Effect of sodium fluoride on radiation sensitivity of barley seeds

Barley seeds soaked in 0.01 M sodium fluoride (NaF) in phosphate buffer (pH7) or in buffer alone for 18 h were dried and equilibrated to 10% moisture, either in air or in nitrogen. Pre-treated and re-dried seeds were irradiated in air or in nitrogen with 0, 13, 20, 26 and 32 kR of γ rays, and were immediately hydrated in oxygen- or nitrogen-bubbled water. Parameters of radiation effect considered were seedling injury, mitotic and meiotic cells with bridge aberrations at anaphase and pollen fertility in M₁, and the frequency of chlorophyll mutations in M₂. NaF at 0.01 M was not mutagenic by itself. Pre-treatment with NaF significantly enhanced the radiation effect, when the irradiation was done in air, in comparison with the buffer soaked seeds. The increased effect due to NaF was additional to the oxygen effect. In nitrogen, NaF pre-treatment increased the mutagenic effect but it was not always significant. Post-soaking of irradiated seeds in 0.01 M NaF for 5 h increased seedling injury in comparison with the irradiated seeds soaked in buffer alone or in 0.01 M NaCl. At least a part of the sensitizing effect of NaF may be due to the inhibition of repair.