The boundary layer resistance r_bl (that is the inverse of g_bl) is the last resistance in the pathway of water moving from soil through the plant to the atmosphere (Soil-Plant-Atmosphere Continuum - SPAC). In gas exchange studies at leaf or whole plant level, the rule of g_bl (leaf boundary layer conductance) is often underrated and neglected.

The boundary layer (bl) is affected by factors that influence aerodynamic characteristics of leaves such as leaf shape and structural characteristics of field or orchard. In particular it is strictly correlated to structural characteristics that can influence leaf aerodynamic interaction with the surrounding air: density of plantation, presence of windbreaks, height of plants, wind speed and direction, training system and planting system.

This sensor (leaf replica) utilizes the method of Brenner A.J. and Jarvis P.G. (1995).

Leaf-replica sensor was shown at the "2nd International Conference on Landscape and Urban Horticulture", held in Bologna in June 2009:

Photos of the sensor (for orange trees) at congress stand:

Datasheet