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Abstract Detail

Ecological Section

Zhang, Nana [1], Tonsor, Stephen [2].

Heat stress disruption and contrasting avoidance-tolerance strategies from thermally contrasting climates in Arabidopsis thaliana.

Background/Questions/Methods: Temperature, especially high temperature, is one of the major ecological factors that limit plant distribution. Plants can avoid heat stress by reducing tissue temperature below ambient  temperature. In contrast, plants may exhibit tolerance, i.e. maintain key functions at high temperature. Here Arabidopsis thaliana populations from two ends of an elevational gradient (from above-sea level to mountaintop) in NE Spain were used to ask: 1) Do plants from thermally contrasting environments show dramatically variable heat stress damage and 2) Do they adopt different avoidance-tolerance strategies? 4 low- and 4 high-elevation populations were planted in a growth chamber and then exposed to severe heat stress (45oC) at flowering stage. Plants from low elevation tend to experience more frequent hot and dry conditions, while plants from high elevation experience greater frequency of cold and wet conditions but still experience occasional heat stress. We measure avoidance by recording rosette compared to ambient temperature. We measure tolerance by comparing photosynthetic rate under control (22 oC) and high (45 oC) temperatures.  Finally, we estimated fitness as the summed length of all fruits produced.  We also quantified heat stress disruption on reproduction characteristics (branch number, reproductive length) and resource allocation (root, rosette and inflorescence dry mass).  
Results/Conclusions: We found that for all populations, heat stress equally induced more inflorescence branches, 25% longer reproductive length and 12% less root dry mass compared with control. However, the greater resource allocation to inflorescences with heat stress did not contribute to maintain full fitness. All populations equally reduced 15% of summed fruit length, indicating the same fitness reduction with heat stress.  Importantly, we found that populations from thermally contrasting climates adopt significantly different avoidance and tolerance strategies. For avoidance, all populations showed reduced rosette temperature compared with ambient temperature (45 oC), with mean rosette temperature 38 oC for low elevation and 35 oC  for high elevation populations. For tolerance, low elevation populations reduced ~30% photosynthesis while high elevation populations reduced ~75% photosynthesis with heat stress compared with control. In summary, populations from low elevation exhibit less avoidance but more tolerance, while populations from high elevation show greater avoidance but lower tolerance. The different avoidance–tolerance strategies for populations from thermally contrasting climates indicates constraints on the evolution and variation of both strategies and their adaptive divergence regulated by local climates. This study also gives insight into adopt various and suitable approaches to mitigate the negative effect of heat stress worldwide.

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1 - University of Pittsburgh, Biological Sciences, pittsburgh, PA, 15260, USA
2 - University Of Pittsburgh, Department Of Biological Sciences, A-234 LANGLEY HALL, 4249 FIFTH AVE, Pittsburgh, PA, 15260, USA

abiotic stress
heat stress
local adaptation.

Presentation Type: Oral Paper:Papers for Sections
Session: 24
Location: Clearwater/Grove
Date: Tuesday, July 29th, 2014
Time: 10:30 AM
Number: 24002
Abstract ID:152
Candidate for Awards:None

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