National Aeronautics and Space Administration

A Researcher’s Guide to:

Plant Science
2

This International Space Station (ISS) Researcher’s Guide is published by the NASA 

ISS Program Science Office.

Authors: 

Gary W. Stutte, Ph.D.

Oscar Monje, Ph.D.

Raymond M. Wheeler, Ph.D.

Executive Editor: Amelia Rai

Technical Editor: Neesha Hosein

Designer: Cory Duke

Cover and back cover: 

a. View of Astronaut Peggy Whitson, Expedition 5 NASA International Space Station science officer, 

looking at the Advanced Astroculture Soybean plant growth experiment as part of Expediting the 

Process of Experiments to the Space Station Rack 4 located in the U.S. Laboratory/Destiny. 

b. Back Cover: Both images are Arabidopsis thaliana (Brassica family) plants grown under 

controlled conditions in a plant cultivation module in the BioServe Laboratories. Image courtesy 

of BioServe Laboratories.
Cosmonaut Gennady Padalka harvests radishes from the Lada Plant Chamber (June 22, 2009).

Soaring 250 miles above Earth, the ISS is a modern wonder of the world, 

combining the efforts of 15 countries and thousands of scientists, engineers 

and technicians. The ISS is a magnificent platform for all kinds of research 

to improve life on Earth, enable future space exploration and understand the 

universe. This researcher’s guide is intended to help potential researchers 

plan experiments that would be exposed to the space environment, while 

externally attached to or deployed from the ISS. It covers all the pertinent 

aspects of the space environment, how to best translate ground research to 

flight results and lessons learned from previous experiments. It also details 

what power and data are available on the ISS in various external locations.

The Lab is Open
4
1. Microgravity, or weightlessness, alters many observable phenomena 

within the physical and life sciences. Systems and processes affected by 

microgravity include surface wetting and interfacial tension, multiphase 

flow and heat transfer, multiphase system dynamics, solidification, and 

fire phenomena and combustion. Microgravity induces a vast array of 

changes in organisms ranging from bacteria to humans, including global 

alterations in gene expression and 3-D aggregation of cells into tissue-like 

architecture.

2. Extreme conditions in the ISS environment include exposure to extreme 

heat and cold cycling, ultra-vacuum, atomic oxygen, and high energy 

radiation. Testing and qualification of materials exposed to these extreme 

conditions have provided data to enable the manufacturing of longlife reliable components used on Earth as well as in the world’s most 

sophisticated satellite and spacecraft components.

3. Low Earth orbit at 51degrees inclination and at a 90-minute orbit 

affords ISS a unique vantage point with an altitude of approximately 240 

miles (400 kilometers) and an orbital path over 90 percent of the Earth’s 

population. 

This can provide improved spatial resolution and variable lighting 

conditions compared to the sun-synchronous orbits of typical Earth 

remote-sensing satellites.

Unique Features of the ISS 

Research Environment

1. Microgravity, or weightlessness, alters many observable phenomena 

within the physical and life sciences. Systems and processes affected by 

microgravity include surface wetting and interfacial tension, multiphase 

flow and heat transfer, multiphase system dynamics, solidification, and 

fire phenomena and combustion. Microgravity induces a vast array of 

changes in organisms ranging from bacteria to humans, including 

global alterations in gene expression and 3-D aggregation of cells into 

tissue-like architecture.

2. Extreme conditions in the ISS space environment include exposure to 

extreme heat and cold cycling, ultra-vacuum, atomic oxygen, and high 

energy radiation. Testing and qualification of materials exposed to these 

extreme conditions have provided data to enable the manufacturing of 

long-life reliable components used on Earth as well as in the world’s most 

sophisticated satellite and spacecraft components.

3. Low Earth orbit at 51 degrees inclination and at a 90-minute orbit 

affords ISS a unique vantage point with an altitude of approximately 240 

miles (400 kilometers) and an orbital path over 90 percent of the Earth’s 

population. This can provide improved spatial resolution and variable 

lighting conditions compared to the sun-synchronous orbits of typical 

Earth remote-sensing satellites.

Unique Features of the ISS 

Research Environment
6

Unique Features of the International Space Station (ISS) 

 Research Environment 5

Why use the ISS as a Laboratory? 7

Results from Past Microgravity Research 9

Microgravity as a Research Tool 9

Results from Microgravity 10

Opportunities on ISS for Plant Research 11

Lessons Learned 13

Physical Phenomena and Primary Effects of Microgravity 13

ISS Atmospheric Conditions 14

Gravity 16

Lack of Convection 17

Gas Exchange 18

Root Zone Aeration 20

Root Zone Fluid Dynamics 21

Temperature Control 22

Lighting 23

Approaches to Mitigate Effects Of Microgravity Environment 25

Biological Approaches 25

Engineering Approaches 26

Research Facilities on ISS and How to Choose Them 27

Plant Growth Facilities 27

The Advanced Biological Research System (ABRS) 27

Biological Research in Canisters (BRIC) 27

BRIC Petri Dish Fixation Unit (BRIC/PDFU) 27

Commercial Generic Bioprocessing Apparatus (CGBA) 27

European Modular Cultivation System (EMCS) 28

Lada 28

Plant Experiment Unit / Cell Biology Experiment Facility (PEU/CBEF) 28

Plant Habitat (in development) 29

Vegetable Production System (Veggie) 29

Support Facilities 29

Developing and Flying Research to ISS 32

Process for Payload Development and Implementation 32

Environmental Conditions on ISS 33

Sponsorship Opportunities 35

What Should Principal Investigators Know About 

Conducting Research on ISS? 35

Process for Payload Development and Implementation 36

Funding Opportunities/Points of Contact 38

Citations 39

Acronyms 47

Table of Contents
The progress in plant space biology over the past quarter century has greatly 

increased our understanding of how plants: respond to gravity; informed the 

design of advanced plant growth facilities; achieved the completed life cycle; and 

demonstrated that physiological processes necessary for biological life support are 

sustainable. In the process, the horticulture of plants in the unique environment of 

microgravity was being developed, and plant/microbe interactions were explored. 

The advances made during the decades of spaceflight experimentation have also 

identified critical gaps in our understanding of the role of gravity and the spaceflight 

environment on plant biology at the cellular, tissue, whole plant, and community 

levels. 

In this context, the International Space Station is a unique platform where 

reduced gravity can be used to probe and dissect biological mechanisms in plants 

for understanding how terrestrial biology responds to gravity. This knowledge is 

important for supporting safe and long-term human habitation in space using 

bioregenerative life support, utilizing plants and microbial communities, and for 

reducing exploration risks to crews by designing countermeasures to problems 

associated with living in space. In addition, by using the facilities with centrifuges, 

scientists can investigate how plants respond to the reduced gravity environments on 

the Moon and Mars. 

The National Research Council’s 2011 Decadal Survey Report, “Recapturing 

a Future for Space Exploration: Life and Physical Sciences Research for a New 

Era,” (http://www.nap.edu/catalog/13048.html) 

recognized the significance of understanding plant 

responses in microgravity for both space exploration 

and terrestrial applications. The report had a number 

of recommendations for plant research including the 

following: 

1. The establishment of a robust spaceflight program of 

research analyzing plant and microbial growth and 

physiological responses to multiple stimuli encountered 

in the spaceflight environments.

2. The establishment of a research program aimed at demonstrating the roles of 

microbial-plant systems in long-term life support systems.

Why Use the ISS as 

a Laboratory?
8

A number of knowledge gaps were identified that are well-suited to the current 

capabilities of spaceflight hardware and analytical capabilities of the ISS. These 

gaps clearly point to the necessity of maximizing the science return from each 

spaceflight opportunity and the need for both basic research in transcriptional 

profiling, proteomic and metabolomic analysis in model systems. These as well as 

life cycle studies are necessary for developing horticultural techniques and validating 

environmental conditions to establish the feasibility of incorporating plants in 

bioregenerative life support systems. A partial listing of these research questions is 

included in Table 1.

