title: EPR studies on gamma-irradiated barley seeds: identification of trapped electrons.
abstract: Electron paramagnetic resonance (EPR) studies were conducted on barley seeds exposed to normal (H(2)O) and deuterated (D(2)O) moisture, irradiated with 750 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/solvated with an increase in the moisture content (H(2)O/D(2)O) of seeds. The recombination of the trapped electron with radical cation gave intense thermoluminescence emission at 110 K. With the increase in temperature and the destruction of singlet, unmasking of an underlying heterogeneous population of free radicals was observed. These free radicals emanate mainly from the endosperm (approximately 95% by wt of the seed), whereas irradiated embryos show a broad multiplet of comparatively low amplitude. Radiolysis of carbohydrate, proteins (approximately 95% of endosperm), and lipids could possibly be responsible for the heterogeneous population of free radicals. Peroxyl radicals were also observed on annealing.
authors.affiliation: School of Life Sciences, Jawaharlal Nehru University, New Delhi 110 067, India. latashukla@yahoo.com
authors.forename: L I
authors.initials: LI
authors.lastname: Shukla
authors.forename: V
authors.initials: V
authors.lastname: Natarajan
authors.forename: T P
authors.initials: TP
authors.lastname: Devasagayam
authors.forename: M D
authors.initials: MD
authors.lastname: Sastry
authors.forename: P C
authors.initials: PC
authors.lastname: Kesavan
mesh_terms: D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D004583:Electrons; D005720:Gamma Rays; D001467:Hordeum / Q000196:embryology*; D008163:Luminescent Measurements; D012639:Seeds / Q000737:chemistry* / Q000528:radiation effects