Thomas Graham | NASA Kennedy Space Center (original) (raw)
Papers by Thomas Graham
HortScience, Mar 2015
Significant advances in controlled environment (CE) plant production lighting have been made in r... more Significant advances in controlled environment (CE) plant production lighting have been made in recent years, driven by rapid improvements in light emitting diode (LED) technologies. Aside from energy efficiency gains, LEDs offer the ability to customize the spectrum delivered to a crop, which may have untold benefits for growers and researchers alike. Understanding how these specific wavebands are attenuated by plant tissue is important if lighting engineers are to fully optimize systems for CE plant production. In this study seven different greenhouse and field crops (radish, Raphanus sativus ‘Cherry Bomb II’; red romaine lettuce, Lactuca sativa ‘Outredgeous’, green leaf lettuce, Lactuca sativa ‘Waldmann’s Green’; pepper, Capsicum annuum ‘Fruit Basket’; soybean, Glycine max ’Hoyt’; cucumber, Cucumis sativus ‘Spacemaster’; canola, Brassica napus ‘Westar’) were grown in CE chambers under two different light intensities (225 and 420 µmol·m-2·s-1). Intact, fully expanded upper canopy leaves were used to determine the level of light transmission, at 2-3 different plant ages, across seven different wavebands with peaks at 400, 450, 530, 595, 630, 655, and 735 nm. The photosynthetic photon flux (PPF) environment that plants were grown in affected light transmission across the different LED wavelengths in a crop-dependent manner. Plant age had no effect on light transmission at the time intervals examined. Specific waveband transmission from the seven LED sources varied similarly across plant types, with low transmission of blue and red wavelengths, intermediate transmission of green and amber wavelengths, and the highest transmission at the far-red wavelengths. Higher native PPF increased anthocyanin levels in red romaine lettuce compared to the lower native PPF treatment. Understanding the differences in light transmission will inform the development of novel, energy-saving lighting architectures for CE plant growth.
Fluorescent imaging offers the ability to monitor biological functions, in this case biological r... more Fluorescent imaging offers the ability to monitor biological functions, in this case biological responses to space-related environments. For plants, fluorescent imaging can include general health indicators such as chlorophyll fluorescence as well as specific metabolic indicators such as engineered fluorescent reporters. This paper describes the Flex Imager a fluorescent imaging payload designed for Middeck Locker deployment and now tested on multiple flight and flight-related platforms. The Flex Imager and associated payload elements have been developed with a focus on ‘flexibility’ allowing for multiple imaging modalities and change-out of individual imaging or control components in the field. The imaging platform is contained within the standard Middeck Locker spaceflight form factor, with components affixed to a baseplate that permits easy rearrangement and fine adjustment of components. The Flex Imager utilizes standard software packages to simplify operation, operator training, and evaluation by flight provider flight test engineers, or by researchers processing the raw data. Images are obtained using a commercial cooled CCD image sensor, with light emitting diodes for excitation and a suite of filters that allow biological samples to be imaged over wavelength bands of interest. Although baselined for the monitoring of green fluorescent protein and chlorophyll fluorescence from Arabidopsis samples, the Flex Imager payload permits imaging of any biological sample contained within a standard 10 cm by 10 cm square Petri plate. A sample holder was developed to secure sample plates under different flight profiles while permitting sample change-out should crewed operations be possible. In addition to crew-directed imaging, autonomous or telemetric operation of the payload is also a viable operational mode. An infrared camera has also been integrated into the Flex Imager payload to allow concurrent fluorescent and thermal imaging of samples. The Flex Imager has been utilized to assess, in real-time, the response of plants to novel environments including various spaceflight analogs, including several parabolic flight environments as well as hypobaric plant growth chambers. Basic performance results obtained under these operational environments, as well as laboratory-based tests are described. The Flex Imager has also been designed to be compatible with emerging suborbital platforms.
Designs for an Antarctic plant production system to be deployed at Germany’s Neumayer Station III... more Designs for an Antarctic plant production system to be deployed at Germany’s Neumayer Station III are presented. Characterization and testing of several key controlled environment agriculture technologies are ongoing at the German Aerospace Center’s Institute of Space Systems. Subsystems under development at the Evolution and Design of Environmentally-Closed Nutrition-Sources (EDEN) laboratory include, tuned LED lighting, aeroponic nutrient delivery, ion-selective sensors and modular growth pallets. The Antarctic greenhouse module baseline form factor is a standard sea shipping container, which allows for use of nominal Antarctic logistics networks. The facility will be fixed onto a specially constructed platform and co-located near the Alfred Wegner Institute’s Neumayer Station III. The plant production facility will be operated year-round with maximum production per unit volume achieved through the deployment of modular grow units in a stackable rack architecture. In such a configuration the greenhouse module system can provide several kilograms of fresh edible biomass per day. Forty foot and 20 ft container configurations are described as well as the general design requirements, including specifics relevant to operations at Neumayer III. Successful deployment of such a facility will further the technology readiness and operational experience of space-based bioregenerative life support systems. Finally, the general design is presented in the context of an historical review of past Antarctic plant production facilities. This first known inventory of documented Antarctic plant production facilities, organizes the facilities with respect to Antarctic station, dates of operation, internal/external configuration and estimated production area.
