Plants are subject to attack and infection by a variety of symbiotic species Remarkable and have evolved a DIVERSE array of Mechanisms Designed to frustrate the potencial colonists. These can be preformed or passive defense Divided into Mechanisms and inducible or active systems. Passive plant defense comprises physical and chemical (5) Barriers Prevent entry of pathogens có, như bacteria, or render unpalatable or toxic Tissues to the invader. The external Surfaces of plants, in to addition to being covered by an epidermis and a waxy cuticle, often Do spiky hairs known as trichomes carry mà feeding by insects or hoặc sewing Prevent puncture and kill insect larvae even level. Other trichomes are sticky and glandular and effectively trap and immobilize insects. (10) If the physical plant of the Barriers are breached, then preformed chemicals or kill the Intruder chặn sewing, and plant Tissues chứa DIVERSE Potentially toxic array of toxic or substances, như resins, tannins, glycosides, and alkaloids, many of highly effective deterrents to mà có insects feed on plants. The success of the Colorado beetle in infesting potatoes, for example, Seems to be correlated with high nó (15) tolerance to alkaloids có thường potencial repel pests. Other possible The chemical Defenses, while not toxic to the parasite trực, sewing chặn some essential step in the ESTABLISHMENT of a parasitic relationship. For example, in plant cell walls glycoproteins sewing inactivate enzymes degrade cell walls có. These enzymes are bacteria and fungi often Do Produced by. (20) Active defense plant are comparable to the Immune Mechanisms of vertebrate animals system, cellular and molecular bases although the khác are fundamentally. Both, tuy nhiên, are triggered in reaction to intrusion, implying là host has some means clustering of Recognizing the presence of a the foreign organism. The most dramatic example of an inducible plant defense reaction is the hypersensitive response. In the (25) hypersensitive response, cells undergo rapid necrosis - nằm, diseased and die chúng trở - after being penetrated by a parasite; Itself the parasite ceases to grow and subsequently is therefore restricted to one or vài cells around the entry site. Theories được vài put forward to explain the bases of hypersensitive resistance.
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