Disease resistance mechanisms of vascular plants

Plant that contain all the components necessary to sustain life are extreme ly attractive to a vast array of fungi, bacteria, viruses and nematodes, Th e tissues of plants are resistant to invaders because of the presence of di fferent defense Systems. Resistance of vascular plants to diverse microorga nisms is based upon an arsenal of innate defense reactions that preexist in the plant and on inducible resistance mechanisms that are prosed;by tissue s of an infected plant. Some Of them are broadly effective against a wide r ange of invaders whereas others are specific for individual infectious agen ts. The innate mechanisms represented by anatomical structures and biochemi cal resistance mechanisms act to exclude invaders, Physical barriers, altho ugh very helpful, are not entirely effective in themselves. Other protectiv e mechanisms, the local defenses? such as lignification, hypersensitivity r esponse, papillae formation and Vascular occlusion restrict the invaders wi thin the infected tissues. The inducible protective mechanisms, mostly phyt oalexins and pathogenesis related proteins that act deep within the plant, destroy microorganisms that succeed in avoiding the innate immune defenses. Genetic manipulations to increase resistance of crop plants create an attr active prospect for food production.