Possible chemical methods for the treatment of ammonia in the air of livestock holding faciliti... more Possible chemical methods for the treatment of ammonia in the air of livestock holding facilities, with particular focus on poultry production, are reviewed in the context of eliminating ammonia by oxidation to elemental nitrogen. Gas phase catalytic oxidation processes are incompatible with the needs of the poultry industry on grounds of both capital cost and energy intensiveness. Most chemical oxidants convert ammonia princi- pally to nitrate rather than N2. So-called advanced oxidation processes are unsuited to ammonia oxidation because the hydroxyl radicals that characterize these oxidations react poorly with both NH3 and NHþ4 . One promising option is electrochemical oxidation, which does not require the purchase of stoichiometric amounts of chemical oxidants. Among possible electrochemical methods, we favour electrochemical hypochlorination, whereby the denitrification of ammonia to elemental nitrogen is mediated by hypochlorous acid, which is formed reversibly from chloride ion. This technique is compatible with currently available scrubbing technology, with the modification of using acidic brine as the scrubbing solution. Because electrochemical hypochlorination can be applied without costly and complicated pH adjustment of the scrubbed solution with chemical additives, it constitutes an example of best available technology.
Higher plants are an integral part of strategies for sustained human presence in space. Space-bas... more Higher plants are an integral part of strategies for sustained human presence in space. Space-based greenhouses have the potential to provide closed-loop recycling of oxygen, water and food. Plant monitoring systems with the capacity to remotely observe the condition of crops in real-time within these systems would permit operators to take immediate action to ensure optimum system yield and reliability. One such plant health monitoring technique involves the use of reporter genes driving fluorescent proteins as biological sensors of plant stress. In 2006 an initial prototype green fluorescent protein imager system was deployed at the Arthur Clarke Mars Greenhouse located in the Canadian High Arctic. This prototype demonstrated the advantageous of this biosensor technology and underscored the challenges in collecting and managing telemetric data from exigent environments. We present here the design and deployment of a second prototype imaging system deployed within and connected to the infrastructure of the Arthur Clarke Mars Greenhouse. This is the first imager to run autonomously for one year in the un-crewed greenhouse with command and control conducted through the greenhouse satellite control system. Images were saved locally in high resolution and sent telemetrically in low resolution. Imager hardware is described, including the custom designed LED growth light and fluorescent excitation light boards, filters, data acquisition and control system, and basic sensing and environmental control. Several critical lessons learned related to the hardware of small plant growth payloads are also elaborated.
Scientia Horticulturae, Jun 2012
Aqueous ozone is increasingly used to treat irrigation source water in greenhouse and nursery ope... more Aqueous ozone is increasingly used to treat irrigation source water in greenhouse and nursery operations; however, the ozone is typically removed prior to crop application. Until recently, this was appropriate as there was a paucity of data to suggest any other course of action. Recent research examining the application of aqueous ozone, through drip irrigation, to a mineral wool grown hydroponic tomato crop suggests that ozone can remain in solution during distribution to the crop without negative effect. What isnot known from this recent work is the upper limit or phytotoxic threshold for aqueous ozone application, beyond which crop damage would occur. The present study examined the effects of high aqueous ozone concentrations applied daily in this same production system. Suppression of some growth metrics was observed at 6.0 mg L−1. The ancillary effect of enhanced oxygenation of the irrigation solution, as a result of the ozonation process, was also examined to disentangle the oxygen/aeration effects from the ozone effects. No significant productivity effects were observed at elevated dissolved oxygen levels relative to the fully aerated control, therefore any productivity influence was attributed to aqueous ozone. The degree to which aqueous ozone penetrated the mineral wool substrate was also examined to aid in the development of horticultural management protocols. Even at volumetric ratios well in excess of typical commercial irrigation events, aqueous ozone still did not penetrate the mineral wool medium beyond 4 cm, with most of the ozone being lost in the upper 2 cm. Only after excessive volumes of aqueous ozone solution had been applied was a residual observed past 4 cm. Based on the results of this study and previous work, an upper limit of 3.0 mg L−1 for this type of production system is recommended until further research is completed.
