Advanced Life Support Research and Technology Transfer at the University of Guelph

Open Agriculture. 2017; 2: 139–147

Communication Open Access

M. Dixon*, M. Stasiak, T. Rondeau Vuk, T. Graham Advanced Life Support Research and Technology Transfer at the University of Guelph

DOI 10.1515/opag-2017-0013 development of poor indoor air quality and biological Received January 17, 2017; accepted March 13, 2017 approaches to mitigate this (i.e., biofitration) were Abstract: Research and technology developments developed and tested (Darlington et al. 1998). The driving surrounding Advanced Life-Support (ALS) began at the force behind this research was actually a terrestrial University of Guelph in 1992 as the Space and Advanced Life application designed to address what is commonly Support Agriculture (SALSA) program, which now represents known as “sick building syndrome.” The initial projects Canada’s primary contribution to ALS research. The early were supported by the Institute for Space and Terrestrial focus was on recycling hydroponic nutrient solutions, Science (ISTS), part of the Ontario Centres of Excellence atmospheric gas analysis and carbon balance, sensor (OCE), and the Canada Life Assurance Co. at whose research and development, inner/intra-canopy lighting and headquarters building in Toronto, Canada the technology biological filtration of air in closed systems. With funding was initially deployed. from federal, provincial and industry partners, a new As Guelph was developing indoor air biofiltration generation of technology emerged to address the challenges technology for terrestrial applications, an issue related of deploying biological systems as fundamental components to air quality in space exploration was revealed on the of life-support infrastructure for long-duration human space Russian Space Station Mir. Wheat that was grown on Mir exploration. Accompanying these advances were a wide returned to Earth exhibiting serious consequences of range of technology transfer opportunities in the agri-food exposure to elevated levels of ethylene (Levinskikh et al. and health sectors, including air and water remediation, 2000). A more detailed study of this phenomenon was plant and environment sensors, disinfection technologies, warranted and this led to the development of the initial recyclable growth substrates and advanced light emitting Guelph Sealed Environment Chambers (SECs) (Figure diode (LED) lighting systems. This report traces the evolution 1A-1C) (Dixon et al. 1999) and followed by more detailed of the SALSA program and catalogues the benefits of ALS modeling studies of sealed environment plant growth research for terrestrial and non-terrestrial applications. chambers (McLean et al. 2012). As Guelph’s research in sealed environment Keywords: terrestrial technology transfer; Canada; technology expanded, a major collaboration was advanced Life-support; bio-regenerative life-support established with the European Space Agency‘s Micro Ecological Life Support System Alternative (MELiSSA) program. The University of Guelph, represented by the Space and Advanced Life Support Agriculture (SALSA) 1 Introduction program formally joined the international consortium in 1997 and remain the only Canadian partner detailing The first research objective at the University of Guelph a long history of contributions to the Higher Plant related to the niche Advanced Life Support (ALS) field Compartment (HPC) of the MELiSSA loop (Godia et al. in space exploration was based on the management of 2002). In collaboration with the Canadian Space Agency, air quality in sealed (or partially sealed) spaces. The research objectives related to the integration of the HPC accumulation of volatile organic compounds (VOCs) and as the food production and atmosphere revitalization trace hydrocarbons in closed spaces contributed to the compartment in the MELiSSA recycling loop were pursued (Waters et al. 2005). A major milestone was achieved in *Corresponding author: M. Dixon, University of Guelph, Guelph, 2009 with the deployment of the prototype HPC in the Ontario, Canada. N1G 2W1, E- mail: [email protected] MELiSSA Pilot Plant at the Universitat Autònoma de M. Stasiak, T. Rondeau Vuk, T. Graham, University of Guelph, Guel- Barcelona (UAB) in Spain (Figure 2). ph, Ontario, Canada. N1G 2W1

