Select the correct statements (s) regarding auxins.

Options

A. Auxins promote root growth only at extermely low concentrations and they inhibit root growth at higher concentrations.
B. Concentration of auxins which is inhibitroy to root growth causes initiation of adventitions roots from the nodes or basal regions of stem.
C. Auxins such as NA A and IBA are used to induce rooting in stem cuttings.
D. All of these

Answer

To solve the question regarding the correct statements about auxins, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Auxins**: Auxins are plant hormones that play a crucial role in the growth and development of plants. They are involved in various processes such as cell elongation, root formation, and response to light and gravity.

2. **Analyze Each Statement**:
- **Statement 1**: "Auxins promote root growth only at extremely low concentration and they inhibit root growth at higher concentration."
- **Analysis**: This statement is correct. Auxins indeed promote root growth at low concentrations, while higher concentrations can inhibit root growth.

- **Statement 2**: "Concentration of auxins which is inhibitory to root growth cause initiation of advantageous root from the nodes and the basal region of stem."
- **Analysis**: This statement is also correct. High concentrations of auxins can lead to the initiation of advantageous roots from nodes and the basal region of the stem.

- **Statement 3**: "Auxin such as NAA and IBA are used to induce rooting in stem cutting."
- **Analysis**: This statement is correct as well. NAA (Naphthalene acetic acid) and IBA (Indole-3-butyric acid) are auxins commonly used to promote rooting in stem cuttings.

- **Statement 4**: "All of the above statements are correct."
- **Analysis**: Since all the previous statements are correct, this statement is also correct.

3. **Conclusion**: All the statements regarding auxins are correct. Therefore, the answer to the question is that all of the statements are correct.

### Final Answer:
All the statements regarding auxins are correct.

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