Topic Area Potential Research Questions Suitable for ISS Investigations

Gravity 

Sensing

• What are the primary gravity receptors in leaf stem and root tissue?

• What are intermediate signals at transcriptional, biomolecular and 

physiological levels?

• What interactions with thigmotrophic, phototrophic and hydrotropic stimuli 

occur, and how are they differentiated?

Plant 

Physiology

• How do light and gravity responses interact?

• Does the spaceflight environment induce stresses (μ-gravity, elevated CO2, 

diffusion limited chemical exchange, root zone hypoxia, etc.), and what 

are primary signals and hormonal changes affecting development?

• What are the effects of spaceflight environments on primary physiology: 

photosynthesis, respiration, transpiration, nutrition, and secondary 

metabolism?

• How do the interactions of multiple environmental stimuli affect 

productivity and bioavailability of bioactive products?

• How does the gravity effect on structural carbohydrates manifest itself 

over multiple generations?

• Does microgravity affect genetic stability?

Plant/

Microbe 

Interactions

• What aspects of the spaceflight environment regulate resistant and/or 

susceptibility to plant pathogen infection? 

• Is the gravity effect on virulence universal or species/strain specific?

• How does the spaceflight environment affect the development of 

beneficial plant/microbe associations?

Life Support 

Systems

• How can horticultural approaches to sustained production of edible crops 

be implemented?

• What are the effects of environmental stresses (lighting, CO2, root zone 

moisture, O2, trace gases) on productivity?

• Are models of crop productivity developed in terrestrial conditions valid in 

spaceflight environments?

• How do plants and microbes interact with physical and chemical life 

support systems?

Table 1. Partial listing of research questions.
Microgravity as a Research Tool

The effects of gravity on the growth and development of plants have been the 

subject of scientific investigation for more than a century with the early work 

of Charles Darwin demonstrating the gravitropic response of roots (Darwin, 

1881). The effect of spaceflight environment on plants has been studied since the 

early BioSatellite experiments in the 1960s (e.g., Johnson and Tibbitts, 1968). 

Subsequent investigations of plant responses in the spaceflight environment have 

allowed our understanding of the mechanisms of plant responses to gravity to be 

unraveled (Sachs, 1991; Bancaflor and Masson, 2003; Swarup and Bennet, 2009; 

Paul et al., 2013). 

The microgravity environment has also been instrumental in understanding how 

the unique aspects of the spaceflight (microgravity, lack of convective currents) 

will affect biological life support systems for long-duration space missions (Ferl 

et al., 2002; Wolverton S.C., J.Z. Kiss. 2009. An update on plant space biology. 

Gravitational and Space Biology 22: 13-20. Monje et al., 2003; Wheeler, 2010). 

The past quarter century has provided remarkable progress in our understanding 

of how to grow plants in the unique environment of space and progressed from 

simple, short-duration experiments with limited environmental control to 

complex, long-duration experiments with sophisticated environmental control and 

monitoring. The complex effects of the spacecraft environment on nutrient and 

water uptake, temperature control and diffusion gradients have been identified; the 

effects of gravity on signal perception and transcription are being unraveled, and 

technology to support long-duration, multiple-generation plant growth is being 

developed. 

This report provides a general overview of the results from these spaceflight 

studies and identifies the unique aspects of the spaceflight environment that lend 

themselves to scientific investigation and understanding of space plant biology.

Results from Past 

Microgravity Research
10

Results from Microgravity

Studies from satellites in the 1960s showed that photosynthesis proceeded as 

expected in space (Ward et al., 1970) and that plants (peppers) developed leaf 

epinasty in a free-fall environment (Johnson and Tibbitts, 1968). The photosynthetic 

observations were later confirmed in a more thorough study as part of the first 

plant experiment flown on the ISS (Monje et al., 2005, Stutte et al., 2005). 

The observation of leaf epinasty in space confirmed the long-observed linkage 

between gravity and ethylene mediated responses observed on horizontal clinostats 

and when plants were gravitationally disoriented (Denny, 1936; Leather et al., 

1972). Further analysis of the epinasty data showed that the extent of leaf curling 

for peppers in space and on horizontal clinostats was different, yet confirmed its 

occurrence under both conditions (Brown et al., 1974). 

A long-standing challenge for space biological research was to determine whether 

plants could successfully complete a life cycle in space—a so-called “seed-to-seed” 

experiment. This was first demonstrated with Arabidopsis by Merkys et al. (1984) 

on the Russian Salyut-7 and then later by Link et al. (2003) as well as with other 

species including Brassica rapa (Musgrave et al., 2000) and wheat (Sytchev et al., 

2001), which were both carried out on the Russian Mir Space Station. Subsequent 

studies on the International Space Station using the “Lada” plant chamber 

demonstrated successive generations of pea (Pisum sativum) plants (Sytchev 

et al., 2007).

Other researchers used the free-fall environment of spaceflight to finally test 

Charles Darwin’s hypothesis that circumnutation of growing plant stems is an 

endogenous rhythm rather than just gravitational overshoot of the plumb-line 

following by continuous self-correction (Darwin, 1881). Brown et al. (1990) 

reported that sunflower hypocotyls showed circumnutation in weightlessness but 

at a different frequency than in 1-g. Thus, a spaceflight experiment was needed to 

answer this more than 100-year-old question. (Johnson A., Solheim B.G.B. Iverson, 

T.-H. (2009) Gravity amplifies and microgravity decreases circumnutations in 

Arabidopsis thaliana stems: results from a space experiment. New Phytologist 182, 

621-629. Others have taken advantage of the free-fall environment in low-Earth 

orbit to carefully study plant phototropic responses (Heathcoat et al., 1995; Kern 

and Sack, 1999; Millar et al., 2010) and other fundamental influences on plant 

growth and development such as magnetic fields (Hasenstein et al., 2005) or 

water-potential gradients on root growth (Takahashi et al., 2003). 
In addition, by preserving plant tissue retrieved from spaceflight, space biologists 

have been able to detect differential expression of genes between the μ-g and 1-g 

environments and draw inferences on the types of enzymes and metabolic responses 

that might occur in plants while growing in space (Paul et al., 2001). Spaceflight 

testing has also allowed assessment of amyloplast (statolith) positions in gravitysensing organs and tissues in microgravity environments (Kern et al., 2001). 

Opportunities on ISS for Plant Research

Research on the ISS offers the opportunity to study how gravity and other factors 

influence the physical and biological processes in plant biology. It also provides 

the opportunity to exploit these findings to advance the understanding of basic 

phenomena and to promote the commercialization of these results. The designation 

of the U.S. portion of the ISS as a National Laboratory (NL) by the U.S. congress 

in 2005 opened the door to use this unique research environment by government 

agencies, academic institutions, private foundations, and commercial interests.

Figure 1. Wheat cv. USU Apogee grown in Biomass Production System during 

Photosynthesis Experiment and System Testing and Operation experiment during 

International Space Station Increment IV.
12

The ISS NL provides a variety of purpose-built, state-of-the-art equipment to 

enable research in the life sciences. These include access to multipurpose facilities 

with supporting hardware fitted with standard interfaces for power, data, cooling, 

water, and other critical resources to maintain and monitor an experiment. Cold 

stowage facilities (down to -80°C) exist to maintain samples collected on ISS NL 

and a work environment suited to contain samples and conduct research with 

liquids and/or hazardous materials. There is specialized hardware for conducting 

plant research aboard the ISS NL that has been developed by NASA, international 

partners and commercial payload providers. 
Physical Phenomena and Primary Effects of Microgravity

Our understanding of how the spaceflight environment affects growth, development 

and physiology of plants can be traced to the earliest days of space exploration. On 

Biosatellite II (launched 7 September 1967), wheat (Triticum sativum L.) seedlings 

were examined for orientation, morphogenesis and biochemical changes (Gray and 

Edwards, 1968), and leaf orientation of young pepper (Capsium annum) leaves was 

monitored (Johnson and Tibbitts, 1968). The research developed since that time 

revealed that plants can perceive microgravity as a stress either directly via effects 

on biological process (e.g., movement of gravity sensing statoliths) or indirectly 

because of secondary effects of the spaceflight environment. For example, there is an 

absence of buoyancy-driven convective currents in microgravity, resulting in thicker 

boundary layers on plant surfaces. This increase in boundary layer thicknesses 

affects rates of gas exchange, rate of evaporative cooling, and heat transfer through 

aerial organs of plants. 

