ABSTRACT
Pasture plant communities respond to biotic, abiotic, and management factors at community, species, and individual plant levels (Turkington and Mehrhoff, 1990). Each level of response, in tum, can modify the other so that a resilient and dynamic community occurs. For example, one can deduce from a large body of agronomic and applied botanical research that botanically complex swards respond to external factors and their interactions by shifts in species, lines within species, and reallocation of resources within individual plants. Our interest as agriculturalists is in plant adaptability that sustains productive and persistent swards under dynamic conditions in a given production system, often with disregard to floristic diversity. Pastures are usually relegated to marginal sites on the landscape imposing additional challenges to reliable production of quality herbage. This chapter focuses on morphological and chemical plasticity within Festuca species, a major component of humid-temperate region pastures, attributable to a mutualistic symbiosis between host grasses and endophyte infection. We consider genotypic responses of particular endophyte-tall fescue associations to
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abiotic stresses common to marginal soil resources (e.g., acidity, water deficit, limited P availability), which should enable us to establish reference points from which we can develop plant resources to suit specific production system needs.
