Plant defense systems: Mechanism of self-protection by plants against pathogens

Abstract

Plants respond against biotic and abiotic stresses through various morphological, biochemical, and molecular mechanisms. Biochemical mechanisms of self-defense against plant pathogens are widespread, extremely dynamic, and mediated by both direct and indirect defenses. Physical or morphological and biochemical mechanisms such as formation of different protective layers, modified natural openings, synthesis of secondary metabolites, and sometimes primary metabolites are known to protect to some extent from pathogens and other biotic and abiotic stresses. Both morphological and biochemical mechanisms are further of two types, namely, preexisting such as special morphological and biochemical characteristics of plants and postexisting which are developed in plants in response to different pathogenic attacks. Apart from the production of secondary metabolites and others, two types of resistance such as systemic acquired resistance and induced systemic resistance also have a significant role in the self-protection of plants against different pathogenic attacks.