The lack of gravity and lack of convective mixing also has implications for the 

movement of water, oxygen and solutes through the root zone. This occurs 

directly because of the movement of water and solutes in root zones by diffusion 

(Porterfield, 2002), and indirectly by reducing the rate of evapotranspiration from 

the leaves (Monje et al., 2003). As a consequence, most plants returned from 

microgravity experience some degree of hypoxia stress (Stout et al., 2001). In 

addition, the reduction in evapotranspiration, combined with diffusion limited 

movement of solutes, can affect nutrient uptake by the roots (Wolff et al., 2013).

The series of experiments by Musgrave and co-workers from 1997 to 2002 

illustrates how spaceflight improved our understanding of the impact of secondary 

effects of microgravity and physiological responses measured in space. Prior to her 

work, the only positive result in completing plant reproduction in a spacecraft was 

achieved on Salyut-7 in a miniature plant growth chamber called Phyton (Merkys 

et al., 1984).

In 1993, a series of experiments Chromosone and plant cell division in space 

(CHROMEX) studied the apparent sensitivity of reproductive events to the 

spaceflight environment using the Plant Growth Unit (PGU), a mid-deck locker 

payload on the space shuttle. Arabidopsis thaliana (L.) Heynh was selected for use 

in these experiments because of its compact size, low light requirement and short 

life cycle. Early events in reproductive development were studied: gametophyte 

development, pollination, fertilization, and early embryogenesis during three flight 

Lessons Learned
14

experiments: CHROMEX-03 on STS-54 (6 d), CHROMEX-04 on 

STS-51 (10 d), and CHROMEX-05 on STS-68 (11 d). In CHROMEX-03, 

plants were grown in closed plant growth chambers (PGCs), and male and 

female gametophyte development aborted at an early stage in the flight material. 

In CHROMEX-04, CO2 enrichment was provided to the closed PGCs, and 

reproductive development proceeded normally until the pollination stage 

when there was an obstacle to pollen transfer in the spaceflight material. In 

CHROMEX-05, an air-exchange system was used to ventilate the PGCs with cabin 

air that had been filtered to remove volatile organic compounds (VOCs). Under 

these conditions, the spaceflight plants finally exhibited reproductive development 

comparable to the ground controls with immature seeds similar to those from the 

ground control plants (Musgrave et al., 1997).

This example showed that many physical changes will occur in the plant’s 

environment because of microgravity. Because microgravity changes the behavior of 

fluids and gases, protocols established for successfully growing plants on the ground 

do not necessarily provide the same physical environment for plants growing inorbit. The growth conditions provided in CHROMEX-03 allowed ground control 

plants to complete their early reproductive development, but the same protocol 

resulted in aborted development at an early stage in spaceflight. Since subsequent 

modifications of the gaseous environment in CHROMEX-04 (CO2 enrichment) 

and CHROMEX-05 (gas flow-through) allowed reproduction to proceed normally 

during spaceflight, it was concluded that the gaseous environment around the 

spaceflight plants in CHROMEX-03 was inadequate to support continued 

reproductive development (Musgrave et al., 2000).

ISS Atmospheric Conditions

The atmospheric composition of ISS can differ from terrestrial environments (e.g., 

drier [30 to 50 percent relative humidity (RH)], CO2 enriched [3,000 to 7,000 

ppm], warm [>230C]), and contains many VOCs. Evaluation of both in-flight and 

post-flight cabin air quality samples from the ISS demonstrates that even though 

onboard air revitalization and control systems can maintain acceptable cabin air 

quality, significant spatial and temporal effects still occur (Perry and Peterson, 

2003). Such effects are directly influenced by ISS’s configuration and operational 

activities, the functional status of trace contaminant control equipment and 

equipment failures. Chief contributors to the total trace contaminant load include 

methane, alcohols and organosilicones. Other minor contributors include ketones, 

halocarbons, hydrogen, and carbon monoxide.
The atmospheric composition may have direct effects on plant growth when the 

plant experiments are exposed to cabin air. During the International ShuttleMir Greenhouse Project wheat cv. Super dwarf was grown for an entire life cycle, 

resulting in approximately 300 sterile heads because of high ethylene (0.4 ppm 

during anthesis; Campbell et al., 2001). This was 

the first case identifying ethylene, a plant hormone, as a deleterious contaminant 

found on spacecraft.

Ethylene also affected the growth and morphology of Arabidopsis seedlings 

conducted in Biorack during STS-84 (Guisinger and Kiss, 1999), the 

sixth shuttle/Mir docking mission. Air samples of shuttle air taken during the 

mission revealed the presence of up to 1.6 ppm ethylene, suggesting that the 

shuttle air was contaminated during docking with Mir. Kiss et al. (1999), and 

it was observed that two striking features of Arabidopsis seedlings developed in 

spaceflight: anomalous hypocotyl hook structure (Fig. 2) and a higher density of 

root hairs. Experiments subsequently confirmed that these responses were similar 

to those induced by ethylene, or ethylene analogs and suggested that ethylene-like 

compounds were present in the spacecraft cabin. 

Figure 2. Shannon Lucid inspects wheat grown in Svet plant growth chamber on Mir.
16

Currently, the ISS is required to maintain 

ethylene below 0.05 ppm. However, 

ethylene is seldom measured and requires 

specialized instrumentation to detect. 

Thus, most plant chambers utilize 

engineering controls (e.g., potassium 

permanganate sorbents like Purafil© or 

photocatalytic oxidation) for removing ethylene produced by the plants. During 

rapid growth, the ethylene production rates from lettuce and wheat plants range 

between 1.6 -2.5 nmol m-2 d-1 but could be as high as 93 nmol m-2 d-1 for 

tomatoes during fruit ripening (Wheeler et al., 2004). Plant growth chambers 

like the Svet on Mir, Lada on ISS, and Veggie that circulate cabin air for cooling, 

providing CO2

 and humidity control remain exposed to ethylene from the 

spacecraft. Apparently, the current ethylene control on the ISS is sufficient to allow 

seed formation as seed-to-seed experiments have been recently accomplished using 

the Lada open-chamber system on ISS (Sychev et al., 2007). 

Gravity

Orbiting spacecraft are ideal platforms for studying direct effects of weightlessness 

(microgravity) on living organisms. In reality, spacecraft such as the ISS are still 

under about 90 percent of Earth’s gravitational pull, but their continuous free-fall 

provides a unique environment for scientific research. Ideally, it would be best to 

have centrifugation capabilities along with the spaceflight microgravity treatments 

to provide side-by-side 1-g or fractional g comparisons, and this approach has 

been used in the past (e.g., Brown et al., 1990) and exists with research hardware 

such as the European Modular Cultivation System (EMCS). Reduced or fractual 

Figure 3. Light micrographs of hypocotyls of 

Arabidopsis seedlings from the F μg (A), 

the ground controls (B = F 1 g; C = G 1 g), 

and the ethylene control (D = G ethy). Note the 

anomalous hook that developed in hypocotyls 

of the light seedlings (both F μg and F 1g) 

and in the ethylene ground control. A typical 

hypocotyl hook, characteristic of dark-grown 

seedlings, developed in G 1-g seedlings. 

Bar = 500 μm (Kiss et al. 1999).
gravity can be used to study plants in 

the gravity levels found on the moon 

and Mars (Kiss J.Z., P. Kumar, R.N. 

Bowman, M.K. Steele, M.T. Eodice, 

M.J. Correll, R.E. Edelmann. 2007. 

