EPR studies on gamma-irradiated barley seeds: Identification of trapped electrons

Electron paramagnetic resonance (EPR) studies were conducted on barley seed s exposed to normal (H2O) and deuterated (D2O) moisture, irradiated with 75 0 Gy at 77 K. Reported here, for the first time, are the trapped electrons formed on gamma -irradiation of seeds at 77 K. Electrons are stabilized/sol vated with an increase in the moisture content (H2O/D2O) of seeds. The reco mbination of the trapped electron with radical cation gave intense thermolu minescence emission at 110 K. With the increase in temperature and the dest ruction of singlet, unmasking of an underlying heterogeneous population of free radicals was observed. These free radicals emanate mainly from the end osperm (similar to 95% by wt of the seed), whereas irradiated embryos show a broad multiplet of comparatively low amplitude. Radiolysis of carbohydrat e, proteins (similar to 95% of endosperm), and lipids could possibly be res ponsible for the heterogeneous population of free radicals. Peroxyl radical s were also observed on annealing.