Early induction of phenolic compounds in aluminum-treated roots of Brassica oleracea L.

There are evidences showing that adverse impacts of aluminum (Al) on plants growth and development are associated with its effect on plasma membrane and cell wall. Influence of Al on peroxidation of membrane lipids, wall-bound phenolics, lignin, soluble phenolics and the activity of certain enzymes involved in metabolism of phenols, i.e., phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO) was measured in red cabbage (Brassica oleracea L. cv. Red Dynasty). The plants in their vegetative growth phase were treated with 60 ?M AlCl3 in a Hoagland solution, pH 4.5, for 6 h. Aluminum was rapidly absorbed by the plants. The effect of Al on the peroxidation of membrane lipids of both roots and shoots was not significant compared to those of the control plants. The activity of PAL in both roots and shoots and of PPO of roots was significantly higher in Al-treated groups, compared with the control ones. The contents of pectin-bound phenolics as well as lignin contents of plants were significantly enhanced by Al and the increase of phenolics of shoots in Al-treated plants were much more pronounced. While anthocyanin content of the plants increased by Al, total contents of flavonoids were not significantly affected by Al treatment.