Short-term Application of the Concentrated Deep Seawater for Production of High Quality Tomatoes by Single-truss and High Density Cultivation

Abstract

Single-truss and high density cultivation of tomato plants (Lycopersicon escultentum Mill.) has great advantages in controlling the plants and stable production. In this cultivation, an effective application of short-term salt stress for high quality tomatoes was examined by analyzing mass transport to fruits via phloem. Tomato plant were grown by soil-less culture with non-woven fabric system for single-truss and high density cultivation, where short-term salt stress was induced for just 2 weeks at the stage of rapid fruit growth by adding the concentrated deep seawater to the standard nutrient solution (electric conductivity (EC), 1.2 dS m⁻¹) to increase EC by 13.5 dS m⁻¹. Although fresh weight of the fruits was restricted by salt stress, dry matter ratio of the fruits was increased. Soluble solid concentration and flux in the phloem sap was accelerated not only during the short-term salt stress but also after the removal. Concentrations of Na⁺, K⁺, and Mg⁺ in the phloem sap were also enhanced by the concentrated deep seawater. Consequently, sugar concentration of the fruits was significantly increased by short-term salt stress. These results may contribute to stable and high production of high quality tomatoes in single-truss and high density cultivation.