenhouses to deploy on the Moon and Mars, using local resources like regolith (lunar or Martian soil).
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