Question

The Avena curvature is used for bioassay of
A. ABA
B. $GA_3$
C. IAA
D. Ethylene

Answer 1

Hint: Guthrie (1940) found that the contents of auxin increased in tubers that had ended their dormancy by ethylene chlorohydrin therapy using an Avena bioassay.

Complete Answer:
- Avena is a kind of grass family Eurasian and African plants. Collectively referred to as oats some plants have been grown as a source of food for humans and animals for thousands of years. It is common across Europe, Asia and northwest Africa.
- In many parts of the world many plants have become naturalistic and are considered to compete with the production of crops as invasive weeds. While they are small and difficult to harvest in most species, all oats seeds are edible. Coleoptile is protective covers of emerging shoots in grasses in which some shoot apex and leaf primordial of monocot remains enclosed.
- The geo-curvature test from Avena is a bioassay for growth regulators of auxin type. Etiolated oat coleoptiles are used and the measurement is done under diffuse daylight in special perspex trays.
- The coleoptiles are arranged in grooves in 4 series of 6 coleoptiles each and are cut to 10mm in size with intact primary leaves. The test substance is applied on an agar band which covers only the lower half of each series' apical cut surfaces. The coleoptile cylinders have been printed on a 30mm photographic film after a 4 hour stay in the dark in the humid Petri dishes. The curvatures are determined by an expanded shadow graph projection.

Thus, the correct answer is option C. i.e., IAA.

Note: Different organic tests are performed to assess the concentration in plants of the auxin hormone, like avena coleoptile test, curvature of the split pea stem and root cress testing. The avena coleoptile test can calculate the angle of the curvature of a decapitated coleoptile.