3种药用甘草对重金属镉的生长响应、镉耐性及富集特征

Growth response,cadmium tolerance and enrichment characteristics of three medicinal licorice species to heavy metal cadmium

通过3种药用甘草对重金属镉(Cd)生长响应、镉耐受性差异和镉积累特征的研究,为药用甘草种植和药材安全控制提供理论依据。本研究采用水培法育苗,分析不同浓度镉(0、50、100、150μmol·L^(-1))胁迫对生长30 d的3种药用甘草的生长指标、生物量和丙二醛(MDA)含量的影响,并用石蜡切片法制片观察根解剖结构;采用耐镉系数法和隶属函数值法对药用甘草的耐镉性差异进行评价;同时,利用电感耦合等离子体光谱仪(ICP)测定根、茎和叶中镉离子的含量,并计算镉富集系数和转移系数,分析镉富集特性。镉处理下3种药用甘草的株高、根长、叶片数和生物量显著下降,根横截面积显著减小,维管柱面积占根总面积比例上升,根部MDA含量升高,氧化胁迫加重;以生物量下降至75%时的镉浓度为适宜生长阈值,胀果甘草为12.462μmol·L^(-1),乌拉尔甘草为14.715μmol·L^(-1),光果甘草为1.952μmol·L^(-1);综合耐镉系数和隶属函数综合评价结果显示乌拉尔甘草的耐镉性最强,光果甘草最弱;镉富集系数在1.960~8.683之间,转运系数远小于1,镉主要富集在根中。在50μmol·L^(-1)处理下,胀果甘草根中镉含量是叶中的7.5倍,乌拉尔甘草为21.3倍,光果甘草为16.5倍,均超过国家标准GB/T 19618—2004。镉胁迫显著抑制了3种药用甘草根和叶片生长,药材根生物量显著下降,其镉耐受性表现为乌拉尔甘草>胀果甘草>光果甘草;镉主要积累在根部,在50μmol·L^(-1)镉处理下,3种药用甘草根中镉含量均超国家标准。因此,应关注野生甘草采挖和人工栽培地的土壤镉监测,以保证甘草药材生产的安全性;同时也应重视药材Cd 2+含量的抽检,进行甘草药材的安全性控制管理。

By studying the growth response,cadmium tolerance differences,and cadmium accumulation characteristics of three medicinal licorice species to heavy metal cadmium(Cd),a theoretical basis is provided for the cultivation and safety control of medicinal licorice.This study used hydroponic method for seedling cultivation and analyzed different concentrations of cadmium(0,50,100 and 150μmol·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 tolerance of medicinal licorice were evaluated by cadmium tolerance coefficient and membership function value method.Meanwhile,inductively coupled plasma spectrometer(ICP)was used to measure root,stem,and leaf cadmium(Cd 2+)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 content increased,and oxidative stress worsened.The cadmium concentration at the time of biomass decline to 75%as the appropriate growth threshold was 12.462μmol·L^(-1)for Glycyrrhiza inflata,14.715μmol·L^(-1)for Glycyrrhiza uralensis,and 1.952μmol·L^(-1)for Glycyrrhiza glabra.Combining the results of cadmium tolerance coefficients and affiliation function indices showed that Glycyrrhiza uralensis 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 50μmol·L^(-1),the content of cadmium in the roots of Glycyrrhiza inflata was 7.5 times higher than that in the leaves,Glycyrrhiza uralensis was 21.3 times,Glycyrrhiza glabra was 16.5 times,all of which exceeded the minimum cadmium content stipulated by the national 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 50μmol·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 Cd 2+content in the harvested medicinal materials,and carry out control management of medicinal licorice herbs.