Radial transport of IAA ± two polar auxin transport inhibitors compared to a diffusion control.

Radiolabeled IAA and BA (benzoic acid, diffusion control) were supplied in lanolin at 100 nM concentrations via a pith cavity to 4-month-old stems of Populus tremula x alba. PAT inhibitors N-1-naphthylphthalamic acid (NPA) and quercetin (QUE) were added at 10 µM. Radioactivity was collected from developing xylem strips after an 18 hour incubation. Two-tailed paired t-tests† comparing transport to that of IAA alone indicate a highly significant increase in IAA transport relative to BA, and a small but significant decrease in IAA transport when NPA or QUE were added to the lanolin. Note that the pairing of segments within each tree (i.e., treatment replication was nested within tree) is not reflected in the overall mean but is accounted for with paired t-tests.