Nitrogen-intensive Plastic Responses to Herbivory: Primary Role for a Secondary Metabolite
Ian Baldwin Principal Investigator
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The growth of herbivores is recognized by most researcher to be limited in large part by a plant's nitrogen content. When a plant is eaten, its remaining tissues exhibit a plethora of responses that include not only the dramatic increases in the concentrations of "secondary" metabolites (the putative induced defenses which presumably contribute to a plant's resistance to herbivory) but also a suite of physiological responses that include increases in photosynthetic rates( which presumably contribute to a plant's resilience to herbivory). This proposal examines how a plant integrates these two suites of responses and thus asks how a plant resolves the potentially conflicting demands of its "defensive" and "civilian" biochemical responses to herbivore attack. This metabolic integration will be examined in a species of plant (Nicotiana sylvestris) where both the "defensive" responses--the production of toxic alkaloids--and the "civilian" responses--included photosynthetic capacity--make large demands on a plant's nitrogen budget. Since nitrogen is frequently the important limiting element for plants growth, we will choreograph the movement of nitrogen between alkaloid and protein synthesis in order to examine this metabolic integration. Research on pest-resistance in agriculture has been focused on two fronts: the chemical and physical of plants that confer resistance to pest attack and the physiological attributes of plants associated with resilience to herbivory. Little, if any research has explored the integration of both the defense against and the tolerance to herbivory. And understanding of this integration is essential if we are to proceed beyond the "pesticide-approach" to plant protection. This will be the first project to examine chemical defense as an integral part of the physiological processes by which plants regrow those tissues lost to herbivores.