Which phenomenon inhibits the formation of tumors in the human body? Can plants also develop tumors? Explain.

The phenomenon that inhibits the formation of tumors in the human body is contact inhibition. In general, cell division stops when cells come in contact with neighbouring cells. This prevents unnecessary cell growth and helps maintain proper tissue structure. Cancer cells lose this property of contact inhibition and continue dividing uncontrollably, leading to the formation of tumors.

Plants can also develop tumours, but the process is different from that in animals. Plant cells have rigid cell walls, so they do not show contact inhibition in the same way as animal cells. Their growth is controlled mainly by plant hormones and specific growth regions.

A common example of a plant tumor is Crown gall disease, caused by the bacterium Agrobacterium tumefaciens. This bacterium enters the plant through cuts or wounds and transfers part of its DNA into the plant cells. The infected cells then start dividing rapidly and uncontrollably, forming swollen growths called galls, which resemble tumors.