Systemic agents are substances that affect the entire body rather than just a specific area. They are often used in medicine to treat various conditions by entering the bloodstream and distributing throughout the body. Examples include certain medications, like antibiotics or chemotherapy drugs, which target infections or cancer cells. In agriculture, systemic agents refer to chemicals that are absorbed by plants and transported through their tissues. This allows them to control pests or diseases more effectively than surface treatments. Common examples include systemic insecticides and fungicides, which help protect crops from harmful organisms.