Beijernick concluded that the cause of tobacco mosaic disease was not a filtrate toxin because

Options

A. the infectious agent could be crystallized
B. the infections agent could be crystallized
C. the infectious agent reproduced and could be passed on from a plant infected with filtered sap
D. the sap was infectious even though it was filtered to remove bacterias.

Answer

To solve the question regarding Beijernick's conclusion about the cause of tobacco mosaic disease, we will break down the reasoning step by step.

### Step-by-Step Solution:

1. **Understanding the Disease**:
- Tobacco mosaic disease is caused by a virus that infects tobacco plants. It leads to characteristic mottling and discoloration of the leaves.

2. **Beijernick's Experiment**:
- In 1898, M.W. Beijernick conducted experiments using extracts from infected tobacco plants. He found that this extract could cause the same disease in healthy plants.

3. **Contagium Vivum Fluidum**:
- Beijernick referred to the infectious fluid extracted from the infected plants as "contagium vivum fluidum," which translates to "infectious living fluid." This indicated that the fluid contained a living infectious agent.

4. **Filtrate Toxin Hypothesis**:
- Initially, it was thought that the cause of the disease could be a toxin released by the infected plants. However, Beijernick's findings suggested otherwise.

5. **Key Findings**:
- Beijernick demonstrated that the infectious agent could reproduce and could be passed on from plants infected with the filtered sap. This indicated that the agent was not merely a toxin, as toxins do not reproduce.

6. **Crystallization of Viruses**:
- Although viruses can be crystallized (as later shown by W.M. Stanley in 1935), this was not the basis for Beijernick's conclusion. He focused on the infectious nature of the fluid rather than its crystallizable properties.

7. **Size of Infectious Agents**:
- Beijernick also noted that the sap remained infectious even after being filtered through bacteria-proof filters. This demonstrated that the infectious agents (viruses) were smaller than bacteria, which allowed them to pass through these filters.

8. **Conclusion**:
- Beijernick concluded that the cause of tobacco mosaic disease was not a filtrate toxin because the infectious agent could reproduce and was able to infect healthy plants even after being filtered, indicating it was a virus rather than a toxin.

### Final Answer:
Beijernick concluded that the cause of tobacco mosaic disease was not a filtrate toxin because the infectious agent reproduces and could be passed on from plants infected with the filtered sap.