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Volatile Organic Compound Analysis (VOCA): A System for Evaluating Atmospheric Contaminants on Plant Growth
Abstract and Figures
A set of contained environment chambers have been
designed to study the effects of Volatile Organic
Compounds (VOCs) on plant growth and development.
The Volatile Organic Compound Analysis (VOCA)
system consists of six Lexan chambers, each with
independent VOC monitoring and control capacities. The
VOC exposure chambers are located within a larger
controlled environment chamber (CEC) which provides a
common air temperature, photoperiod, and light control.
Relative humidity, CO2 concentration, and VOC
concentration of the atmosphere are independently
controlled in each VOCA exposure chambers. CO2, air
temperature, relative humidity and PPF are continuously
monitored with software developed using IOControlTM
and IODisplayTM.
Figures - uploaded by Lawrence L Koss
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Content may be subject to copyright.
... At 100 ppm (10% of crew and worker exposure guidelines) the harvest index, leaf area index and absolute growth rate of the three cultivars was reduced. A seedling bioassay system was designed in order to rapidly screen VOCs for bioactivity to prioritize compounds for further whole plant testing (Stutte et al., 2005). These experiments utilized the radish seedling bioassay to establish preliminary threshold, sensitivity, and lethal concentrations for the bioactivity of light alcohols in order to establish reasonable exposure guidelines for plant systems to support long duration space systems (Stutte, 1999;Stutte et al., 2005). ...
... A seedling bioassay system was designed in order to rapidly screen VOCs for bioactivity to prioritize compounds for further whole plant testing (Stutte et al., 2005). These experiments utilized the radish seedling bioassay to establish preliminary threshold, sensitivity, and lethal concentrations for the bioactivity of light alcohols in order to establish reasonable exposure guidelines for plant systems to support long duration space systems (Stutte, 1999;Stutte et al., 2005). ...
... This system was controlled by a modifi cation of a LabView program described by Stutte et al. (2005). VOC concentrations, from each chamber, are detected by the GC and recorded in a text fi le by PeakSimple. ...
A series of experiments were conducted to determine the sensitivity of radish to four light alcohols (ethanol, methanol, 2-propanol, and t-butanol) identified as atmospheric contaminants on manned spacecraft. Radish (Raphanus sativus L. 'Cherry Bomb' Hybrid II) seedlings were exposed for 5 days to concentrations of 0, 50, 100, 175, 250, and 500 ppm of each alcohol and the effect on seedling growth was used to establish preliminary threshold response values. Results show a general response-pattern for the four alcohol exposures at threshold responses of 10% (T10), 50% (T50) and 90% (T90) reduction in seedling length. There were differences in the response of seedlings to the four alcohols, with the T10 for t-butanol and ethanol (25 to 40 ppm) being 3 to 5x lower than for methanol or 2-propanol (110 to 120 ppm). Ethanol and t-butanol exhibited similar T 50 values (150 to 160 ppm). In contrast, T50 for methanol (285 ppm) and 2-propanol (260 ppm) were about 100 ppm higher than for ethanol or t-butanol. Chronic exposures to 400 ppm t-butanol, ethanol or 2-propanol were highly toxic to the plants. Radish was more tolerant of methanol, with T 90 of 465 ppm. Seeds did not germinate at the 500 ppm treatment of t-butanol, 2-propanol, or ethanol. There were significant differences in projected performance of plants in different environments, dependent upon the regulatory guidelines used. The use of exposure guidelines for humans is not applicable to plant systems.
... A large step-in CEC (EGC M-36; Environmental Growth Chambers, Chagrin Falls, OH) was used to provide a consistent light quality, light intensity, and photoperiod to six smaller plant growth chambers that contained six plants each. The plant growth chambers had been originally designed as volatile organic compound analysis chambers (Stutte et al., 2005) and had high-fidelity control of relative humidity (RH), temperature, and CO 2 concentration. Photosynthetic photon flux (PPF) was provided by T8 triphosphor fluorescent (TPF) lamps (Sylvania FP541/841/HO; Osram Sylvania, Westfield, IN) with dimmable ballasts. ...
... Each nutrient delivery system consists of a calibrated nutrient reservoir, replenishment solution, nutrient containment chamber, siphon assembly, and the individual plant chamber. The interaction of nutrient solution level and root matrix is used to establish and maintain the desired moisture content conditions (Stutte et al., 2005). ...
