Ground Based Study on Culturing Garlic as a Source of Vegetable Food and Medicine in Space- Growth and Ajoene Accumulation in Garlic Plants Cultured with Different CO₂ Regimes

摘要

Life support and effective countermeasures against damaging space radiation for humans on long-duration space missions will be highly dependent on the amount of food and efficient conversion of CO_(2)/O_(2). The cultivation of fresh vegetables enriched in phytomedicine is an alternative option for keeping crews' health and recycling of CO_(2) in a closed environment.A whole garlic plant cultured hydroponically is edible and a rich source of medicinal compound, carbohydrates, proteins and vitamins. Garlic plants were cultured for 60 days at 400 (control), 450, 800 and 900 μmol mol~(-1) carbon dioxide in controlled environment chambers to study growth and ajoene accumulation. Lighting was provided with fluorescent lamps as a 12 h photoperiod with 450 μmol m~(-2) s~(-1) PPFD. Fresh and dry mass accumulation of each parts of garlic plants were significantly increased by increasing the CO_(2) levels from 400 to 900 μmol mol~(-1). Fresh mass in bulbs, leaves and roots were 28.6, 66.3 and 92.2 g per plant, respectively, and 1.9, 1.8 and 2.0 times, respectively, greater at 900 μmol mol~(-1) CO_(2) than at 400 μmol mol~(-1) CO_(2). Transpiration rate and stomatal conductance were decreased by increasing the CO_(2) levels while water use efficiency and relative chlorophyll contents were increased. The concentrations of ajoene accumulation were significantly increased with increasing of CO_(2) levels from 400 to 800 μmol mol~(-1) but no significant increase of ajoene accumulation was observed with increasing CO_(2) level from 800 to 900 μmol mol~(-1). Total ajoene accumulation in bulbs, leaves and roots were 2.3, 2.6 and 2.6 times, respectively, greater at 900 μmol mol~(-1) CO_(2) than at 400 μmol mol~(-1) CO_(2). The results indicate that elevated CO_(2) can increase ajoene accumulation as well as biomass production and water-use efficiency in garlic plants.