Post-irradiation modification of O2, N2, and N2O-mediated damage in dry barley seeds by glutathione and cysteine: probable radiation chemical events.

Dry barley seeds were exposed to 60Co gamma-rays in vacuo and post-hydrated at 4 degrees C for 8 h in O2, N2 or N2O-saturated water. Post-irradiation damage was assessed in terms of seedling injury and peroxidase activity in the 8 day-old seedlings. Both cysteine (CySH) and glutathione (GSH) afford significant radioprotection against O2-dependent damage. CySH does not exert any effect on the N2 and N2O-mediated post-irradiation damage. GSH, on the other hand, significantly potentiates these two components of damage. Buthionine sulfoximine (BSO) exerts no effect on the uptake of exogenously added GSH. BSO also exerts significant radioprotection against oxic damage, and simulates GSH in potentiating the N2 and N2O-mediated radiation damage. An equimolar mixture of GSH and BSO also behaves in the same way as either of these two additives on O2, N2 and N2O-mediated radiation damage: the two agents do not show additive action.