Which of the following phytohormones have similar effect on leaf senescence?

Options

A. ABA and ethylene
B. ABA and zeatin
C. ABA and GA
D. Ethylene and 2-4D

Answer

To determine which phytohormones have similar effects on leaf senescence, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Leaf Senescence**:
- Leaf senescence is the process of aging in leaves, characterized by biochemical changes that lead to the degradation of macromolecules. This process is crucial for the plant's lifecycle, especially during stress conditions.

2. **Identify Key Phytohormones**:
- The question involves identifying phytohormones that influence leaf senescence. The primary hormones to consider are:
- Abscisic Acid (ABA)
- Ethylene
- Other phytohormones (not specified in the question)

3. **Examine the Role of Abscisic Acid (ABA)**:
- ABA is known to be released from mature leaves during stress conditions such as water or mineral shortage. It promotes leaf senescence by facilitating the breakdown of leaf components, leading to nutrient and water depletion.

4. **Examine the Role of Ethylene**:
- Ethylene is a gaseous plant hormone that is also involved in the senescence process. It promotes yellowing of leaves and their eventual abscission (detachment from the plant).

5. **Compare Effects**:
- Both ABA and ethylene promote leaf senescence through similar mechanisms, such as nutrient mobilization and degradation of leaf tissues.

6. **Conclusion**:
- Based on the roles of ABA and ethylene in promoting leaf senescence, we can conclude that these two phytohormones have similar effects on this process.

### Final Answer:
The phytohormones that have similar effects on leaf senescence are **Abscisic Acid (ABA) and Ethylene**.

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