Systemic Acquired Resistance (SAR) is a long-lasting, broad-spectrum defence response that can develop throughout a plant after a localized infection. Signals from the affected tissue activate defence responses in uninfected parts of the plant, leaving them better prepared to resist subsequent pathogen attack.
SAR is strongly associated with salicylic acid signalling and increased production of pathogen-related defence proteins. It is a form of induced defence rather than a continuously active constitutive defence.
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