Quantitative Estimation of Leaf Heat Transfer Coefficients by Active Thermography at Varying Boundary Layer Conditions

Abstract

Quantifying heat and mass exchanges processes of plant leaves is crucial for detailed understanding of dynamic plant-environment interactions. The two main components of these processes, convective heat transfer, and transpiration, are inevitably coupled as both processes are restricted by the leaf boundary layer. To measure leaf heat capacity and leaf heat transfer coefficient, we thoroughly tested and applied an active thermography method that uses a transient heat pulse to compute t, the time constant of leaf cooling after release of the pulse. We validated our approach in the laboratory on intact leaves of spring barley (Hordeum vulgare) and common bean (Phaseolus vulgaris), and measured t-changes at different boundary layer conditions.By modeling the leaf heat transfer coefficient with dimensionless numbers, we could demonstrate that t improves our ability to close the energy budget of plant leaves and that modeling of transpiration requires considerations of convection. Applying our approach to thermal images we obtained spatio-temporal maps of t, providing observations of local differences in thermal responsiveness of leaf surfaces. We propose that active thermography is an informative methodology to measure leaf heat transfer and derive spatial maps of thermal responsiveness of leaves contributing to improve models of leaf heat transfer processes.

Water Use, Leaf Cooling and Carbon Assimilation Efficiency of Heat Resistant Common Beans Evaluated in Western Amazonia

“…On the other hand, isohydric (“water-saving”) genotypes such as SEF 70 and SCR 56 presented low E that caused a greater increase in LTD . These genotypes were characterized by having the ability to have greater WUE , which is attributed to higher water content within the leaves, which allowed leaf-morphology-related thermal capacity to sustain gs under high temperatures ( Blum, 2009 ; Albrecht et al, 2020 ; Eustis et al, 2020 ). However, water savers in drought conditions are known to have low biomass accumulation and likely lower yield in comparison with spenders (dependent on water-availability scenario, if early, intermittent or terminal drought occur).…”

Application of the Machine Vision Technology and Infrared Thermography to the Detection of Hoof Diseases in Dairy Cows: A Review

“…Resolution of Thermal Images [64] 60 × 80 (0.005 MP) [65,66] 160 × 120 (0.019 MP) [67][68][69][70][71][72][73][74][75][76][77][78][79][80] 320 × 240 (0.077 MP) [63,81,82] 320 × 256 (0.085 MP) [83,84] 336 × 256 (0.086 MP) [85,86] 384 × 288 (0.111 MP) [59][60][61][62][87][88][89][90][91][92][93][94] 640 × 480 (0.307 MP) [95,96] 640 × 512 (0.328 MP)…”

Numerical simulation of the nocturnal cooling effect of urban trees considering the leaf area density distribution

“…The relationship between the CHTC of leaves and the mean wind speed for Z. serrata and C. camphora was obtained in the experimental field with an open area of 8800 m 2 in the city of Miyoshi, Aichi Prefecture, Japan (35.1355° N, 137.1001° E). Although the relationship between the CHTC of an isolated plate (single leaf) and dimensionless numbers (Grashof number and Reynolds number) is available in the literature (Schuepp, 1993;Albrecht et al, 2020), we parameterized the CHTC experimentally to better represent the characteristics of our target species (leaf size and movement of a leaf with the flow). The CHTC was estimated using the method of 14 simultaneous heat-balance equations by using the thermography of sunlit and shaded parts of a crown (similar to the methods of Horie et al, 2006).…”