As the SALSA program continued to evolve, attention Ontario Innovation Trust funded infrastructure project was also paid to additional International collaborations in 2000. With industry partners in the aerospace and and linkages. A close relationship with colleagues at greenhouse industry sectors, the Controlled Environment NASA’s Kennedy Space Center (Florida) was developed Systems Research Facility (CESRF) was established and and a productive research collaboration based on officially opened in May, 2001. The core of the research personnel exchanges and technology transfer has been infrastructure was embodied in a suite of 14 variable sustained to this day (Figure 1D). This relationship has pressure hypobaric plant growth chambers (Figure 3 A, been formally recognized in the form of a Memorandum B, C) designed to address the question – “How low can of Understanding by the respective institutions and was we take the atmospheric pressure while maintaining updated and renewed in 2016, with further agreements the contributions of plants to human life support?” The and collaborations currently under consideration. research campaign addressing this and related issues is A significant expansion of the research and technology ongoing and has yielded a broad range of findings including development objectives of the SALSA program was the low pressure limits of plant survival (Chamberlain et al. realized through a Canada Foundation for Innovation/ 2003; Stasiak et al. 2007; Wehkamp et al. 2012), microbial

Figure 1: Space Agriculture Research at the University of Guelph. A) The first Controlled Environment Plant Production Chambers at the University of Guelph dedicated to space exploration related research. B) Canopy-scale hypobaric plant growth chambers as part of the Controlled Environment Systems Research Facility (CESRF). C) Advanced LED Lighting system development; a key part of the CESRF advanced plant production capabilities. D) General timeline of SALSA and CESRF developments

A B C

Figure 2: Higher Plant Compartment (HPC) of the European Space Agency’s MELiSSA program. The HPC was developed by the University of Guelph as an international partner in the MELiSSA program. A) Exterior of HPC at the Melissa Pilot Plant (MPP) showing glovebox airlocks (both ends) and basic mechanical systems; B) Example of a staggered, conveyor-style planting protocol for continuous lettuce production; C: Example of a batch production protocol in the same chamber Advanced Life Support Research and Technology Transfer at the University of Guelph 141

A B C

Figure 3: Hypobaric Plant production facilities at the University of Guelph’s Controlled Environment Systems Research Facility. A) Evaluation of tomato and pepper growth and development under sub-atmospheric pressure. B) Smaller scale hypobaric chambers outfitted with multi- spectral (9 tunable wavebands) high output (10,000 µmol/m2/s @ full spectrum and full intensity) LED arrays. C) Suite of five (three shown) 1.5 m2 full canopy hypobaric plant production chambers (note: lighting is high pressure sodium) responses to hypobaric conditions (MacIntyre et al. 2011), from a single wave band at variable photon flux densities, plant responses to rapid decompression simulating a leak to any combination of up to seven separate wavebands of the “greenhouse” to the vacuum of space (Wheeler ranging from ultraviolet to far red. The intensity of each et al. 2011), response of bees as pollinators to hypobaric waveband is also individually controlled, providing in any conditions (Nardone et al. 2012) and the rearing of practical sense, limitless combinations of light quality mealworms (Li et al. 2016). Additional ALS studies include and quantity. Initial testing of the prototype PS1000 has studies on MELiSSA candidate crop selection (Paradiso demonstrated the range of capabilities for assessing plant et al. 2014; Stasiak et al. 2012), integrated crop production responses to environment variables such as CO2, vapour (Stasiak et al. 2003) staged plant production (Waters et al. pressure deficit, temperature, light quantity and spectral 2003) and investigations on inner/intra canopy lighting quality, nutrient and water all of which inform ALS crop (Dixon et al. 1999; Stasiak et al. 1998). production strategies. Some typical results are shown in Fundamental to the main research activities at (Figure 6). It is expected that tools like the PS1000 will the CESRF has been the development of increasingly continue to provide answers to critical questions related sophisticated controlled environment systems as research to the reliable deployment of biological systems in space tools in addressing questions related to the use of plants for human life support, while generating a whole new in space for human life support. The Guelph BlueBox series of questions related to plant physiology, growth Sealed Environment Chamber (BBSEC) technology and development in both terrestrial and spaceflight includes a range of technical advances designed to applications. enhance the fidelity of environment control protocols and the reliability of the experimental findings. Over the past two decades a number of iterations of the Guelph 2 Terrestrial Technology Transfer BlueBox have been developed and deployed including Although space exploration is the technical “pull” for single plant and full canopy hypobaric chambers (Figure the research agenda at the CESRF, most of the research 1) and a customized version designed for Syngenta Crop and technology development activities provide equally Protection LLC (Triangle Park, North Carolina, USA)) as valuable contributions to terrestrial applications and a phenotype testing tool in their plant breeding program provided commercialization opportunities for our (Figure 4). The most recent expression of the BBSEC industry partners. Developments in products, processes technology has been dubbed the PS1000 and is the and sensors related to recycling have been driven by the product of a collaboration between the CESRF, Conviron necessity to limit waste in space as a fundamental precept Ltd. of Winnipeg, Canada and Intravision Group Ag of a reliable life support strategy. Similarly, here on Earth of Oslo, Norway. The PS1000 variation of the Guelph the necessity to limit waste is becoming ever more evident BlueBox (Figure 5) was specifically designed to provide and the agrifood sector is no exception. Indeed, many a very high level of detail in assessing plant-environment agricultural jurisdictions around the world have legislated interactions. It takes advantage of recent advances in LED the extent to which the “leakage” of fertilizer and pesticide lighting technology to allow the delivery of light spectra residues will be tolerated. As humans approach the further 142 M. Dixon, et al.

