Evidence for Auxin Production in Isolated Roots Growing In vitro

Evidence is presented which shows that auxin is produced in isolated pea roots cultivated in vitro under sterile conditions. The roots were cultured in such a way that at the end of each week the culture was continued with the 10-mm. tip only. The basal parts of the roots, that grew approximately 70 mm. per week, were discarded. The total amount of auxin extracted from these discarded bases during 20 weeks of culture was nine times as much as that extracted from the initial tip from which the cultures originated. 2. Even at the end of 34 weeks of culturing, roots were found to contain as much as 1000 x 10-6 γ indoleacetic acid equivalents of auxin per root.