Question

Dr. F. Went noted that if coleoptile tips were removed and placed on agar for one hour, the agar would produce a bending when placed on one side of freshly-cut coleoptile stumps of what significance is this experiment?

• A. It made possible the isolation and exact identification of auxin.
• B. It is the basis for quantitative determination of small amounts of growth-promoting substances.
• C. It supports the hypothesis that IAA is auxin.
• D. It demonstrated polar movement of auxins.

Answer 1

Answer: (D)

There are various bioassays to determine the concentration of auxin hormone in the plant. The Avena coleoptile test is a bioassay firstly done by F. W. Went. It is for IAA (indole-3-acetic acid). It measures the angle of the curvature of a decapitated coleoptile after placing an agar block containing auxin on one side. It is seen that when coleoptile tips are placed on agar, agar produced bending when placed on one side of freshly cut coleoptile stumps. This is due to the polar movement of auxin in the stem.