Leafy greens like cress have generated significant interest worldwide due to their health and nutritional benefits. Cress is a nutrient-dense leafy green unique for its peppery flavor and phytonutrient content. Its hydroponic cultivation coupled with targeted nutrient fertilization provides a controlled environment enabling optimal growth conditions and phytonutrient accumulation. Particularly, magnesium as a macronutrient is known for influencing biosynthesis of plant metabolites including chlorophyll, carotenoids and other antioxidants. The need for biofortification and optimization of hydroponic cultivation for nutrient-dense crops warrant this study. Due to the importance of beta-carotene in human health and its role as a source of vitamin A, it is crucial to understand how fertilization affects its accumulation. Therefore, this study seeks to contribute to optimization of nutrient management in hydroponics and ultimately improve nutritional value of leafy greens. In this research, four magnesium fertilization rates (100 mg/l, 150 mg/l, 200 mg/l and 250 mg/l) were applied to watercress and upland cress in a hydroponic environment. The study aimed to examine the effects of these treatments on phytonutrient accumulation with a focus on beta-carotene. The hydroponic cultivation was done under controlled environment, ensuring desirable nutrient application, temperature, light, pH and electrical conductivity. The treatments were applied in a Nutrient Film Technique (NFT) system under a split-plot design. Biomass, chlorophyll, beta-carotene and antioxidant activity were analyzed to determine the relationship between magnesium application and the biosynthesis of phytonutrients. Spectrophotometric methods were used to quantify beta-carotene and chlorophyll and determine antioxidant potential. Initial findings indicate increasing content of beta-carotene, chlorophyll, biomass and antioxidant activity with increasing magnesium application rates, with the highest rate maximizing beta-carotene accumulation. The results show variations between watercress and upland cress, indicating strain-specific responses under magnesium application. These results will contribute to insights into the influence of magnesium fertilization on the synthesis of phytonutrients in leafy greens, particularly cress plants. It will guide farmers on optimizing fertilization, eventually improving yields and nutritional quality of the two cress varieties. Additionally, it will recommend dietary guidelines, catering to the demand for nutrient-rich foods among health-conscious consumers. Keywords: Cress, Magnesium fertilization, Phytonutrients, Hydroponics, Spectrophotometry
