It’s fairly common knowledge: where you grow a plant makes all the difference. Botanists, gardeners, and farmers alike have worked for thousands of years to perfect plant growth in any environment. From the fields of the Midwestern United States to the arid climate of the Middle East, humans will grow plants wherever they’re needed. And as technology has only gotten better and better, its ushered in a new era of “we can grow plants anywhere” . Timed lighting and watering systems have made indoor gardening a real option for urban environments. Vertical gardening is being discussed to remedy spacing issues. Hydroponics is becoming ever more popular. These are the solutions being created to address the challenge of -growing plants anywhere we damn well please- and solidifying our status as the true masters of plant science. But, for an even greater challenge, we look no further than our solar system. The real question is: can we grow plants in space? What tools will be used to grow our plants in space?

These are the questions that are essential for astrobotany (the study of plants in space) research. They are the questions that academic botanists ask themselves daily, and they are questions that may have crossed your mind as well. While astrobotany is generally considered to be a younger discipline, its history is richer than one might expect. For as long as we’ve had dreams of space travel, we’ve recognized the need for our plants. And as long as we’ve tried to grow plants in space, we’ve needed a place to grow them.

Here is a brief history of plant habitats in space.

1946 – Inside V-2 Rockets

Using the term very loosely, the first “space plant habitat” could technically be considered V-2 rockets. No actual plant growth occurred in 1946, when NASA launched maize seeds on repurposed V-2 rockets, but this is the first time plant material was ever subject to spaceflight. A true plant habitat? Maybe not so much. The first attempt at spaceflight plant biology? Yes, very much so.

1973 – “Unnamed Plant Growth Compartment” on Skylab

One of the oldest spaceflight plant biology experiments was a student project and joint collaboration with NASA. A true feat of engineering, and one of the oldest space stations, “Skylab” was a modified Saturn V rocket in which early spaceflight research was performed. Among them, the growth of rice in their plant growth chamber. Here is a description of the chamber from NASA experiment archives.

“The growth container for this experiment consisted of eight compartments arranged in two parallel rows of four. The growth container was similar to cardboard potting cartridges found at plant nurseries. Each compartment had two windowed surfaces, which allowed periodic photography of the developing seedlings from both a front and side view. The study of light intensities on plants was accomplished by using light filters. For this purpose, five windows were covered with special filters with different degrees of light transmittance, two windows were blocked to prevent any light from reaching the seeds, and the remaining window had no filter, allowing 100 percent transmission of light. Three rice seeds were inserted into each compartment through covered holes. Twenty-four seeds were inserted into a nutrient agar medium with the aid of an automatic seed planter. Photographs were taken at regular intervals for 30 days.” – Plant Growth/Plant Phototropism (ED61_62)

This pioneering experiment addressed one of the major variables that influence plant growth: lighting. As early as 1973, plant space habitats already included light filters, nutrient agar, and an automatic seed planter.

1982 – “Fiton 3 micro-greenhouse” on Салют-7 (Salyut 7)

Arabidopsis thaliana is an important research plant for botanists and astrobotanists alike. Its relatively small genome, fast growth, and compact size make it a model organism for research. It’s no surprise that this was the first plant to complete its life cycle (flower and produce seeds) in space. There is not a lot of information* about the elusive Fiton-3 greenhouse, but an excerpt from Humans in Spaceflight offers a quick description:

“Fiton-3 had transparent walls and contained growth vessels filled with an agar-nutrient medium, a unit for sowing seeds in microgravity, a ventilation system that maintained sterile conditions inside the container, and a daylight-type fluorescent light.” – Humans in Spaceflight, pg. 52

The literature also states that there was a centrifuge aboard Salyut 7. Lettuce was examined under 0.01, 0.1 and 1 g conditions using this equipment.

* Quick searches of Soviet era space equipment often yield few results. This could be a consequence of strict science rules imposed upon Russian scientists to prevent American technology theft during the Cold War. During this time, many researchers were forbidden to release detailed papers about their experiments.

1990 – “SVET” on Мир (Mir)

The plant habitat SVET (Russian: light) was installed in 1990 aboard the spacecraft Mir. SVET was located in the Kristall module of Mir and consisted of 4 basic units:

the plant growth chamber itself

the root module

the light and control unit

the GEMS (Gas Exchange Measurement System)

Plant varieties such as dwarf wheat and Brassica rapa were grown in SVET, with important variables being controlled and measured using these equipment. Substrate moisture was one of those being studied.

2002 – “Lada” on the International Space Station

Lada, named for the Slavic Goddess of Fertility, is the oldest greenhouse system on the International Space Station. Lada is a traditional spaceflight plant habitat with two different growth compartments for growth comparison. It design and technology are modeled after its predecessor “SVET” on Mir.

“Lada consists of four major components (a control module, two vegetation modules and a water tank) and is designed to be deployed on a cabin wall. This deployment scheme was chosen to provide the crew therapeutic viewing and easy access to the plants. The two independently controlled vegetation modules allow comparisons between two vegetation or substrate treatments. The vegetation modules consist of three sub-modules, a light bank, the leaf chamber, and a root module.”

– Lada: The ISS Plant Substrate Microgravity Testbed [accessed May 27 2018]

2014 – “VEGGIE” on the International Space Station

The VEGGIE vegetable production unit was developed by Sierra Nevada subsidiary ORBITEC and installed on the ISS in 2014. There are currently two VEGGIE modules on the ISS. Plants are grown with root mats and ‘plant pillows’, which are small, wicked pillows that contained calcined clay and fertilizer for the plants to grow in. The lights on VEGGIE are primarily red and blue light, which are LEDS optimized for plant growth, because they have the highest energy wavelengths. Air flow and pressure are also controlled in each of the VEGGIE systems. Below, NASA describes the process of beginning a plant experiment in the growth compartment.

“Wearing sunglasses, Swanson activated the red, blue and green LED lights inside Veggie on May 8. A root mat and six plant “pillows,” each containing ‘Outredgeous’ red romaine lettuce seeds, were inserted into the chamber. The pillows received about 100 milliliters of water each to initiate plant growth. The clear, pleated bellows surrounding Veggie were expanded and attached to the top of the unit.” – NASA KSC 05/16/14

Summary

The timeline of plant habitats for space has ebbed and flowed with the construction and maintenance of space stations, research vessels, and spacecraft. Plant biologists involved with these projects have largely (and rightly) stuck to their wheelhouse. The control over as many variables as possible is key in the development of these plant habitats. This is a common thread amongst all the discussed equipment above. Air flow, pressure, watering, nutrients, and light are all closely controlled and monitored. In addition to this, sterilization from start to finish as a plant goes through its life cycle is essential. Contamination could jeopardize important data. These are concepts realized and practiced as early as the 70s and they are still continued to this day.

This overview of important plant habitats left out hardware such as BRIC (Biological Research In Canisters) and SIMBOX, as those are less “greenhouse”, but more petri-dish, or biological organism related. These smaller research tools have less specificity when it comes to growing plants, but yield equally important data when it comes to astrobotany research.

There is still much to learn when it comes to our endeavors in space agriculture. Despite a history spanning nearly six decades, the world’s space programs still have yet to produce the first bioregenerative life support system. As our rocket technology advances, our biological sciences must keep up. We must push for the development of more and more advanced plant habitats. To further our space legacy, we will continue to learn, continue to build, and continue to grow plants in space.

Let’s grow plants in space.