Impact of High Concentration Potassium Application on Lycopene Concentration in Tomato Fruit during Maturation and Ripening

Abstract

This study investigated the effect of high concentration potassium (K) application on promotion of lycopene concentration in tomato fruit during maturation and ripening process. The hydroponically cultivated tomato plants were treated with either a standard (4 mM; NK) or high (24 mM; HK) concentration of K in a nutrient solution. Fruit were harvested at green, coloring, pink, and fully mature stage; and fresh weight, K concentration, soluble solid content (Brix), fruit surface color value, and chlorophyll concentration and lycopene concentration were analyzed. Additionally, a subset of pink-stage harvested fruit was stored in the dark at 20°C to facilitate ripening. The HK treatment significantly reduced fruit weight but increased Brix and accelerated fruit coloring. Chlorophyll concentration in fruit decreased from the green stage to the pink stage under NK but remained constant under HK treatment. In the NK group, lycopene concentration was detected at the coloring stage which gradually increased to the mature stage. In contrast, lycopene concentration in the HK group was detected at the green stage and rapidly increased to reach twice the concentration observed in the NK group at the fully mature stage. The lycopene promoting effect of HK treatment persisted during ripening process, with the lycopene concentration in ripened HK-treated fruit almost similar to that in mature on -plant fruit. These findings revealed that high concentration K application enhances lycopene concentration in tomato fruit from early maturation and sustains this effect throughout the ripening process.