This research focuses on two major areas of environmental stress physiology with the overall long-term goal of determining how environmental stress can alter the chemical constitution of medicinal plants. The two specific aims of this project are (1) determine adaptive mechanisms to drought and nutrient stress of five medicinal plants that can be commercially produced in the Southwest, and (2) determine whether drought and nutrient stress affects the quantity and quality of pharmacologically active components of medicinal plants. Research conducted within those major objectives will benefit consumer health by providing medicinal herb consumers more precise information on water and nutrient stress effects on medicinal plants. To meet specific aim one, the adaptations to drought and nutrient stress on Catnip (Nepata catalaria), echinacea (Echinacea purpurea), mullein (Verbascum thapsus), valerian (Valeriana officinalis), and yerba mansa (Anemopsis californica) will be determined. Treatments will include three nutrient (no nutrients, organic fertilizer, 0.076 KgN/ha) and water deficit stress (well irrigated vs. cyclic drought) and will be applied in a completely randomized design. Analysis of variance procedures (PROC GLM) will be used to evaluate differences and interactions among treatments. The following responses which indicate some of a plant's response to water deficit stress and nutrient stress will be evaluated, pre-dawn and midday leaf water potential, stomatal conductance, relative growth rate, plant biomass, specific lamina mass, osmotic potential and carbon allocation among plant parts. To meet specific aim two, high pressure liquid chromatography will be used to separate, isolate, purify, and quantify pharmaceutically active compounds that have accumulated in response to water deficit stress and nutrient stress. The allocation of nutrients and carbon to primary production and the production and the production of secondary metabolites will be determined for each species. The experimental design and taxa used to meet specific aim one will also be used in this study.
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