Q. 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 a freshly cut coleoptile stumps. Of what significance is this experiment :
(a) It demonstrated polar movement of auxins
(b) It made possible the isolation and exact identification of auxin
(c) It is basis of quantitative determination of small amounts of growth promoting substances
(d) It supports the hypothesis that IAA is auxin
Solution :
Correct option : A It demonstrated polar movements of auxins Darwin and his son observed that the coleoptiles of canary grass responded to unilateral illumination by growing towards the light source. This is called phototropism. They performed series of experiments which concluded that the tip of coleoptile was the site of transmittable influence that caused the bending of the entire coleoptile. F.W. Went isolated auxin from the tips of coleoptiles of oat seedlings and concluded that phototropism of oat seedlings occur. They also concluded that phototropism in the tips of coleoptiles is due to the polar movement of auxin in the stem.
So, the correct answer is ‘it demonstrated polar movements of auxins’.
