Evaluating the effects of a newly developed nutrient solution on growth, antioxidants, and chicoric acid contents in Crepidiastrum denticulatum

The medicinal plant Crepidiastrum denticulatum, which is found throughout East Asia, contains various health-promoting phytochemicals. The aim of this study was to evaluate the effects of a newly developed nutrient solution (referred to as NSC) on the growth of this plant and to determine the proper EC level of NSC for stable phytochemical production in plant factories. Three-week-old seedlings were transplanted to a wick culture system supplied with Hoagland solution (EC 1.0 dS·m ⁻¹) as a control or with five different concentrations of NSC (EC 0.5, 1.0, 1.5, 2.0, and 2.5 dS·m ⁻¹). We grew the plants under normal conditions (20°C, 310 ± 10 µmol·m ⁻²·s ⁻¹ PPF, CO₂ 1,000 µmol·mol ⁻¹, and a 16 hours photoperiod) for 6 weeks and evaluated their photosynthetic rates and growth characteristics, such as the fresh and dry weights of shoots and roots, leaf area, number of leaves, and S/R ratios, at 6 weeks after transplanting. We also measured the total phenolic content, antioxidant capacity, and chicoric acid content each week for 6 weeks after transplanting. The fresh weights of shoots and roots, leaf area, and number of leaves significantly increased in plants supplied with 2.0 and 2.5 dS·m ⁻¹ NSC compared with the control, while the photosynthetic rate did not change under different concentrations of NSC. The total phenolic content and antioxidant capacity per shoot significantly increased with increasing in EC level of NSC; this trend became more pronounced over time. Moreover, the chicoric acid content significantly increased during growth up to 6 weeks after transplanting. These results suggest that NSC increases the biomass of C. denticulatum and that an EC level of 2.0 or 2.5 dS·m ⁻¹ is proper for accumulating high levels of phytochemicals, such as chicoric acid, in C. denticulatum grown in plant factories.