Which of the following statements regarding gibberellins is incorrect?

Options

A. `GA_(3)` was one of the first gibberellins to be discovered
B. All GA are acidic
C. They increase the length of plant axis as in graphs sugarcanes etc.
D. They promote senescence.

Explanation

To determine which statement regarding gibberellins is incorrect, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Gibberellins**:
- Gibberellins are a class of plant hormones that promote growth and influence various developmental processes in plants. They are weakly acidic and have a specific chemical structure known as the gibbane ring.

2. **Analyzing the Options**:
- **Option A**: "GA3 was one of the first gibberellins to be discovered."
- This statement is **correct**. GA3 (Gibberellic Acid) was indeed one of the first gibberellins discovered and is widely studied.

- **Option B**: "All GA are acidic."
- This statement is also **correct**. Gibberellins are classified as weakly acidic growth hormones.

- **Option C**: "They increase the length of plant axis as in grafts, grapes, sugarcane, etc."
- This statement is **correct** with a minor correction. Gibberellins are known to promote elongation in plants, including grapes and sugarcane. However, the mention of "grafts" is misleading as grafting is a technique rather than a plant type that responds to gibberellins.

- **Option D**: "They promote senescence."
- This statement is **incorrect**. Senescence refers to the aging process in plants, which is typically associated with the loss of cell division and function. Gibberellins do not promote senescence; instead, they are known to delay it in certain contexts.

3. **Conclusion**:
- The incorrect statement regarding gibberellins is **Option D**: "They promote senescence."

### Final Answer:
The incorrect statement regarding gibberellins is: **They promote senescence.**

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