Growing in Zero-G: Simulated Microgravity and Space Agriculture

There are a litany of reasons to study plants under extreme conditions, one of which is efficient cultivation on extended space travel. These investigations will also refine terrestrial horticultural finesse.

As it is with other experiments, sending plants into space is prohibitively expensive. High throughput simulations, like those provided by Litegrav, can cost-effectively expedite discovery.

Past spaceflight experiments have shown that plants can germinate, mature, bloom, and fruit in space (JAEA, n.d.). 

NASA’s Vegetable Production System, which runs on just 115 watts, grows vegetables as diverse as lettuce, tomatoes, and beans (Regan, 2012). Since its inception, Veggie, as the system is known, has grown three types of lettuce, mizuna mustard, Chinese cabbage, zinnia flowers, and red Russian kale (NASA, n.d.). 

Earlier experiments like those conducted in the 1960s on Kosmos 110 resulted in yields greater than control groups on earth (Harvey, 2011).  

More recent space experiments have revealed that plants are inclined to become longer and thinner in microgravity. Both shoots and roots develop differently, and they may unexpectedly bend or curve. Cell wall formation is altered; microgravity yields peculiar forms and sizes for plants grown in these conditions (Hoson, 2014).

Given the low energy demands and potentially more abundant harvests in space, things are looking sanguine considering the absolute need for fresh produce on long flights. 

Nutritional Importance of Fresh Produce 

While energy requirements for astronauts remain largely unchanged, protein deficiencies, vision problems, as well as both bone and muscle wasting, are well-documented issues.

Dietary protein type is essential for bone health, and plant-based protein appears to be more helpful for this purpose than animal protein (Lane, 2013).

A survey of hundreds of articles dealing specifically with spacefarers nutritional challenges and requirements found that optimal and sustainable nutrition can (and likely must) be supported by fresh food production. This is vital for long-term life support systems (Tang, 2021).

Fresh foods, like plant-based vegetables, provide the needed vitamins, minerals, fiber, and secondary components that packaged foods lack. Prepackaged foods do not provide adequate nutrition for astronauts due to nutrients loss associated with food preparation and storage (Tang, 2021).

The Challenges of Zero-G 

Staying fed in space is fraught with challenges. There are physical constraints related to farming at an adequate scale. There are criteria for selecting the plants suitable for microgravity conditions, and issues with designing water and lighting systems to catalyze growth (Carillo, 2020).

A study inquiring into soil-based farming for the establishment of settlements on Mars found that the planet's soil reduces water loss by 90 % and boosts microbial activity, counteracting the possibly deleterious effects of reduced water flow due to gravitational changes (Maggi, 2010). 

The primary challenge to off-world horticulture is the stifling of photosynthesis by the scarcity or absence of sunlight. This can be overcome. NASA does so with light emitting diodes (LEDs). NASA’s Veggie system chamber uses primarily magenta pink light to optimize absorption of light for proper photosynthesis.

Gravimorphogenesis and Gravitropism

Although estimated to have evolved over 450 million years exclusively on earth, experiments in microgravity conditions have shown the remarkable adaptivity and survival ability of plants in an entirely new environment. 

In low gravity conditions, plant seedlings grow in ways quite different from earth. They display what is called automorphogenesis, where shoots and roots curve and bend in unusual ways (Hoson, 2014). These aberrations are not uniform among all types of plants, however.

Roots frequently reveal greater variation in their maturation patterns than shoots. In a study, approximately 20% of rice roots shot up right into the air, yet most formed with a consistent baseline angle, similar to how they would on earth under simulated microgravity (Hoson, 2014).

Auxin in Space

Experiments in space show that low gravity environments act as a disruptor to the balance between cellular growth and division (Medina, 2010). These mutual processes work in unison to help plants grow on Earth. 

Auxin is pivotal here. It is chiefly responsible for changes in the direction of rooting due to microgravity; auxin movement permits roots to respond to and adapt to changes in gravity (Ferl, 2016).

When roots detect changes in gravity, its starch-filled structures shift to the root’s lower side, shuffling the auxin to the bottom. The uneven distribution bends the root, moving it into a vertical position. The auxin flows in what is known as a reverse fountain model, ensuring the health of the plant (Ferl, 2016). 

Conclusion

Auxin illustrates how readily familiar flora can adapt to unfamiliar territory. This research will lay the foundation for a deeper understanding that can be only gained by extending botany’s, and agriculture’s, domains.  

If civilization in the twenty-first century is to thrive, venturing into a terrain hitherto untouched, it is essential that we continue the necessary research in sustainable plant agriculture in space. 

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References and Works Cited

Carillo, P., Morrone, B., Fusco, G., De Pascale, S., Rouphael, Y. (2020). Challenges for a sustainable food production system on board of the International Space Station: A technical review. Agronomy, 10(5), 1-17. https://doi.org/10.3390/agronomy10050687

Ferl, R., Paul, AL. The effect of spaceflight on the gravity-sensing auxin gradient of roots: GFP reporter gene microscopy on orbit. npj Microgravity 2, 15023 (2016). https://doi.org/10.1038/npjmgrav.2015.23

Harvey, Brian; Zakutnyaya, Olga (2011). Russian Space Probes: Scientific Discoveries and Future Missions. Springer Science & Business Media. p. 315. ISBN 978-1-4419-8150-9.

Hoson T. Plant Growth and Morphogenesis under Different Gravity Conditions: Relevance to Plant Life in Space. Life (Basel). 2014 May 16;4(2):205-16. doi: 10.3390/life4020205. PMID: 25370193; PMCID: PMC4187158.

Japan Aerospace Exploration Agency. (n.d.). Interview with Takashi Takahashi: Investigating plant growth under the influence of gravity. Japan Aerospace Exploration Agency (JAXA). https://global.jaxa.jp/article/special/kibo/takahashi_e.html

Lane HW, Bourland C, Barrett A, Heer M, Smith SM. The role of nutritional research in the success of human space flight. Adv Nutr. 2013 Sep 1;4(5):521-3. doi: 10.3945/an.113.004101. PMID: 24038244; PMCID: PMC3771136.

Maggi, F., Pallud, C. (2010). Martian base agriculture: The effect of low gravity on water flow, nutrient cycles, and microbial biomass dynamics. Advances in Space Research, 46(10), 1257-1265. https://doi.org/10.1016/j.asr.2010.07.012

Medina FJ, Herranz R. Microgravity environment uncouples cell growth and cell proliferation in root meristematic cells: the mediator role of auxin. Plant Signal Behav. 2010 Feb;5(2):176-9. doi: 10.4161/psb.5.2.10966. Epub 2010 Feb 17. PMID: 20173415; PMCID: PMC2884128.

National Aeronautics and Space Administration. (n.d.). Growing plants in space. NASA. https://www.nasa.gov/exploration-research-and-technology/growing-plants-in-space/

Regan, Rebecca (16 October 2012). "Station Investigation to Test Fresh Food Experience". NASA. Archived from the original on 23 January 2016. Retrieved 30 September 2024.

Tang H, Rising HH, Majji M, Brown RD. Long-Term Space Nutrition: A Scoping Review. Nutrients. 2021 Dec 31;14(1):194. doi: 10.3390/nu14010194. PMID: 35011072; PMCID: PMC8747021.

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