| Panax notoginseng is the dried root and rhizome of P.notoginseng,a plant of the genus Panax in the family of Araliaceae.Its main active ingredient is P.notoginseng saponins(PNS).Its main efficacy is promoting blood circulation and removing blood stasis,relieving swelling and pain.It is often used in the treatment of cardiovascular and cerebrovascular diseases.P.notoginseng is the main raw material of many Chinese patent medicines,including Yunnan Baiyao,Pianzaihuang,Xuesaitong,Sanqi Tongshu Capsules and so on.Therefore,P.notoginseng has high medicinal value and economic benefits.Yunnan Province is China's largest producer of cadmium,with an annual cadmium output of 63 tons,accounting for 46%of China's total output.Unfortunately,the suitable planting areas of P.notoginseng are small and overlap with non-ferrous metal mining areas,which lead to serious cadmium pollution problems in P.notoginseng and planting soils.Previous studies showed that the over-standard rates of Cd content in P.notoginseng medicinal materials and soils were 22.7%and 35.14%respectively.Cadmium stress can inhibit the growth and development of P.notoginseng,cause oxidative stress damage and reduce the accumulation of saponins.Therefore,reducing the accumulation of cadmium in P.notoginseng and reducing the stress damage of cadmium is of great significance to the safety of P.notoginseng.The effects of potassium on the growth and development of P.notoginseng under cadmium stress and its mechanism were studied with P.notoginseng as experimental material.The main results are as follows:(1)Investigation of Cadmium and Potassium Content in P.notoginseng-planting Soil in Yunnan ProvinceThe results of field investigation showed that the highest cadmium content in soil was 0.46 mg kg-1,and that in the main roots of P.notoginseng was 1.32 mg kg-1.Cadmium content in the soil of P.notoginseng was negatively correlated with the sum of five saponins in the main roots of P.notoginseng,while available potassium and potassium content in the main roots of P.notoginseng were positively correlated with the saponins content in the main roots of P.notoginseng.Soil available potassium was positively correlated with soil pH,TOM and CEC values,while pH,TOM and CEC values were negatively correlated with Cd content in the main roots of P.notoginseng and bioavailable Cd(except TOM)content in soil.The contents of total potassium and available potassium in soil were negatively correlated with the Bioavailable Cadmium Content in soil and the main root cadmium content of P.notoginseng.The results showed that Cd content in P.notoginseng and planted soils was significantly correlated with K content and physicochemical properties,and saponin content was also significantly correlated with Cd and K content in P.notoginseng.(2)Reduction of cadmium accumulation in P.notoginseng-soil by balanced application of nitrogen and potassium fertilizerField and pot experiments showed that PNS and biomass accumulation increased with the increase of potassium fertilizer application under the same nitrogen application rate.Reducing the application of nitrogen fertilizer could reduce the soil pH,TOM and CEC values of P.notoginseng.Under the same nitrogen application rate,the Bioavailable Cadmium Content in P.notoginseng soil decreased with the increase of potassium application rate,and the cadmium content in P.notoginseng also decreased.The results showed that under the current conditions of P.notoginseng cultivation and fertilization,reducing the amount of nitrogen fertilizer could alleviate the deterioration of soil physical and chemical properties,and increasing potassium fertilizer could not only promote the accumulation of saponins and biomass,but also further improve soil physical and chemical properties,reduce the content of bioavailable ecological cadmium in soil,thereby reducing the accumulation of cadmium in Panax notoginseng.(3)Effects of different potassium fertilizer varieties and application rates on cadmium accumulation of P.notoginseng under Cadmium StressPot experiments showed that the application of potassium fertilizer could significantly reduce the accumulation of cadmium in the main roots,shears and tendons of P.notoginseng.With the increase of potassium fertilizer application,PNS content increased,while cadmium content decreased significantly.With the increase of potassium fertilizer application,the abundance of Proteobacteria and Bacteroidetes increased and Acidobacteria decreased.The abundance of Mortierellomycota increased and Ascomycota decreased,which affected soil pH,CEC and TOM,thus affecting the Bioavailable Cadmium Content in soil.Cadmium content in roots of P.notoginseng(main roots,shears and tendons)decreased significantly.Therefore,proper improvement of soil physical and chemical properties can not only ensure the normal production of P.notoginseng,but also reduce the content of available heavy metals in soil.At the same time,it can increase the content of active ingredients of P.notoginseng.(4)Effects of Potassium on Cadmium Accumulation of Panax notoginseng under Cadmium Stress under HydroponicsThe results of hydroponic experiment showed that potassium fertilizer could reduce the cadmium content of the main roots of P.notoginseng by 24.68-45.02%.The cadmium content in the subcellular structures of the main roots of P.notoginseng ranged from high to low as follows:cell wall(?46%)>cytoplasm and supernatant(?40%)>organelles(?14%).Cadmium treatment significantly promoted the expression of PnMTP and PnNRAMP family genes.Potassium treatment could significantly reduce the expression of PnMTP and PnNramp family genes,thus reducing the cadmium content in roots of Panax notoginseng.The results showed that cell wall,cytoplasm and supernatant were the main binding sites of cadmium.Potassium treatment could significantly reduce the accumulation of cadmium in the above-mentioned parts of P.notoginseng root,thereby reducing the cadmium content. |
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