Chemical eustress and biofortification: Targeted nutrient solution management for enhancing quality in hydroponically grown vegetables

Soilless cultivation including both open and closed loop systems is considered an efficient tool to increase crop productivity all year round, as well as enhancing nutritional and qualitative aspects of vegetables. Manipulation of secondary metabolites or phytochemicals in vegetables, by management of the nutrient solution is an exciting research area attracting scientists, growers and extension specialists. Proper management of salt concentration (all ions, salinity or electrical conductivity), cationic and/or anionic composition in the nutrient solution can improve the quality of a wide range of vegetables. After a brief introduction on the advantages of soilless cultivation systems and the concept of quality of fresh vegetables, the paper focuses on the effective application of salinity or nutritional eustress to improve the sensorial and functional traits of several leafy and fruit vegetables. Accurate control of essential and beneficial micronutrients (iron, silicon and selenium) concentrations in the nutrient solution, as an instrument for the biofortification of vegetables will be also covered. The present paper concludes by providing an overview of the future perspective and challenges on scientific advances in open/closed soilless cultivation aimed at enhancing the phytochemical profiling of vegetables.