What does the decay caused by root rot primarily affect?

Root rot primarily affects the outer surface of the roots and the surrounding soil because it involves the decay of plant roots due to the presence of pathogens in overly saturated conditions. This decay compromises the root system's ability to take up water and nutrients effectively, which in turn impacts the entire plant. The initial damage occurs at the roots where the pathogens invade and decompose the root tissue, leading to a deterioration of the root structure itself.

While it's true that the health of the roots can ultimately affect the overall plant's health, including leaves, flowers, and the internal stem structure, those parts are indirectly impacted by the problems that originate at the root level. When roots are decayed, the plant cannot transport essential nutrients or water, causing symptoms like wilting, yellowing leaves, and stunted growth, which may eventually affect the above-ground portions of the plant. However, the primary site of infection and decay that leads to these effects is specifically the root system and its immediate environment in the soil.