In plants auxin synthesis. with high concentration occurs in

Options

A. cortex of leaves
B. phloem cells
C. shoot tip
D. root tip

Answer

### Step-by-Step Solution:

1. **Understanding Auxin**: Auxin is a plant hormone that plays a crucial role in regulating plant growth and development. It is primarily involved in processes such as cell elongation, apical dominance, and root formation.

2. **Location of Auxin Synthesis**: Auxin is synthesized in the meristematic tissues of plants. These tissues are regions of active cell division and are typically found at the tips of roots and shoots.

3. **Identifying High Concentration Areas**: The highest concentrations of auxin are found in the shoot tips and root tips. This is because these areas contain the most active meristematic tissues, which are responsible for growth.

4. **Analyzing the Options**:
- **Cortex of Leaves**: While auxin may be present here, it is not synthesized in high concentrations.
- **Phloem Cells**: Phloem is primarily involved in the transport of nutrients and does not synthesize auxin.
- **Shoot Tip**: This is one of the primary sites of auxin synthesis and has high concentrations.
- **Root Tip**: This is another primary site of auxin synthesis and also has high concentrations.

5. **Conclusion**: Based on the analysis, the correct answer to the question is that auxin synthesis with high concentration occurs in both the shoot tip and the root tip.

### Final Answer:
The correct options are the **shoot tip** and the **root tip**.

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