Growing spinach (Spinacia oleracea) with different seawater concentrations: Effects on fresh, boiled and steamed leaves

Agriculture is the human activity requiring the higher amount of freshwater. Nevertheless, water availability isalready an issue in many regions of the world, suggesting the need of alternative water sources to face theincreasing food demand.Spinacia oleraceaplants have been cultivated in afloating hydroponic system wherenutrient solution was integrated with 10% and 20% of seawater. Plant growth was monitored during the ex-periment together with morphological adaptations at the shoot level. At the end of the crop cycle, leaves werecollected and processed with the two most common cooking processes such as boiling and steaming. Raw, boiledand steamed leaves were then analyzed to determine their sodium and potassium concentrations, the totalphenolic content and the nitrates concentration. Our results showed that the use of seawater in the hydroponicspinach cultivation determined positive effects on growth parameters, with an increased relative growth rateassessed for both seawater treatments compared to the control. Leaves morphological adaptations were assessedonly in 20% seawater treated plants (i.e. reduced leaf water content, leaf area and specific leaf area; increasedspecific leaf weight and leaf succulence), whereas the moderate seawater treatment did not lead to any differ-ence compared to the control. Seawater treatments significantly increased sodium content in leaves, which couldbe consumed without adding any salt. Potassium was not affected by salinity treatments, whereas both totalphenolic content and nitrates decreased accordingly with increasing salinity Concerning the cooking processes,steaming proved to be a better cooking method compared to boiling with the aim of preserving the nutritionalvalues of spinach leaves. In conclusion, our results suggest that the use of a certain level of seawater in thespinach cultivation is a practical possibility to be explored in the direction of saving freshwater and increasingcrop production enhancing the quality and taste of vegetables.