Is Auxin Produced in Roots?

Abstract

In 1933 Boysen Jensen [2] conclusively demonstrated that auxin is present in roots. When this problem was solved a new one arose: Is auxin produced in root tips, or is it merely accumulated there from elsewhere in the plant? Thimann [3] determined the amount of auxin which was given off by excised tips of Avena roots into dextrose-agar blocks and compared it with the amount of auxin that was obtained by ether extraction of such tips. In both cases he found the same amount of auxin and concluded that it is merely accumulated in the Avena roots and not actually produced by them. Other authors [4], however, found that from the roots of Avena and other plants two to twenty times as much auxin could be obtained by diffusion as by extraction. They came to the conclusion that auxin is produced in roots. As we had obtained surprisingly large amounts of auxin from pea roots [5] it seemed of interest to compare the amounts of auxin obtained from excised root tips of germinating peas by diffusion and by extraction with improved techniques.