不同基质条件下西洋参皂苷提取物的自毒作用

Autotoxic effect of ginsenoside extrats on growth of American ginseng in different medium

人参皂苷是西洋参Panax quinquefolium中所含的主要次生代谢产物,西洋参生长过程中,植株内的人参皂苷可以通过根系分泌及腐解进入到土壤环境中。研究利用高效液相色谱法(HPLC)测定了土壤中人参皂苷含量,根据西洋参田间的实测数据设计皂苷提取物的系列浓度(0.2~125 mg·L^(-1)溶液或0.2~125 mg·kg^(-1)土壤),通过在溶液及土壤基质中的添加实验,观察环境中的皂苷提取物对西洋参种胚和成株苗生长的作用。结果表明,在北京市怀柔区三至四年生西洋参根际土中,检测到人参皂苷Rb_1,Rb_2,Rd,总量为0.80~3.19 mg·kg^(-1),按照田间持水量为20%计算,总皂苷在土壤溶液中的质量浓度为4~16 mg·L^(-1)。在溶液基质中,0.2~125 mg·L^(-1)西洋参皂苷提取物对西洋参种胚胚根的抑制作用在6%~23%,在125mg·L^(-1)时达到显著水平(P<0.05);对西洋参胚芽无显著抑制作用。营养液中添加25 mg·L^(-1)皂苷提取物,培养20 d时,三年生西洋参成株苗株高下降28%,地上部的生物量下降50%(P<0.05);对新生须根生长的抑制作用不显著。在土壤基质中,添加同样浓度的皂苷提取物在灭菌和未灭菌土中对西洋参胚根、胚芽生长均无显著影响。由此推论,西洋参的皂苷成分对自身胚根和成株苗生长有自毒作用,但在田间土壤条件下,这种作用有所下降。

Ginsenosides are the abundant secondary metabolites in American ginseng （Panax quinquefolium）, it could be released into soil through root exudation and decomposition during plant growth. This study determined ginsenoside contents in American ginseng cultivated soil by HPLC. Three ginsenosides, Rb1, Rb2 and Rd, were detected in the rhizosphere soil of 3-4 years old American gin- seng cultivated in Huairou District, Beijing, and their contents were 0. 80-3. 19 mg · kg-1. Correspondingly, the contents of the three ginsenosides in soil solution were 4-16 mg · L-1 at field water-holding capacity of 20%. According to the field soil test data, we de- signed the concentration of ginsenosides for bioassays （0. 2-125 mg · L-1 in solution or 0. 2-125 mg· kg-1 in soil）. The results showed that radicle lengths of American ginseng were reduced by 6%-23% in solution containing 0. 2-125 mg· L-1 ginsenoside ex- tract, and a significant difference was observed at concentration of 125 mg · L-1 （P 〈 0. 05 ）. The shoot lengths of American ginseng were not significantly inhibited by 0. 2-125 mg · L-1 ginsenosides extractions. After 20 days of growth in nutrient solution amended with 25 mg · L-1ginsenosides extraction, plant height of 3-year-old American ginseng seedling was decreased by 28% compared to the con- trol, and the biomass of aerial parts was also reduced by 50% （P 〈 0. 05）. However, the growth of newly-grown fibrous root was not significantly inhibited. Comparatively, when American ginseng embryos were cultivated into sterile or non-sterile soil, neither radiclelengths nor shoot lengths were significantly affected by 0. 2-125 mg·kg- 1 ginsenoside extracts. In conclusion, ginsenosides showed au- totoxic effect on growth of American ginseng radicle and adult seedling, however, this effect was weakened in field soil.