Cancer is a condition characterized by the uncontrolled division and spread of cells, which can lead to the formation of malignant tumors in animals. While plants do exhibit abnormal growths, these occurrences differ significantly from animal cancers in their underlying mechanisms and biological impacts. Understanding these distinctions helps clarify why the term “cancer” is not precisely applicable to plants, despite some visual similarities.
Understanding Abnormal Plant Growth
Fruits and other plants can develop unusual growths that might resemble tumors, often referred to as galls or hypertrophies. These abnormal formations typically result from external factors or internal genetic changes.
One common cause is infection by bacteria, such as Agrobacterium tumefaciens, which induces crown gall disease in many fruit crops like apples, pears, and grapes. This bacterium enters the plant through wounds and stimulates plant tissues to grow in a disorganized way, producing knobbly swellings on roots, stems, or trunks.
Viruses, fungi, environmental stressors, physical injuries, and genetic mutations can also contribute to these unusual growths, sometimes resulting in distorted tissues like fasciation. For instance, some viral infections can cause stunted growth or mottled leaves. These plant responses are generally localized, forming visible outgrowths that can vary in size and texture.
Key Differences from Animal Cancer
Despite the appearance of tumor-like growths, plant abnormal growths are fundamentally different from animal cancers. A primary distinction lies in the absence of metastasis, which is the spread of cancerous cells from their original site.
Plant cells are encased in rigid cell walls, which prevent them from migrating freely throughout the plant body like animal cancer cells. Plants also lack a circulatory system analogous to the bloodstream or lymphatic system found in animals, which is a common pathway for cancer metastasis.
Plant immune responses also operate differently from the complex adaptive immune systems of animals. While plants possess an innate immune system to detect pathogens and wall off infected areas, they do not mount a systemic response that actively seeks out and destroys abnormal cells throughout the organism.
Consequently, plant tumors rarely pose a widespread threat to the entire plant’s survival. They may disfigure the plant or divert nutrients, but the plant often manages to isolate the affected tissues, allowing the rest of the organism to continue growing.
Safety and Consumption of Affected Fruits
A common concern arises about the safety of eating fruits that display these abnormal growths. Generally, plant diseases, including those that cause galls or other tumor-like formations, are highly specific to plants and do not pose a direct health risk to humans when consumed.
The pathogens responsible for these plant conditions, such as bacteria or viruses, typically cannot infect or cause disease in humans. Most fungi, bacteria, and viruses that cause disease in plants are different from those that cause disease in humans and animals.
While direct infection is unlikely, it is always a good practice to wash fruits thoroughly before consumption to remove any dirt or surface microorganisms. If a fruit has a localized gall or abnormal growth, simply cutting away the affected portion often makes the rest of the fruit perfectly safe to eat.
Discarding severely impacted fruits is usually due to aesthetic or quality reasons, such as altered texture or taste, rather than a safety concern. However, it is important to avoid eating any fruit that appears moldy or rotten, as certain molds can produce toxic compounds.