Auxin transport in roots : III. Dependence of the polar flux of IAA in Zea roots upon metabolism.

The dependence upon metabolism of the acropetal polar flux of IAA through 6-mm Zea root segments has been investigated using IAA-I-(14)C.The results are as follows: 1. At 0°C the acropetal movement of IAA is reduced to the level of basipetal movement and the polar flux is thus abolished, even after transport periods of 24 hours. 2. In dead tissue the acropetal polar flux is abolished and replaced by a basipetal polar flux. 3. On exposing segments to anaerobic conditions, the acropetal polar flux of IAA is severely reduced during the first 4 hours, but reappears during the subsequent 4 hours. The tissue thus appears to have the ability of adapting to anaerobic conditions and of resuming the acropetal transport of IAA. 4. The acropetal flux of IAA found in segments deprived of oxygen for 8 hours is dependent upon anaerobic metabolism since it is abolished and replaced by a net basipetal flux in the presence of sodium fluoride.The acropetal polar flux of IAA through the Zea root segments is thus entirely dependent upon metabolic energy.