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Abstract Detail



Bryological and Lichenological Section/ABLS

Moore, Jonathan David [1], Franke, Morgan [2], Kollar, Leslie [3], McLetchie, D. Nicholas [1].

A test for sex differences in heat and desiccation stress responses in Bryum argenteum.

Among dioecious bryophytes, female-biased population sex ratios predominate. Assuming 1:1 spore sex ratios, skewed adult sex ratios are evidence of life history differences, which may be caused by sex-specific physiologies. Because spore sex ratio in Bryum argenteum is 1:1 and population sex ratios are female-biased especially in stressful environments, we hypothesized male plants tolerate less stress than female plants. We conducted two experiments to address this hypothesis. First, we assessed recovery from desiccation and heat stress on field-collected plants. We haphazardly collected 96 clumps of plants (unknown sex except one male clump) along foot paths on the University of Kentucky campus (Lexington, KY, USA) and randomly selected 68 of the collection. Evidence of sexual reproduction was lacking, so we assumed each clump was unisexual. We assessed recovery using chlorophyll fluorescence (Fv/Fm) from desiccation for 72 hours using three shoots from each clump. Another three hydrated shoots were placed at 40 oC for 1 hr and recovery (Fv/Fm) was tracked for 72 hours. One shoot from all 96 original clumps was cultured to sex expression to assign sex retroactively to clumps. Second, the effect of wet heat stress was measured on growth chamber cultured plants. Four replicates (three shoots each) of 19 males and 19 female isolates were assigned to one of four treatments: 20 oC dry, 20 oC wet, 45 oC dry, or 45 oC wet all for 1 hr. Recovery was tracked for 96 hrs. Shoots were then planted to assay growth rate. Experiment 1: sex had no overall effect on desiccation recovery, but only 8 of the 68 were male. For the first experiment, sex had no overall effect on recovery from desiccation or heat stress. Experiment 2: the sex effect was marginal (F=2.14, df=20, p=0.0641) on heat stress recovery with females recovering on average slightly better at 24 hours than males, but no clear cut sex-specific patterns emerge, and sex did not affect growth rate. However, high temperature significantly decreased Fv/Fm (F=55.74, df=1, p<.0001) and growth rate (F=55.74, df=1, p<0.0001). Despite clearly stressful conditions we found no physiological evidence that would explain the local female biased sex ratio. Often physiological sex differences occur after the onset of maturity due to investment in sexual reproduction, and all but one of our plants were immature, which limits our study. A future direction would be to test the effects of stress on sex-expressing plants.


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1 - University Of Kentucky, Department Of Biology, 101 Morgan Build., Lexington, KY, 40506-0225, USA
2 - Virginia Tech, Plant Pathology, Physiology, and Weed Science, 413 Price Hall, 170 Drillfrield Drive, Virginia Tech, Blacksburg, VA, 24061-0331, USA
3 - University of Florida, Biology, P.O. Box 118525, 220 Bartram Hall, Gainesville, FL, 32611-8525, USA

Keywords:
stress tolerance
sex differences
sex ratio.

Presentation Type: Oral Paper:Papers for Sections
Session: 16
Location: Salon 11/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 2:30 PM
Number: 16005
Abstract ID:1284
Candidate for Awards:A. J. Sharp Award


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