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
Mesoderm two layers cover the intraembryonic cavity. The parietal layer together with overlying ectoderm forms the lateral body wall folds. The visceral layer forms the walls of the gut tube. Mesoderm cells of the parietal layer form the mesothelial membranes or serous membranes which line the peritoneal, pleural and pericardial cavities. Mesoderm In all bilaterian animals, the mesoderm is one of the three primary germ layers in the very early embryo. The other two layers are the ectoderm (outside layer) and endoderm (inside layer), with the mesoderm as the middle layer between them. The mesoderm forms mesenchyme, mesothelium, non-epithelial blood cells