Question

The Avena curvature is used for bioassay of
(1) Ethylene
(2) GA3
(3) ABA
(4) lАА

Answer 1

Hint: Avena curvature is a bioassay or it is the quantitative method of obtaining 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 based on the polar transport of the auxins in the coleoptile of the Avena plant.
Where the auxin is applied on one side of the cut coleoptile of the Avena, so that applied auxin is diffused down to only one side, so that only one side is grown, that causes the coleoptile to curve.
When coming to the procedure first the Avena grains are germinated and grown in complete darkness. The seedlings of Avena are exposed to short periods of red light two days after germination.
In this method, the seedlings with roots of about 2mm in length, now the seedlings are planted in water in glass holders by water culture method.
So later the germinated 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 coleoptile, an agar block of 1mm size with injected auxin is placed or stumped.
After some time that is about 3 hours a second decapitation of the coleoptile of 4mm is made to remove the tip which might have regenerated and at the sometimes first leaf of the seedling is pulled so that its connection from the base is broken
Now the agar block contain 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 curvature is directly proportional to the concentration of auxin 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 liter.

So, the correct option is D.

Note: Avena curvature test is for auxin regulators in that plants, 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.