Growth and Quality of Plug Seedlings of Three Indigenous Medicinal Plants as Affected by Ionic Strength of the Nutrient Solution

The objective of this study was to investigate the effect of ionic strength of the nutrient solution on growth and quality of plug seedlings of three indigenous medicinal plant species. Seeds were sown in 200-cell plug trays, containing a commercial medium in a glasshouse. The pH of a nutrient solution supplied was adjusted to 5.96. The electrical conductivities (EC) of the nutrient solutions supplied were 0.43 dS.m(-1) (1/4x ionic strength), 0.84 dS.m(-1) (1/2x ionic strength), and 1.20 dS.m(-1) (1x ionic strength). Growth and quality of P. frutescens var. acuta Kudo and A. gigas Nakai were the greatest in the 1/2x ionic strength, while those of S. tonkinensis were the greatest in the 1x ionic strength. Elemental contents in the shoot and root of P. frutescens var. acuta Kudo were the greatest in the 1/2x ionic strength, while those of S. tonkinensis were the least in the 1/2x ionic strength and of A. gigas Nakai were the greatest in the 1x ionic strength. Effect of ionic strength of the nutrient solution on plant growth was not the same in all species, but slightly different depending on the plant species. Seedlings applied with a solution with a proper ionic strength grew faster and were of better quality.