Question

Avena coleoptile auxin is
A.IBA
B.Indole 3-lactic acid
C.Indole 2-acetic acid
D.Indole 3-acetic acid

Answer 1

Hint: Avena curvature is defined as a bioassay or it is the quantitative method of producing the curvature of the tip of the Avena or oat plant when the plant is subjected to external stimuli by endogenous growth substances of the plants.

Complete answer:
Avena curvature test is dependent on the polar transport of the auxins in the coleoptile of the Avena plant. Where the auxin is used and applied on one side of the cut coleoptile of the Avena, so that applied auxin goes and moves down to only one side, so that only one side is grown, that causes the coleoptile to curve.
When we see the procedure first the Avena grains are germinated and grown in complete darkness. The seedlings of Avena are diffused to short periods of red light two days after germination. In this method, the seedlings with roots that are 2mm in length, now the seedlings are planted in water in glass holders by water culture method. So later the germinated and accumulating seedling with the straight coleoptile is selected, after they are selected the tips of the coleoptile about 1mm are removed.
In the area of the removed-out coleoptile, an agar block of 1mm size with injected auxin is stumped. After some time say about 3 hours a second decapitation of the coleoptile of 4mm is made to remove the tip which may have regenerated and at the sometimes first leaf of the seedling is pulled so that its connection from the base is degenerated
Now the agar block that carry auxin is placed on one side of the coleoptile which was cut down, and the primary leaf which was projecting may give support to the block, so we can observe that coleoptile growing in the form of curvature, and the angle of curvature is measured by drawing the vertical line and also the line along the curvature.
The degree of bending is directly proportional to the concentration of auxin y that was injected in the agar block, if the indole acetic acid is used, then the amount of curvature that is produced is 0.2mg/ per litre.

Hence, the correct answer is option (D)

Note: Avena curvature test is performed auxin regulators in that plants, at the spot where these plants are grown and the coleoptile are removed and auxin containing agar blocks are placed, and this causes polar movement of auxin and it causes the growth of coleoptile in a curved manner.