The effect of gamma irradiation on biosynthesis of gibberellins in germinating wheat

Abstract

Reduction in the rate of gibberellin (GA) biosynthesis in gamma irradiated wheat during germination can be attributed to the adverse effect of radiation on certain steps in the GA-synthesizing system. The activities of two key enzymes, namely, mevalonate kinase and adenosine triphosphatase, involved in the initiation of GA synthesis from precursors, are impaired in irradiated seeds. Further, the incorporation of [¹⁴C]-acetate into GA₃, the most bioactive gibberellin in wheat, is reduced significantly. This is accompanied by concomitant accumulation of radioactivity in GA₄ and GA₇ species, which are intermediate precursor products on the biosynthetic pathway leading to GA₃ formation. These results indicate that radiation treatment reduces the efficiency of GA interconversion and it is quite probable that it interferes with the interconversion of a less active GA to a highly active one. This can be partially attributed to the overall disturbance in the protein-synthetizing system.