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Morphological and Physiological Characteristics of Eucalyptus urophylla × E. grandis(DH_(32-29)) Seedlings Under Different Cadmium Concentrations

Cadmium is one of the most common heavy metals causing soil contamination problems. Bioremediation is an effective way to rehabilitate soils contaminated with this comp. An pot trial was conducted to measure various morphological and physiological indices of Eucalyptus urophylla × E. grandis(DH32-29) grown under treatments of eight different soil concentrations of Cadmium(Cd) ranging from 10 to 140 mg·kg-1. There were no significant differences found among seedling grown at low concentration(10 mg·kg-1) of Cd and the control(i.e. no Cadmium). Under higher Cd concentrations(20 mg·kg-1) seedling growth was significantly impacted. As Cd concentration increases, the biomass, chlorophyll content, fluorescent parameter(PS Ⅱ), maximum photochemical quantum yield(Fv/Fm), efficiency of PS Ⅱ photochemistry(φPS Ⅱ), non-photochemical quenching coefficient(Np) and nitrogen balance index(NBI) decreased, photochemical quenching(q P) showed little change, whilst malondialdehyde(MDA) increased. Seedlings of clone DH32-29 show clear visible symptoms of injury at levels above 20 mg·kg-1 and at plant growth stagnated at Cd concentration exceeding 40 mg·kg-1. It was concluded that DH32-29 seedlings can grow normally at lower Cadmium concentrations(≤20 mg·kg-1). But as the concentration increases, above this level, the morphological and physiological characteristics of seedlings start to display significant impacts. Surveys of soil Cadmium levels in areas suited to Eucalyptus plantations and related research results in combination with this current study illustrate the potential soil remediation value of DH32-29 for areas where soils are affected by Cd pollution.