A Sensitized Avena Curvature Test and Identification of the Diffusible Auxin in Avena Coleoptile

(1) Curvature of Avena coleoptile induced by IAA is increased in presence of ferrous sulfate. The optimum concentration of ferrous sulfate for the promotion of Avena coleoptile curvature is about 5×10-3M.(2) And in this concentration, ferrous sulfate increases the sensitivity of Avena curvature test about three times.(3) Curvature of Avena coleoptile induced by NAA is also increased in presence of ferrous sulfate.(4) The auxin diffused from Avena coleoptile tips into agar blocks is identified as IAA according to the above mentioned sensitive Avena curvature test. And no growth substance other than IAA was found in agar blocks.