Biocompatibility studies in preparation 

for a spaceflight experiment on plant 

tropisms (TROPI). Advances in Space 

Research 39: 1154-1160). However, 

the results obtained in space to test 

specific hypotheses on gravitropism, 

gene expression, seed formation, 

growth rate, etc., can be compromised 

by secondary effects caused by changes 

in the physical environment compared 

to 1 g. As noted earlier, the absence of 

gravity induces a number of physical 

effects that alter the microenvironment 

surrounding plants and their organs. These effects include increased boundary layers 

surrounding plant organs and the absence of convective mixing of atmospheric gases. 

In addition, altered behavior of liquids and gases in microgravity are responsible for 

phase separation and for dominance of capillary forces (Porterfield, 2002). 

Thus, the design of biological experiments (e.g., cells, plants, animals, etc.) 

conducted in microgravity must account for: 1) changes in gravity-dependent fluid 

and gas behavior, 2) potential effects of spacecraft atmosphere, and 3) hardwarespecific limitations (ventilation, light level, CO2

 supply, humidity and temperature 

control, and ethylene removal; Monje et al., 2003; Wolff et al., 2013). 

Lack of Convection

In the presence of gravity, buoyancy-driven thermal convection induces the 

movement of fluids surrounding plant organs and tissues (e.g., hot air rises and cold 

air sinks). This movement enhances mass and heat transport between the tissues 

and the surrounding bulk-air (Porterfield, 2002). In space, plants without adequate 

ventilation will become surrounded by stagnant air layers that may translate into 

significant effects on plant metabolism. At 1 g, the boundary layers are thin enough 

so that metabolic processes such as respiration and transpiration are rarely diffusionFigure 4. Water droplet on pea leaf grown in 

Lada chamber on ISS. The lack of buoyancydriven convection in microgravity alters the behavior of fluids and gases at the leaf interface.
18

limited (Monje et al, 2003). In microgravity, the thickness of these boundary layers 

increase and heat-and-mass transfer is sustained only by molecular diffusion when 

there is no forced air convection. 

The supply and removal of metabolic gases (O2, CO2, H2O, and ethylene) to 

and from plant organs (seeds, flowers, shoot tips, leaves and roots) also becomes 

diffusion limited, which can lead to plant stress and reduced growth because 

most biological processes (e.g. photosynthesis and respiration) quickly exceed the 

supply rates that can be achieved by diffusion alone (Porterfield 2002; Monje et al., 

2003). These secondary effects of microgravity operate by limiting heat and mass 

transport across boundary layers. They affect shoot and root organs. However, roots 

are affected by an additional factor, microgravity-induced moisture redistribution 

within the root media, 

which further reduces 

the availability of oxygen 

to roots (Jones and Or, 

1998; Liao et al, 2004). In 

the absence of convective 

mixing, the secondary 

effects associated with 

increased resistance across 

the boundary layer for 

gas exchange, reduced 

capacity of evaporative 

heating, and accumulation 

of volatiles in localized 

areas require that careful 

attention be paid to 

the design of ground 

control experiments and 

appropriate selection of 

flight hardware. 

Gas Exchange 

A number of experiments have investigated the effects of microgravity on gas 

exchange in plants (Ward et al., 1970; Tripathy et al., 1996; Stutte et al., 2005). 

The early spaceflight experiments were conducted in poorly ventilated growth 

chambers, and this resulted in net decreases in growth and apparent photosynthetic 

Figure 5. On Earth, buoyancy-driven convective mixing 

results in the boundary layers around plant organs being smaller than in microgravity. Under 1-g conditions, the 

boundary layers are usually small enough that gas exchange 

is not diffusion limited. In contrast, these processes are 

often diffusion limited in μ-g.

CO2

H2O 

O2

Radiative 

heat transfer 

Buoyancy-driven 

convection 

CO2

H2O 

O2

Radiation 

Radiative 

heat transfer 

Buoyancy-driven 

convection 
rates. A series of parabolic experiments by Kitaya et al. (2003) suggested this could 

be mitigated by increasing air velocity across the leaf, thus reducing size of the 

boundary layer. In similar parabolic flights, the photosynthetic rates of barley leaves 

decreased by 13 to 20 percent when exposed to low air velocity (<0.2 m s-1) and 

microgravity (Kitaya et al., 2004).

During the International Shuttle-Mir Greenhouse Project, CO2 and water vapor 

fluxes of wheat cv. Superdwarf were measured with the Gas Exchange Measurement 

System in Svet and together with soil moisture data; this provided simultaneous 

measurements of photosynthesis, transpiration and water balance in space (Monje 

et al., 2000; Ivanova, 2002). However, those measurements were made without 

environmental control as the Svet chamber used CO2 supplied from cabin air, 

which fluctuated between 3,000 and 9,000 ppm. 

The gas exchange measurements during the Photosynthesis Experiment and System 

Testing and Operation (PESTO) plant experiment were made under tightly 

controlled light, air temperature, CO2 concentration, root zone moisture, and 

Figure 6. Net photosynthesis of wheat cv. USU Apogee was maintained at same rates in 

microgravity as 1 g when environmental conditions were maintained to minimize boundary 

layer effects (Monje et al. 2005).
20

humidity. The Biomass Production System (BPS) hardware used for the PESTO 

experiment was able to effectively control air velocity across the leaf, and there 

were no differences in stomatal resistance, gas exchange rates or evapotranspiration 

between flight and ground controls (Stutte et al., 2006). This suggests that gas 

exchange is not affected directly by microgravity, but indirectly by the lack of 

buoyancy-driven convective currents that limit diffusion of gases to the leaf 

(Porterfield, 2002; Monje et al., 2005). As such, it is important to ensure that a 

sufficient rate of air mixing is occurring in the plant chamber to prevent confounding 

of results by the secondary effects of the spaceflight environment. 

Root Zone Aeration

Oxygen can fall to low concentrations within plant tissues either because of 

environmental factors that decrease the external oxygen concentration or because 

the movement of oxygen through the plant tissues cannot keep pace with the rate of 

consumption. The lack of buoyancy-driven convection in microgravity may inhibit 

oxygen transport to roots by increasing the boundary layers surrounding the root 

zone thereby making oxygen supply diffusion limited (Porterfield, 2002; Liao et 

al., 2004; Monje et al., 2004). Hypoxia can develop when root respiration exceeds 

the rate of diffusion-limited oxygen supply (Porterfield, 2002). Root zone hypoxia 

during spaceflight can cause changes in mitochondrial ultrastructure, decreases in 

tissue starch reserves (Moore, 1990; Kordyum, 1994), and increased root alcohol 

dehydrogenase activity (Porterfield et al., 1997; Stout et al., 2001). Although 

transcript levels of genes involved in glycolysis and fermentation pathways, ethylene 

synthesis and perception, calcium signaling, nitrogen utilization, and alkaloid 

Figure 7. The absence of buoyancy-driven convection in microgravity results in a barrier at 

the soil/atmosphere interface that limits the diffusion of O2 into the root zone.

CO2

H2O 

O2

Buoyancy-driven 

convection 

Buoyancy-driven 

convection CO2

H2O 

O2

Earth Space 
synthesis of Arabidopsis thaliana are significantly altered in response to oxygen 

limitation at 1 g (Liu et al., 2005); roots exposed to microgravity did not exhibit 

differential expression of genes associated with hypoxia (Paul et al., 2005).

