Role of endogenous purine metabolism in thidiazuron-induced somatic embryogenesis of peanut (Arachis hypogaea L.)

Somatic embryogenesis was induced at the hypocotyledonary notch region of i ntact peanut (Arachis hypogaea L.) seedings cultured on a medium containing 10 mu mol.L-1 thidiazuron (TDZ). Inclusion of the purine analogs 2,6-diami nopurine (DAP), azaadenine or azaguanine to the thidiazuron amended medium inhibited the embryogenic response of the seedlings. DAP-mediated inhibitio n was not overcome by the addition of adenine sulphate. Inhibition of the e mbryogenic response by DAP provides evidence that the TDZ-induced accumulat ion of purine cytokinins is an essential component of TDZ-induced somatic e mbryogenesis process. Analyses of the endogenous level of purine metabolite s indicated that supplementation of the media with TDZ resulted in an overa ll increase in the endogenous cytokinins while DAP inhibited the purine rec ycling resulting in decreased levels of endogenous adenine and zeatin.