The influence of endophyte on host N metabolism was among the early discoveries related to mineral nutrition of host-endophyte associations. Lyons et al. (1990) showed that concentrations of tissue N were less in E+ than in E- plant leaves, regardless of N supply. This led to work suggesting a more efficient conversion of N to growth in E+ plants (Arachevaleta et al., 1989). Several experiments have shown that N fertilization enhanced alkaloid production in E+ tall fescue and thus could lead to plants more harmful to livestock than plants growing in N-poor soils (Arechavaleta et al., 1992; West et al., 1994). Nutrient deficiency, specifically N deficiency, seemed to restrict growth of some E+ plants of Lolium and taxonomically related species (Cheplick et al., 1989) and poverty grass [Danthonia spicata (L.) P. Beauv. ex Roem. & Schult.], a species common on marginal and low fertility sites (McCormick et al., 2001). Recently, Pecetti et al. (2007) observed that N fertilization seemed to benefit the persistence of E+ plants, but that the extent of benefit depended on an interaction of local growing conditions with origin of host-endophyte association. When N was supplied, the stand declined regardless of host-endophyte association or location. Stand decline was related to increased competition from co-occurring warm-season grass species, indicating the complex interaction of host-endophyte associations and management on plant community structure.
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