Auxin was first isolated from:

Step-by-step solution

Auxins (from Greek ‘auxein’: to grow) was first isolated from human urine. The term ‘auxin’ is applied to the indole-3-acetic acid (IAA), and to other natural and synthetic compounds having certain growth-regulating properties. They are generally produced by the growing apices of the stems and roots, from where they migrate to the regions of their action.