Root Zone Fluid Dynamics

Plants grown in chambers aboard spacecraft have been supported in various rooting 

media employing both passive (agar, phenolic foam) and active (zeolites, clays, 

and porous tubes) means for delivering water and nutrients (Morrow et al., 1994; 

Dreschel et al., 1994; Steinberg and Henninger, 1997; Hoehn et al, 2000; Jones and 

Or, 1998). Agar and foams have been used during short-duration flights (seven days) 

or when very small seedlings are used. In longer-duration experiments (7 to 60 days), 

plants become large and the use of root modules filled with porous substrates and 

active moisture control is required. The porous media provides a network for root 

support, facilitates liquid and nutrient supply and provides capacitance. Root and 

microbial respiration consume oxygen and generate carbon dioxide, creating 

gradients between the chamber bulk air and the air within the porous media. The 

challenge in systems utilizing porous media is to provide sufficient water to the plants 

without filling the air spaces, which prevents proper aeration. Higher water content 

leads to reduced gas exchange because diffusion of gases through water is four orders 

Figure 8. Moisture distribution in media is different in microgravity that at 1 g. The picture 

on the left shows the effect of particle size on moisture distribution between the 0 and 1.8 

g during a parabolic flight. The image on the right shows the distribution of water around a 

porous tube under 0-g (upper) and 1-g (lower) conditions.
22

of magnitude slower than diffusion through the air. The gas diffusion process near 

roots is dependent on air-filled pores and is often described in terms of a gas diffusion 

coefficient. Measurement and modeling of porous media physical characteristics are 

needed to design and model improved plant rooting environments for space (Jones 

and Or, 1998; Scovazzo et al., 2001, Jones et al., 2003).

In space, water flow and distribution in porous media are affected by 

changes in buoyancy, dominance of capillary forces and particle rearrangement, 

which can be affected by vibration during launch (Ivanova and Dandolov, 1992; 

Podolsky and Mashinsky, 1994; Heinse et al., 2007). Figure 8 shows results from 

water-addition experiments conducted during parabolic flights in preparation for 

the PESTO experiment (left), and a simulation of how gravity affects root zone 

water distribution (right) in the 15-centimeter-deep root modules of the Svet plant 

chamber (Jones and Or, 1999). When water was added to substrates using porous 

tubes, the shape of the wetting fronts was gravity dependent. In gravity, water 

drains along the gravity vector leaving the rooting media moist but well-aerated. 

Substrates with smaller particle sizes only partially overcome the pull of gravity 

because of capillary forces. In space, water distribution within rooting media is 

more homogenous because capillary forces dominate, which in turn may contribute 

to poor aeration.

The moisture distribution of the Svet root module, obtained from data collected by 

an array of moisture sensors (right), clearly shows that water collects at the bottom 

of the root module in 1 g. In contrast, the same amount of water is more evenly 

distributed throughout the root module in microgravity. This behavior can lead 

to hypoxia during spaceflight if root zone moisture is controlled using setpoints 

derived during ground-based experiments. This example illustrates how a difference 

in gravitational 

force can result in significant offsets in control parameters developed on Earth 

because of these shifts in water distribution (Jones et al., 2003). These effects can 

be partially offset through appropriate selection of rooting media and soil moisture 

potential. For example, in the PESTO experiment, these effects were mitigated by 

using 1 to 2 mm arcillite media and 3-centimeter-deep root modules (Monje et al., 

2005; Stutte et al., 2005). 

Temperature Control

Heat and mass transfer between plants and the ambient air surrounding them 

occurs through boundary layers. Plant organs (leaves, growth and reproductive 
structures) are heated by incident radiation from the lighting system. Heat is then 

dissipated by heat transfer across boundary layers surrounding the plants and by 

evaporative cooling from transpiration. 

In microgravity, without any forced air circulation, heat and mass transfer are 

sustained only by diffusion as buoyancy-driven convection ceases. 

Parabolic flights have been used to determine the effect of gravity on the surface 

temperature of leaves (Kitaya et al., 2003). Researchers observed that the leaf 

temperature of sweet potatoes and barley increased rapidly by 1.90C 

and 1.3 C, respectively, during the 20 s of microgravity in each parabola. They 

observed that leaf boundary layer conductance to sensible heat exchange decreased 

by 5 percent when gravity decreased from 1.0 to 0.01 g at an air velocity of 0.2 m 

s

-1. In contrast, leaf temperatures decreased by 0.50C during the 2 g portions of the 

parabolas because increasing gravity levels reduce the thickness of the boundary 

layers and enhance buoyancy-driven convection. They concluded that reduced 

convection resulted in less leaf-to-air heat exchange at lower gravity levels because 

of reduced evaporative cooling. The leaf temperatures increased by smaller amounts 

when the air velocity over the leaves was raised from 0.2 m s-1 to 1.0 m s-1 (Kitaya et 

al., 2001). 

Lighting

Various types of electric-lighting approaches have been used to grow plants in space. 

Many plant chambers have used small fluorescent lamps, which provide a broad 

spectrum for photosynthesis and photomorphogenesis and have a vast literature on 

their use in controlled environments (Withrow and Withrow, 1947; Sager et al., 

1982). Examples of plant chambers that used fluorescent lighting include: NASA 

PGU; NASA’s Plant Growth Facility (PGF); the Russian Svet chamber used on 

Mir; the Russian Lada chamber on the ISS; NASA’s (Orbitec) Biomass Production 

System (BPS); and the BioServe commercial Plant Growth Bioprocessing Apparatus. 

Another NASA-funded commercial group, the Wisconsin Center for Automation 

and Space Robotics (WCSAR), proposed the concept of using light-emitting diodes 

(LEDs) to provide lighting in space (Bula et al., 1991; Barta et al., 1992). LEDs are 

solid state devices that do not radiate much heat (i.e., long wave), are easily dimmable 

and have a long operating life; hence, LEDs had a lot of appeal for space applications. 

Moreover, they do not contain mercury vapor found in fluorescent lamps, which can 

be a safety concern in space. The WCSAR group and partner company Quantum 

Devices, Inc. patented the concept for using LEDs to grow plants (Ignatius et al., 

1991). WCSAR subsequently used LEDs in their Astroculture plant chambers in the 
24

1990s and early 2000s (Morrow et 

al., 1995), and other groups such 

as the European Space Agency (for 

the EMCS chamber) and NASA 

(for the ABRS) chamber have also 

used LEDs. 

A challenge with LEDs is that the 

spectral output is very narrow, 

e.g., approximately 25 nm half 

band width, and thus providing 

adequate spectral combinations 

became the focus of research. 

Subsequent testing, much of which 

was focused on space applications, 

demonstrated that both red and 

blue lights were essential for 

normal growth and development 

for many species (Hoenecke et al., 

1992; Kim et al., 2007). Blue becomes especially important in the μ-gravity of space 

to orient plants through phototropic responses. Since their early use for growing 

plants in the 1990s, LED electrical efficiencies have improved by nearly an order of 

magnitude, especially blue LEDs (Bourget, 2008) and thus have even greater appeal 

for space applications.

Regardless of the source, the requirement for light to sustain plant growth 

makes plant chambers and plant testing in space more challenging for thermal 

management. Even though some of the light is fixed by the plants into biochemical 

energy through photosynthesis, from a thermal management perspective, nearly 

all of the power required to generate the lighting in a plant chamber ultimately 

becomes heat. Hence, plant chambers and experiments for space should have 

adequate air mixing and sufficient cooling capacity to maintain temperature 

control. This often translates into higher electric power requirement for conducting 

plant research in space when it requires light. (Note: dark experiments, such as 

germination studies, would not require such high power budgets.) 

The majority of plant experiments to date have been conducted at fairly low to 

moderate light levels (75-300 μmol m-2 s-1 of photosynthetically active radiation) 

because of constrained power allotments to spaceflight plant growth chambers. The 

Figure 9. The Advanced Astroculture designed and 

built by the Wisconsin Center for Space Automation 

and Robotics was one of the first plant-growth 

facilities to use Light Emitting Diodes on the 

International Space Station.
results from the PESTO flight experiment indicate that there is no difference in the 

rates of photosynthetic carbon uptake, water loss via transpiration growth between 

flight and ground plants at moderate light levels (~300 μmol m-2 s-1) and saturating 

CO2 concentration (Stutte et al., 2005). These findings suggest that plants stand 

water purification, and food production rates will not change in space because 

the underlying biological processes operate at the same rates as in 1 g at those light 

levels (Monje et al., 2005). However, this does not mean that direct and indirect 

effects of microgravity cannot affect plant growth at higher, more demanding light 

levels (e.g., 600 to 900 μmol m-2 s-1). 

