Effects of different phosphorus concentrations on soil physicochemical property, growth and medicinal materials quality of Saposhnikovia divaricata

Objective  To discuss the effects of different phosphorus concentrations on soil characteristics, growth status and chromone content of Saposhnikovia divaricata, and provide theoretical basis for technical strategy formulation of S. divaricata artificial cultivation and responding mechanism research of S. divaricata to low phosphorus stress.

Method  Two-year-old S. divaricata was used as material, and three phosphorus treatments with NH₄H₂PO₄ concentration of 1.0, 0.1 and 0 (no phosphorus) mmol/L respectively were set up. The soil physical and chemical properties, and the growth characteristics and total contents of four kinds of chromones inS. divaricata were determined on the 30th, 60th, and 90th day to analyze the correlativity between the various indicators and total chromone content under different phosphorus concentrations.

Result  The root diameter and weight of 2-year-old S. divaricata in no phosphorus treatment were lower than those of 1.0 mmol·L⁻¹ phosphorus treatment during the whole treatment period, and the root length after 90 d of treatment was significantly higher than those of 1.0 and 0.1 mmol·L⁻¹ phosphorus treatments. After 60 d of treatment, the soil pH of 1.0 mmol·L⁻¹ phosphorus treatment was significantly higher than those of 0.1 mmol·L⁻¹ and no phosphorus treatments. The contents of soil organic matter in 1.0 and 0.1 mmol·L⁻¹ phosphorus treatments were significantly lower than that in no phosphorus treatment during the whole treatment period. After 90 d of treatment, the alkali-hydrolyzable nitrogen content in soil of no phosphorus treatment was significantly higher than those of 1.0 and 0.1 mmol·L⁻¹ phosphorus treatments, whereas the available phosphorus content in soil of 0.1 mmol·L⁻¹ phosphorus treatment was significantly higher than that of no phosphorus treatment, the total content of four chromones of 0.1 mmol·L⁻¹ and no phosphorus treatments were significantly higher than that of 1.0 mmol·L⁻¹ phosphorus treatment. On the 30 th day of treatment, the activities of acid phosphatase in soil among three treatments were significantly different. There were positive correlations between root diameter/root fresh biomass and chromone content in 1.0 mmol·L⁻¹ phosphorus treatment, between alkali-hydrolyzable nitrogen content/available phosphorus content/root fresh biomass and chromone content in 0.1 mmol·L⁻¹ phosphorus treatment, between pH/alkali-hydrolyzable nitrogen content /acid phosphate activity and chromone content in no phosphorus treatment, respectively.

Conclusion  S. divaricata has a series of response mechanisms to phosphorus stress, including chromone content significantly increasing, synergistic interaction of pH, organic matter, alkali-hydrolyzable nitrogen and acid phosphatase, which ensures the absorption and utilization of nutrients by S. divaricata.