Function of heterocysts in cyanobacterium

Options

A. Perennation
B. Assimilation
C. Spore production
D. Nitrogen fixation

Answer

### Step-by-Step Text Solution:

1. **Definition of Heterocyst**: Heterocysts are specialized cells found in certain cyanobacteria. They are differentiated cells that play a crucial role in the nitrogen fixation process.

2. **Appearance of Heterocyst**: Heterocysts typically appear pale yellow and have a thick cell wall. This structural adaptation helps protect the nitrogen-fixing enzymes from the oxygen produced during photosynthesis.

3. **Function of Heterocyst**: The primary function of heterocysts is to facilitate nitrogen fixation. This is the process where atmospheric nitrogen (N₂) is converted into ammonia (NH₃), a form that can be utilized by plants.

4. **Trigger for Heterocyst Formation**: Heterocysts are formed in response to a lack of fixed nitrogen in the environment. When cyanobacteria detect low levels of nitrogen, they differentiate some of their cells into heterocysts to enhance their ability to fix atmospheric nitrogen.

5. **Example of Cyanobacteria with Heterocysts**: An example of a cyanobacterium that produces heterocysts is Nostoc. This organism showcases the ability to fix nitrogen effectively through its specialized cells.

6. **Conclusion**: Therefore, the function of heterocysts in cyanobacteria is primarily nitrogen fixation, allowing these organisms to thrive in nitrogen-poor environments.