Marchantia polymorpha L. (a thalloid liverwort) is a common plant pest in nursery and greenhouse ... more Marchantia polymorpha L. (a thalloid liverwort) is a common plant pest in nursery and greenhouse production systems. The rapid growth and dissemination of this pest can result in heavy mats of thallus tissue on the surface of pots, which restrict water penetration, compete for nutrients, and provide a habitat for other pests and disease vectors. The sensitivity of liverwort to aqueous ozone was examined to determine if routine use of ozone, as a component of an irrigation water remediation strategy, could provide ancillary services in the form of liverwort management. Three experiments were performed to evaluate contact time (CT) thresholds and application frequencies suitable for liverwort management applications. The first two experiments confirmed that CT is a suitable process control parameter with a base liverwort management threshold occurring between CT 0.84 and 1.68 mg·L−1·min under the conditions used. The third experiment examined the effect of application frequency at a CT of 3.75 mg·L−1·min, which was previously determined to be compatible with select woody perennial species. Three and five applications per week resulted in reduced liverwort growth and fecundity.
OPEN ACCESS The ability to monitor and control plant nutrient ions in fertigation solutions, on a... more OPEN ACCESS
The ability to monitor and control plant nutrient ions in fertigation solutions, on an ion-specific basis, is critical to the future of controlled environment agriculture crop production, be it in traditional terrestrial settings (e.g., greenhouse crop production) or as a component of bioregenerative life support systems for long duration space exploration. Several technologies are currently available that can provide the required measurement of ion-specific activities in solution. The greenhouse sector has invested in research examining the potential of a number of these technologies to meet the industry's demanding requirements, and although no ideal solution yet exists for on-line measurement, growers do utilize technologies such as high-performance liquid chromatography to provide off-line measurements. An analogous situation exists on the International Space Station where, technological solutions are sought, but currently on-orbit water quality monitoring is considerably restricted. This paper examines the specific advantages that on-line ion-selective sensors could provide to plant production systems both terrestrially and when utilized in space-based biological life support systems and how similar technologies could be applied to nominal on-orbit water quality monitoring. A historical development and technical review of the various ion-selective monitoring technologies is provided.
Abstract. Phytotoxic responses of five container-grown nursery species (Spiraea japonica ‘Goldmou... more Abstract. Phytotoxic responses of five container-grown nursery species (Spiraea japonica ‘Goldmound’, Hydrangea paniculata ‘Grandiflora’, Weigela florida ‘Alexandra’, Phys- ocarpus opulifolius ‘Summer Wine’, and Salix integra ‘Hakura Nishiki’) to chlorinated irrigation water and critical free chlorine thresholds were evaluated. Plants were overhead-irrigated with water containing 0, 2.5, 5, 10, and 20 mgL–1 of free chlorine for 6 weeks. The following measurements were used to assess the treatments: visual injury, growth, leaf chlorophyll content index, leaf chlorophyll fluorescence, leaf net CO2 exchange rate, and stomatal conductance. All species exhibited one or more signs of chlorine injury, including foliar necrotic mottling, foliar necrosis and chlorosis, decreased plant height, and increased premature abscission of foliage with species varying in sensitivity to free chlorine concentrations of irrigation water. The results indicated that the critical free chlorine threshold of S. japonica, H. paniculata, W. florida, and S. integra was 2.5 mgL–1 and 5 mgL–1 for P. opulifolius. Our results suggested that irrigation water containing free chlorine less than 2.5 mgL–1 should not adversely affect the growth or appearance of ornamental woody shrubs.
Future space exploration will require advanced life support (ALS) systems capable of in situ reso... more Future space exploration will require advanced life support (ALS) systems capable of in situ resource recycling. Hypobaric, bioregenerative life support systems have been proposed to address this requirement. The need to explore the limits of plant tolerance to hypobaric conditions is clear, however, research has been limited due to the difficulties and costs associated with this field. The Controlled Environment Systems Research Facility (CESRF), at the University of Guelph, Canada, has been designed to address the issues surrounding plant production under reduced pressure conditions. The measurement of plant physiological responses to hypobaric conditions is the subject of this study. Measurements of whole plant water relations, in terms of transpiration and plant water potential, are the ultimate goal. This phase of the work includes development and testing of the variable pressure plant growth chamber, and calibration of the in situ stem psychrometer for measuring plant water potential.
Abstract: Ensuring high plant yields is critical for the application of higher plants to space- b... more Abstract: Ensuring high plant yields is critical for the application of higher plants to space- based biological life support systems. An imager capable of monitoring several fluorescent biological markers in real-time would provide a robust health monitoring system and allow growers to minimize environmental stressors. This article reports the results of the design and development of a multispectral plant health imager prototype, employed in a low- pressure plant growth chamber as a test of its functionality in spaceflight systems. Images were collected every four hours with a monochromatic camera and a commercial liquid crystal tunable filter. This arrangement permitted the monitoring of emission from introduced green fluorescent proteins as well as chlorophyll fluorescence. Data were saved locally and accessed in real-time from the exterior of the chamber.
