Abstract:
Copper (Cu), a redox-active transition metal, is known
to be involved in protein metabolism, photosynthetic and respiratory
electron transport, cell wall metabolism, antioxidant activity,
nitrogen fixation, ion metabolization, and hormone perception,
among others in plants. Though Cu has been listed among the
essential elements, it could potentially result in complete inhibition
of plant growth and development at excess concentrations.
Measures available for alleviating Cu toxicity in plants are
discussed in the present paper. Exogenous application of nitric
oxide through up-regulating the components of antioxidant
defense system [catalase (CAT-EC 1.11.1.6), peroxidase (POD-EC
1.11.1.7), superoxide dismutase (SOD-EC 1.15.1.1), and ascorbate
peroxidase (APX-EC 1.11.1.11) activities] and stimulating the
enzyme P5CS (D1-pyrroline-5-carboxylate synthetase), which
catalyzes proline biosynthesis, has been proved to stand against
the adverse impacts of Cu toxicity. Addition of cations (such as
Ca2+ and Mg2+) through stimulating site-specific competition for
metal ions could also prevent excess accumulation of Cu in cell
interior. Silicon application, through nutrient balancing and
physically blocking the apoplastic bypass flow has also been
recognized to be effective in alleviating Cu toxicity. Addition of
organic amendments and use of arbuscular mycorrhizal fungi as
soil inoculants have also proved successful in amelioration of Cu contaminated soils. Though molecular and physiological
mechanisms associated with Cu toxicity have been substantially
investigated, information on the regulation of the expression of
stress-related genes in key agricultural plant species is still
lacking. Additional research efforts focusing at field validation of
the toxicity alleviation methods are also equally important