Scutellaria L. is a genus of herbaceous perennials of the Lamianaceae that includes several species with medicinal properties. The medicinal species of Scutellaria are rich in physiologically active flavonoids with a range of pharmacological activity. Experiments were conducted to determine the feasibility of increasing the growth rate and flavonoid content of Scutellaria barbata D. Don and Scutellaria lateriflora L. with CO2 enrichment in a controlled environment. Both species showed an increased growth rate and total biomass in response to CO2 enrichment from 400 to 1200 μmol·mol-1 CO2, and time to flowering was accelerated by 7 to 10 days. The bioactive flavonoids scutellarein, baicalin, apigenin, baicalein, and wogonin were detected in vegetative tissue of S. barbata. Total flavonoid content increased 50% with enrichment of CO2 to 1200 and 81% with 3000 μmol·mol-1. Scutellarein, baicalin, and apigenin concentrations increased with increasing CO2, whereas baicalein and wogonin did not. The flavonoids baicalin, baicalein, wogonin, and chrysin were detected in the vegetative tissue of S. lateriflora. The total concentration of the bioactive flavonoids measured in the vegetative tissue of S. lateriflora was much higher than S. barbata under ambient CO2 conditions (1144 vs. 249 μg·g-1 dry weight). The total content of the measured bioactive flavonoids increased 2.4 times with enrichment to 1200 μmol·mol-1 CO2, and 5.9 times with enrichment to 3000 μmol·mol-1 CO2. These results indicate that the yield and pharmaceutical quality of Scutellaria species can be enhanced with controlled environment production and CO2 enrichment.
... Seeds were germinated under a translucent cover for 5 days, and then thinned at 7 and 14 days after planting (DAP), resulting in 4 plants per block (168 plants/m 2 ) at harvest. Nutrients were supplied as full strength Hoagland solution (Hoagland and Arnon, 1950) using a bottom feed irrigation system (Stutte et al., 2005). ...
Space missions beyond Low Earth orbit will expose crew members to higher doses of cosmic radiation than currently received onboard the Space Shuttle or the International Space Station. Providing a diet high in bioprotective compounds is a potential biological countermeasure for radiation exposure. Spectral quality is one means of regulating the production of bioactive compounds in plant tissues. Narrow band-width LEDs were used to evaluate the effect of timing and duration of exposure of blue (440 nm) light on anthocyanin production in Lactuca sativa cv. Outredgeous. Lettuce were grown for 14 days under red (660 nm) LED's with blue light (440 nm) applied for the final 7 days, and the subsequent anthocyanin development was monitored. There was rapid increase in anthocyanin content observed from <50 µg/g fresh mass to greater than 800 µg/g fresh mass within 48 hr of blue light exposure. Removal of the blue light resulted in a decrease in anthocyanin concentration to the same level as the red-only control within 72 hr. Leaves that had developed under red-only did not develop anthocyanin under blue light exposure, while developing leaves did.
Controlled environment (CE) experiments were initiated at Kennedy Space Center, FL to determine the feasibility of using CE for the production of S. barbata and S. lateriflora in order to increase productivity and reduce variability in production. Scutellaria are a genus of herbaceous perennials of the Lamiaceae family of dicots that include several species with purported medicinal properties. A number of preliminary experiments were conducted in specialized plant growth chambers to determine conditions for seed germination, temperature for early growth and development, and CO2 conditions for optimal growth. Plant nutrition and water was regulated using soilless production with rockwool as the rooting media. Light inhibited seed germination at temperatures less than 26°C, and pre-soaking for seeds for 96 h at 4°C greatly enhances germination rate at all temperatures in both the light and dark. The optimum temperature for seedling establishment was 26°C for S. lateriflora and 30°C for S. barbata. Increasing CO2 concentration from 400 to 1200 μmol mol-1 increased total biomass of S. barbata by 65% and S. lateriflora by 89%. Further increases to 3000 μmol mol-1 had no additional effect on growth S. barbata, but increased biomass another 20% in S. lateriflora. Increasing CO2 also decreased time to flowering in CE chambers by 7 to 10 days. These preliminary experiments suggest that significant improvements in Scutellaria growth and productivity can by achieved using CE production.
