Tolerance range for dormancy loss and germination differs among dispersal strategies.
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Middle Tennessee State University
Abstract
Tolerance range for dormancy loss and germination differs among dispersal strategies
Ridma G. Bandara
Abstract
Germination has an optimum temperature and minimum and maximum thresholds [hereafter, tolerance range (TR)]. I reasoned that species with limited dispersal would be more specialized to local conditions and have narrower TR than those with wide dispersal. Four species contrasting in dispersal strategies were studied: Penstemon digitalis, P. tubaeflorus (gravity), Physalis longifolia (animal) and Asclepias syriaca (wind). I hypothesized that TR would differ (narrowest to widest): Penstemon < Physalis < Asclepias. Seeds were collected from MO to MN; stratified at 1, 5, and 9C; and incubated at 15/6, 20/10, 25/15, and 30/15C. Levins B was calculated; values approaching 1 vs. 0 represent a wide vs. narrow TR. Asclepias and Physalis seeds germinated highest at 20/10-30/15C regardless of stratification temperature, and Penstemon seeds at 15/6-30/15C following 1C stratification. TRs for cold-stratified seeds were: Penstemon < Physalis < Asclepias. Thus, my hypothesis was supported that TR varied according to dispersal strategy.
Ridma G. Bandara
Abstract
Germination has an optimum temperature and minimum and maximum thresholds [hereafter, tolerance range (TR)]. I reasoned that species with limited dispersal would be more specialized to local conditions and have narrower TR than those with wide dispersal. Four species contrasting in dispersal strategies were studied: Penstemon digitalis, P. tubaeflorus (gravity), Physalis longifolia (animal) and Asclepias syriaca (wind). I hypothesized that TR would differ (narrowest to widest): Penstemon < Physalis < Asclepias. Seeds were collected from MO to MN; stratified at 1, 5, and 9C; and incubated at 15/6, 20/10, 25/15, and 30/15C. Levins B was calculated; values approaching 1 vs. 0 represent a wide vs. narrow TR. Asclepias and Physalis seeds germinated highest at 20/10-30/15C regardless of stratification temperature, and Penstemon seeds at 15/6-30/15C following 1C stratification. TRs for cold-stratified seeds were: Penstemon < Physalis < Asclepias. Thus, my hypothesis was supported that TR varied according to dispersal strategy.