Biochemical Responses of Two Species of Eucalyptus Exposed to Aluminium Toxicity: Oxidative Stress and Antioxidant Metabolism

Abstract

In response to oxidative damage resulting from overproduction of reactive oxygen species, plants have developed complex and efficient antioxidant machinery. The aims of this research were to measure composts used as stress indicators, quantifying non-enzymatic compounds and activities of antioxidant enzymes, and to explain probable differences between two species of the gender Eucalyptus exposed to low and high aluminium. The experiment employed a factorial that was entirely randomised, with two species (Eucalyptus platyphylla and E. grandis) combined with aluminium concentrations (and 0.08 and 1.60 mM Al, which are described as low and high Al, respectively). This study revealed that the E. platyphylla presented intense modifications on malondialdehyde and electrolyte leakage in leaf and root, being also detected increases to oxidized glutathione, reduced glutathione and total glutathione. In addition, E. platyphylla had strong accumulations linked to superoxide and hydrogen peroxide, while E. grandis were detected minor alterations to both tissues. In relation to superoxide dismutase, catalase, ascorbate peroxidase and peroxidase were showed similar behaviours, with higher activities in E. grandis, if compared to E. platyphylla. Therefore, is possible to conclude that E. grandis is more tolerant to aluminium due to minor production of reactive oxygen species and decreased alterations on stress indicators. Concomitantly, the antioxidant enzymes effectively contribute to reduce the oxidative stress generated in root and leaf of E. grandis exposed to high aluminium.