Plants defensive mechanisms

The seeds and vegetative part of plants contain several sorts of inhibitors of insect, fungal, mammalian, and endogenous proteinases. These inhibitors may be involved in plant defense mechanisms against predators and participate in the development of the plant itself. Peptidic proteinase inhibitors are well studied in the families Fabaceae, Poaceae, Asteraceae, and Solanaceae (37). Non-proteinaceous inhibitors of serine... 

Frey, M., Chomet, P., Glawischnig, E. et al. (1997). Analysis of a chemical plant defense mechanism in grasses. Science 277 696-699. 

Bennett R.N., Wallsgrove R.M. Secondary metabolites in plant defense mechanisms. New Phytol 1994 127 ... 

Over the past 20 years, chemical ecologists have proposed hypotheses regarding the evolution of chemical defenses in plants and animals.9 158,261-262 315 380-383 Many of these hypotheses suggest that the evolution of plant defense mechanisms is responsive to factors such as the plant s risk of discovery by herbivores, the cost of defense, and the relative value of various plant parts. These predictions are based on preliminary data, and in many cases still have not been rigorously tested. 

Insects are so successful because of their mobility, high reproductive potential, ability to exploit plants as a food resource, and to occupy so many ecological niches. Plants are essentially sessile and can be seen to produce flowers, nector, pollen, and a variety of chemical attractants to induce insect cooperation in cross-pollination. However, in order to reduce the efficiency of insect predation upon them, plants also produce a host of structural, mechanical, and chemical defensive artifices. The most visible chemical defenses are poisons, but certain chemicals, not intrinsically toxic, are targeted to disrupt specific control systems in insects that regulate discrete aspects of insect physiology, biochemistry, and behavior. Hormones and pheromones are unique regulators of insect growth, development, reproduction, diapause, and behavior. Plant secondary chemicals focused on the disruption of insect endocrine and pheromone mediated processes can be visualized as important components of plant defensive mechanisms. 

Table I. Some Enzymes of Plant Defense Mechanisms...

Gang, D.R., Kasahara, H., Xia, Z.Q., Vander Mijnsbrugge, K., Bauw, G., Boerjan, W., Van Montagu, M., Davin, L.B. and Lewis, N.G. (1999b) Evolution of plant defense mechanisms. Relationships of phenylcoumaran benzylic ether reductases to pinoresinol-lariciresinol and isoflavone reductases. /. Biol. Chem., 274, 7516-27. 

Arthropods produce a wide range of metabolites derived from simple fatty acid or polyacetate precursors. The most well-studied fatty acid-derived natural products are no doubt the volatile sex pheromones prevalent among the Lepidoptera, although fatty acids and derivatives also function in additional roles, including defense, as well as in their recently discovered capacity as elicitors of plant defense mechanisms. Fatty acids furthermore serve as biosynthetic precursors to some important families of defensive alkaloids, such as the coccinellines and polyazamacrolides (PAMLs) (Section 2.04.6.1). As mentioned earlier, volatile pheromones are discussed in Chapter 4.04. 

Tannins are secondary metabolites distributed widely in the plant kingdom, which have been closely associated with plant defense mechanisms towards phytopathogens, insects and mammalian herbivores... 

Astragalus gummifer. Exudate gums are a plants defense mechanism. These polysaccharides are exuded from plants as a result of injury or fungal attack. 

Arman, M. Qader, S.A.U. Structural analysis of kappa-carrageenan isolated from Hypnea musciformis (red algae) and evaluation as an elicitor of plant defense mechanism. Carbohydr. Polym. 2012, 88 (4), 1264-1271. 

Not all Narcissus species are equally dangerous. The bulbs of N. poeticus, for example, are more dangerous than those of N. pseudonarcissus. Neither do all plant tissues have the same concentration or profile of alkaloids. Thus, the alkaloid content of N. papyraceus is five times higher in the aerial part than in the bulbs, being toxic for herbivorous mammals (137). The distribution of the alkaloids in the plant tissues can be related with the plant defense mechanism. 

Benhamou N. 1995. Immunocytochemistry of plant defense mechanisms induced upon microbial attack. Microsc Res Tech 31 63-78. 

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