Biosynthesis of cytokinin takes place via

Options

A. Mevalonic acid cycle
B. Citric acid cycle
C. Calvin cycle
D. `C_(4)` cycle.

Answer

To answer the question regarding the biosynthesis of cytokinin, we will follow these steps:

### Step 1: Identify the Options
The question provides four options for the biosynthesis pathway of cytokinin:
- A) Mevalonic acid cycle
- B) Citric acid cycle
- C) Calvin cycle
- D) C4 cycle

### Step 2: Analyze Each Option
- **Mevalonic Acid Cycle**: This cycle is known for the synthesis of isoprenoids, which include gibberellins and cytokinins. It converts mevalonic acid into isopentyl pyrophosphate, which is a precursor for cytokinin synthesis.

- **Citric Acid Cycle**: This cycle primarily deals with energy production and does not directly synthesize cytokinins.

- **Calvin Cycle**: This cycle is involved in photosynthesis and the fixation of carbon dioxide, not in the biosynthesis of cytokinins.

- **C4 Cycle**: This cycle is also related to photosynthesis, specifically in certain plants that have adapted to high light and temperature conditions, and does not synthesize cytokinins.

### Step 3: Determine the Correct Answer
From the analysis, the **Mevalonic Acid Cycle** is the only pathway that directly leads to the synthesis of cytokinins. Therefore, the correct answer is option A.

### Step 4: Explain the Biosynthesis Process
The biosynthesis of cytokinins begins with mevalonic acid, which is converted into isopentyl pyrophosphate. This compound is then transformed into isopentyl adenine, which ultimately leads to the formation of cytokinins.

### Conclusion
The biosynthesis of cytokinin takes place via the **Mevalonic Acid Cycle**.

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