| Abstract: | It was shown earlier (Laisk, Oja, and Kull, 1980) that differentstomata on a barley leaf are open to different degrees. Therefore,stomatal conductance is a quantity which is statistically distributedover a large range in the geometry of one leaf. Gas exchangemeasurements based on transpiration rates represent the averagevalue of stomatal conductance in the leaf chamber. The conventionalmethod of calculating mesophyll resistance involves subtractingstomatal resistance from total leaf resistance. It is incorrect,however, to average the stomatal resistance before this subtraction.Therefore, the conventional method for calculating the mesophyllresistance contains an error as it neglects the statisticaldistribution of stomatal apertures. The error is significantwhen the diffusion resistance between neighbouring substomatalcavities is large and when stomatal apertures vary over a widerange. Key words: Mesophyll resistance, Stomatal conductance, Statistics |
