Influence of 2,3,5-triiodobenzoic acid and 1-N-naphthylphthalamic acid on indoleacetic acid transport in carnation cuttings: Relationship with rooting

H-3-IAA transport in excised sections of carnation cuttings was studied by using two receiver systems for recovery of transported radioactivity: agar blocks (A) and wells containing a buffer solution (B). When receivers were periodically renewed, transport continued for up to 8 h and ceased before 2 4 h. If receivers were not renewed, IAA transport decreased drastically due to immobilization in the base of the sections. TIBA was as effective as NP A in inhibiting the basipetal transport irrespective of the application sit e (the basal or the apical side of sections). The polarity of IAA transport was determined by measuring the polar ratio (basipetal/acropetal) and the inhibition caused by TIBA or NPA. The polar ratio varied with receiver, whe reas the inhibition by TIBA or NPA was similar. Distribution of immobilized radioactivity along the sections after a transport period of 24 h showed t hat the application of TIBA to the apical side or NPA to the basal side of sections, increased the radioactivity in zones further from the application site, which agrees with a basipetal and acropetal movement of TIBA and NPA , respectively. The existence of a slow acropetal movement of the inhibitor was confirmed by using H-3-NPA. From the results obtained, a methodologica l approach is proposed to measure the variations in polar auxin transport. This method was used to investigate whether the variations in rooting obser ved during the cold storage of cuttings might be related to changes in pola r auxin transport. As the storage period increased, a decrease in intensity and polarity of auxin transport occurred, which was accompanied by a delay in the formation and growth of adventitious roots, confirming the involvem ent of polar auxin transport in supplying the auxin for rooting.