SYSTEMIC ACQUIRED RESISTANCE Meaning and
Definition
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Systemic acquired resistance (SAR) refers to a plant's inducible defense response against pathogens, which is initiated by a localized infection but is effective against subsequent infections in distant parts of the plant. SAR is a broad-spectrum resistance mechanism that involves a series of physiological and molecular changes that enhance the plant's ability to resist diseases caused by a diverse range of pathogens.
This defense response is triggered by the recognition of pathogen-associated molecular patterns (PAMPs) by the plant's pattern recognition receptors (PRRs), leading to the activation of signaling cascades. These cascades activate the transcription of specific genes involved in SAR, resulting in changes in the plant's metabolism and physiology.
SAR is characterized by the synthesis and accumulation of antimicrobial compounds, such as phytoalexins, proteins, and enzymes that inhibit pathogen growth. It also involves the reinforcement of cell walls, which physically prevents the pathogen's penetration into plant cells. Additionally, SAR induces the production of signaling molecules, including salicylic acid, which act as systemic signals to communicate the presence of pathogens to other parts of the plant, priming them for potential attacks.
Overall, SAR represents a systemic and long-lasting defense response that provides enhanced resistance against a wide range of pathogens. It enables plants to efficiently defend themselves against future infections by mounting a coordinated and robust defense, ultimately promoting plant survival and health.
