Addendum 
 
CIRAS-2 Operator's Manual Version 2.04 
- 162 - 
Addendum 
 
Corrections to Stomatal Resistance Measurements for Differing Transpiration 
Rates from Upper and Lower Leaf Surfaces 
 
The assumption is made that the internal diffusion resistance to water vapor and CO
2
 are small compared 
with the stomatal resistances, so that there are uniform H
2
O and CO
2
 concentrations within the leaf. 
 
 
 
 
 
 
   
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Where: 
 
(ea) and (el) are the water vapor pressures of the cuvette air and the leaf air spaces respectively 
 
RB is the boundary layer resistance for whole leaf, with RBu = RBl = 2(RB) (m
2
 s mol
-1
) 
 
RS is the total leaf resistance 
 
 
Then for the two leaf surfaces: 
 
N and (1-N) are the fractions of the total evaporation E in mol m
-2 
s
-1
 from the upper (u) and lower (l) leaf 
surfaces 
 
                (1) 
and 
 
                 (2)