The Impact of Pre-Harvest EC Adjustment on Growth and Secondary Metabolites of Three Brassicaceae Plants in a Plant Factory

This study investigated the growth and secondary metabolite changes in three species of Brassicaceae when the electrical conductivity (EC) concentration was modified before harvest.Seeds of leaf mustard (Brassica juncea (L.) Czern.), red mustard (Brassica juncea L.), and kale (Brassica oleracea L. var.acephala (DC.)Alef.) were sown in rock wool and grown for three weeks.Then, the EC concentration was modified from 1.5 dSm -1 to 1.5 (Control), 3.0, 4.5, and 6.0 dSm -1 at 1 week (1W) and 3 weeks (3W) before harvest, and plants were cultivated for four weeks.In leaf mustard, the shoot fresh weight, dry weight and total phenolic content decreased by 63.6%, 70.2%, and 63.2%, respectively, at 6.0 dSm -1 compared to the control in the 1W treatment.For the 3W treatment, the shoot fresh weight, dry weight, and total glucosinolate content increased by 57.5%, 52.5%, and 50.3%, respectively, at 3.0 dSm -1 compared to the control.In red mustard, the shoot fresh weight and dry weight increased by 20.8% and 13.3%, respectively, at 4.5 dSm -1 in the 1W treatment, while total phenolic content decreased by 52.2% at 6.0 dSm -1 compared to the control.For the 3W treatment, the shoot fresh weight, dry weight and total phenolic content decreased by 36.6%, 29.2%, and 54.0%, respectively, at 4.5 dSm -1 compared to the control.In kale, under the 1W treatment, the shoot fresh weight, dry weight, and total phenolic content increased by 51.6%, 14.6%, and 56.9%, respectively, at 4.5 dSm -1 compared to control.In the 3W treatment, the shoot fresh weight, dry weight, total glucosinolate, and total phenolic content increased by 162.5%, 230.6%, 232.9%, and 392.7%, respectively, at 6.0 dSm -1 compared to the control.Excessive EC concentration inhibits the shoot fresh and dry weight, making it necessary to conduct further research to determine the relationship between optimal EC levels and secondary metabolite for each plant.