Scientia Horticulturae, 2011
Recycling of greenhouse irrigation water in hydroponic tomato production requires a water remedia... more Recycling of greenhouse irrigation water in hydroponic tomato production requires a water remediation process to reduce the risk of pathogen proliferation and the accumulation of other chemical compounds. The dissolution of ozone into bulk irrigation solutions is an effective technology for reducing chemical contaminant and pathogen levels in greenhouse irrigation water. Greenhouse managers utilizing ozonation typically remove residual ozone prior to distribution to the crop. Removal of the active compound in this treatment process has been deemed a prudent measure intended to prevent ozone-based plant damage. This said, although atmospheric ozone has been extensively studied with respect to its phytotoxicity, there are very few studies available on ozone in the aqueous phase in which evidence to support the removal of ozone (on the basis of phytotoxicity) is provided. Furthermore, removal limits the overall efficacy of the treatment as the ozone is not available to treat distribution lines and emitters. The purpose of this study was to determine if aqueous ozone impacts tomato (Lycopersicon esculentum Mill. cv Matrix F1) productivity when applied directly to a mineral wool growth substrate via drip irrigation. At the highest aqueous ozone treatment level (3.0 mg L−1) significant increases in leaf area, shoot dry matter, and stem thickness were observed. There were no differences across all treatments in terms of net CO2 assimilation rate, stomatal conductance, internal leaf CO2 concentration, chlorophyll content index, and fruit production. A qualitative assessment of algae growth on the substrate surface was conducted. Both ozone treatments resulted in a visually discernible reduction in algae prevalence on the substrate surface. The results of this study do not support the removal of aqueous ozone (at the concentrations examined) prior to distribution when the solution is applied via drip irrigation in mineral wool hydroponic tomato production.
Telemetric data collection has been widely used in spaceflight applications where human participa... more Telemetric data collection has been widely used in spaceflight applications where human participation is limited (orbital mission payloads) or unfeasible (planetary landers, satellites, and probes). The transmission of digital data from electronic sensors of typical environmental parameters, growth patterns and physical properties of materials is routine telemetry, and even the collection and transmission of deep space images is a standard tool of astrophysics. But telemetric imaging for current biological payloads has thus far been limited to the collection of standard white-light photography that is largely confined to reporting the surface characteristics of the specimens involved. Advances in imaging technologies that facilitate the collection of a variety of light wavelengths will expand the science return on biological payloads to include evaluations of the molecular genetic response of organisms to the spaceflight or extraterrestrial environment, with minimal or no human intervention. Advanced imaging technology in combination with biologically engineered sensor organisms can create a system that can report via telemetry on the patterns of gene expression required to adapt to a novel environment. The utilization of genetically engineered plants as biosensors has made elegant strides in the recent years, providing keen insights into the health of plants in general and particularly in the nature and cellular location of stress responses. Moreover, molecular responses to gravitational vectors have been elegantly analyzed with fluorescent tools. Green Fluorescence Protein (GFP) and other fluorophores have made it possible for analyses of gene expression and biological responses to occur telemetrically, with the information potentially delivered to the investigator over large distances as simple, preprocessed fluorescence images. Having previously deployed transgenic plant biosensors to evaluate responses to orbital spaceflight, we wish to develop both the plants and the imaging devices required to conduct such fluorescence imaging experiments robotically, without direct operator intervention, within the operational constraints of extraterrestrial environments. This requires the development of an autonomous and remotely operated plant fluorescence imaging system and concomitant development of the infrastructure to manage dataflow. Here we report the results of the deployment of our spaceflight prototype GFP imaging system within the Arthur Clarke Mars Greenhouse (ACMG), an autonomously operated greenhouse located within the Haughton Mars Project in the High Canadian Arctic (75° 22'N Latitude: 89° 41'W Longitude). Results demonstrate both the applicability of the fundamental GFP biosensor technology and highlight the difficulties in collecting and managing telemetric data from challenging deployment environments.
Advances in Space Research, 2009
J. Horticult. Sci. Biotechnol., 2009
In order to quantify the shelf-life response of cut roses when stored in aqueous ozone solutions,... more In order to quantify the shelf-life response of cut roses when stored in aqueous ozone solutions, cut ‘Pascha’ roses were stored in either de-ionised water or aqueous ozone solutions containing an initial dissolved ozone residual of 5.5 mg l–1. The results showed that storing cut roses in aqueous ozone solutions (5.5 mg l–1; renewed daily) can extend vase- life approx. three-fold, from 5 d to 13 d, with a corresponding improvement in their aesthetic appearance throughout the vase-life of the cut rose stem. Results suggest that vase-life improvements are achieved through a reduction in bacterial populations present in the storage solution. Bacteria accumulate on the cut surface of the stems, thereby reducing their water uptake capacity. Microbial accumulation was reduced by 1.15 log10 CFU g–1 FW when stems were stored in holding solutions containing 5.5 mg l–1 dissolved ozone, with a corresponding increase in water uptake. Roses stored in ozonated water exhibited higher numbers of functional xylem vessels, water uptake, relative water content, relative fresh weight, acid fuchsin uptake rate, leaf stomatal conductance, and net CO2 assimilation rate, compared to those stored in de-ionised water. The results suggest that ozone can extend cut rose vase-life.
