Aeroponics: An Alternative Production System for High-Value Root Crops

An aeroponic system was developed for the production of root crops used in the herbal and phytopharmaceutical industries. The variability in the phytochemical quality of botanical products precludes the ability to administer uniform dosing in clinical studies. Aeroponic systems allow the producer to precisely control root zone nutrient and water regimes and environmental conditions, as well as have complete access to the roots throughout the life of the crop. This control promises a more uniform harvest. An A-frame aeroponic system was designed to maximize root yields and permit free access to the roots for monitoring. Burdock (Arctium lappa L.) plants were grown in aeroponics with controls grown in a greenhouse soilless potting mix for ten weeks in a research greenhouse in Tucson, Arizona. The plants were harvested and the dry weights of aerial parts and roots were determined, as well as the chlorogenic acid concentration in the dried roots. Chlorogenic acid is a caffeoylquinic acid derivative known to have antioxidant activity. The biomass yields of the aerial parts were significantly higher in the aeroponically grown plants compared to the controls. The root biomass yields showed no significant difference between treatments. The chlorogenic acid concentrations were also not significantly different, however the plant-to-plant variability was significantly lower in the aeroponically grown plants, suggesting the potential for more consistent phytochemical yields using this production technique. INTRODUCTION The natural products and phytopharmaceutical industries are facing some formidable challenges by regulatory agencies around the world. The issues of safety, sustainability, and supply of raw materials permeate discussions of production of medicinal and aromatic crops (Craker, 1999). Variability in the quality of the raw materials is a recognized problem. Most approaches to quality control have centered on various methods of standardizing the herbal extracts and selection of marker compounds (Brinker, 1999). However, using chemistry techniques alone to standardize botanical preparations ignore one of the major causes of the variability: the horticultural production of the raw materials. Improving the uniformity of the raw 1 Department of Agricultural and Biosystems Engineering, PO Box 210038, Tucson, AZ 85721 2 Deceased, Office of Arid Lands Studies, Southwest Center for Natural Products Research & Commercialization