Figure 4: Guelph Bluebox sealed environment chamber designed for precision measurement of plant productivity, photosynthesis and evapotranspiration as it relates to rapid phenotype testing

Figure 5: The Guelph PS1000 advanced analytical plant growth Figure 6: Preliminary capability data of the PS1000 analytical plant chamber. The combined advanced environmental manipulation, growth chamber. A) Changes in net photosynthesis in response to control, and physiological (e.g., photosynthesis, gas exchange, etc.) increasing concentrations of ambient carbon dioxide. As long as monitoring capabilities incorporated into this chamber technology light is not limiting, more carbon dioxide = faster growing plants; B) represent some of the most advanced whole plant in situ analytical Change in the rate of evapotranspiration in response to increasing systems currently available. These infrastructure developments, irradiance. Higher light = increased photosynthesis = increased driven by the needs of ALS system research, are informing terrestrial water use; C) Changes in net photosynthesis in response to increa- plant biology and agricultural systems and driving innovation in sing irradiance. Light curves help identify the optimal light intensity emerging fields such as controlled environment phyto-pharmaceu- for growth. Tomato and pepper are able to utilize higher intensities tical production, plant-based medicinal products, and vertical of light than lettuce agriculture Advanced Life Support Research and Technology Transfer at the University of Guelph 143 exploration of the Moon and eventually venture to Mars, Ontario Ministry of Agriculture, Food and Rural Affairs, has maintenance of recycling processes for nutrients, water, sustained a long-term focus on evaluating and developing growing substrates and pathogen control will be critical reliable sensor technologies to support feedback control technical requirements in ALS systems. of solution quality and eliminate the requirement to dump solutions. To that end, and in collaboration with the Canadian Space Agency, COM DEV International Ltd., and 2.1 Nutrient Solution Management with funding from the Natural Sciences and Engineering Research Council (NSERC) including a collaboration with Amongst all the environment variables which we seek the SETI Institute, the latest developments in this field to manage in plant production controlled environments, are represented by ion specific optical-based (optrode) the nutrient solution represents the most significant sensors (Figure 7) (Thompson 2015; Bamsey et al. 2012) technical challenge. The quality of an irrigation or which will be deployed in a field trial at the German fertigation (fertilizer added to irrigation solution) solution Neumeyer III research station in Antarctica in 2017-18 as is based on three primary quality factors: 1) plant nutrient part of the EDEN ISS project (http://eden-iss.net) under composition, 2) microbiological composition, and 3) the EU Horizon 2020 program. organic chemical composition, specifically any potentially detrimental chemical contaminants. If any one of these three quality domains is outside of acceptable limits, the 2.1.2 Pathogen and Chemical Contaminant Management solution may not be suitable for plant production. This can be a significant issue particularly if the plants are the Pathogens and chemical contaminants are two distinct basis of a crew’s life-support system. solution quality concerns in both spaceflight and terrestrial plant production systems; however, concurrent management can be achieved through the selection 2.1.1 Nutrient Composition Management of appropriate technologies. Developing disinfection protocols that are spaceflight compatible also leads to Nutrient solution quality, as represented by both the improved processes for terrestrial greenhouse operators relative and absolute concentrations of mineral nutrients who face many of the same conceptual constraints, in the solution, is typically managed by feedback control although not at the same level of closure. The restrictions offered by electrical conductivity (EC) sensors common imposed by spaceflight with respect to disinfection to the greenhouse industry. These sensors are physically robust but lack specificity; they measure the combined electrical conductivity contribution of all the mineral ions in the