HortScience, Mar 2015
Significant advances in controlled environment (CE) plant production lighting have been made in r... more Significant advances in controlled environment (CE) plant production lighting have been made in recent years, driven by rapid improvements in light emitting diode (LED) technologies. Aside from energy efficiency gains, LEDs offer the ability to customize the spectrum delivered to a crop, which may have untold benefits for growers and researchers alike. Understanding how these specific wavebands are attenuated by plant tissue is important if lighting engineers are to fully optimize systems for CE plant production. In this study seven different greenhouse and field crops (radish, Raphanus sativus ‘Cherry Bomb II’; red romaine lettuce, Lactuca sativa ‘Outredgeous’, green leaf lettuce, Lactuca sativa ‘Waldmann’s Green’; pepper, Capsicum annuum ‘Fruit Basket’; soybean, Glycine max ’Hoyt’; cucumber, Cucumis sativus ‘Spacemaster’; canola, Brassica napus ‘Westar’) were grown in CE chambers under two different light intensities (225 and 420 µmol·m-2·s-1). Intact, fully expanded upper canopy leaves were used to determine the level of light transmission, at 2-3 different plant ages, across seven different wavebands with peaks at 400, 450, 530, 595, 630, 655, and 735 nm. The photosynthetic photon flux (PPF) environment that plants were grown in affected light transmission across the different LED wavelengths in a crop-dependent manner. Plant age had no effect on light transmission at the time intervals examined. Specific waveband transmission from the seven LED sources varied similarly across plant types, with low transmission of blue and red wavelengths, intermediate transmission of green and amber wavelengths, and the highest transmission at the far-red wavelengths. Higher native PPF increased anthocyanin levels in red romaine lettuce compared to the lower native PPF treatment. Understanding the differences in light transmission will inform the development of novel, energy-saving lighting architectures for CE plant growth.
Fluorescent imaging offers the ability to monitor biological functions, in this case biological r... more Fluorescent imaging offers the ability to monitor biological functions, in this case biological responses to space-related environments. For plants, fluorescent imaging can include general health indicators such as chlorophyll fluorescence as well as specific metabolic indicators such as engineered fluorescent reporters. This paper describes the Flex Imager a fluorescent imaging payload designed for Middeck Locker deployment and now tested on multiple flight and flight-related platforms. The Flex Imager and associated payload elements have been developed with a focus on ‘flexibility’ allowing for multiple imaging modalities and change-out of individual imaging or control components in the field. The imaging platform is contained within the standard Middeck Locker spaceflight form factor, with components affixed to a baseplate that permits easy rearrangement and fine adjustment of components. The Flex Imager utilizes standard software packages to simplify operation, operator training, and evaluation by flight provider flight test engineers, or by researchers processing the raw data. Images are obtained using a commercial cooled CCD image sensor, with light emitting diodes for excitation and a suite of filters that allow biological samples to be imaged over wavelength bands of interest. Although baselined for the monitoring of green fluorescent protein and chlorophyll fluorescence from Arabidopsis samples, the Flex Imager payload permits imaging of any biological sample contained within a standard 10 cm by 10 cm square Petri plate. A sample holder was developed to secure sample plates under different flight profiles while permitting sample change-out should crewed operations be possible. In addition to crew-directed imaging, autonomous or telemetric operation of the payload is also a viable operational mode. An infrared camera has also been integrated into the Flex Imager payload to allow concurrent fluorescent and thermal imaging of samples. The Flex Imager has been utilized to assess, in real-time, the response of plants to novel environments including various spaceflight analogs, including several parabolic flight environments as well as hypobaric plant growth chambers. Basic performance results obtained under these operational environments, as well as laboratory-based tests are described. The Flex Imager has also been designed to be compatible with emerging suborbital platforms.
Designs for an Antarctic plant production system to be deployed at Germany’s Neumayer Station III... more Designs for an Antarctic plant production system to be deployed at Germany’s Neumayer Station III are presented. Characterization and testing of several key controlled environment agriculture technologies are ongoing at the German Aerospace Center’s Institute of Space Systems. Subsystems under development at the Evolution and Design of Environmentally-Closed Nutrition-Sources (EDEN) laboratory include, tuned LED lighting, aeroponic nutrient delivery, ion-selective sensors and modular growth pallets. The Antarctic greenhouse module baseline form factor is a standard sea shipping container, which allows for use of nominal Antarctic logistics networks. The facility will be fixed onto a specially constructed platform and co-located near the Alfred Wegner Institute’s Neumayer Station III. The plant production facility will be operated year-round with maximum production per unit volume achieved through the deployment of modular grow units in a stackable rack architecture. In such a configuration the greenhouse module system can provide several kilograms of fresh edible biomass per day. Forty foot and 20 ft container configurations are described as well as the general design requirements, including specifics relevant to operations at Neumayer III. Successful deployment of such a facility will further the technology readiness and operational experience of space-based bioregenerative life support systems. Finally, the general design is presented in the context of an historical review of past Antarctic plant production facilities. This first known inventory of documented Antarctic plant production facilities, organizes the facilities with respect to Antarctic station, dates of operation, internal/external configuration and estimated production area.
