What type of growth is often seen at the site of an old wound on a tree?

Response growth is the correct choice because it refers to the growth that occurs in response to damage or stress factors, such as an old wound on a tree. When a tree experiences injury, such as from a cut or disease, it initiates a biological response to heal itself. This healing process can involve the formation of new tissues, like callus or lignified tissue, to protect the underlying vascular system and restore structural integrity.

In the context of an old wound, the tree generates this response growth around the affected area as a means of compartmentalizing the injury and preventing further decay or invasion by pathogens. This adaptive mechanism is crucial for the tree's survival and overall health, allowing it to manage stresses and recover from physical damage.

The other choices, while related to tree physiology, do not specifically correlate with the healing process initiated by an old wound. Fruiting body formation is associated with fungal infections, root expansion pertains to below-ground growth in response to various factors, and leaf shedding is a seasonal or stress response but does not directly relate to wound healing.