solution, giving the system manager little or no indication of the actual mineral composition. Plant nutrient uptake is a dynamic process, being influenced by numerous environmental and developmental factors, and does not necessarily match the nutrient ratios of the fertilizer stock solutions that are used to maintain nutrient balances within the system. Combine this with fertilizer replenishment based on the non-specific data provided by EC sensors and the nutrient balance can quickly become unsettled, ultimately leading to deficiencies, toxicities or both. Once a solution reaches this level of imbalance, it is too degraded to be recoverable at any reasonable level of expense or effort and is ultimately discharged from the production system as a waste product. This is not an Figure 7: Prototype Optrode system (fibre optic-based ion-selective option in spaceflight applications and is quickly becoming sensor). Deployed for a field test at Laguna Negra, a high-altitude so terrestrially with the implementation and evolution of lake near Santiago, Chile as part of the 2013 Planetary Lake Lander mission of the SETI Institute. This project demonstrated the techni- environmental legislation (Ontario 2006; 2002; 1990). cal feasibility of performing optrode field-measurements in extreme Therefore, the SALSA research program at the CESRF, environments as calcium and sodium ions were detected in lake supported by the Ontario Centres of Excellence and the samples. Photo Credit: Dr. C. Thompson, UGuelph 144 M. Dixon, et al. technologies are significant and severely limit available various physiological factors related to production of options. Keeping the challenges of spaceflight in mind, secondary metabolites. These projects are (i) enhancing disinfection and contaminant degradation protocols that the production of the cancer drug Herceptin (trastuzumab) leave no toxic residue are particularly appropriate, and following vacuum infiltration of the target protein and, aqueous ozone and other Advanced Oxidation Processes (ii) developing standardized production protocols for (AOPs) seem to best meet this technical challenge. medicinal cannabis. The latter project has supported the Collaboration with local industries has seen the development of the Guelph PS1000 technology (Figure development of various applications of these technologies 5) and promises to be a rich source of new technology ranging from shelf life extension of cut flowers (Robinson development in controlled environment systems. et al. 2009) to mitigating the effects of pathogens and In terms of spaceflight applications, such in situ organic contaminants in hydroponic solutions (Graham molecular production (aka molecular farming) can have et al. 2012, 2011, 2009). far-reaching implications when considering more distant human exploration colonization missions. It can be easily conceived that targeted neutraceuticals and phyto- 2.2 Plant Growth Substrate pharmaceuticals could be produced as a life-support service provided by ALS crop plants. Such a capacity Continuing with the recycling theme the program has would contribute to the countermeasures available for contributed to the development of recyclable plant combating the rigors of spaceflight and extraterrestrial growth substrates in collaboration with the relevant agricultural supply industry. Two such substrates (Royal Grow 1 and Royal Grow 2) have been licensed and are now commercially available in Canada. The SALSA program also shared an Ontario Centres of Excellence Mind to Market award with an industry partner in the development of a recyclable plant growth substrate for the greenhouse industry.

2.3 Biofiltration of Indoor Air

The activities in the laboratory developing and testing hypotheses related to biofiltration and maintenance of air quality in closed spaces (Darlington et al. 2001; Munz et al. 2002) were concurrent with using biofiltration technology to address indoor air quality issues. (Figure 8). Four (4) initial patents resulted from the early investigations and the opportunity to commercialize was presented. Through an award provided by the Ontario Centres of Excellence Martin Walmsley Fellowship program, Dr. A. Darlington commercialized the technology and created Air Quality Solutions Inc. This venture currently operates under the banner of Nedlaw Living Walls Inc. (Breslau, ON, Canada).

