Growth response,cadmium tolerance and enrichment characteristics of three medicinal licorice species to heavy metal cadmium
By studying the growth response,cadmium tolerance differences,and cadmium accumulation characteristics of three medici-nal licorice species to heavy metal cadmium(Cd),a theoretical basis is provided for the cultivation and safety control of medicinal lico-rice.This study used hydroponic method for seedling cultivation and analyzed different concentrations of cadmium(0,50,100 and 150 μmol·L-1)stress on the growth indicators,biomass,and malondialdehyde(MDA)content of three medicinal licorice species grown for 30 days,and the root anatomical structure was observed using paraffin sectioning method.The differences in cadmium toler-ance of medicinal licorice were evaluated by cadmium tolerance coefficient and membership function value method.Meanwhile,induc-tively coupled plasma spectrometer(ICP)was used to measure root,stem,and leaf cadmium(Cd2+)ion content,and the calculate Cd enrichment coefficients and transfer coefficients were calculated to analyze the cadmium enrichment characteristics.Under cadmium treatment,the plant height,root length,leaf number,and biomass of the three medicinal licorice species significantly decreased,the root cross-sectional area decreased significantly,the proportion of vascular column area to total root area increased,the root MDA con-tent increased,and oxidative stress worsened.The cadmium concentration at the time of biomass decline to 75%as the appropriate growth threshold was 12.462 μmol·L-1 for Glycyrrhiza inflata,14.715 μmol·L-1 for Glycyrrhiza uralensis,and 1.952 μmol·L-1 for Glycyrrhiza glabra.Combining the results of cadmium tolerance coefficients and affiliation function indices showed that Glycyrrhiza ura-lensis was the most cadmium tolerant and Glycyrrhiza glabra was the weakest;The cadmium enrichment coefficient was between 1.960～8.683,and the transfer coefficient was much less than 1.Cadmium was mainly enriched in the roots,Under the treatment of 50 μmol·L-1,the content of cadmium in the roots of Glycyrrhiza inflata was 7.5 times higher than that in the leaves,Glycyrrhiza ura-lensis was 21.3 times,Glycyrrhiza glabra was 16.5 times,all of which exceeded the minimum cadmium content stipulated by the na-tional standard GB/T 19618-2004 of the People's Republic of China.Cadmium stress significantly inhibited the root and leaf growth of the three medicinal licorice species,and the root biomass of the herbs decreased significantly,The order of cadmium tolerance is manifested as Glycyrrhiza uralensis>Glycyrrhiza inflata>Glycyrrhiza glabra;cadmium was mainly accumulated in the roots,and its absolute cadmium content already far exceeded the national standard at a low concentration of 50 μmol·L-1 treatment.Therefore,in the excavation and artificial cultivation of wild licorice,soil cadmium should be monitored to ensure the safety of medicinal licorice herb production.It is also necessary to carry out sampling inspection of Cd2 + content in the harvested medicinal materials,and carry out control management of medicinal licorice herbs.
medicinal licoricecadmium stressanatomicalbioconcentration factormembership function
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