ABSTRACT
Plant toxicants may include endogenous substances such as secondary plant metabolites (e.g., phenolics, alkaloids, flavonoids) or xenobiotic compounds. Xenobiotics (from Greek words meaning ‘‘foreign chemicals’’) are natural or synthetic substances that cannot be utilized by plants for energy-yielding processes. Chemicals classified commonly as xenobiotics include pesticides and air pollutants. Higher plants are exposed to xenobiotics either deliberately, i.e., pesticide application, or accidentally, as a result of industrial emissions or misuses of agrochemicals.
