title: Do thick leaves avoid thermal damage in critically low wind speeds?
abstract: Transient lulls in air movement are rarely measured, but can cause leaf temperature to rise rapidly to critical levels. The high heat capacity of thick leaves can damp this rapid change in temperature. However, little is known about the extent to which increased leaf thickness can reduce thermal damage, or how thick leaves would need to be to have biological significance. We evaluated quantitatively the contribution of small increases in leaf thickness to the reduction in thermal damage during critically low wind speeds under desert conditions. We employed a numerical model to investigate the effect of thickness relative to transpiration, absorptance and leaf size on damage avoidance. We used measured traits and thermotolerance thresholds of real leaves to calculate the leaf temperature response to naturally occurring variable low wind speed. Our results demonstrated that an increase in thickness of only fractions of a millimetre can prevent excursions to damaging high temperatures. This damping effect of increased thickness was greatest when other means of reducing leaf temperature (transpiration, reflectance or reduced size) were lacking. For perennial desert flora, we propose that increased leaf thickness is important in decreasing the incidence of extreme heat stress and, in some species, in enhancing long-term survival.
authors.affiliation: School of the Environment, University of Technology, Sydney, PO Box 123, Broadway, NSW 2007, Australia.
authors.forename: A
authors.initials: A
authors.lastname: Leigh
authors.affiliation: Earth and Environmental Sciences Division, Los Alamos National Laboratory, PO Box 1663, MS J495, Los Alamos, NM 87545, USA.
authors.forename: S
authors.initials: S
authors.lastname: Sevanto
authors.affiliation: Plant Science Division, Research School of Biology, The Australian National University, ACT 0200, Australia.
authors.forename: M C
authors.initials: MC
authors.lastname: Ball
authors.affiliation: Quantum Science, Research School of Physics and Engineering, The Australian National University, ACT 0200, Australia.
authors.forename: J D
authors.initials: JD
authors.lastname: Close
authors.affiliation: Centre for Plants and the Environment, University of Western Sydney, Locked Bag 1797, Penrith South DC, NSW 1797, Australia.
authors.forename: D S
authors.initials: DS
authors.lastname: Ellsworth
authors.affiliation: Department of Biological Sciences, California Polytechnic State University, San Luis Obispo, CA 93407, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Knight
authors.affiliation: Evolution, Ecology and Genetics, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia.
authors.forename: A B
authors.initials: AB
authors.lastname: Nicotra
authors.affiliation: Department of Biology, Duke University, Box 90338, Durham, NC 27708-0338, USA.
authors.forename: S
authors.initials: S
authors.lastname: Vogel
mesh_terms: D000042:Absorption; D002140:California; D003889:Desert Climate; D008954:Models, Biological; D009929:Organ Size; D018515:Plant Leaves / Q000033:anatomy & histology* / Q000502:physiology*; D018526:Plant Transpiration / Q000502:physiology; D010944:Plants / Q000033:anatomy & histology; D019655:Quantitative Trait, Heritable; D012621:Seasons; D013045:Species Specificity; D013696:Temperature; D014919:Wind