Which subject the same energy fluxes the leaf

770 36 Thermography to Measure Water Relations of Plant Leaves

The transfer velocity kheat can be defined as the ratio of the diffusion coefficient D to the diffusion length ∆x:

kheat = −D∆x	(36.11)

∆cwv jwv = −Dwv ∆x = kwv ∆cwv

∆cwv is the difference between water vapor concentrations inside the leaf and in the surrounding turbulent air. The concentrations can be ex-pressed as relative humidities (fractions of the water vapor saturation concentration at the given temperature):

Equation (36.2) can now be expressed by the individual contributing terms:

leaf

=	solin +	IR	surr−

(36.15)

+2kleaf heatρ cp (Tair − Tleaf) + kwv λ cwv (hleaf − hair)

ref

=	solin +	IR	surr−	ref +

If both the leaf and the object are in the same environment, Tair and Tsurr can be considered equal in both equations and, therefore, one of these temperatures can be eliminated to obtain one single equation. If this is done for T4 surr, we get
�	C A	+ 2αleaf IRσ�T4 ref− T 4 leaf�+ 2ρcp�kleaf heat−αleaf αref IR IRkref heat�Tair + 2ρcp�αleaf αref IR IRkref heatTref − kleaf heatTleaf�+ jlat

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