Final answer:
Plant viruses mainly enter the host plant through wound sites, often requiring mechanical damage for the virus to access the plant's interior cells.
Step-by-step explanation:
Plant viruses enter the host plant primarily via wound sites. These wounds can be caused by various factors such as weather, insects marring the surface, human activities, or other types of physical damage. Unlike animal viruses that may use specific receptors for entry, plant viruses often rely on mechanical damage to bypass the plant's protective cell wall. This entry can be facilitated through vectors such as insects or by direct contact with infected plant sap. Moreover, plant offspring can sometimes inherit viruses from their parents, which is referred to as vertical transmission.