In previous studies, a significant (approximately 17 percent) reduction in wholechain electron transport was observed in chloroplast extracts from plants raised in 

microgravity at high light levels (Tripathy et al., 1996). These higher light levels 

translate into faster plant growth rates, which result in proportionally higher rates of 

water demand and greater rates of respiratory O2 consumption by both shoots and 

roots. In turn, these higher rates impose greater loads (e.g., greater water supplied 

to the root zone, greater dehumidification capacity, and increased oxygen consumed 

in respiration) that could cause plant stress if the flight hardware cannot control or 

sustain mass exchange rates. The Plant Habitat (PH), currently under development, 

is designed to accommodate plant experiments at higher light intensities. Its 

development has demanded improved technologies to provide higher capacity water 

supply and condensate recovery, heat rejection, and CO2 control because the higher 

light and accelerated plant growth impose larger demands on chamber subsystems. 

Approaches to Mitigate Effects of Microgravity Environment

Biological Approaches 

In order to mitigate the secondary effects of the spaceflight environment, a 

number of biological approaches can be taken. These include the selection of plant 

material that is more resistant to the stress. During the International ShuttleMir Greenhouse Project, Salisbury (1997) grew wheat cv. Superdwarf in the Svet 

chamber for an entire life cycle, but only sterile wheat heads were obtained because 

of exposure to the 0.4 ppm ethylene present in the Mir atmosphere (Campbell 

et al., 2001). Musgrave et al. (2000) conducted the Greenhouse 3 seed-to-seed 

experiments with Brassica in 1997 in spite of exposure to 1.1 ppm ethylene. 

Ethylene exposure experiments with wheat cv. Apogee during the ground testing 

found that Apogee was more resistant to ethylene than Superdwarf. When Apogee 

was substituted for Superdwarf in the Greenhouse 4 experiment, seed-to-seed 

experiments with wheat were possible on Mir even though only few seeds per head 
26

were produced at 1 ppm ethylene (Sytchev et al., 2001). 

Alternatively, the inclusion of lines of plant material with a range of responses to 

stress can be used. This is a particularly powerful approach when defined genetic 

material is available, allowing for the use of biomolecular tools to differentiate 

between direct and indirect effects of microgravity (Muday et al., 2008). Kiss 

and co-workers (1999, 2000, 2012) performed spaceflight experiments (Biorack, 

TROPI-1; TROPI-2) to address issues associated with starch-statolith theory 

of gravity perception and to study phototropism in microgravity. This series of 

experiments allowed the genetic and gravitropic responses to be decoupled and 

indicated that the responses in microgravity are consistent with the statolith model 

of gravity perception. The Kiss group also was able to use microgravity to identify 

a novel red-light-based phototropism in plants (Miller et al 2010; Kiss J.Z., P. 

Kumar, R.N. Bowman, M.K. Steele, M.T. Eodice, M.J. Correll, R.E. Edelmann. 

2007. Biocompatibility studies in preparation for a spaceflight experiment on 

plant tropisms (TROPI). Advances in Space Research 39: 1154-1160). Similarly, 

Hoson et al. (2009) used tubulin mutants of Arabidopsis to differentiate the effects 

of microgravity from developmental signals for cell wall properties of microgravity 

grown tissues. 

Engineering Approaches 

The designs of the latest generation of plant growth chambers (e.g., EMCS, 

ABRS and PH) under development have incorporated sophisticated engineering 

controls for CO2

 concentration with active addition and/or removal of CO2 from 

the plant growth chamber, maintenance of relative humidity through the use of 

porous tube or plate technology, and removal of VOCs such as ethylene, with 

selective absorbents or photo-catalytic scrubbers. Air flow through the chambers is 

maintained to minimize the effects of microgravity on boundary layer formation, 

without inducing thigmomorphogenic effects on the plants, and automatic water/

nutrient delivery systems to mitigate microgravity effects on water and oxygen 

movement throughout the media. The ability to control these parameters in situ 

provides the opportunity to fully investigate the role of the spaceflight environment, 

and coupled with biological control measures, to differentiate the unique effects 

of microgravity from the secondary environmental effects of the spaceflight 

environment.
Plant Growth Facilities

The Advanced Biological Research System (ABRS) 

The ABRS is a single, mid-deck, locker-sized plant growth unit that is split into two 

growing compartments, each 260 cm2 in growing area (Levine et al., 2009). Each 

of the growing compartments is independently controlled, with an LED lighting 

system capable of providing up to 300 μmol m-2 s-1 PAR and has temperature, RH 

and CO2 control for independent control of the internal atmosphere. ABRS allows 

for imaging the experiment from three cameras installed in the chamber, and one 

of the compartments also has the capability to image green-fluorescent, proteinmodified plants or other organisms.

Biological Research in Canisters (BRIC) 

BRIC canisters provide a carrier to house Petri plates of various sizes to 

accommodate study of tissue or cell cultures, microbes or other organisms that 

could be contained in a dark environment. A series of BRIC hardware exists to 

accommodate various experiment requirements. These include: the BRIC-60, 

which has two compartments that each have the capacity for 12 60-mm Petri 

dishes; BRIC-100, which is a single anodized-aluminum cylinder that can 

accommodate up to nine 100 mm Petri plants; and the BRIC-100 (VC), which 

has additional structural support for vacuum containment of specimens.

BRIC Petri Dish Fixation Unit (BRIC/PDFU) 

A more sophisticated version of using Petri dish type studies can be 

carried out using the BRIC/PDFU hardware, which can also accommodate in situ 

fixation of the tissue with chemical fixatives and provide unilateral stimuli of red 

LED light during growth (Kern et al., 1999). The PDFU is a specialized holder for 

a 60-mm Petri dish and reservoir for the containment and delivery of fixative. Each 

BRIC canister can contain up to six individual PDFUs.

Commercial Generic Bioprocessing Apparatus (CGBA) 

The Commercial Generic Bioprocessing Apparatus (CGBA) provides programmable, 

accurate temperature control for applications ranging from cold stowage to 

customizable incubation. The CGBA is used for experiments on cells, microbes, 

and plants. The CGBA provides temperature control for a variety of applications 

Research Facilities on ISS 

and How to Choose Them
28

ranging from cold stowage to customizable incubation. The CGBA can be used in a 

variety of biological studies, such as protein crystal growth, small insect habitat, plant 

development, antibiotic-producing bacteria, and cell culture studies.

European Modular Cultivation System (EMCS) 

The EMCS provides temperature and atmosphere control, water supply, 

illumination, imaging, and variable g-levels on two independent centrifuge rotors. 

This is the only plant growth facility that has variable g control capability in-orbit. 

Experiment Containers (EC) hold experiment unique equipment (EUE) to support 

particular experiments; there are four ECs per centrifuge rotor. Ames Research 

Center has developed EUE for the EC’s, which consist of five seed cassettes with 

cover heaters for imaging clarity, LED lighting, hydration bellows, hydration 

pumps, control circuit boards, and an air circulation fan. The EMCS computer 

commands the heaters, LEDs, and hydration system in the EC/EUEs during 

the experiments. (Kiss J.Z., P. Kumar, R.N. Bowman, M.K. Steele, M.T. Eodice, 

M.J. Correll, R.E. Edelmann. 2007. Biocompatibility studies in preparation for 

a spaceflight experiment on TROPI. Advances in Space Research 39: 1154-1160). 

The seed cassettes can be removed by the crew for sample processing, e.g., freezing 

(Brinkman, 2005).

Lada 

The Lada plant chamber is housed in the Russian module of the ISS and owned 

and operated by the Russian Institute for Biomedical Problems. The Lada chamber 

provides about 0.034 m2 of growing area with fluorescent lighting and a sub-irrigated 

root module. The Lada chamber is open to the cabin atmosphere and uses cabin air 

for CO2 supplement and thermal and humidity control (Sytchev et al., 2007). 

