Plant Pathology Perfect Paragraph

Plant pathology and animal pathology differ greatly. While animals have an adaptive immune system that allows them to generate defences as new infections arise, plants do not. Plant pathogens come in three general classes, necrotrophs, biotrophs, and hemibiotrophs. Necrotrophs are organisms that kill plant tissue through enzymes and tend to be generalists that can infect many plants. Biotrophs are parasitic organisms which, in order to complete their life cycle, require host survival. These pathogens will cause slowed senescence and build haustorums that usurp metabolites from plant epithelial cells. Hemibiotrophs are biotrophs in the first part of their life cycle and necrotrophs during the second part of their life cycle.. Pathogens have three main ways of egress into a plant. They can either directly penetrate the plant through the use of a pilus or penetration peg, enter through pre-existing openings such as stomata, or enter through wounds. Plants have a series of defencive strategies to resist infection. The first line of defence is physical, plants have a waxy cuticle and cell walls that aim to prevent direct access to the cytoplasm of plant cells. In addition to a physical barrier, plants produce toxins to kill certain pathogens or create papillae in the epithelial cell walls to prevent pathogenic penetration. The second line of defence is specific, and is known as resistance (R) gene immunity that follows a gene for gene model. Pathogens produce effectors that mask their presence, and plants produce proteins that are able to detect effectors. If a plant can detect an effector then it will engage a hypersensitive response that involves immediate cell death around the infected area. At the cost of a few cells, this method enables the plant to prevent the infection from spreading.