Abstract
The ‘classical’ basipetal transport of auxin in sunflower and marrow hypocotyls can be inhibited by the application of auxin transport inhibitors. However, when a hypocotyl is ringed with such an inhibitor just beneath the apical hook, the growth rate of the hypocotyl is not depressed within the first few hours. It is concluded that the supply of auxin by the basipetal auxin transport system to the elongating cells in the hypocotyl is not rate-limiting in the short term.