Abstract
Cadmium inhibits the growth of plants even in the low concentrations, provably due to the induction of oxidative stress. Although some phenolic compounds can act as antioxidants, it remains unknown whether these compounds play a protective role for the Cd stress. In this study, we examined the role of phenolic compounds for the Cd stress using Arabidopsis, which was grown in a hydroponic culture system without carrier, facilitating the Cd treatment. In this cultivation method, when the 14-d-old plants were grown in the presence of 25 μM Cd2+ for 7 days, the content of total phenolic compounds increased to 1.4-fold, compared with that of non-treated plants. This indicates that phenolic compounds were accumulated by the Cd treatment.
Among phenolic compounds, flavonoids are known to be defensive molecules for UV photooxidation. Next, we examined the effects of Cd on the growth of the flavonoid deficient mutant, tt4. The result showed that in the presence of 25 μM Cd2+, the dry weight of WT and tt4 was reduced to 77% and 63%, respectively, compared with that of non-treated plants. This result suggests that flavonoids can act as the defensive molecules for Cd toxicity.
