Root growth and antioxidant enzyme responses to aluminium stress in sugarcane

Aluminium (Al) toxicity in acid soils is a major abiotic stress that can limit plant production worldwide. Al toxicity directly inhibits root development and exacerbates oxidative stress in the plant. Sugarcane is mostly cultivated in tropical regions and is often exposed to phytotoxic concentrations of soil Al. In this study, our objectives were to evaluate nine sugarcane cultivars on their tolerance to Al in a hydroponic system, investigating the effects of 143 mu M {Al3+) on root growth and on activity of the antioxidant enzymes ascorbate peroxidase (APX), catalase (CAT) and superoxide dismutase (SOD). The screening method proposed was suitable for a rapid, reliable and reproducible procedure of the sugarcane cultivars. Exposure to Al for three days altered root growth and activity of enzymes of the nine sugarcane cultivars. However, the magnitude of the alterations varied significantly among cultivars. The cultivar RB928064 was classified as Al-tolerant and the cultivar RB835486 as Al-sensitive. Increases in enzyme activity after Al exposure varied from 4 to 46%, with average increases of 19% in APX, 20% in CAT, and 8% in SOD. The variations induced by Al in enzyme activity, however, did not correlate significantly with those variations induced by Al in the root growth.