Allelochemics deleterious effects

Reese (37) has studied nutrlent-allelochemical Interactions using diets supplemented by plant extracts. He has concluded that many of the deleterious effects may be due primarily to various Interactions between these allelochemical and essential nutrients. It Is Important to not only consider the presence of nutrients, but also the bloavallability of these nutrients to the phytophagous Insect. He cited findings where neonate larvae were found more sensitive to plant allelochemicals than older larvae, and Interpreted the greater resistance of the older larvae In terms of Increasing capability to utilize available nutrients, probably because of the Induction of enzymatic detoxification systems. 

Once consumed, allelochemics have assorted deleterious effects. Otherwise, they can pass through the insect with no effect, be sequestered, or detoxified. Many enzyme systems are involved in biochemical defense against plant allelochemics, but the most familiar and perhaps most important are the mixed function oxidases. Brattsten (1979) describes the three major characteristics that contribute to their importance in biochemical waste disposal (i) they catalyze numerous oxidative reactions that produce more polar and hence more excretable compounds, (ii) they are non-specific in that a wide range of chemicals are acceptable substrates, (iii) they can adjust rapidly (within minutes) to the presence of allelochemics or synthetic insecticides via induction. The MFO detoxification system is not confined to insects MFO activity has been identified in a wide range of vertebrates and invertebrates. A variety of flies, mosquitoes, cockroaches, crickets and a minimum of 40 species of Lepidoptera (as well as representatives from other insect orders) possess MFO activity (review Brattsten, 1979). 

The plant cell is a basic unit for germination, growth and development of plants. The allelochemicals first come in contact with the cell and then allelopathic interactions take place. Some allelochemicals have broad-spectrum activity that extends to the tissues of host plants, where their effects may be either beneficial or deleterious to plant germination, growth, development or yield. Hence, to understand the mechanisms of such intercations interactions the study of the cell and its various processes is very necessary. Therefore, this book has been been prepared (a) to make available all methods for such studies and (b) scientists can understand the scope of allelopathic research in relation to the cell. Hence, we have explained and discussed various techniques to study cell processes etc. 

The biochemical mechanisms through which allelochemicals exert deleterious or toxic effects on plants are, for the most part, unknown (1). Some phenolic acids, cinnamic acids, coumarins, and flavonoids have been reported to inhibit photosynthesis and respiration of intact plants and microorganisms. However, the mechanisms, at the molecular level, through which the compounds interfere, remain to be ascertained. Some phenolic acids, coumarins, and flavonoids were reported to Inhibit C02-dependent 0 ... 

A characteristic feature of allelopathy is that the inhibitory effects of allelopathic compounds are concentration dependent. Dose-response curves with known compounds show an inhibition threshold. Below this level either no measurable effect occurs, or stimulation may result. Although the concentration of a compound required to exceed the inhibition threshold varies extensively according to different sensitivities among species and also among phases of the growth cycle for higher plants, the concept of an inhibition threshold seems consistent. Thus, it is reasonable to evaluate how, and if, a subthreshold concentration of an allelochemical may contribute to allelopathic interference. Also in need of evaluation is how environmental conditions may influence the deleterious action of an allelochemical and the concentration required for an effect. Such interactions are especially pertinent for those environmental situations that place some degree of stress on plant functions. 

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