The existence of indication of auxin came from the work of Darwin. In 1880, Darwin when was working with the canary grass he could demonstrate the bending of the grass coleoptile towards the unilateral source of light. The coleoptile bends towards the light when it is exposed to unilateral light. But when an opaque cap was placed over the coleoptile tip the coleoptile never bend. When the seedling was buried in black sand except the tip portion of the coleoptile; again the coleoptile curved towards the light. By this Darwin could demonstrate the tip of the coleoptile perceived light and has an influence of the growth.
Later in 1924, F.W. Went could prove that some substances are involved in the unilateral growth of the plant. In his experiment on Avena plant, he cut off the tip of the coleoptile and so that remaining part does not possess auxin to elongate. Then this excised piece of coleoptile was placed on a cube of agar; then the auxins diffused into the cube of agar. Another coleoptile tip of the Avena plant was removed and the agar block containing auxin was placed on this decapitated tip. The auxin moved down to the coleoptile so that it resulted in the greater elongation of the cell along that side of the coleoptile resulting in the curvature. F.W. Went named this substance as the auxin.
