Transport of indoleacetic acid in intact roots of Phaseolus coccineus.
Indoleacetic acid (IAA)-5-(3)H (2×10(-9)) was applied to intact roots of Phaseolus coccineus seedlings at the apex or 2 cm above the apex, and the movement of IAA-(3)H and its metabolites traced by sectioning and chromatography. Basipetal movement of label occurred for 2 cm or less, declining exponentially, and the amount increased with time. Acropetal transport from above the apex showed quantitatively less movement of radioactivity. After a 6h treatment period a decline of label occurred in the first 0.5cm, below which there was a long distance movement of small amounts of label, mainly in IAA, towards the apex where the label concentrated by a factor of approximately 2. Short-distance basipetal movement consisted of about equal amounts of IAA and metabolites, and only metabolites were found in areas more basipetal than 2cm. Label from solutions of sucrose-(14)C and (3)H2O followed the same general pattern of movement as label from IAA-(3)H, except that acropetal movement of water showed a steady decrease in the amount of label as the distance from the area of application increased. The short distance basipetal transport of label with the breakdown of IAA-(3)H indicates that the extent of basipetal movement was limited by catabolic processes. The acropetal pattern of IAA-(3)H movement with the concentration of the transported material close to the apex, is possibly the result of transport in the phloem.
Section of Genetics, Development and Physiology, Division of Biological Sciences, Cornell University, Ithaca, N.Y..
P J
PJ
Davies
E K
EK
Mitchell