Growth and bioactive phytochemicals of Panax ginseng sprouts grown in an aeroponic system using plasma-treated water as the nitrogen source

Abstract

Ginseng (Panax ginseng Meyer) sprouts are grown to whole plants in 20 to 25 days in a soil-less cultivation system and then used as a medicinal vegetable. As a nitrogen (N) source, plasma-treated water (PTW) has been used to enhance the seed germination and seedling growth of many crops but has not been investigated for its effects on ginseng sprouts. This study established an in-situ system for N-containing water production using plasma technology and evaluated the effects of the PTW on ginseng growth and its bioactive phytochemicals compared with those of an untreated control. The PTW became weakly acidic 30 min after the air discharge at the electrodes because of the formation of nitrate (NO₃^‒) and nitrite (NO₂^‒) in the water. The NO₃^‒ and NO₂^‒ in the PTW, together with potassium ions (K⁺), enhanced the shoot biomass of the ginseng sprout by 26.5% compared to the untreated control. The ginseng sprout grown in the PTW had accumulated more free amino acids and ginsenosides in the sprout at 25 days after planting. Therefore, PTW can be used as a liquid N fertilizer for P. ginseng growth and phytochemical accumulation during sprouting under aeroponic conditions.

Figure 1

Shoot emergence (a) and shoot biomass (b) of Panax ginseng, each sprayed with deionized water (DW) and plasma-treated water (PTW) containing potassium ions (K⁺) up to 25 days after planting. The shoot emergence was expressed as a percentage of the total number of emerged shoots out of 98 P. ginseng rhizomes. The shoot biomass was averaged from 14 P. ginseng shoots harvested for each sampling date. An asterisk indicates a significant difference between the DW and PTW + K⁺ at each day (P < 0.05).

Figure 2

Total contents of the 14 free amino acids of Panax ginseng at 25 days after planting, each sprayed with deionized water (DW) and plasma-treated water (PTW) containing potassium ions (K⁺) up to 25 days. The fourteen free amino acids include 4 essential amino acids (threonine (Thr), methionine (Met), lysine (Lys), and histidine (His)) and 10 non-essential amino acids (phosphoserine (P-Ser), phosphoethanolamine (PEA), urea, aspartic acid (Asp), alanine (Ala), 2-aminoethanol (EOHNH₂), ornithine (Orn), arginine (Arg), hydroxyproline (Hypro), and proline (Pro)). Each bar represents the mean of four replicates with each replicate containing three shoots (or roots). The error bars represent the standard error of that mean. An asterisk indicates a significant difference between the DW and PTW + K⁺ at 25 days (P < 0.05).

Figure 3

Protopanaxadiol (PPD)-type (a,b) and protopanaxatriol (PPT)-type (c,d) ginsenosides in the aboveground shoot (a,c) and belowground root (b,d) of Panax ginseng, each sprayed with deionized water (DW) and plasma-treated water (PTW) containing potassium ions (K⁺) for 25 days. Each symbol represents the mean of four replicates with each replicate containing three shoots (or roots). The error bars represent the standard error of that mean. An asterisk indicates a significant difference between DW and PTW + K⁺ at each day (P < 0.05).

Figure 4

The percentages of individual ginsenosides in the aboveground shoot (a) and belowground root (b) of Panax ginseng, each sprayed with deionized water (DW) and plasma-treated water (PTW) containing potassium ions (K⁺) for 25 days.