The Effect of Aluminium on Oxidative Stress-Related Enzyme Activity in Two Clover Species


Abstract: The impact of aluminium (Al) stress on the production of hydrogen peroxide and on the activity of antioxidant enzymes involved in oxidative metabolism, such as ascorbate peroxidase (APX), peroxidase (POD), and catalase (CAT), were studied in seedlings of 2 clover species (Trifolium alexandrinum L. and Medicago sativa L.). A uniform decrease in germination and root elongation were detected as the primary signs of Al injury. A significant increase in hydrogen peroxide content was also related to an increase in Al uptake by the roots of the 2 clover species, especially at relatively highly toxic Al concentrations (2-6 mM) for 7 days. APX-, POD-, CAT-, and H_{2}O_{2}-consuming enzymes were activated and followed similar patterns of expression in each species, exhibiting a relationship between their elevated activity and inhibition of root growth. Furthermore, it was shown that clover roots of the Al-tolerant (M. sativa) species accumulated more Al than the Al-sensitive (T. alexandrinum) cultivar during long-term Al treatment. Proline content increased more in M. sativa than in T. alexandrinum, especially at relatively highly toxic Al levels after 7 days of exposure.

Keywords: Aluminium, Egyptian clover (berseem), antioxidant enzymes, root growth, Al uptake, proline

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