Soil plant atmosphere continuum Soil plant atmosphere continuum The soil-plant-atmosphere continuum (SPAC) is the pathway for water moving from soil through plants to the atmosphere. Continuum in the description highlights the continuous nature of water connection through the pathway. The low water potential of the atmosphere, and relatively higher (i.e. less negative) water potential inside leaves, leads to a diffusion gradient across the stomatal pores of leaves, drawing water out of the leaves as vapour. As water vapour transpires out of the leaf, further water molecules evaporate off the surface of mesophyll cells to replace the lost molecules since water in the air inside
Double layer (biology) Double layer (biology) In biological systems, a double layer is the surface where two different phases of matter are in contact. Biological double layers are much like their interfacial counterparts, but with several notable distinctions. The surface of biological cells carry many different types of chemical groups, each with a different dissociation constant, causing them to have varying electric charges at a physiological pH. This indicates that biosurfaces are chemically heterogeneous. This biospecific feature is typical for all biosurfaces, including proteins, macromolecules and biological cells. In certain organisms, cells are covered with the glycocalyx layer, which can be modeled as