NASA's Controlled Ecological Life Support System (CELSS) biomass production chamber at John F. Kennedy Space Center provides a test bed for bioregenerative studies using plants to provide food, oxygen, carbon dioxide removal, and potable water to humans during long term space travel. Growing plants in enclosed environments has brought about concerns regarding the level of volatile organic compounds (VOC's) emitted from plants and the construction materials that make up the plant growth chambers. In such closed systems, the potential exists for some VOC's to reach toxic levels and lead to poor plant growth, plant death, or health problems for human inhabitants. This study characterized the air in an enclosed environment in which wheat cv. Yocora Rojo was grown. Ninty-four whole air samples were analyzed by gas chromatography/mass spectrometry throughout the eighty-four day planting. VOC emissions from plants and materials were characterized and quantified.
A system and methodology were developed for the nondestructive qualitative and quantitative analysis of volatile emissions from hydroponically grown 'Waldmann's Green' leaf lettuce (Lactuca sativa L.). Photosynthetic photon flux (PPF), photoperiod, and temperature were automatically controlled and monitored in a growth chamber modified for the collection of plant volatiles. The lipoxygenase pathway products (Z)-3-hexenal, (Z)-3-hexenol, and (Z)-3-hexenyl acetate were emitted by lettuce plants after the transition from the light period to the dark period. The volatile collection system developed in this study enabled measurements of volatiles emitted by intact plants, from planting to harvest, under controlled environmental conditions.
Phytochemicals are naturally occurring compounds produced by plants. These compounds are essential for normal growth and development and can be specific for a given plant species or cultivar. Phytochemicals also are essential components of human nutrition and include carbohydrates, lipids, proteins, fiber, and vitamins. Secondary phytochemicals, such as polyphenols and flavanoids, provide human nutritional and health benefits. Phytochemicals associated with flavor and aroma play a significant, yet currently unquantified, psychological role in human mental health. In addition to the phytochemicals contained within plants, releasing of volatile and soluble phytochemicals into the environmentoccurs during growth and development. Examples of volatile phytochemicals include the fragrance of flowers and the aroma of freshly cut grass. Examples of soluble phytochemicals include allelopathic substances such as pyrethrins.
Radish (Raphanus sativus L.) is a salad type crop that is being evaluated for possible use on the International Space Station (ISS). The study will determine the growth and development of radish in the microgravity environment. A series of experiments were initiated to determine whether volatile organic compounds (VOC) that are commonly accumulated in closed systems of spacecraft atmosphere are biologically active. A survey of existing atmospheric samples from the space shuttle and ISS revealed over 260 compounds with potential biogenic activity of which a subset of 14 compounds have been selected for detailed evaluation. Initial screening is achieved by exposing radishes to VOC concentrations corresponding to 0.1 and 1.0 the Spacecraft Maximum Allowable Concentration (SMAC) of the contaminants. Biogenic effects of ethanol at 0.1 of the SMAC resulted in lower chlorophyll content, reduced growth rate, and lower yields. Chronic exposure to ethanol concentrations at 0.5 SMAC were lethal to radish. Radishes exposed to acetone did not show phytotoxic responses at concentrations up to the SMAC.
Among the challenges in the development of a viable plant production system in a closed environment is the management of potentially toxic trace gases emitted by plants. In order to assess possible dangers that volatile plant chemicals might pose to the safety of a space crew, the qualitative and quantitative determinations of these plant emissions are essential. Differential pressure measurements obtained during the transition from the light to the dark period did not vary significantly during the temperature change from 23 C to 18 C. This result was consistent with the fact that although the air within the glass jar was pressurized relative to external air, there was a significant amount of leakage at each of the three ports on the top of the jar and around its base where it was supported by the aluminum plate. Backflow of contaminants into the jar was prevented by this leakage. The flow of purified air into the glass jar purged the jar 1-1.5 times/min. This continual flushing of the jar minimized accumulation of vapor phase volatile products and the consequent formation of a gradual chemical potential gradient around the leaves. The continual evacuation of airborne compounds may enhance volatile emission rates somewhat by increasing the chemical gradient at this interface. Analyses of air samples collected during the 2 hour period immediately after the end of the light period consistently indicated the presence of 3 compounds beginning at 21 DAT. None of these compounds were detected during other periods of the diurnal cycle. In order to confirm that the compounds detected originated from the lettuce and not from the collection system, chromatograms representing background collections in which the glass jar was empty were compared to those from collections in which the jar was placed over a lettuce plant. The nondestructive sampling of volatile compounds emitted by plants was accomplished in the controlled environment of a growth chamber. Lettuce plants were undisturbed by the methodology employed. Consequently, volatiles were collected from plants up to 32 DAT. The capabilities of this system are valuable for Controlled Ecological Life Support System (CELSS) -related research in that environmental conditions can be controlled and volatile emissions measured over the growth cycle of the plants. Determinations of volatile plant emissions are important as possible indicators of stress responses within plants, for air quality studies, and for investigations of the natural pest resistance provided by certain volatile compounds.
