The respiratory system extends from the nose and upper airway to the alveolar surface of the lungs, where gas exchange occurs. Inhaled tobacco smoke moves from the mouth through the upper airway, ultimately reaching the alveoli. As the smoke moves more deeply into the respiratory tract, more soluble gases are adsorbed and particles are deposited in the airways and alveoli. The substantial doses of carcinogens and toxins delivered to these sites place smokers at risk for malignant and nonmalignant diseases involving all components of the respiratory tract including the mouth

TMV causes disease in tobacco plants.

Tobacco mosaic virus (TMV) is a highly contagious virus that primarily affects tobacco plants. TMV is a member of the Tobamovirus genus and is one of the most well-studied plant viruses. It was first identified in the late 19th century by Adolf Mayer and Dmitri Ivanovski.

Transmission of TMV:
- TMV can be transmitted through contact with infected plant material, such as sap, leaves, or even contaminated tools.
- It can also be spread by insect vectors, such as aphids, which feed on infected plants and then transmit the virus to healthy plants.

Symptoms of TMV infection:
- TMV infection leads to distinct symptoms in tobacco plants, including mosaic-like patterns on the leaves, stunted growth, and yellowing or mottling of the foliage.
- The virus affects the chloroplasts in plant cells, disrupting their normal functioning. This results in a reduced capacity for photosynthesis and ultimately affects the plant's overall health and productivity.

Impact of TMV on tobacco production:
- TMV is a significant concern for tobacco farmers as it can cause severe economic losses.
- Infected tobacco plants may have reduced leaf quality, resulting in lower market value.
- The virus can also lead to crop yield reduction and even complete loss in some cases.

Management and control:
- Preventing the introduction of TMV into tobacco fields is crucial for disease management.
- This can be achieved by using disease-free seeds, ensuring proper sanitation practices, and implementing strict quarantine measures.
- Pest management strategies, such as controlling insect vectors, can also help reduce the spread of TMV.
- Planting resistant tobacco varieties can provide some level of protection against TMV infection.

In conclusion, TMV is a plant virus that causes disease in tobacco plants. Its impact on the tobacco industry highlights the importance of disease prevention and control measures to minimize economic losses and ensure the production of healthy crops.