2.4 Phyto-Pharmaceuticals

Among the most potentially lucrative applications of Figure 8: Guelph-Humber Living Wall, Humber College, Rexdale, ON. controlled environment technology is in the production Investigating contributions of microbes in the root zone to address of pharmaceutical commodities using plants. Currently sick building syndrome in closed environments. Designed and the SALSA program is engaged in two (2) projects in installed with Nedlaw Livings Walls, Breslau, ON. Integrated into the collaboration with industry sponsors investigating buildings HVAC system to remove air borne pollutants and VOCs Advanced Life Support Research and Technology Transfer at the University of Guelph 145 planetary habitation. In targeting such advanced access to space flights, hardware and crew time on board spaceflight applications, there will no doubt be many the ISS. terrestrial spinoffs. The SALSA and related programs at the University of Guelph’s Controlled Environment Systems Research Facility also supports numerous other education and outreach 3 STEM Outreach and Education activities including, but not limited to, the hosting of elementary and secondary school field trips, an active intern The attraction of space exploration to the younger program, international academic personnel exchanges, and generations is undeniable and the SALSA program at a substantial graduate student program. Two of the authors the University of Guelph has leveraged this attraction are also developing undergraduate and graduate level in a very successful educational outreach project called courses in controlled environment systems, with a strong Tomatosphere™ (www.tomatosphere.org) (Morrow et al. focus on ALS as the model system. It is the hope that these 2010). Since 2000 the University of Guelph has collaborated activities will stimulate interest and participation in research with the H.J. Heinz Company, the Canadian Space Agency, and development related to Agriculture in Space. Agriculture and AgriFood Canada, the Ontario Centres of Excellence and Stokes Seeds Ltd. to distribute tomato seeds that have been in space (Figure 9), or received 4 Conclusions simulated space treatments, to thousands of classrooms across Canada and the United States. Annual distribution The universal attraction of space exploration topics now reaches more than 20,000 classrooms in Canada and has provided a very desirable context within which the promises to grow significantly in the coming years as the SALSA program at the University of Guelph continues to project expands into the United States. The project was flourish. The field of Advanced Life Support as it relates to awarded the prestigious Alouette Award in 2007 from space exploration is necessarily over-shadowed by other the Canadian Aeronautics and Space Institute and the engineering challenges such as next generation space Natural Sciences and Engineering Research Council’s craft, propulsion technologies and robotic exploration PromoScience Award in 2012 for the promotion of science vehicles. The requirements for life support technologies in Canada. The project has recently been licensed to Let’s based on plants and other biological organisms are still Talk Science in Canada and First the Seed Foundation perceived to be relatively far into the future of space in the USA who will continue to build the impact of this science. Indeed, the investments by many space agencies project for years to come working collaboratively with the in this field are quite modest and even diminishing in Center for Advancement of Science in Space (CASIS) for recent times.

Figure 9: Canadian astronaut, Dr. Robert Thirsk, displaying 1.2 million tomato seeds aboard the International Space Station. The seeds were returned to Earth and distributed to nearly 20,000 classrooms as part of the on-going TomatosphereTM STEM education and outreach program 146 M. Dixon, et al.

