The Avena curvature is used for bioassay of IAA (Indole Acetic Acid).

Went worked on oat coleoptiles. He placed several decapitated tips of Avena coleoptile over a thin block of agar agar. The block was then cut to small pieces and each piece was placed asymmetrically on the cut end of coleoptile. The characteristic bending was observed even in dark. This clearly demonstrated that the substance responsible for growth is synthesized in the apex and translocated downwards into the agar block and finally to one side of decapitated stump. This resulted in unequal growth and thus curvature. The above experiment is a bioassay test for auxins.