Comparison of growth characteristics, functional qualities, and texture of hydroponically grown and soil-grown lettuce

Hydroponics has become one of the most popular approaches in today's agricultural production. Yet it is questionable whether hydroponics produce vegetables with comparable quality to soil-grown vegetables. In this study, hydroponically and soil-grown lettuce were compared for morphology, texture, antioxidant capacity, and functional quality. Giant Caesar lettuce was grown in laboratory-constructed hydroponic or soil systems for 35 days. Above-ground plant size, biomass, and leaf size of hydroponic lettuce were not significantly different from soil-grown lettuce. Hydroponic lettuce had significantly (p < 0.05) longer roots, higher moisture and lower ash. No significant difference in ascorbic acid, chlorophyll, β-carotenes, and total phenolics was found in freeze-dried lettuce. However, all compounds analyzed were significantly higher in soil-grown lettuce based on fresh weight. Antioxidant capacity of soil-grown lettuce was significantly higher on both dry- (15.32%) and wet-basis (41.20%). Hydroponic lettuce had softer leaves and firmer midribs; potentially linked to increased lignin (24.18%) in plant cell walls. This represents the first comprehensive side-by-side growth study demonstrating that lettuce grown hydroponically is not the same quality as that grown in soil.