Notwithstanding the relatively few space missions References directly related to plant biology and ALS applications in space, the field persists and will certainly grow in Bamsey M., Graham T., Thompson C., Berinstain A., Scott A., Dixon importance as we near the milestones of Lunar and Martian M., Ion-specific nutrient management in closed systems: the necessity for ion-selective sensors in terrestrial and bases. It is clearly understood that food limits the distance space-based agriculture and water management systems. from Earth and duration of human space exploration Sensors 12, 2012, 13349–13392, doi:10.3390/s121013349 missions. We must develop reliable and self-sustaining Chamberlain C.P., Stasiak M.A., Dixon, M.A., Response of plant food production systems if we are to prevail in long term water status to reduced atmospheric pressure. Presented exploration activities within our solar system and beyond. at the SAE Technical Paper Series, SAE International, 400 Commonwealth Drive, Warrendale, PA, United States, 2003, pp. In other words, we absolutely must take edible plants with 2003–01–2677 doi:10.4271/2003-01-2677 us if we intend to travel very far from our home. What is Darlington A., Dixon M.A., Pilger C., The use of biofilters to also abundantly clear is that technologies developed improve indoor air quality: the removal of toluene, TCE, and to address the life support challenges of the Moon and formaldehyde. Life Support Biosphere Science, 1998, 5, 63–69 Mars are possibly even more valuable in addressing Darlington A.B., Dat J.F., Dixon M.A., The biofiltration of indoor air: environmental sensitivity and agricultural sustainability air flux and temperature influences the removal of toluene, ethylbenzene, and xylene. Environ. Sci. Technol, 2001, 35, here on Earth. 240–246, doi:10.1021/es0010507 The SALSA program and the CESRF at the University Dixon M.A., Grodzinski B., Cote R., Stasiak M., Sealed environment of Guelph have represented Canada’s contributions to chamber for canopy light interception and trace hydrocarbon this niche field in space exploration science for many analyses. Advances in Space Research, 1999, 24, 271– 280 years. There has been a growing list of technology Godia F., Albiol J., Montesinos J.L., Pérez J., Creus N., Cabello transfer and commercialization opportunities yielded by F., Mengual X., Montras A., Lasseur C., MELISSA: a loop of interconnected bioreactors to develop life support in space. J. this program of research and technology development Biotechnol., 2002, 99, 319–330 since its inception in the mid-1990s. By virtue of a timely Graham T., Zhang P., Dixon M.A., Closing in on upper limits for root investment in a new generation of technology by the zone aqueous ozone application in mineral wool hydroponic governments of Canada, Ontario and an industry partner tomato culture. Scientia Horticulturae, 2012, 143, 151–156 consortium in 2000, a world class research venue has Graham T., Zhang P., Woyzbun E., Dixon M., Response of hydroponic tomato to daily applications of aqueous ozone via drip evolved. The program continues to support international irrigation. Scientia Horticulturae, 2011, 129, 464–471 collaborations and provide a training venue for the next Graham T., Zhang P., Zheng Y., Dixon M.A., Phytotoxicity of aqueous generation of Canadian and international scientists in a ozone on five container-grown nursery species. Hortscience, fascinating field. 2009, 44, 774–780 Levinskikh M.A., Sychev V.N., Derendyaeva T.A., Signalova O.B., Salisbury F.B., Campbell W.F., Bingham G.E., Bubenheim D.L., Acknowledgements: The authors would like to Jahns G., Analysis of the spaceflight effects on growth and acknowledge and thank the many Federal and Provincial development of super dwarf wheat grown on the space station funding sources (CFI, NSERC, OMAFRA, OCE) including mir. Journal of Plant Physiology, 2000, 156, 522–529 the Canadian Space Agency, the European Space Agency Li L., Stasiak M., Li L., Xie B., Fu Y., Gidzinski D., Dixon M., and the EU Commission along with a multitude of Rearing tenebrio molitor in blss: dietary fiber affects larval industry and academic partners in both the aerospace growth, development, and respiration characteristics. Acta Astronautica, 2016, 118, 130-136 and agricultural sectors for their generous support of MacIntyre O.J., Trevors J.T., Dixon M.A., Cottenie K., Application of this unique research field since 1997. The list of industry plant growth promoting rhizobacteria in a hydroponics system partners is far too numerous to capture here however for advanced life support in space. Acta Horticulturae, 2011, this does not diminish the significance of their role 1285–1292 in leveraging the research dollars and propelling the Maclean H., Dochain D., Waters G., Stasiak M., A model technology and training of Highly Qualified Personnel development approach to ensure identifiability of a simple mass balance model for photosynthesis and respiration in a (HQP) into the next generation. Special mention must go plant growth chamber. Ecological Modeling, 2012, 246, 105-118 to the University of Guelph’s senior administration whose Morrow R., Rondeau Vuk T., Dixon M., Tomatosphere – Mission to leadership efforts over the past two decades has supported Mars. An evaluation of a space science outreach program. AIAA the expanding field of Biological Life Support technology 2010 6209, 40th International Conference on Environmental by incorporating elements in its Strategic Research Plan Systems. July 11-15, 2010. Barcelona, Spain Munz G., Dixon M., Darlington A., The removal of carbon monoxide and continuing their support for the development of by botanical systems. SAE Technical Paper Series 1, undergraduate and graduate based curricula in Controlled 2002–01–2265, doi:10.4271/2002-01-2265 Environments. Advanced Life Support Research and Technology Transfer at the University of Guelph 147

