The presence of auxins in a solution could be tested by
(a) Avena sativa stem tip test
(b) Carbon tetrachloride test
(c) Iodine test
(d) Defoliation test

Options

A. Avena sativa stem tip test
B. Carbon tetrachloride test
C. Iodine test
D. Defoliation test

Answer

To determine the presence of auxins in a solution, we can follow these steps:

1. **Understand the Concept of Auxins**: Auxins are a class of plant hormones that play a crucial role in the regulation of plant growth and development. They are involved in processes such as cell elongation, apical dominance, and root formation.

2. **Identify the Testing Method**: Among the options provided, we need to identify which one is specifically used to test for the presence of auxins. The Avena sativa stem tip test, also known as the Avena curvature test, is a well-established bioassay for auxins.

3. **Describe the Avena Sativa Stem Tip Test**: In this test, the tip of an Avena sativa (oat) plant is removed. The tip is then placed on one side of the coleoptile (the protective sheath covering the emerging shoot). The auxins produced in the tip will diffuse into the coleoptile and cause differential growth, leading to curvature towards the side where the tip was placed. This curvature indicates the presence of auxins.

4. **Evaluate Other Options**:
- **Carbon Tetrachloride Test**: This is not a method for testing auxins.
- **Iodine Test**: This is typically used to test for the presence of starch, not auxins.
- **Defoliation Test**: This involves the removal of leaves and is not a specific test for auxins.

5. **Conclusion**: Based on the above analysis, the correct answer to the question is (a) Avena sativa stem tip test.