NASA has intensively studied the use of plants to regenerate the atmosphere, purify water, and produce food within a bioregenerative life support system for many years. A unique aspect of growing plants in a controlled environment is chronic exposure to low levels of atmospheric volatiles. Alcohols are one of the most common classes of atmospheric contaminants currently detected onboard the International Space Station. A series of experiments were performed in specialized volatile organic compound analysis (VOCA) chambers in order to determine sensitivity of three Raphanus sativus L. to atmospheric exposures of ethanol. Three radish cultivars, Sora, Cherry Belle, and Cherry Bomb Hybrid II, were grown under continuous exposure to 0, 50, 100, 300, 500, or 1000 ppm ethanol for 21 days in the VOCA chambers with environmental setpoints of 23 °C, 75% relative humidity, and 18/6 photoperiod under T8 triphosphor fluorescent lamps at 300 μmol·m-2·s-1 PAR and 1200 μmol·mol-1 CO2. These concentrations corresponded to 5%, 10%, 30%, 50%, and 100% of the human exposure limits established by NASA and OSHA. Exposures to less than 10% of the legal exposure limit resulted in a 30% reduction in total biomass, 12% reduction in leaf area, and a 6% reduction in harvest index. Extreme stunting, chlorosis, and plant death were observed at only 50% of the exposure limit. All three cultivars were sensitive to ethanol exposure, with Cherry Bomb Hybrid II being slightly less sensitive than either Sora or Cherry Belle.
Gary Stutte and Ignacio Eraso
Gary W. Stutte, Ignacio Eraso, and Agnes M. Rimando
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.