Reversal of Hydroxyproline-Induced Inhibition of Elongation of Avena Coleoptiles

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Abstract
Hydroxy-l-proline-induced inhibition of elongation of Avena coleoptile segments was measured in water and in indole-3-acetic acid. This inhibition was completely reversed by l-proline. Time-sequence experiments revealed that some time had to elapse, or some elongation had to occur, prior to the onset of hydroxyproline inhibition. The presence of sucrose supported the rate of auxin-induced elongation throughout a 24-hour period, and enhanced the effectiveness of hydroxyproline as an inhibitor of elongation. The application of adenosine triphosphate effectively counteracted the hydroxy-proline-induced inhibition of elongation; completely in water, and partially in indole-3-acetic acid. Optimal ATP concentrations were between 0.25 and 0.75 mm. Similarly, guanine-HCL, l-glutamic acid, and l-ornithine-HCL were capable of reversing the hydroxyproline inhibition. Other compounds that were tested but which proved to be less effective are tabulated. It is suggested that hydroxyproline may exert its inhibitory effect on the protein and/or RNA synthesis necessary for elongation of the oat coleoptile by interference with the metabolism of adenosine triphosphate or other high energy compounds.