Wednesday, August 8, 2007

PS 52-172: Resource trade-offs associated with prolonged dormancy in Astragalus scaphoides, a sagebrush steppe geophyte

Jennifer R. Gremer, University of Montana

Prolonged dormancy, a life history stage in which adult plants fail to re-sprout for one or more growing seasons, may be highly influenced by stored resource levels, since plants must use stored resources to initiate seasonal growth as well as survive dormant episodes. Although previous studies have suggested that stored resources influence patterns of prolonged dormancy, none have directly measured the impact of prolonged dormancy on stored resource pools. Since it has been hypothesized that dormant plants lack the necessary resources to emerge, I investigated the change in stored resource pools associated with prolonged dormancy in Astragalus scaphoides, a native perennial wildflower with large underground storage organs. I tested whether dormant plants had lower levels of stored resources at the beginning and end of the growing season than plants that emerged above ground. I harvested plants and compared stored available nitrogen and phosphorus between dormant, vegetative, and reproductive plants. Preliminary data show that dormant plants are not depleted in nitrogen or phosphorus at either the beginning or end of the growing season as compared to emergent plants. My results suggest that prolonged dormancy provides a way for individuals to conserve mineral resources while avoiding the risk of above ground growth. Prolonged dormancy may serve as a bet-hedging strategy, allowing plants to remain alive below ground and avoid the risk of catastrophic conditions above ground.   

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