Possible chemical methods for the treatment of ammonia in the air of livestock holding faciliti... more Possible chemical methods for the treatment of ammonia in the air of livestock holding facilities, with particular focus on poultry production, are reviewed in the context of eliminating ammonia by oxidation to elemental nitrogen. Gas phase catalytic oxidation processes are incompatible with the needs of the poultry industry on grounds of both capital cost and energy intensiveness. Most chemical oxidants convert ammonia princi- pally to nitrate rather than N2. So-called advanced oxidation processes are unsuited to ammonia oxidation because the hydroxyl radicals that characterize these oxidations react poorly with both NH3 and NHþ4 . One promising option is electrochemical oxidation, which does not require the purchase of stoichiometric amounts of chemical oxidants. Among possible electrochemical methods, we favour electrochemical hypochlorination, whereby the denitrification of ammonia to elemental nitrogen is mediated by hypochlorous acid, which is formed reversibly from chloride ion. This technique is compatible with currently available scrubbing technology, with the modification of using acidic brine as the scrubbing solution. Because electrochemical hypochlorination can be applied without costly and complicated pH adjustment of the scrubbed solution with chemical additives, it constitutes an example of best available technology.
Higher plants are an integral part of strategies for sustained human presence in space. Space-bas... more Higher plants are an integral part of strategies for sustained human presence in space. Space-based greenhouses have the potential to provide closed-loop recycling of oxygen, water and food. Plant monitoring systems with the capacity to remotely observe the condition of crops in real-time within these systems would permit operators to take immediate action to ensure optimum system yield and reliability. One such plant health monitoring technique involves the use of reporter genes driving fluorescent proteins as biological sensors of plant stress. In 2006 an initial prototype green fluorescent protein imager system was deployed at the Arthur Clarke Mars Greenhouse located in the Canadian High Arctic. This prototype demonstrated the advantageous of this biosensor technology and underscored the challenges in collecting and managing telemetric data from exigent environments. We present here the design and deployment of a second prototype imaging system deployed within and connected to the infrastructure of the Arthur Clarke Mars Greenhouse. This is the first imager to run autonomously for one year in the un-crewed greenhouse with command and control conducted through the greenhouse satellite control system. Images were saved locally in high resolution and sent telemetrically in low resolution. Imager hardware is described, including the custom designed LED growth light and fluorescent excitation light boards, filters, data acquisition and control system, and basic sensing and environmental control. Several critical lessons learned related to the hardware of small plant growth payloads are also elaborated.
Scientia Horticulturae, Jun 2012
Aqueous ozone is increasingly used to treat irrigation source water in greenhouse and nursery ope... more Aqueous ozone is increasingly used to treat irrigation source water in greenhouse and nursery operations; however, the ozone is typically removed prior to crop application. Until recently, this was appropriate as there was a paucity of data to suggest any other course of action. Recent research examining the application of aqueous ozone, through drip irrigation, to a mineral wool grown hydroponic tomato crop suggests that ozone can remain in solution during distribution to the crop without negative effect. What isnot known from this recent work is the upper limit or phytotoxic threshold for aqueous ozone application, beyond which crop damage would occur. The present study examined the effects of high aqueous ozone concentrations applied daily in this same production system. Suppression of some growth metrics was observed at 6.0 mg L−1. The ancillary effect of enhanced oxygenation of the irrigation solution, as a result of the ozonation process, was also examined to disentangle the oxygen/aeration effects from the ozone effects. No significant productivity effects were observed at elevated dissolved oxygen levels relative to the fully aerated control, therefore any productivity influence was attributed to aqueous ozone. The degree to which aqueous ozone penetrated the mineral wool substrate was also examined to aid in the development of horticultural management protocols. Even at volumetric ratios well in excess of typical commercial irrigation events, aqueous ozone still did not penetrate the mineral wool medium beyond 4 cm, with most of the ozone being lost in the upper 2 cm. Only after excessive volumes of aqueous ozone solution had been applied was a residual observed past 4 cm. Based on the results of this study and previous work, an upper limit of 3.0 mg L−1 for this type of production system is recommended until further research is completed.
