Differential effect of sodium azide on the frequency of radiation-induced chromosome aberrations vs. the frequency of radiation-induced chlorophyll mutations in Hordeum vulgare

Abstract

A considerable synergistic increase of the frequency of cells carrying chromosome aberrations was observed in seeds of Hordeum vulgare , variety Himalaya, irradiated dry with gamma rays and hydrated in sodium azide solutions buffered at pH 3, 7 and 11. This effect, which was most evident at pH 3, was detected throughout development up to the formation of the male gametophyte. No synergistic increase of the frequency of radiation-induced chlorophyll-deficient mutants was observed. This differential effect of the sodium azide post-irradiation treatment on the frequency of chromosome aberrations vs. the frequency of mutations is attributed to the formation of two kinds of lesions in the genetic material of barley following exposure to gamma rays. One kind of lesion, similar to those leading to point mutations in procaryotes, is reparable at low energy potentials and, thus, its frequency is not affected by the sodium azide treatment. The other kind of lesion is associated with chromosome breaks and its repair is affected by the presence of the enzymatic inhibitor.