NEW MOLYBDENUM-HYPERACCUMULATOR AMONG PLANT SPECIES GROWING ON MOLYBDENUM MINE- A BIOCHEMICAL STUDY ON TOLERANCE MECHANISM AGAINST METAL TOXICITY

Abstract

The aim of this work was to determine metal accumulation by plants growing on three molybdenum-mine zones and their tolerance strategies. The plants from tailing, extracting and non-contaminated zones were sampled with their corresponding soils. The results show that molybdenum (Mo) and copper (Cu) were at toxic levels in soils and their levels varied in 44 collected species from 21 families. Ajuga chamaecistus and Cramb orientalis L. excluded Mo and Cu, respectively. Achilla tenuifollia as Mo-hyperaccumulator with total Mo (1979 mg kg⁻¹) and then Erodium ciconium with 1308 mg kg⁻¹ Mo and Conyza Canadensis with 618 mg kg⁻¹ Cu were moderate metal accumulators. They stored considerable levels of metals in their leaves vacuoles and elevated the levels of phytochelatins, cysteine and glutathione and induced antioxidant enzymes. In conclusion, this study indicated that some collected plants excluded metals. In metal-accumulators, antioxidant enzymes, phytochelatins and sequestration of excess metals were involved in their tolerance mechanism.

Keywords:

• tolerance strategies
• phytochelatins
• Mo-hyperaccumulator
• antioxidant enzymes
• oxidative damage

ACKNOWLEDGMENTS

This work was financially jointly supported by the Iran National Science Foundation (INSF). We are also grateful to research deputy of Tarbiat Moallem University for assistance with the field work.