2018 ASHS Annual Conference

Plants of genus Lysimachia including L. mauritiana L. inhabit in the relatively desiccate environment such as crevice of coast rock, and they are known to have antioxidant, anti-inflammatory, anticancer, and antimicrobial activities due to their flavonol glucosides. This study was conducted to investigate the effect of substrate volumetric water contents on growth and secondary metabolites of L. mauritiana which are one of the native plants in Korea. The seeds of L. mauritiana provided by Korean National Institute of Biological Resources (NIBRGR0000175023) were sown on 128 plug tray in a greenhouse in May 2017, and the germination rate and days to germinate were 74.2% and 14.8 days. The seedlings were transplanted into 4-inch pots with a soilless substrate (Sunshine Mix4, Sun Gro Horticulture, Agawam, MA, USA) mixed with a controlled released fertilizer (Multicote 6, Haifa Chemicals, Israel) at a ratio of 4g·L^-1 at 45 days after sowing. After a month of the acclimation period, soil moisture sensor-based automated irrigation system maintained the substrate volumetric water contents at four different levels (0.3, 0.4, 0.5, or 0.6 m³·m^-3) using capacitance sensors and a datalogger. Plant height, number of leaves, leaf area, leaf water potential, chlorophyll content, fresh weight, dry weight, and photosynthetic rate were measured at 0, 5, 11, 18 days after treatment. At 5 days after treatment, there were no significant differences in vegetative growth among all the treatments, but leaf water potential, photosynthetic rate, transpiration rate and stomatal conductance were the lowest in 0.3 m³·m^-3 treatment, indicating physiological drought stress. On the contrary, at 11 days after treatment, there were no significant differences in leaf water potential and photosynthetic rate, but all vegetative growth parameters except root dry weight were lower in 0.3 m³·m^-3 treatment than those in other treatments. As substrate volumetric water content decreases, root fresh weight decreases, indicating root water content was affected by substrate volumetric water content. The results at 18 days after treatment was similar to those at 11 days after treatment, which showed significant differences in physiological responses but no significant differences in vegetative growth in most parameters. However, photosynthetic rate was lower in 0.3 m³·m^-3 treatment than other treatments, although there were no differences in stomatal conductance and transpiration rate. It was likely due to severe and continuous drought stress, possibly imposing disorders of certain enzymes related to photosynthesis such as Rubisco. Although there was a slightly increasing tendency in antioxidant capacity under drought at 5 days after treatment, there were no significant differences in total phenolic content and antioxidant capacity among the treatments. When cultivating L. mauritiana, the growth and secondary metabolites would be affected by the substrate volumetric water contents, and they could be changed by the duration of drought. To optimize the growth and secondary metabolite contents in plants, further experiments with controlled drought at various levels, imposing times, and the duration of drought may be required.