It has been shown in earlier papers (8, 9) thatudphotoperiodic induction of the cocklebur is inhibitedudby application to the plant of the pyrimidine, 5-fluorouracilud(5-FU). It was further found that the inhibitorudis most effective in this function if applied directlyudto the bud at the beginning of the otherwise inductiveuddark period. It has been further concludedudthat the inhibitor functions by adversely affectingudprocesses which take place in the bud during the inductiveuddark period and which are essential to photoperiodicudinduction.udIn this paper we shall show that the process in theudbud which is inhibited by 5-FU and which is relatedudto inhibition of induction is the synthesis of ribonucleicudacid (RNA).
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