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Title: The influence of leaf size and shape on leaf thermal dynamics: does theory hold up under natural conditions?

Laboratory studies on artificial leaves suggest that leaf thermal dynamics are strongly influenced by the two-dimensional size and shape of leaves and associated boundary layer thickness. Hot environments are therefore said to favour selection for small, narrow or dissected leaves. Empirical evidence from real leaves under field conditions is scant and traditionally based on point measurements that do not capture spatial variation in heat load. Here in this study, we used thermal imagery under field conditions to measure the leaf thermal time constant (τ) in summer and the leaf-to-air temperature difference (ΔT) and temperature range across laminae (T range) during winter, autumn and summer for 68 Proteaceae species. We investigated the influence of leaf area and margin complexity relative to effective leaf width (w e), the latter being a more direct indicator of boundary layer thickness. Normalized difference of margin complexity had no or weak effects on thermal dynamics, but w e strongly predicted τ and ΔT, whereas leaf area influenced T range. Unlike artificial leaves, however, spatial temperature distribution in large leaves appeared to be governed largely by structural variation. Therefore, we agree that small size, specifically we, has adaptive value in hot environments but not with the ideamore » that thermal regulation is the primary evolutionary driver of leaf dissection.« less
Authors:
 [1] ; ORCiD logo [2] ;  [3] ;  [4]
  1. Univ. of Technology Sydney, Broadway, NSW (Australia)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. Australian National Univ., Canberra, ACT (Australia)
  4. Australian National Univ., Canberra, ACT (Australia). Research School of Biology
Publication Date:
Report Number(s):
LA-UR-17-27765
Journal ID: ISSN 0140-7791
Grant/Contract Number:
AC52-06NA25396; A00103546
Type:
Accepted Manuscript
Journal Name:
Plant, Cell and Environment
Additional Journal Information:
Journal Volume: 40; Journal Issue: 2; Journal ID: ISSN 0140-7791
Publisher:
Wiley
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Laboratory Directed Research and Development (LDRD) Program; Australian Research Council
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; Biological Science; Earth Sciences; boundary layer; cooling time constant; effective leaf width; infrared imagery; leaf dissection; leaf shape; leaf size; leaf temperature; thermal dynamics; heat; high light; transpiration
OSTI Identifier:
1412871

Leigh, A., Sevanto, Sanna Annika, Close, J. D., and Nicotra, A. B.. The influence of leaf size and shape on leaf thermal dynamics: does theory hold up under natural conditions?. United States: N. p., Web. doi:10.1111/pce.12857.
Leigh, A., Sevanto, Sanna Annika, Close, J. D., & Nicotra, A. B.. The influence of leaf size and shape on leaf thermal dynamics: does theory hold up under natural conditions?. United States. doi:10.1111/pce.12857.
Leigh, A., Sevanto, Sanna Annika, Close, J. D., and Nicotra, A. B.. 2016. "The influence of leaf size and shape on leaf thermal dynamics: does theory hold up under natural conditions?". United States. doi:10.1111/pce.12857. https://www.osti.gov/servlets/purl/1412871.
@article{osti_1412871,
title = {The influence of leaf size and shape on leaf thermal dynamics: does theory hold up under natural conditions?},
author = {Leigh, A. and Sevanto, Sanna Annika and Close, J. D. and Nicotra, A. B.},
abstractNote = {Laboratory studies on artificial leaves suggest that leaf thermal dynamics are strongly influenced by the two-dimensional size and shape of leaves and associated boundary layer thickness. Hot environments are therefore said to favour selection for small, narrow or dissected leaves. Empirical evidence from real leaves under field conditions is scant and traditionally based on point measurements that do not capture spatial variation in heat load. Here in this study, we used thermal imagery under field conditions to measure the leaf thermal time constant (τ) in summer and the leaf-to-air temperature difference (ΔT) and temperature range across laminae (Trange) during winter, autumn and summer for 68 Proteaceae species. We investigated the influence of leaf area and margin complexity relative to effective leaf width (we), the latter being a more direct indicator of boundary layer thickness. Normalized difference of margin complexity had no or weak effects on thermal dynamics, but we strongly predicted τ and ΔT, whereas leaf area influenced Trange. Unlike artificial leaves, however, spatial temperature distribution in large leaves appeared to be governed largely by structural variation. Therefore, we agree that small size, specifically we, has adaptive value in hot environments but not with the idea that thermal regulation is the primary evolutionary driver of leaf dissection.},
doi = {10.1111/pce.12857},
journal = {Plant, Cell and Environment},
number = 2,
volume = 40,
place = {United States},
year = {2016},
month = {11}
}