The key difference between the circulatory system of the human body (or that of any animal) and the water transport system in a plant is that of the underlying forcing mechanism. In case of human body, the circulation of fluids takes place due to the presence of heart, which acts as a pump. In comparison, there is no pumping mechanism in a plant and the water movement occurs by capillary pressure against the gravity.
As per the attached figures, a difference between system B of human body and the water transport system in plants is the directional movement.While the water transport is unidirectional and flows from roots to stems to leaves; system B of human body has bi-directional flow with system C and all other body parts, and exchanges gases and other materials. System B receives gases X and Y from System C and all parts of the body, respectively, while supplying materials to these components.