Question

The bioassay of auxin is
(a)Avena curvature test
(b)Callus formation
(c)Culture of fungus
(d)Seed dormancy

Answer 1

Hint: This experiment was first conducted by Guthrie in the year 1940. He used rose plants for his experiment. This experiment is for the testing of biological activity like the growth response of a substance by employing a living material like a plant or plant part.

Complete answer:
The bioassay of auxin is the Avena curvature test. Auxin bioassay is a quantitative test as it measures the concentration of auxin to produce the effect and the amount of effect produced. In this test, the shoot tip of a plant is removed and placed on an agar block so that the auxin can easily diffuse into the agar. The agar piece is cut after some time and is placed on one side of the coleoptile of the plant from where the shoot tip was taken off for the experiment. As a result, an angle of curvature is obtained, so named the Avena curvature test.

Additional Information: -In Avena Curvature Test, a 10-degree curvature is produced by an auxin concentration of 150 µg/liter at 25 degrees Celsius and ${ 90 }$% relative humidity.
-After producing the curvature the auxin from a shoot tip or any other plant organ is allowed to diffuse in a standard size agar block. Auxin can also be dissolved directly in agar.
-After some time it is observed that 15-30 mm long oat coleoptile grown in the dark is held vertically over water. Without injuring the primary leaf 1 mm tip of coleoptile is removed.
-After 3 hours a second decapitation is carried out for a distance of 4 mm. The primary leaf is now pulled loose and the agar block is supported against it at the tip of the decapitated coleoptile.
-The coleoptile is found to have bent after 90-110 minutes. The curvature is measured.
-Callus formation is forming a connecting bridge across a bone fracture during the repair.
-Culture of fungus is used to determine the presence of fungus in the area of the body.
-Seed dormancy is a property that defines the environmental conditions in which the seed can germinate.
So, the correct answer is,’ Avena curvature test’.

Note: -Auxin is synthesized in shoot apices, leaf primordia, and developing seeds from the amino acid tryptophan. Auxin passes from the shoot tip to the region of elongation. The Movement of auxin is always polar.
-Avena Curvature Test is based upon the experiments done by Went in 1928.
-The test can measure auxin up to 300 pg/liter.
-A tryptophan independent pathway has also been discovered recently.