SYSTEMIC ACQUIRED-RESISTANCE

This paper examines induced resistance (SAR) in plants against various insect and pathogenic invaders. SAR confers quantitative protection a gainst a broad spectrum of microorganisms in a manner comparable to im munization in mammals, although the underlying mechanisms differ. Disc ussed here are the molecular events underlying SAR: the mechanisms inv olved in SAR, including lignification and other structural barriers, p athogenesis-related proteins and their expression, and the signals for SAR including salicylic acid. Recent findings on the biological role of systemin, ethylene, jasmonates, and electrical signals are reviewed . Chemical activators of SAR comprise inorganic compounds, natural com pounds, and synthetic compounds. Plants known to exhibit SAR and induc ed systemic resistance are listed.