Variability of cadmium, lead, and zinc tolerance and accumulation among and between germplasms of the fiber crop Boehmeria nivea with different root-types.

Crop germplasms substantially vary in their tolerance for and accumulation of heavy metals, and assessment of this variability plays a significant role in selecting species to use in phytoremediation projects. Here, we examined germplasm-variations in cadmium (Cd), lead (Pb), and zinc (Zn) tolerance and accumulation in ramie (Boehmeria nivea), a fiber crop native to China, which has received little attention. In an 8-week greenhouse test, fourteen germplasms of ramie, among and within deep, middle, and shallow rooted-types, were compared for growth and metal accumulation traits. Results showed that both tolerance and accumulation traits varied across germplasms and rooted-types. The deep rooted-type germplasms produced more biomass and had higher tolerance to metals than the two others. In addition, considerable variations in metal accumulation were observed among plant organs (root, stem, and leaf), rooted-types, germplasms, and metal supply. However, the observed variations in metal tolerance and accumulation among both germplasms and rooted-types were not significant in most cases. In addition to supporting the idea of a certain degree of constitutional metal tolerance for ramie, our results also contribute to deep-rooted germplasms of ramie as a good candidate, rather than middle-/shallow- ones as a least-bad option, for the remediation of multi metal-contaminated soils.