The organizatin of shoot apex into tunica and corpus is determined largely on the basis of
(a) Regions of meristematic activity
(b) Planes of cell division
(c) Rate of shoot tip growth
(d) Rate of cell division

Options

A. Regions of meristematic activity
B. Planes of cell division
C. Rate of shoot tip growth
D. Phase of cell division

Answer

To solve the question regarding the organization of the shoot apex into tunica and corpus, we need to analyze the options provided and understand the underlying concepts.

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the basis for the organization of the shoot apex into tunica and corpus. This refers to a specific theory in plant anatomy known as the tunica-corpus theory.

2. **Identifying Key Terms**:
- **Tunica**: The outer layer of cells in the shoot apex.
- **Corpus**: The inner layer of cells in the shoot apex.
- **Meristematic Activity**: Refers to the regions where cells are actively dividing.
- **Planes of Cell Division**: The orientation in which cells divide (e.g., horizontal, vertical).
- **Rate of Cell Division**: How quickly cells are dividing in a given area.

3. **Analyzing the Options**:
- **(a) Regions of meristematic activity**: While this is relevant, it does not specifically determine the organization into tunica and corpus.
- **(b) Planes of cell division**: This relates to how cells divide but does not directly address the organization into tunica and corpus.
- **(c) Rate of shoot tip growth**: This is more about overall growth rather than the specific organization of cell layers.
- **(d) Rate of cell division**: This option directly relates to how the tunica and corpus are formed based on the rate at which cells are dividing in these regions.

4. **Conclusion**: Based on the analysis, the organization of the shoot apex into tunica and corpus is determined largely by the **rate of cell division**. Therefore, the correct answer is **(d) Rate of cell division**.

### Final Answer:
(d) Rate of cell division

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