Marchantia polymorpha L. (a thalloid liverwort) is a common plant pest in nursery and greenhouse ... more Marchantia polymorpha L. (a thalloid liverwort) is a common plant pest in nursery and greenhouse production systems. The rapid growth and dissemination of this pest can result in heavy mats of thallus tissue on the surface of pots, which restrict water penetration, compete for nutrients, and provide a habitat for other pests and disease vectors. The sensitivity of liverwort to aqueous ozone was examined to determine if routine use of ozone, as a component of an irrigation water remediation strategy, could provide ancillary services in the form of liverwort management. Three experiments were performed to evaluate contact time (CT) thresholds and application frequencies suitable for liverwort management applications. The first two experiments confirmed that CT is a suitable process control parameter with a base liverwort management threshold occurring between CT 0.84 and 1.68 mg·L−1·min under the conditions used. The third experiment examined the effect of application frequency at a CT of 3.75 mg·L−1·min, which was previously determined to be compatible with select woody perennial species. Three and five applications per week resulted in reduced liverwort growth and fecundity.
OPEN ACCESS The ability to monitor and control plant nutrient ions in fertigation solutions, on a... more OPEN ACCESS
The ability to monitor and control plant nutrient ions in fertigation solutions, on an ion-specific basis, is critical to the future of controlled environment agriculture crop production, be it in traditional terrestrial settings (e.g., greenhouse crop production) or as a component of bioregenerative life support systems for long duration space exploration. Several technologies are currently available that can provide the required measurement of ion-specific activities in solution. The greenhouse sector has invested in research examining the potential of a number of these technologies to meet the industry's demanding requirements, and although no ideal solution yet exists for on-line measurement, growers do utilize technologies such as high-performance liquid chromatography to provide off-line measurements. An analogous situation exists on the International Space Station where, technological solutions are sought, but currently on-orbit water quality monitoring is considerably restricted. This paper examines the specific advantages that on-line ion-selective sensors could provide to plant production systems both terrestrially and when utilized in space-based biological life support systems and how similar technologies could be applied to nominal on-orbit water quality monitoring. A historical development and technical review of the various ion-selective monitoring technologies is provided.
Abstract. Phytotoxic responses of five container-grown nursery species (Spiraea japonica ‘Goldmou... more Abstract. Phytotoxic responses of five container-grown nursery species (Spiraea japonica ‘Goldmound’, Hydrangea paniculata ‘Grandiflora’, Weigela florida ‘Alexandra’, Phys- ocarpus opulifolius ‘Summer Wine’, and Salix integra ‘Hakura Nishiki’) to chlorinated irrigation water and critical free chlorine thresholds were evaluated. Plants were overhead-irrigated with water containing 0, 2.5, 5, 10, and 20 mgL–1 of free chlorine for 6 weeks. The following measurements were used to assess the treatments: visual injury, growth, leaf chlorophyll content index, leaf chlorophyll fluorescence, leaf net CO2 exchange rate, and stomatal conductance. All species exhibited one or more signs of chlorine injury, including foliar necrotic mottling, foliar necrosis and chlorosis, decreased plant height, and increased premature abscission of foliage with species varying in sensitivity to free chlorine concentrations of irrigation water. The results indicated that the critical free chlorine threshold of S. japonica, H. paniculata, W. florida, and S. integra was 2.5 mgL–1 and 5 mgL–1 for P. opulifolius. Our results suggested that irrigation water containing free chlorine less than 2.5 mgL–1 should not adversely affect the growth or appearance of ornamental woody shrubs.
Future space exploration will require advanced life support (ALS) systems capable of in situ reso... more Future space exploration will require advanced life support (ALS) systems capable of in situ resource recycling. Hypobaric, bioregenerative life support systems have been proposed to address this requirement. The need to explore the limits of plant tolerance to hypobaric conditions is clear, however, research has been limited due to the difficulties and costs associated with this field. The Controlled Environment Systems Research Facility (CESRF), at the University of Guelph, Canada, has been designed to address the issues surrounding plant production under reduced pressure conditions. The measurement of plant physiological responses to hypobaric conditions is the subject of this study. Measurements of whole plant water relations, in terms of transpiration and plant water potential, are the ultimate goal. This phase of the work includes development and testing of the variable pressure plant growth chamber, and calibration of the in situ stem psychrometer for measuring plant water potential.
Abstract: Ensuring high plant yields is critical for the application of higher plants to space- b... more Abstract: Ensuring high plant yields is critical for the application of higher plants to space- based biological life support systems. An imager capable of monitoring several fluorescent biological markers in real-time would provide a robust health monitoring system and allow growers to minimize environmental stressors. This article reports the results of the design and development of a multispectral plant health imager prototype, employed in a low- pressure plant growth chamber as a test of its functionality in spaceflight systems. Images were collected every four hours with a monochromatic camera and a commercial liquid crystal tunable filter. This arrangement permitted the monitoring of emission from introduced green fluorescent proteins as well as chlorophyll fluorescence. Data were saved locally and accessed in real-time from the exterior of the chamber.
