The Role of Adenine and Adenosine in the Synthesis of Cytokinins by Excised Maize Roots

While cytokinin-like activity was detected in aseptically cultured excised roots of Zea mays no evidence could be found that (8-¹⁴C)adenine or (U-¹⁴C)adenosine was incorporated into the biologically active compounds over a 42 day culturing period. This information raises serious doubts as to whether adenine and/or adenosine serve as primary precursors for cytokinin biosynthesis. The possibility does however, exist that the excised roots lacked a shoot produced precursor necessary for cytokinin production.