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.