Rye oxidative stress under long term Al exposure.

Aluminium (Al) toxicity decreases plant growth. Secale cereale L. is among the most Al-tolerant crop species. In order to study the response to Al-long term exposure, two rye genotypes with different Al sensitivity ('D. Zlote' and 'Riodeva') were exposed to 1.11 and 1.85mM Al and the antioxidant responses were followed for 2 and 3 weeks in roots and leaves. Al toxicity signals, such as a severe decrease in root growth, occurred sooner in 'Riodeva.' The antioxidant response was dependent on the genotype, the organ, Al concentration and the exposure period. Al-exposed roots of 'D. Zlote' showed earlier enhancements of APX, SOD and G-POX activities than those of 'Riodeva.' 'D. Zlote' roots showed stimulation of the AsA-GSH cycle after the second week (when root growth inhibition was less severe), while later (when severe root growth inhibition was observed), oxidation of AsA and GSH pools was observed. In leaves of both genotypes, CAT, SOD and G-POX activities increased with Al exposure. In these leaves, the effect of AsA-GSH was time dependent, with maximum oxidation at the second week, followed by recovery. We confirmed that the oxidation state of AsA and GSH pools is involved in the detoxification of Al-induced oxidative stress. Moreover, our data demonstrate that the production of ROS does not correlate with the Al-induced root growth decrease. Finally, the differences observed over time indicate that long term exposure may provide additional information on rye sensitivity to Al, and contribute to a better understanding of this species' mechanisms of Al tolerance.