Scientia Horticulturae, 2011
Recycling of greenhouse irrigation water in hydroponic tomato production requires a water remedia... more Recycling of greenhouse irrigation water in hydroponic tomato production requires a water remediation process to reduce the risk of pathogen proliferation and the accumulation of other chemical compounds. The dissolution of ozone into bulk irrigation solutions is an effective technology for reducing chemical contaminant and pathogen levels in greenhouse irrigation water. Greenhouse managers utilizing ozonation typically remove residual ozone prior to distribution to the crop. Removal of the active compound in this treatment process has been deemed a prudent measure intended to prevent ozone-based plant damage. This said, although atmospheric ozone has been extensively studied with respect to its phytotoxicity, there are very few studies available on ozone in the aqueous phase in which evidence to support the removal of ozone (on the basis of phytotoxicity) is provided. Furthermore, removal limits the overall efficacy of the treatment as the ozone is not available to treat distribution lines and emitters. The purpose of this study was to determine if aqueous ozone impacts tomato (Lycopersicon esculentum Mill. cv Matrix F1) productivity when applied directly to a mineral wool growth substrate via drip irrigation. At the highest aqueous ozone treatment level (3.0 mg L−1) significant increases in leaf area, shoot dry matter, and stem thickness were observed. There were no differences across all treatments in terms of net CO2 assimilation rate, stomatal conductance, internal leaf CO2 concentration, chlorophyll content index, and fruit production. A qualitative assessment of algae growth on the substrate surface was conducted. Both ozone treatments resulted in a visually discernible reduction in algae prevalence on the substrate surface. The results of this study do not support the removal of aqueous ozone (at the concentrations examined) prior to distribution when the solution is applied via drip irrigation in mineral wool hydroponic tomato production.
Telemetric data collection has been widely used in spaceflight applications where human participa... more Telemetric data collection has been widely used in spaceflight applications where human participation is limited (orbital mission payloads) or unfeasible (planetary landers, satellites, and probes). The transmission of digital data from electronic sensors of typical environmental parameters, growth patterns and physical properties of materials is routine telemetry, and even the collection and transmission of deep space images is a standard tool of astrophysics. But telemetric imaging for current biological payloads has thus far been limited to the collection of standard white-light photography that is largely confined to reporting the surface characteristics of the specimens involved. Advances in imaging technologies that facilitate the collection of a variety of light wavelengths will expand the science return on biological payloads to include evaluations of the molecular genetic response of organisms to the spaceflight or extraterrestrial environment, with minimal or no human intervention. Advanced imaging technology in combination with biologically engineered sensor organisms can create a system that can report via telemetry on the patterns of gene expression required to adapt to a novel environment. The utilization of genetically engineered plants as biosensors has made elegant strides in the recent years, providing keen insights into the health of plants in general and particularly in the nature and cellular location of stress responses. Moreover, molecular responses to gravitational vectors have been elegantly analyzed with fluorescent tools. Green Fluorescence Protein (GFP) and other fluorophores have made it possible for analyses of gene expression and biological responses to occur telemetrically, with the information potentially delivered to the investigator over large distances as simple, preprocessed fluorescence images. Having previously deployed transgenic plant biosensors to evaluate responses to orbital spaceflight, we wish to develop both the plants and the imaging devices required to conduct such fluorescence imaging experiments robotically, without direct operator intervention, within the operational constraints of extraterrestrial environments. This requires the development of an autonomous and remotely operated plant fluorescence imaging system and concomitant development of the infrastructure to manage dataflow. Here we report the results of the deployment of our spaceflight prototype GFP imaging system within the Arthur Clarke Mars Greenhouse (ACMG), an autonomously operated greenhouse located within the Haughton Mars Project in the High Canadian Arctic (75° 22'N Latitude: 89° 41'W Longitude). Results demonstrate both the applicability of the fundamental GFP biosensor technology and highlight the difficulties in collecting and managing telemetric data from challenging deployment environments.
Advances in Space Research, 2009
J. Horticult. Sci. Biotechnol., 2009
In order to quantify the shelf-life response of cut roses when stored in aqueous ozone solutions,... more In order to quantify the shelf-life response of cut roses when stored in aqueous ozone solutions, cut ‘Pascha’ roses were stored in either de-ionised water or aqueous ozone solutions containing an initial dissolved ozone residual of 5.5 mg l–1. The results showed that storing cut roses in aqueous ozone solutions (5.5 mg l–1; renewed daily) can extend vase- life approx. three-fold, from 5 d to 13 d, with a corresponding improvement in their aesthetic appearance throughout the vase-life of the cut rose stem. Results suggest that vase-life improvements are achieved through a reduction in bacterial populations present in the storage solution. Bacteria accumulate on the cut surface of the stems, thereby reducing their water uptake capacity. Microbial accumulation was reduced by 1.15 log10 CFU g–1 FW when stems were stored in holding solutions containing 5.5 mg l–1 dissolved ozone, with a corresponding increase in water uptake. Roses stored in ozonated water exhibited higher numbers of functional xylem vessels, water uptake, relative water content, relative fresh weight, acid fuchsin uptake rate, leaf stomatal conductance, and net CO2 assimilation rate, compared to those stored in de-ionised water. The results suggest that ozone can extend cut rose vase-life.