Induction of DNA single-strand breaks in barley by sodium azide applied at pH 3.

Sodium azide (1 to 50 mM), adjusted to pH 3 and applied for 2 h to presoaked barley seeds, induced a dose-dependent frequency of single-strand breaks in DNA of non-germinating embryos. This was demonstrated by sedimentation analyses of isolated DNA samples in alkaline sucrose gradients and in neutral sucrose gradients with 80% formamide. The doses applied also inhibited dose dependently the root length, seed germination and partially the seedling height. Only the sub-lethal doses (10 and 12.5 mM) induced a low frequency of chromatid breaks and translocations in the root tip metaphases. The sedimentation rate (in alkaline sucrose gradients) of calf thymus DNA treated with sodium azide at pH 3, was similar to that of the control DNA treated with buffer (pH 3) alone.