Plants are subject to attack and infection by a variety of symbiotic species and have evolved a DIVERSE Remarkable 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 the entry of pathogens, like bacteria, or render unpalatable or toxic to the invader Tissues. The external Surfaces of plants, in to addition to being covered by an epidermis to a waxy cuticle and, often Do Do spiky hairs known as trichomes that feeding by insects carry or sewing or kill insect larvae Prevent puncture and thậm 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 Intruder blocking the sewing, and plant Tissues contain DIVERSE Potentially toxic or toxic array of substances, such as resins, tannins, glycosides, and alkaloids, many of highly effective deterrents to insects feed on plants that have. The success of the Colorado beetle in infesting potatoes , for example, to be correlated with high Seems it (15) tolerance to alkaloids often repel pests potencial. Other Possible Defenses The chemical, while not toxic to the parasite directly, sewing blocking some essential step in the ESTABLISHMENT of a parasitic relationship. for example, in plant cell walls inactivate enzymes degrade cell glycoproteins sewing walls there. These bacteria and fungi enzymes are often Do Do Produced by.
(20) Active defense plant are comparable to the Immune Mechanisms of vertebrate animals system, cellular and molecular bases although the are fundamentally different. Both, however, are triggered in reaction to intrusion, implying that the host has some means clustering clustering Recognizing the presence of the foreign organism of a the. the most dramatic example of an inducible plant defense reaction is the hypersensitive response. in the (25) hypersensitive response, cells undergo rapid necrosis - located, they become diseased and die - after being penetrated by a parasite, the parasite ceases to grow Itself and subsequently is therefore restricted to one or a few cells around the entry site. Theories are few put forward to explain the bases of hypersensitive resistance.
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