The substance known as the blood of the plant is called sap. Sap is a fluid that circulates through the vascular system of a plant, carrying essential nutrients, hormones, and water to various parts. In trees, the most well-known type of sap is xylem sap, which transports water and minerals from the roots to the leaves. Another type is phloem sap, which carries sugars and other metabolic products downward from the leaves to roots and other parts of the plant. Sap plays a crucial role in maintaining the plant's health, growth, and overall functioning, similar to how blood functions in animals.