Oxygen supply Membrane diffusion

The results of such studies are consistent with the concept that the polarity of auxin transport is imposed by the active secretion of auxin molecules out of the cytoplasm through the membrane at the base of the cell and that the molecules then diffuse passively into the adjacent cell below. This model, first developed by Hertel (1962), Hertel and Leopold (1962, 1963), Leopold (1963), assumed that secretion is mediated by metabolically driven carriers which is a feature consistent with the facts that auxin transport depends upon an adequate oxygen supply (e.g., Gregory and Hancock 1955, Brown and Wet-... 

Laboratory-scale bubble columns for ozonation preferably have a reactor liquid phase volume of VL = 2-10 L, with a height-to-diameter-ratio of hid = 5-10. The ozone/oxygen (ozone/air) gas mixture is supplied through a ceramic or stainless steel porous plate fine pore diffuser (porosity 3,10-40 pm hole diameter). PTFE-membranes are a comparatively new alternative for the ozone gas-to-water transfer (Gottschalk et al., 1998). 

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