Biomass, Flavonol Levels and Sensory Characteristics of Allium Cultivars Grown Hydroponically at Ambient and Elevated CO2

Nine cultivars of four Allium species (Allium cepa, A. fistulosum, A. schoenoprasum, and A. tuberosum) were evaluated for use in Advanced Life Support (ALS) applications by hydroponic propagation in environmental growth chambers to evaluate the effect of elevated CO₂ (1200 ppm) versus ambient CO₂ (400 ppm) on biomass, total flavonols and folate, and to determine if sensory panelists could distinguish between plants grown at elevated or ambient CO₂ when harvested at 49, 63 and 77 days after planting (dap). Regardless of cultivar or dap, plants grown at elevated CO₂ had greater biomass and % edible biomass than plants grown at ambient CO₂. Of the cultivars evaluated from the 63-dap-harvest_, all, with one exception, exhibited increased total flavonols when grown at elevated CO_2. Consumer panelists were able to discern differences in sensory characteristics between ambient- versus elevated-CO₂-grown ‘Choesty’ but not the other three cultivars evaluated. Based on biomass and flavonol levels ‘Cal 296’ and ‘Purplette’ were the best candidate cultivars for further testing for ALS applications using a single harvest strategy.