Plant responses to herbivory

There is some evidence for induction in pasture plants. A furanocoumarin, isopimpinellin, increases in floral stands of wild parsnip, Pastinaca sattva, after clipping that simulates herbivory (Nitao, 1988). 

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. 

2 Chemical defense versus growth rate of plants 

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Jazdzewski K, Teodorczyk W, Sicinski J, Kontek B (1991) Amphipod crustaceans as an important component of zoobenthos of the shallow Antarctic sublittoral. Hydrobiologia 223 105-117 Karban R, Meyers JH (1989) Induced plant responses to herbivory. Ann Rev Ecol Syst 20 331-348... 

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