Aluminum stress increases carbon-centered radicals in soybean roots

The formation of radical species was examined in roots of soybean seedlings exposed to aluminum (Al). Electron spin resonance (ESR) spectra of root homogenates with the spin-trapping reagent 5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide (DEPMPO) indicated the presence of carbon-centered radicals in plants not exposed to Al. Plants exposed to 50 μM Al showed a similar spectrum, with increased signal intensity. These radicals were likely produced through a H-atom abstraction reaction by hydroxyl (OH) radicals, the synthesis of which was initiated by the formation of superoxide (O2−) anions. The increased production of the carbon-centered radicals may be responsible for the lipid peroxidation in Al-treated roots.