Plants deficient of element zinc, show its effect on the biosynthesis of plant growth hormone

Options

A. abscisic acid
B. auxin
C. cytokinin
D. ethylene

Explanation

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the effect of zinc deficiency on the biosynthesis of plant hormones. Specifically, we need to identify which plant hormone is affected by the lack of zinc.

2. **Identifying Plant Hormones**: Plant hormones, also known as phytohormones, are substances that regulate various physiological functions in plants, including growth, differentiation, and abscission. The major types of plant hormones include auxins, cytokinins, gibberellins, abscisic acid, and ethylene.

3. **Zinc's Role in Hormone Synthesis**: It is important to know that certain elements, including zinc, play a crucial role in the biosynthesis of specific plant hormones.

4. **Analyzing the Options**: The options provided in the question include various plant hormones. We need to determine which of these hormones requires zinc for its biosynthesis:
- **Abscisic Acid**: Does not require zinc.
- **Auxin**: Requires zinc for its biosynthesis.
- **Cytokinin**: Does not require zinc.
- **Ethylene**: Does not require zinc.

5. **Conclusion**: Since auxin is the only hormone listed that requires zinc for its biosynthesis, we conclude that a deficiency of zinc will affect the synthesis of auxin. This, in turn, can lead to various physiological effects in the plant, such as impaired apical dominance and phototropism.

6. **Final Answer**: The plant hormone that is affected by zinc deficiency is **Auxin**.