Oxygen-induced free radical in wheat roots.

ESR experiments have shown that free radicals are formed in wheat plant roots as a result of exposure to O2. Although the radical(s) has not been positively identified, the nature of the spectra allows simple oxygen-derived radicals, such as O2-, HO2. and OH., to be excluded as possibilities. Adsorption of Cu(II), but not Zn(II) or Cd(II) by the root results in a rapid decay of the radical signal to reach a level of 10% of its original intensity after a few minutes.