镉铅胁迫对桑树种子萌发和幼苗生长以及重金属累积的影响

Effects of Cadmium and Lead Stress on Seed Germination,Seedling Growth and Heavy Metal Accumulation of Mulberry

[目的]研究重金属胁迫对桑树种子萌发及幼苗生长的影响,分析桑树幼苗对重金属的吸收和累积规律。[方法]以冀桑3号和鲁杂1号2个品种桑树种子和幼苗为材料,采用滤纸萌发法分析重金属镉、铅对2个品种桑树种子萌发的影响,采用土培盆栽法分析镉和铅对2个品种桑树幼苗生物量的影响及幼苗对镉和铅的吸收转运规律。[结果]桑树种子萌发受到镉、铅的抑制作用,并且镉和铅对胚根毒害作用更强。镉和铅元素对桑树种子胚根生长有显著抑制作用的浓度分别为114、331 mg/L;2个品种幼苗的生物量随着镉和铅处理浓度的升高而降低,冀桑3号幼苗能耐受20 mg/kg的镉胁迫和500 mg/kg的铅胁迫而不降低其生物量。2个品种桑树幼苗对镉和铅的吸收水平均随着镉、铅处理浓度的升高而升高;幼苗对镉的富集系数和转移系数分别为0.53~3.58和0.41~0.84,对铅的富集指数和转移系数分别为0.02~0.58和0.11~0.78。从2个品种的富集系数和转移系数的对比来看,冀桑3号幼苗与鲁杂1号幼苗对镉、铅的耐受能力、富集能力存在一定程度的差异,且2个品种幼苗均不能有效地将镉和铅转运至植株地上部分。[结论]该研究可为植物修复重金属污染提供一定依据,为进一步利用桑树进行土壤修复奠定一定的理论基础。

[Objective]To study the effects of heavy metal stress on seed germination,seedling growth and the heavy metals absorption and accumulation of mulberry trees.[Method]Seeds of two mulberry cultivars(Jisang No.3 and Luza No.1)were exposed to five cadmium(Cd)and lead(Pb)concentrations by using petri-dish method,the germination percentage and root lengths were measured.Seedlings of these two mulberry cultivars were used as materials,the heavy metal treatment was carried out by using pot-culture method,the biomass and heavy metal content of two mulberry cultivars were examined.[Result]The germination of mulberry seeds was inhibited by lead and cadmium treatment,cadmium and lead had stronger toxic effects on the root elongation of mulberry.The roos of mulberry seeds were significantly inhibited at concentration of 114 mg/L and 331 mg/L for cadmium and lead,respectively;at the cadmium concentration of 20 mg/kg and the lead concentration of 500 mg/kg,mulberry seedlings of Jisang No.3 grew well without reducing biomass.Both of the two mulberry cultivars absorbed more elements with increasing cadmium or lead dose.The bioconcentration factor and transfer factor for cadmium in the two mulberry seedlings ranged from 0.53 to 3.06 and from 0.41 to 0.84,respectively.The bioconcentration factor and transfer factor for lead ranged from 0.02 to 0.58 and 0.11 to 0.78,respectively.By comparing the bioconcentration factor and transfer factor of the two cultivars,we found that there was a certain degree of difference in tolerance and uptake capacity to cadmium and lead between seedlings of Jisang No.3 and Luza No.1,and the two cultivars could not effectively transport cadmium and lead from root to shoot.[Conclusion]These results provided a basis for phytoremediation of heavy metal pollution,and indicated that mulberry can be a candidate for repairing heavy metal contaminated soil.