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.). | Turk J Bot 32 (2008) 345-352 © TÜBİTAK Research Article The Effect of Aluminium on Oxidative Stress-Related Enzyme Activity in Two Clover Species Fayza A. FAHEED Botany Department, Faculty of Science, Sohag University, 82524 Sohag, EGYPT Received: Accepted: 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 H2O2-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 Altolerant (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. Key Words: Aluminium, Egyptian clover (berseem), antioxidant enzymes, root growth, Al uptake, proline Introduction Due to the rapid increase of acid soil, Al toxicity is a major agricultural problem in several countries across the globe. Industrial pollution is a major concern near the aluminium factory in Ngha Hammadi, Upper Egypt. Pollutants discharged from this factory accumulate in soil and are available for uptake by plants. The inhibition of root elongation is a general and very sensitive response by numerous plant .
