Exploring the combined effect of heavy metals on accumulation efficiency of Salix alba raised on lead and cadmium contaminated soils.

ABSTRACT

The present study illustrated that Salix alba can accumulate high level of Pb and Cd in different plant parts, with maximum accumulation in roots followed by stem and leaves in the order Cd > Pb > Cd + Pb. The phytoremediation evaluation factors such as bioconcentration factor (BCF) and translocation factor (TF) was higher for Cd over Pb in all plant parts, further the BCF for both Pb and Cd was maximum in root (BCF > 1) followed by stem and leaves. Higher accumulation of Cd over the Pb was observed inside the plant tissues due to Cd mimics with other elements and gets transported through respective transporters. The combined treatment of Pb and Cd affected the bioaccumulation at every treatment level suggesting the negative effect among both elements. Higher survival rate (>85%) was recorded up to 200mgPb/kg and 15mgCd/kg, while further increase in metal concentration reduced the plant efficiency to remediate contaminated soils, hence results in declined survival rate. The FTIR analysis revealed that Pb and Cd accumulation in plants induced changes in carboxy, amino, hydroxyl and phosphate groups that ultimately caused alteration in physiological and biochemical processes of plant and thus provided an insight to the interaction, binding and accumulation of heavy metals.

The present study conferred that Salix alba is a heavy metal (Pb and Cd) excluder plant on the basis of phytoremediation efficiency evaluation factors such BCF >1 (root) and TF <1. The correlation studies suggested the negative correlation among Pb and Cd accumulation and morphological traits. Physiological studies indicated that Pb and Cd accumulation negatively affect chlorophyll concentration and the antioxidant mechanism of plants gets activated, further these results are confirmed with FTIR studies, which reported the alteration in functional groups and associated compounds in plant tissues under Pb and Cd stress.