The graviresponsiveness of intact and primary maize roots kept horizontally in darkness and humid air is analysed. A precise local application of IAA is possible when using resin beads (diameter: 0.45 +/- 0.05 mm) loaded with IAA. The beads are placed on the upper or lower sides of the caps. They significantly change the root gravireaction. The effect of IAA is discussed in terms of its possible level in the growing and gravibending zones and its transport (acropetal, lateral and basipetal) respectively in the stele, the cap and the cortex of the elongating root.