| Abstract: | Auxin transport was investigated in excised stem segments ofNicotiana tabacum L. by the agar block technique using [1-14C]indol-3yl-acetic acid (IAA). The ability of the stems to transportauxin basipetally increased as secondary development proceeded;by contrast the ability of the pith to transport auxin declinedwith age. By separation of the stem tissues it was shown thatthe great majority of auxin transport took place in cells associatedwith the internal phloem and in cells close to the cambium;in both cases similar velocities of transport were found (c.5.0 mm h1 at 22°C). The effects of osmotic gradientson auxin transport through the internal phloem were investigated.IAA was found by chromatography to account for practically allthe radioactivity in receiver blocks and other extracts of stemsegments. The significance of these results is discussed. |
