Effect of water stress on roots biomass and secondary metabolites in the medicinal plant Stellaria dichotoma L. var. lanceolata Bge

The experiment was carried out with plants grown in pots with soil to determine the effects of different levels of water stress on roots biomass, secondary metabolites in roots and endogenous hormones (IAA, GA(3) and ABA), relative water content (RWC), tissue density (TD) in leaves of Stellaria dichotoma L.var. lanceolata Bge. The results showed that roots biomass, total saponins content firstly increased and then decreased with increasing water stress levels. RWC significantly decreased with increasing water stress levels while the change of TD was inverse. The concentration of IAA and GA3 firstly increased and then decreased with increasing water stress levels and reached maximum value under 60-70% of field capacity (FC). However, ABA concentration sharply increased under 40-50% FC. With correlation analysis and principal component analysis (PCA), total flavonoids content had significant positive with ABA and TD, but had a negative correlation with RWC. Roots biomass had a significant negative correlation with ABA, while ABA had a very significant negative correlation with RWC and a significant positive correlation with TD. The PCA partitioned the total variance into 2 PCs contributing maximum (90.-93%) to the total diversity among the water stress due to the study of various traits. The higher eigenvector of PC I is RWC and ABA, whereas the higher and positive eigenvector of PC II is GA(3), total saponins content and IAA. Our study indicated that roots biomass and secondary metabolites of S. dichotoma were first increases and then decreases with increasing water stress levels. Thus, moderate water stress (60-70% or 80-90% FC) was suitable for roots biomass formation and active ingredient accumulation, which was affected by endogenous hormones and water status.