31. It was first discovered that the plant hormone auxin likely regulates apical dominance in 1934. 32. Auxins typically act in concert with, or in opposition to, other plant hormones.33. However, high concentrations of auxin inhibit root elongation and instead enhance adventitious root formation. 34. Gautheret and Nobecourt were able to maintain callus cultures of carrot using auxin hormone additions. 35. The changed relations in concentration of auxin leads to differential growth of the root tissues. 36. For that purpose, auxins have to be translocated toward those sites where they are needed. 37. Auxin must be removed from the valve margin cells to allow the valve margins to form.38. This theory states that auxin from apical buds travels down shoots to inhibit axiliary bud growth. 39. Their experiments showed that the auxin . 40. In both roots and stems, auxin accumulates towards the gravity vector on the lower side.
