Hydroxyproline-Induced Inhibition of Elongation of Avena Coleoptiles1'

Summa(iry. Hlydroxy-L-proline-induced inhiibition of elongationi of Aven(a coleoptile segments was measuired in water and in indole-3-acetic aci(l. This inhibition was completely reversed by L-proline. Time-sequence experiments revealed that some time had to elapse, or some eloingationi had to occur, prior to the onset of hydroxyproline inhibition. The presence of sucrose supported the rate of atuxin-indtuced elongation throughouit a 24-hour period, and enhanced the effectiveness of hydroxyproline as an inhibitor of elongation. The application of adenosine triphosphate effectively couinteracted the hydroxyproline-induced inhibition of elongation; completely in water, anid partially in indole3-acetic acid. Optimal ATP concentrations were between 0.25 and 0.75 mm. Similarly, guianine-HCL, L-gluitamic acid, and L-ornithine-EHCL were capable of reversing the hydroxyproline inhi,bition. Other compouinds that wvere tested bult which proved to be less effective are tabulated. It is sutggested that hydroxyproline may exert its inhibitory effect on the protein and/or RNA synthesis necessary for elongation of the oat coleoptile by interferenlce with the metabolism of adenlosinle triphosphate or other high energy compollnds.