Nardone E., Kevan P.G., Stasiak M., Dixon M., Atmospheric Drive, Warrendale, PA, United States, 2003, pp. 2003–01–2357, pressure requirements of bumblebees (Bombus impatiens) doi:10.4271/2003-01-2357 as pollinators of lunar or Martian greenhouse grown food. Thompson C.G., Ion-Selective Analysis of Water Quality in The Gravitational and Space Biology, 2012, 26(2), 13- 21 Contexts of Plant Production, Biological Life Support Systems Ontario P.O., Clean Water Act, 2006, S.O. 2006, c. 22, e-laws.gov. and Space Exploration. PhD Thesis University of Guelph, 2015 on.ca Waters G., Gidzinski D., Zheng Y., Dixon M., Empirical relationships Ontario P.O., Nutrient Management Act, 2002, S.O. 2002, c. 4, between light intensity and crop net carbon exchange rate at Affirmed. Ed., e-laws.gov.on.ca the leaf and full canopy scale: towards integration of a higher Ontario P.O., Ontario Water Resources Act, R.S.O. 1990, c. O.40, plant chamber in MELiSSA. Presented at the International e-laws.gov.on.ca Conference on Environmental Systems, SAE International, 400 Paradiso R., Buonomo R., Dixon M.A., Barbieri G., Soybean Commonwealth Drive, Warrendale, PA, United States, 2005, pp. cultivation for bioregenerative life support systems (BLSSS): 2005–01–3071, doi:10.4271/2005-01-3071 the effect of hydroponic system and nitrogen source. Advances Wehkamp C.A., Stasiak M., Lawson J., Yorio N., Stutte G., Richards in Space Research, 2014, 53, 574-584 J., Wheeler R., Dixon M., Radish (Raphanus Sativa L. Cv. Cherry Robinson S., Graham T., Dixon M.A., Zheng Y., Aqueous ozone can Bomb II) growth, net carbon exchange rate, and transpiration at extend vase-life in cut roses, J. Hortic. Sci. Biotech, 2009, 84, decreased atmospheric pressure and / or oxygen. Gravitational 97–101 and Space Biology, 2012, 26, 3-16 Stasiak M., Cote R., Dixon M., Grodzinski B., Increasing plant Wehkamp C., Stasiak M., Dixon M., Response of radish to light and productivity in closed environments with inner canopy oxygen at reduced atmospheric pressure. Presented at the 41st illumination. Life Support Biosphere Science, 1998, 5, 175–181 International Conference on Environmental Systems, American Stasiak M., Gidzinski D., Jordan M., Dixon M., Crop selection for Institute of Aeronautics and Astronautics, Reston, Virigina, advanced life support systems in the ESA Melissa program: 2012, doi:10.2514/6.2011-5169 durum wheat (Triticum turgidum var durum), Advances in Space Wheeler R.M., Wehkamp C.A., Stasiak M.A., Dixon M.A., Rygalov V.Y., Research, 2012, 49, 1684–1690 Plants survive rapid decompression: implications for biorege- Stasiak M., Waters G., Zheng Y., Grodzinski B., Dixon M., Integrated nerative life support. Advances in Space Research, 2011, 47, multicropping of beet and lettuce and its effect on atmospheric 1600–1607 stability. Presented at The International Conference on Environmental Systems, SAE International, 400 Commonwealth