Induced chemical defenses

Toth et al. 2005), induced resistance was found only in the top blades of S.filipendula (Taylor et al. 2002). The authors concluded that valuable basal stipes are mechanically and constitutively defended, while the valuable meristematic tissues have inducible chemical defenses (Taylor et al. 2002). 

Toth GB, Pavia H (2000) Water-borne cues induce chemical defense in a marine alga (Ascophyllwn nodosum). Proc Natl Acad Sci USA 97 14418-14420... 

Toth GB, Pavia H (2000) Water-borne cues induce chemical defense in a marine algaAscophyllum nodosum. Proc Natl Acad Sci USA 97 14418-14420 Uppalapaati SR, Fujita Y (2000) Carbohydrate regulation of attachment, encystment, and appres-sorium formation by Pythium porphyrae (Oomycota) zoospores on Porphyra yezoensis (Rhodophyta). J Phycol 36 359-366... 

In some cases, browsing does not appear to lead to induced defenses. Two species of northern European birch (B. pendula and B. pubescens) do not seem to respond to moose browsing with increased chemical defenses (Danell et ah, 1985). After experimental defoliation, the Emory oak of southwestern North America, Quercus emoryi, produces in its regrown leaves 2.5 times as much hydrolyzable tannins than in mature leaves, but lower amounts of condensed tannins. Refoliated branches suffered more, not less herbivory. New leaves have more protein, more water, and are tender. These properties may override any effects of induced chemical defenses, at least for the current growing season (Eaeth, 1992), but the induced compounds may still protect a plant later on, especially in winter. 

Teeyapant R, Proksch P (1993) Biotransformation of Brominated Compounds in the Marine Sponge Verongia aerophoba — Evidence for an Induced Chemical Defense Naturwissenschaften 80 369... 

Teeyapant, R. and Proksch, P., Biotransformation of brominated compounds in the marine sponge Verongia aerophoba — evidence for an induced chemical defense, Naturwissenschaften, 80,369,1993. 

Plants contain plant secondary metabolites (PSMs) that confer resistance against herbivores and pathogens. The largest classes of PSMs are phenolics, terpenoids, and alkaloids. We distinguish constitutive and induced chemical defenses. The first occur in an entire plant or some of its parts as normal constituents, the latter are formed in response to herbivory or some other trauma to the plant. In some cases mere clipping induces defenses, in others additional factors, such as those in saliva of a herbivore are essential. 

INDUCED CHEMICAL DEFENSES IN CONIFERS BIOCHEMICAL AND MOLECULAR APPROACHES TO STUDYING THEIR FUNCTION... 

In this review, we examine the induced chemical defenses of P. abies, defenses whose levels increase following herbivore or pathogen attack. Induced defenses have attracted much attention in recent years because of their widespread occurrence in plants and their usefulness as subjects for study. Here, we cover the induction of several different classes of induced defenses in P. abies, including terpene-containing resins, phenolic compounds, and chitinases. Our focus is not only on their defensive roles, but also on how the levels of these compounds may be manipulated by biochemical and molecular methods while minimizing other phenotypic changes. Manipulation of defense compoimds in intact plants is a valuable approach to assessing their value to the plant. 

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