Exploring the phytoremediation potential of Toona ciliata grown on lead and cadmium contaminated soils through morphological and anatomical analysis

Abstract

Phytoremediation is a cost-effective and environmentally friendly approach to reclaim heavy metal-contaminated soils. The phytoremediation using tree species has been preferred over annual crops as they produce higher biomass and accumulate heavy metals for prolonged period. Toona ciliata M. Roem is a large perennial tree, known to produce high biomass in short rotation, can be used for phytoremediation experiments due to their alternative use in versatile timber production and absence of linkage with food chain. Thus, present investigations were conducted to untap the potential of T. ciliata grown on lead and cadmium contaminated soils during two constitutive years 2020–21. Regarding T. ciliata raised on soils treated with different concentrations of Pb, Cd, and their combinations for six months, the results depicted that plants accumulated higher concentrations of metals in shoots than roots having bioconcentration factor (BCF) and translocation factor (TF) more than one, indicating that plants have efficient metal translocation and accumulation capability. Further, heavy metal tolerance index and survival percentage (> 85%) denote the plant’s ability to tolerate heavy metals up to 300 mgPb/kg and 25 mgCd/kg. Anatomical changes induced due to heavy metals include reduced root area as well as vascular bundle area as compared to control, also reduced stomatal pore size and increased stomatal index and trichome density suggesting the plant’s adaptive response under heavy metal stress. Furthermore, distinct accumulation patterns of lead (Pb) and cadmium (Cd) in various tissues of both leaves and roots were meticulously identified and validated through the use of cutting-edge techniques like Field Emission Scanning Electron Microscopy and Energy-Dispersive X-ray Spectroscopy (FESEM-EDS), which reflects that plant had strong enrichment ability for Pb accumulation in roots and more Cd translocation, accumulation and sequestration in aerial tissues. Hence, the present study reflects that Toona ciliata had great phytoextraction efficiency for reclaiming Pb- and Cd-contaminated soils.