Plants substances, secondary

The terpenoids, the phenols and the alkaloids constitute the three most important groups of the secondary plant substances. This is a very unfortunate designation since it is all too easy to equate secondary with of secondary importance or, even, unimportant. In actual fact it is not known for many of the substances so classified in what way they could be of use to the plants that produce them. In many cases they do indeed seem to be waste products of metabolism which are withdrawn from metabolism by being transferred to vacuoles or stored in the bark without any demonstrable benefit to the plant other than an easing of the 

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Feeny PP (1976) Plant apparency and chemical defense. Res Adv Phytochem 10 1—40 Fraenkel GS (1959) The raison d etre of secondary plant substances. Science 129 1466-1470 Franklin LA, Yakovleva I, Karsten U, Liming K (1999) Synthesis of mycosporine-like amino acids in Chondrus crispus (Florideophyceae) and the consequences for sensitivity to ultraviolet B radiation. J Phycol 35 682-693... 

Eraenkel, G. S. (1959). The raison d etre of secondary plant substances. Science 129,1466-1470. 

Rotschild, M. 1973. Secondary plant substances and warning coloration in insects. In Insect-Plant Relationships (Van Emden, H. F., ed.), pp. 59-83. Oxford Oxford University Press. 

The nutritional requirements of insect species exhibiting different feeding habits like scavengers, parasites, predators and phytophagous insects, are similar in a qualitative sense (O. Each insect species needs, however, a particular quantitative composition of nutrients in its diet to complete development ( ). The presence of toxic substances in plants, secondary plant substances as they were formerly called by phytochemists, forms a barrier which phytophagous insects have overcome by specialization. Thus, an insect can tolerate or detoxify the secondary plant substances present in its host plants, while the majority of these substances being present in other plants still acts as toxins (J ). In this way phytophagous insects are adapted to the metabolic qualities of their host plants, i.e. a particular chemical composition of nutrients and secondary plant substances. 

In biting their food and by means of a relatively small number of gustatory receptor cells, the larvae are informed about the composition of nutrients and secondary plant substances. Taste perception, the integration of sensory information in the insect s central nervous system, is not merely a process of summation. Synergistic as well as antagonistic effects between individual compounds can be observed in the food uptake of larvae on artificial diets. 

Different insect species posses different gustatory receptor cells, their response spectra being adapted to the perception of chemical components distributed in their host plant species (9 ). Taste perception in P. brassicae larvae forms a representative example for phytophagous insects, which are able to discriminate a number of compounds like sugars, amino acids, salts, and secondary plant substances acting as feeding inhibitors or feeding incitants (3,6,, 10). 

Rothschild M. (1979) Mimicry, butterflies and plants. Symb. Bot. Upsal. 22, 82-99. Rothschild M., Aplin R. T., Cockrum P. A., Edgar J. A., Fairweather P. and Lees R. (1979) Pyrrolizidine alkaloids in arctiid moths (Lep.) with a discussion on host plant relationships and the role of these secondary plant substances in the Arctiidae. Biol. J. Linnean Soc. 12, 305-326. 

Schutte, H.R. (1983) Secondary plant substances. Aspects of carotenoid biosynthesis. Prog. Bot. 45, 120-135. 

Mothes, K., Schutte, H. R. and Luckner, M. 1976. Secondary plant substances as materials for chemical breeding in higher plants. Recent Adv. Phytochem. 10, 385-405... 

L-canavanine and L-canaline. Secondary plant substances may evoke particular types of stereotyped insect behavior via actions within the CNS. An excellent example is the work of Kammer, Dahlman, and Rosenthal (40), who observed that injection of adult Manduca sexta with L-canavanine and L-canaline led, within minutes, to sustained flights lasting many hours. The site of action of L-canavanine and L-canaline was believed to be the CNS. This produced continuous motor output, which became less coordinated with time. L-canavanine and L-canaline are two of some 260 non-protein amino acids accumulated by various plants (41). If an unadapted insect acquired... 

The chemical-ecological literature abounds with descriptions of effects of secondary plant substances on insects, vaguely lumped under the heading "toxic". If we persist in being satisfied with "toxicity" as a description cum explanation of the effect of plant substances on insects, we shall remain very much in the dark as to the action of these important compounds. The only way we can... 

Schiitte, H. (1987) Secondary plant substances aspects of steroid biosynthesis. Prog. Bot., 49,117-36. 

Rothschild, M., Secondary plant substances and warning coloura-... 

Fraenkel, G. S. The raison d etre of secondary plant substances. Science J29, 1466-1470 (1959) Hegnauer, R. Chemotaxonomie der Pflanzen, Vols 1-6. Birkhauser, Basel 1962-1973 Kossel, A. Gber die chemische Zusammensetzung der Zelle. Arch. Physiol. 181 (1891)... 

Luckner, M. Expression and Control of Secondary Metabolism. In Encyclopedia of Plant Physiology, New Series, Vol. 8, Secondary Plant Products (E. A. Bell, B. V. Charlwood. eds.), pp. 23-63, Springer, Berlin-Heidelberg-New York 1980 Mothes, K. Secondary plant substances as materials for chemical high quality breeding in higher plants. In Biochemical Interactions between Plants and Insects (J. W. Wallace, R. L. Mansell, eds.), pp. 385-405. Plenum, New York 1976 Zahner, H. What are secondary metabolites Folia Microbiol. 24, 435-443 (1979)... 

Dethier, V. G. (1980b) Evolution of receptor sensitivity to secondary plant substances with special reference to deterrents. Am. Nat., 115, 45-66. 

We make no attempt to characterize these chemicals beyond the generalizations that (i) wide ranges of both primary and secondary plant substances act as excitatory stimuli (ii) inhibition of investment behaviors is triggered mainly by secondary substances but sometimes by unfavorable balances of primary nutrients and (iii) because they are relatively non-volatile and effectively compartmentalized, many phytochemicals generating the inhibitory inputs influence insect behavior only during or after the examining phase when direct contact has been established. Readers are referred to Hedin et al. (1974) for analysis of behaviorally active phytochemicals by chemical class. 

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