Plant Experiment Unit / Cell Biology Experiment Facility (PEU/CBEF) 

The PEU Series is equipment dedicated to life-science experiments on ISS. Of 

the four types of PEU developed on KIBO, the PEU installed in the CBEF 

provides general environment controls such as temperature, humidity and CO2

concentration. The PEU, connected to the external PC, performs various functions 

required in life science experiments including: culture-medium exchange, water 

delivery, air circulation, data acquisition (temperature, humidity), video capture, 

and sample fixation. 
Plant Habitat (in development) 

The PH provides greater area (0.17 vs. 0.026 m2), height (48 vs. 13 to 20 cm) 

and higher light levels (600-900 μmol m2 s-1) than previous flight chambers, 

which enables the study of a wider range of plant species than before. The PH is 

being designed to temperature (approximately 18 to 300C), humidity (50 to 90 

percent RH) and CO2 (400 to 5,000 ppm) control as well as providing scrubbers 

to remove ethylene. Standard instrumentation will monitor and record the 

environment within the growth chamber, e.g., temperature, humidity, CO2, and O2

concentrations as well as record root zone moisture content, temperature, and O2

concentration. The larger PH can still accommodate growth of model plant species 

(e.g., Arabidopsis) and would provide nondestructive measurements of growth (i.e., 

photosynthetic rates). 

Vegetable Production System (Veggie)

The Veggie plant growth chamber is scheduled for its initial spaceflight test in the 

fall of 2013. The Veggie is a simple, expandable plant growth unit with a LED (red, 

green, blue) lighting system that can provide up to 350 μmol m-2 s-1 of PAR (Stutte 

et al., 2011). Air temperature, humidity, and CO2 control are achieved by drawing 

cabin air through the system. The total plant growing area is 0.13 m2, and water 

is provided passively to packets of rooting media using capillary connections to a 

reservoir. 

Support Facilities 

The International Space Station has a variety of multidisciplinary laboratory facilities 

and equipment available to support the National Laboratory operations. These 

capabilities have been built by NASA and its International Partners and can be 

made available on a time-shared basis to other U.S. government agencies and private 

entities to pursue their own mission-driven research and applications on the ISS. 

In addition to the NASA-supported hardware to support plant experiments (ABRS, 

BRIC, Lada), the EMCS and Commercial Generic Bioprocessing Apparatus are 

available to support plant growth experiments. Temperature-controlled stowage of 

samples is available in Minus Eighty-Degree Laboratory Freezer for the ISS and 

General Laboratory Active Cryogenic ISS Experiment Refrigerant facilities; fixation 

of tissues for microscopic and/or molecular analysis can be achieved with Biotube 
30

and Kennedy Space Center Fixation Tubes. There is a whole suite of facilities 

and instrumentation currently available to support plant experiments on the ISS 

including the Microgravity Science Glovebox for handling hazardous materials and 

Light Microscope Module for analysis of samples in space. In addition to NASA 

provided hardware, facilities from experiment implementation partners are also 

available such as the Nano-racks Microscopes and Nano-racks Plate Reader. 

The most up-to-date descriptions of these facilities and their capabilities can be 

found at a number of different websites including the NASA ISS facilities website 

at http://www.nasa.gov/mission_pages/station/research/facilities_category.html, 

and NASA’s Fundamental Space Biology Science Plan at 

http://www.nasa.gov/pdf/541222main_10-05-17%20FSB%20Sci%20PlanSigned_508.pdf.
Plant Science Hardware and Facilities on ISS

Table 2. * HOBO data logger aceess data postflight.

** BRIC-60, BRIC-100VC, BRIC-Opti use 60 mm and 100 mm petri dishes; Several BRICs 

can be flown per mission.

*** EC - Experiment Container.

  Still in process of flight qualification. Currently scheduled for a test on ISS for SpaceX 3. 

 ABRS  BRIC BRIC / PDFU CGBA EMCS Lada PEU/CBEF PH Veggie Advanced Biological Research System   Biological Research in Canisters Biological Research in Canisters/ Petri Dish Fixation Unit Commercial Generic Bioprocessing Apparatus European Modular Cultivation System Greenhouse chamber Plant Experiment Unit / Cell Biology Experiment Facility Plant Habitat Vegetable Production System Doc. link ABRS BRIC BRIC/PDFU CGBA EMCS N/A BEU / PEU N/A Veggie** ** Contact Jose Camacho; Bryan Onate Howard Smith Howard Smith Stefanie Countryman Ulrich M. Kuebler Gail Bingham; Vladimir N. Sychev Sachiko Yano Bryan Onate Thomas Crabb; Bryan Onate Area (cm2) 2 x 260 BRIC-100 9 x 80; BRIC60 12 x 30 6 x 30 750 8 EC*** X 96 340 273 1700 1300

Light Intensity (umol/m2s)

400 N N 250 75 W/

m2s

250 110 - 190 1000 300

Lighting LED N N Fluorescent LED Fluorescent LED LED LED

Temperature Control (oC)

Y N N Y

Y

Y

Y

Y N

CO2 Control (%)

Y N N Y

Y

Y N Y N

Humidity Control (%)

Y N N Y

Y

Y

Y

Y N

Centrifuge N N N N Y (0-2g) N Y N N

Power to EUE

Y N N N Y

Y

Y

Y N

Data

Y N * N *

Y

Y

Y

Y

Y N

Video

Y N N Y

Y

Y

Y

Y N

Lighting

Y N N Y

Y

Y

Y

Y

Y
32

Process for Payload Development and Implementation

The recommendation of the NRC Decadal Survey (2011) was that all future 

spaceflight research be hypothesis driven. It is thus essential that principal 

investigators (PIs) understand the constraints of spaceflight and incorporate steps 

to mitigate the confounding effects identified in the previous sections. The extent 

and impact of these effects will vary according to the specific experiment and the 

operational characteristics of the flight hardware selected to support the payload.

Once an experiment is selected for development as a spaceflight payload, the PI 

will be working with a payload integrator or hardware developer to identify the 

specific laboratory requirements necessary to support the experiment and develop 

any experiment unique equipment necessary to support the payload. It is highly 

recommended that the PI conduct experiments in the actual flight hardware under 

configuration control conditions similar to those anticipated in flight prior to 

launch. This allows any issues unique to the flight hardware and mission-specific 

constraints to be identified, and mitigated, prior to launch.

The PI is also advised to seek the advice of researchers who have conducted 

spaceflight experiments for tips on how to overcome hardware and mission-specific 

issues and tricks on how to implement solutions during flight. Any issues that are 

identified during preflight testing that may limit success should be mitigated and 

the solution tested in an appropriate environment such as parabolic flights, closed 

systems or reduced pressure facilities prior to flight. It is also advisable, where 

appropriate, to identify possible failure modes and develop responses to those events 

prior to launch. Once these constraints have been identified and mitigated, then the 

experiment configuration for flight should be fixed.

When necessary, the PI will work with the payload integrator to develop 

crew procedures, establish timelines for those operations and provide them 

to the Astronaut Office for validation and crew training purposes. It is highly 

recommended that the PI initiate these discussions early in the experiment 

development process to determine what are the timelines for meeting particular 

milestones. The payload integrator and/or hardware developer will also work 

with the PI to determine stowage requirements, number of spare parts, develop 

experiment unique equipment, and identify special hazards or constraints that will 

affect the success of the experiment. The PI will also need to make a decision of 

Developing and 

Flying Research to ISS
whether to conduct a synchronous or asynchronous ground control, and determine 

where these experiments will be performed.

If using live specimens, the PI should anticipate various launch scrub scenarios 

and develop contingency plans to reduce the effects of launch delays on science 

objectives. The PI will also need to determine where post-landing operations 

will occur, and it is also advisable to determine what must be done at landing 

immediately upon receipt of samples and which operations can be deferred and 

conducted in the PI’s home laboratory.