The Biomass Production Chamber at John F. Kennedy Space Center is a closed plant growth chamber facility that can be used to monitor the level of biogenic emissions from large populations of plants throughout their entire growth cycle. The head space atmosphere of a 26-day-old lettuce (Lactuca sativa cv. Waldmann's Green) stand was repeatedly sampled and emissions identified and quantified using GC-mass spectrometry. Concentrations of dimethyl sulphide, carbon disulphide, alpha-pinene, furan and 2-methylfuran were not significantly different throughout the day; whereas, isoprene showed significant differences in concentration between samples collected in light and dark periods. Volatile organic compounds from the atmosphere of wheat (Triticum aestivum cv. Yecora Rojo) were analysed and quantified from planting to maturity. Volatile plant-derived compounds included 1-butanol, 2-ethyl-1-hexanol, nonanal, benzaldehyde, tetramethylurea, tetramethylthiourea, 2-methylfuran and 3-methylfuran. Concentrations of volatiles were determined during seedling establishment, vegetative growth, anthesis, grain fill and senescence and found to vary depending on the developmental stage. Atmospheric concentrations of benzaldehyde and nonanal were highest during anthesis, 2-methylfuran and 3-methylfuran concentrations were greatest during grain fill, and the concentration of the tetramethylurea peaked during senescence.
Atmospheres of enclosed environments in which 20 m2 stands of wheat, potato, and lettuce were grown were characterized and quantified by gas chromatography-mass spectrometry. A large number (in excess of 90) of volatile organic compounds (VOCs) were identified in the chambers. Twenty eight VOC's were assumed to be of biogenic origin for these were not found in the chamber atmosphere when air samples were analyzed in the absence of plants. Some of the compounds found were unique to a single crop. For example, only 35% of the biogenic compounds detected in the wheat atmosphere were unique to wheat, while 36% were unique to potato and 26% were unique to lettuce. The number of compounds detected in the wheat (20 compounds) atmosphere was greater than that of potato (11) and lettuce (15) and concentration levels of biogenic and non-biogenic VOC's were similar.
Bioregenerative life support systems (BLSS) being considered for long duration space missions will operate with limited resupply and utilize biological systems to revitalize the atmosphere, purify water, and produce food. The presence of man-made materials, plant and microbial communities, and human activities will result in the production of volatile organic compounds (VOCs). A database of VOC production from potential BLSS crops is being developed by the Breadboard Project at Kennedy Space Center. Most research to date has focused on the development of air revitalization systems that minimize the concentration of atmospheric contaminants in a closed environment. Similar approaches are being pursued in the design of atmospheric revitalization systems in bioregenerative life support systems. in a BLSS one must consider the effect of VOC concentration on the performance of plants being used for water and atmospheric purification processes. In addition to phytotoxic responses, the impact of removing biogenic compounds from the atmosphere on BLSS function needs to be assessed. This paper provides a synopsis of criteria for setting exposure limits, gives an overview of existing information, and discusses production of biogenic compounds from plants grown in the Biomass Production Chamber at Kennedy Space Center.
Virtually all scenarios for the long-term habitation of spacecraft and other extraterrestrial structures involve plants as important parts of the contained environment that would support humans. Recent experiments have identified several effects of spaceflight on plants that will need to be more fully understood before plant-based life support can become a reality. The International Space Station (ISS) is the focus for the newest phase of space-based research, which should solve some of the mysteries of how spaceflight affects plant growth. Research carried out on the ISS and in the proposed terrestrial facility for Advanced Life Support testing will bring the requirements for establishing extraterrestrial plant-based life support systems into clearer focus.
Plants synthesize and emit a large variety of volatile organic compounds with terpenoids and fatty-acid derivatives the dominant classes. Whereas some volatiles are probably common to almost all plants, others are specific to only one or a few related taxa. The rapid progress in elucidating the biosynthetic pathways, enzymes, and genes involved in the formation of plant volatiles allows their physiology and function to be rigorously investigated at the molecular and biochemical levels. Floral volatiles serve as attractants for species-specific pollinators, whereas the volatiles emitted from vegetative parts, especially those released after herbivory, appear to protect plants by deterring herbivores and by attracting the enemies of herbivores.