Track 1-01

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True summer dormancy in temperate perennial grasses is the ability to survive summer stresses by ceasing growth and senescing vegetative tissues independently of water supply, as opposed to summer-active grasses, which respond to rains by continuing growth, but senesce during droughts (Volaire and Norton 2006). Summer dormancy is a common drought-escape mechanism for Mediterranean-origin perennial grasses, but is also being considered as a potentially useful trait in semiarid to humid zones whose climates are not strictly Mediterranean, but where temperate grass survival is threatened by summer heat and water deficits (Malinowski et al. 2005). Moreover, summer dormancy may provide a mechanism for adapting to climate change patterns that exacerbate summer stresses (West et al. 2009). Tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbyshire] populations exhibit a range of summer dormancy potentials from nondormant (summer active) to varying levels of incomplete dormancy, but not complete dormancy (Norton et al. 2006). Summer drought survival of tall fescue is generally aided by symbiosis with a fungal endophyte [Neotyphodium coenophialum (Morgan-Jones & Gams) Glenn, Bacon & Hanlin comb.], and this endophyte is endemic in nearly all native populations of tall fescue (West 1994). Little is known of the influence of the endophyte on the expression of summer dormancy in their grass hosts or of the role of endophytes in host drought survival. We investigated the influence of environment and endophyte presence on expression of summer dormancy and survival in tall fescue in relation to expression of biochemical protectants.

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Summer Dormancy and Survival of Tall Fescue in Relation to Endophyte Presence

True summer dormancy in temperate perennial grasses is the ability to survive summer stresses by ceasing growth and senescing vegetative tissues independently of water supply, as opposed to summer-active grasses, which respond to rains by continuing growth, but senesce during droughts (Volaire and Norton 2006). Summer dormancy is a common drought-escape mechanism for Mediterranean-origin perennial grasses, but is also being considered as a potentially useful trait in semiarid to humid zones whose climates are not strictly Mediterranean, but where temperate grass survival is threatened by summer heat and water deficits (Malinowski et al. 2005). Moreover, summer dormancy may provide a mechanism for adapting to climate change patterns that exacerbate summer stresses (West et al. 2009). Tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbyshire] populations exhibit a range of summer dormancy potentials from nondormant (summer active) to varying levels of incomplete dormancy, but not complete dormancy (Norton et al. 2006). Summer drought survival of tall fescue is generally aided by symbiosis with a fungal endophyte [Neotyphodium coenophialum (Morgan-Jones & Gams) Glenn, Bacon & Hanlin comb.], and this endophyte is endemic in nearly all native populations of tall fescue (West 1994). Little is known of the influence of the endophyte on the expression of summer dormancy in their grass hosts or of the role of endophytes in host drought survival. We investigated the influence of environment and endophyte presence on expression of summer dormancy and survival in tall fescue in relation to expression of biochemical protectants.