Cytokinins which have specific effect in cytokinesis are modified forms of

Options

A. Cytosine
B. Adenine
C. Guanine
D. Thiamine.

Answer

**Step-by-Step Solution:**

1. **Understanding Cytokinins**: Cytokinins are a class of plant hormones that play a crucial role in promoting cell division, particularly during the process of cytokinesis, which is the division of the cytoplasm during cell division.

2. **Identifying the Options**: The question provides four options: cytosine, adenine, guanine, and thiamine. All of these are nitrogenous bases, which are fundamental components of DNA and RNA.

3. **Analyzing the Role of Cytokinins**: Cytokinins are specifically known for their role in stimulating cytokinesis. This means they are involved in the process where the cytoplasm of a parental cell divides into two daughter cells.

4. **Determining the Origin of Cytokinins**: To answer the question, we need to identify which nitrogenous base is modified to form cytokinins.

5. **Identifying the Correct Base**: Among the options, adenine is known to be the precursor for cytokinins. Cytokinins are modified forms of adenine, where additional carbon chains are added to the structure of adenine.

6. **Examples of Cytokinins**: Common examples of cytokinins derived from adenine include zeatin and kinetin. These compounds illustrate how adenine is modified to create cytokinins.

7. **Conclusion**: Based on the analysis, the correct answer to the question is that cytokinins, which have specific effects in cytokinesis, are modified forms of adenine.

**Final Answer**: Adenine

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