Who demonstrated that the extract of the infected plants of tobacco could cause infection in healthy plants ?
(a) Pasteur
(b) M.W. Beijerinek
(c) D.J. Ivanowsky
(d) W.M. Stanley

Options

A. Pasteur
B. M.W. Beijerinek
C. D.J. Ivanowsky
D. W.M. Stanley

Answer

To solve the question "Who demonstrated that the extract of the infected plants of tobacco could cause infection in healthy plants?", we will analyze the options provided and identify the correct answer step by step.

### Step 1: Understand the Question
The question asks about the scientist who demonstrated that an extract from infected tobacco plants could infect healthy plants. This relates to the study of plant diseases and the causative agents behind them.

### Step 2: Analyze the Options
The options provided are:
(a) Pasteur
(b) M.W. Beijerink
(c) D.J. Ivanowsky
(d) W.M. Stanley

### Step 3: Recall Relevant Information
- **Pasteur**: Known for his work in microbiology and vaccination but not specifically for plant viruses.
- **M.W. Beijerink**: A Dutch microbiologist who worked on viruses, particularly the tobacco mosaic virus. He demonstrated that the extract from infected tobacco could cause infection in healthy plants.
- **D.J. Ivanowsky**: He was the first to discover that the causative agent of tobacco mosaic disease could pass through a filter that retained bacteria, but he did not demonstrate the infectivity of the extract.
- **W.M. Stanley**: He crystallized the tobacco mosaic virus but did not perform the experiment regarding the infectivity of the extract.

### Step 4: Identify the Correct Answer
Based on the analysis, the correct answer is **(b) M.W. Beijerink**. He demonstrated that the extract from infected tobacco plants could infect healthy plants, coining the term "contagium vivum fluidum" to describe the infectious agent.

### Final Answer
The correct answer is **(b) M.W. Beijerink**.

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