Heterocyst :

Options

A. is a botanical enigma performing variety of functions
B. Has PS-I and PS-II
C. Has two polar nodules if terminally present
D. is present in Oscillatoria

Answer

**Step-by-Step Solution:**

1. **Understanding Heterocysts**: Heterocysts are specialized cells found in certain filamentous cyanobacteria. They are primarily involved in nitrogen fixation, which is the conversion of atmospheric nitrogen into a form that can be utilized by living organisms.

2. **Analyzing the Options**:
- **Option 1**: "A botanical enigma performing a variety of functions." This option correctly describes heterocysts as they perform the crucial function of nitrogen fixation in cyanobacteria.
- **Option 2**: "It has PS1 and PS2." This option is incorrect because heterocysts do not contain photosystems I and II (PS1 and PS2) as they are not involved in photosynthesis.
- **Option 3**: "It has two polar nodules if terminally present." This option is also incorrect as heterocysts do not have polar nodules.
- **Option 4**: "It is present in Oscillatoria." This option is misleading. While Oscillatoria is a type of cyanobacteria, not all cyanobacteria, including Oscillatoria, contain heterocysts.

3. **Conclusion**: Based on the analysis, the most accurate option is Option 1, which states that heterocysts are a botanical enigma performing a variety of functions, primarily nitrogen fixation.

**Final Answer**: Option 1 is correct.

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