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Ecotypic variation in leaf thermoregulation and heat tolerance but not thermal safety margins in tropical trees
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  • Kali Middleby,
  • Alex Cheesman,
  • Richard Hopkinson,
  • Leesa Baker,
  • Sebastian Ramirez,
  • Martin F. Breed,
  • Lucas Cernusak
Kali Middleby
James Cook University College of Science and Engineering

Corresponding Author:kalimiddleby@gmail.com

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Alex Cheesman
James Cook University College of Science and Engineering
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Richard Hopkinson
AeroScan
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Leesa Baker
James Cook University College of Science and Engineering
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Sebastian Ramirez
Universidad Nacional de Colombia Instituto de Ciencias Naturales
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Martin F. Breed
Flinders University College of Science and Engineering
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Lucas Cernusak
James Cook University College of Science and Engineering
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Abstract

To avoid reaching lethal temperatures during periods of heat stress, plants may acclimate either their biochemical thermal tolerance, or leaf morphological and physiological characteristics to reduce leaf temperature (T leaf). While emerging evidence indicates that plants from warmer environments have a greater capacity to regulate T leaf, the extent of intraspecific variation and contribution of provenance is relatively unexplored. We tested whether upland and lowland provenances of four tropical tree species grown in a common garden differed in their thermal safety margins by measuring leaf thermal traits, midday leaf-to-air temperature differences (∆T leaf), and critical leaf temperature defined by chlorophyll fluorescence (T­ crit). Provenance variation was highly species- and trait- specific. Higher ∆T leaf and T­ crit were observed in the lowland provenance for Terminalia microcarpa, and in the upland provenance for Castanospermum australe, with no provenance differences observed in the other two species. Within-species covariation of T crit and ∆T leaf led to a convergence of thermal safety margins across provenances. These findings suggest that when grown under common conditions, lowland and upland provenances may not differ substantially in their vulnerability (defined here as thermal safety margin) to heat stress, despite differences in operating temperatures and T crit.
29 May 2024Submitted to Plant, Cell & Environment
31 May 2024Submission Checks Completed
31 May 2024Assigned to Editor
22 Jun 2024Review(s) Completed, Editorial Evaluation Pending
24 Jun 2024Editorial Decision: Revise Minor
31 Jul 20241st Revision Received
01 Aug 2024Submission Checks Completed
01 Aug 2024Assigned to Editor
01 Aug 2024Review(s) Completed, Editorial Evaluation Pending
12 Aug 2024Reviewer(s) Assigned
22 Aug 2024Editorial Decision: Accept