2009 Volume 59 Issue 2 Pages 187-193
The relative biological effectiveness (RBE) of alpha particles and protons emitted during exposure of barley (Hordeum vulgare L.) seeds to thermal neutrons were estimated. 10B-enriched re-dried seeds were irradiated with thermal neutrons or gamma-rays. Two assumptions so far believed that boron distribution was uniform throughout either natural dormant seeds or 10B-enriched seeds, and that boron atoms enter the seeds as freely as water molecules do, were found to be invalid. A boron addition effect (BAE) as high as 58.2 was obtained after thermal neutron exposure of seeds presoaked in 4800 μg·g−1 of 10B-enriched boric acid solution. Estimates of RBE of alpha particles were nearly constant and independent of the contents of absorbed 10B. RBE averaged 55.0 and 55.1 for the seed and spike presoaking methods of boron absorption, respectively. We could also obtain RBE of protons as high as 48.7 and 43.9 for the seed and spike methods, respectively. Boron addition converted the principal capture element during thermal neutron exposure from protons in dormant seeds to boron in 10B enriched-seeds.