Environmental Conditions on ISS

The ambient environment of the ISS can fluctuate significantly, depending 

upon operation, equipment anomalies and crew activities. Typical ISS control 

parameters are temperatures between 22 and 28°C, relative humidity at 30 to 45 

Figure 10. ISS ambient CO2, pressure, temperature and humidity levels recorded by the 

Biomass Production System flight hardware on flight days 67, 68 and 69 (13-15 June, 

2002) of the Photosynthesis Experiment and System Testing and Operation experiment 

during ISS Increment IV. 
34

percent and CO2 between 3,000 and 7,000 ppm. The absence of buoyancy-driven 

convention has the potential for significant spatial variation in the spacecraft to 

occur. It is desirable to obtain sensor data on ambient conditions as near to the 

experimental payload as possible to increase the fidelity of the ground controls. 

Figure 9 illustrates typical variation in ISS CO2 concentration, cabin pressure, air 

temperature and relative humidity recorded during the PESTO experiment during 

ISS Increment IV.
What Should Principal Investigators Know About 

Conducting Research on ISS?

Supporting research in science and technology is an important part of NASA’s 

overall mission. NASA solicits research through the release of NASA Research 

Announcements (NRA), which cover a wide range of scientific disciplines. All NRA 

solicitations are facilitated through the Web-based NASA Solicitation and Proposal 

Integrated Review and Evaluation System (NSPIRES) http://nspires.nasaprs.com/

external/. Registering with NSPIRES allows investigators to stay informed of newly 

released NRAs and enables submission of proposals. NSPIRES supports the entire 

lifecycle of NASA research solicitations and awards, from the release of new research 

calls through the peer review and selection process. 

In planning the scope of their proposal, investigators should be aware of available 

resources and the general direction guiding NASA research selection. NASA places 

high priority on recommendations from the 2011 National Research Council’s 

NRC Decadal Survey, which placed emphasis on hypothesis-driven spaceflight 

research. In addition, principal investigators (PI) should be aware that spaceflight 

experiments may be limited by a combination of power, crew time, or volume 

constraints. Launch and/or landing scrubs are not uncommon, and alternative 

implementation scenarios should be considered in order to reduce the risk from these 

scrubs. Preliminary investigations using ground-based simulators may be necessary 

to optimize procedures before spaceflight. Also, many experiments require unique 

hardware to meet the needs of the spaceflight experiment. To understand previous 

spaceflight studies, prospective PIs should familiarize themselves with the NASA ISS 

Program Science Office database, which discusses research previously conducted on 

the ISS, including that of the International Partners. A detailed catalog of previous, 

current, and proposed experiments, facilities, and results, including investigator 

information, research summaries, operations, hardware information, and related 

publications is available at www.nasa.gov/iss-science through the NASA ISS Program 

Office. Additionally, details pertaining to research previously supported by the Space 

Life and Physical Sciences Research and Applications Division of NASA’s Human 

Exploration and Operations Mission Directorate can be located in the Space Life 

& Physical Sciences Research and Applications Division Task Book in a searchable 

online database format at: https://taskbook.nasaprs.com/Publication/welcome.cfm.

Sponsorship 

Opportunities
36

Process for Payload Development and Implementation

Following selection of an experiment for spaceflight, the PI will work with a 

payload integrator or hardware developer to define the most suitable hardware, 

and determine if hardware needs to be created or modified. The research team 

in combination with payload integrations will establish the specific laboratory 

requirements needed to support the experiment. Through these collaborative efforts, 

concerns such as crew procedures and crew training, the need for spare parts and/

or contingencies involving hardware, and stowage requirements of the samples will 

be addressed and resolved. It is highly recommended that the PI perform a series 

of investigations using the identical hardware and under configuration and control 

conditions similar to those anticipated inflight prior to the launch. This will prevent 

unforeseen issues with the hardware and allow specific mission constraints to be 

defined, and mitigated, prior to the experiments implementation once aboard the 

ISS. It is also within this time frame that the science team needs to characterize the 

details involved with their synchronous ground controls. The PI’s team should also 

have finalized all post-landing procedures, including sample preservation, storage, 

and transport, and data acquisition prior to the launch. 

Another option to flying your experiment is through the Center for the 

Advancement of Science in Space (CASIS) (http://www.iss-casis.org). CASIS is a 

nonprofit organization tasked by U.S. Congress and NASA with promoting and 

enabling research on ISS. CASIS can be used for all stages of payload development 

and can match PIs with implementation partners (table below) who can provide 

heritage hardware or new flight packages:
Company Contact Information

The Aerospace Corporation www.aero.org

Astrium North America www.astrium-na.com

Astrotech Corporation www.astrotechcorp.com

Aurora Flight Sciences www.aurora.aero

Bionetics Corporation www.bionetics.com

Bioserve www.colorado.edu/engineering/BioServe

Boeing www.boeing.com

CSS-Dynamac www.css-dynamac.com

Hamilton Sundstrand www.hamiltonsundstrand.com

Jamss America www.jamssamerica.com

Kentucky Space, LLC www.kentuckyspace.com

MDA www.mdacorporation.com

MEI Technologies www.meitechinc.com

Nanoracks LLC www.nanoracks.com

Orbital Technologies Corporation www.orbitec.com

Paragon TEC www.paragontec.net

Qinetiq www.qinetiq-na.com

Space Systems Concepts, Inc. www.space-concepts.com

Space Systems Research Corporation www.spacesystemsresearch.com

Tec-Masters, Inc. www.tecmasters.com

Techshot www.techshot.com

Teledyne Brown Engineering, Inc. www.tbe.com

Thales Alenia Space www.thalesgroup.com/space

UAB www.uab.edu/cbse

Wyle Integrated Science and Engineering www.wyle.com

Zin Technologies www.zin-tech.com

Table 3. Implementation Partners for Flight Experiments on the ISS.
38

Funding Opportunities and Points of Contact

There are various avenues that can result in funding for research to be conducted 

on the ISS, and the source of funding often dictates the availability of launch 

opportunities. Generally, funding for research is awarded through NASA-sponsored 

research announcements (NRAs), ISS National Laboratory awards through other 

government agencies, private commercial enterprise, nonprofit organizations, 

and research awards sponsored by the ISS International Partners. It is not the 

responsibility of a researcher awarded an ISS flight experiment to fund costs 

associated with launch or the ISS laboratory facilities. Greater detail concerning 

current funding opportunities for ISS research can be found through the NASA ISS 

research website: http://www.nasa.gov/mission_pages/station/research/ops/research_

information.html. 

The NASA Solicitation and Proposed Integrated Review and Evaluation System 

(NSPIRES) can be accessed via: http://nspires.nasaprs.com/external/. 
Bancaflor, E.B. and P.H. Masson. 2003. Plant gravitropism. Unraveling the ups and 

downs of a complex process. Plant Physiol. 133: 1677-1690.

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Res. 51:465-475. 
ABRS Advanced Biological Research System

BPS Biomass Production System

BRIC Biological Research in a Canister

CASIS Center for the Advancement of Science in Space

CBEF Cell Biology Experiment Facility

CGBA Commercial Generic Bioprocessing Apparatus

CHROMEX Chromosome and Plant Cell Division in Space

EC Experiment Container

EMCS European Modular Cultivation System

EUE Experiment Unique Equipment

ISS International Space Station

LED Light-emitting Diode

NL National Lab

NSPIRES NASA Solicitation and Proposal Integrated Review and Evaluation System

PDFU Petri Dish Fixation Unit

PESTO Photosynthesis Experiment and System Testing and Operation

PEU Plant Experiment Unit

PGC Plant Growth Chambers

PGF Plant Growth Facility

PGU Plant Growth Unit

PH Plant Habitat

PI Principal Investigator

RH Relative Humidity

TROPI Tropism in Plants

VOC Volatile Organic Compounds

WCSAR Wisconsin Center for Automation and Space Robotics

Acronyms
48

The Complete ISS Researcher’s 

Guide Series

1. Acceleration Environment

2. Cellular Biology

3. Combustion Science

4. Earth Observations

5. Fluid Physics

6. Fruit Fly Research

7. Fundamental Physics

8. Human Research

9. Macromolecular Crystal Growth

10. Microbial Research

11. Microgravity Materials Research

12. Plant Science

13. Rodent Research

14. Space Environmental Effects

15. Technology Demonstration
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