Fungal biostimulant-driven phytoextraction of heavy metals from tannery solid waste contaminated soils

Two of the multiple limitations of phytoextraction efficiency (PE %) of TSW polluted soils are: (i) low growth of plant performance, (ii) poor bioavailability of excessive essential and heavy metals (ascribed as Category-I and II metals respectively) The current study reports biostimulant role of allochthonous Trichoderma harzianum (F1) and autochthonous Trichoderma pseudokoningii (F2) in growth of Tagetes patula L. and uptake of Category-I & II metals from TSW-soil (0, 5 & 10%). Significantly higher growth (27.5-47.8% dry wt. than Control) and highly significantly higher uptake of Category-I & II metals (72-80% Ca, 32-69% K, 72-76% Na & 73-86% Cd, 63-100% Cr, 72-77% Cu, 73-78% Fe, 43-77% Mg, 22-33% Ni, 70-73% Zn) was observed in T. patula applied with F1 + F2 treatment. The PE (%) parameters viz.specific extraction yield, tolerance and translocation index of Category-I & II metals were higher in plants cultivated on fungal inoculated TSW:soil. The Trichoderma spp. acted as strong biostimulants for enhancing plant growth and conc. of catalase (CAT, 44-52% than control), superoxide dismutase (SOD, 37-43%), soluble proteins (37-68%) and total chlorophyll (10-26%) in T. patula during metal phytoextraction of TSW:soil. Novelty statement Due to multiple socio-economic constraints for effective management of tannery solid waste (TSW), the heavy metal phytoextraction seems to be one of the promising approaches. However, due to complex composition of TSW, that is, with more than 37 components, high pH, multiple types and high conc. of metals; there lies huge challenge of enhancing phytoextraction efficiency (PE %). This can be done by enhancing growth of hyperaccumulator plants and increasing bioavailable fraction of metals. The current study suggests application of selected fungal biostimulants for increasing growth of T. patula while improving bioavailable fraction of the total metal contents of the TSW: soil.