Induction of cell division activity and delay in senescence is caused by

Options

A. gibberellin
B. auxin
C. cytokinin
D. ethylene

Explanation

**Step-by-Step Solution:**

1. **Understanding the Terms:**
- **Induction of Cell Division Activity:** This refers to the process of stimulating cells to divide and multiply.
- **Delay in Senescence:** Senescence is the process of aging or deterioration in cells. Delaying senescence means prolonging the life span of cells and preventing them from aging prematurely.

2. **Identifying the Hormones:**
- The question asks which plant hormone is responsible for both inducing cell division and delaying senescence.
- The options provided are: gibberellin, auxin, cytokinin, and ethylene.

3. **Analyzing Each Hormone:**
- **Cytokinin:** This hormone is known to promote cell division and delay senescence in plants. It helps in the proliferation of cells and maintains the vitality of leaves.
- **Gibberellin:** Primarily involved in promoting growth, particularly in stems and fruits, but not specifically in cell division or delaying senescence.
- **Auxin:** Mainly responsible for cell elongation and growth, particularly in the tips of roots and shoots, but does not significantly delay senescence.
- **Ethylene:** This hormone is associated with the ripening of fruits and does not play a role in cell division or delaying senescence.

4. **Conclusion:**
- Based on the analysis, the hormone responsible for the induction of cell division activity and the delay in senescence is **Cytokinin**.

**Final Answer: Cytokinin**

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