ABSTRACT
Understanding how plants defend themselves from pathogens and herbivores is essential in order to protect human food supply and develop highly disease-resistant plant species. Plants often wait until pathogens are detected before producing toxic chemicals or defense-related proteins because of the high energy costs and nutrient requirements associated with their production and maintenance. Plants have developed multiple layers of sophisticated surveillance mechanisms that recognize potentially dangerous pathogens and rapidly respond before those organisms have a chance to cause serious damage. These surveillance systems are linked to specific pre-programmed defense responses. The first line of defence in plants is present in its surface. If the pathogen succeeds in penetration; it encounters pre-existing internal structural barriers. Epidermis is the first layer of living host cells that comes in contact with attacking microbes. In many hosts parasite interactions, the pathogen produces host specific toxins, which are responsible for symptoms and disease development.
