Vitamin C Biofortification of Lettuce (Lactuca sativa ‘Salanova’) in a Deep-water Culture System

Vitamin C deficiency remains a widespread nutritional concern, and biofortification of commonly consumed vegetables offers a promising strategy to improve dietary intake. Lettuce ( Lactuca sativa ) is a suitable target for vitamin C enhancement because of its short production cycle, global availability, and consumption in fresh form. We evaluated the effectiveness of foliar ascorbic acid application as an agronomic biofortification method in lettuce grown in deep-water culture (DWC) systems in a greenhouse. Across all trials, foliar sprays were applied 2 and 4 days before harvest at concentrations ranging from 0 to 2500 ppm. Plant growth, nutrient composition, photosynthetic pigments, proline, phenolics, flavonoids, and vitamin C (total and reduced forms) were measured to assess physiological and biochemical responses. Foliar ascorbic acid did not affect plant growth negatively overall. Treatment effects on nutrient content, pigments, and vitamin C were limited and highly dependent on environmental conditions. Environmental variability influenced plant responses strongly across trials. More stable conditions during the first trial corresponded with modest treatment-related differences in nutrients, pigments, and proline, whereas greater temperature fluctuations during the second trial masked most treatment effects. Across both trials, total and reduced ascorbic acid did not increase significantly with foliar application, and correlation analysis indicated that vitamin C was associated positively with light, but associated negatively with temperature and relative humidity. These findings indicate that although foliar ascorbic acid did not enhance vitamin C concentrations consistently under the conditions tested, moderate application rates remain promising for future research. Optimizing spray timing, increasing application frequency, improving foliar uptake, and conducting studies in fully controlled environments may better reveal the potential of foliar ascorbic acid as a practical biofortification strategy.