Theory of Chemiosmotic Polar Diffusion

Recently, Jacobs and Gilbert (1983) succeeded in visualizing in pea stem tissue by means of an indirect immunofluorescence technique the presumptive auxin transport carrier in the plasma membranes at the basal ends of parenchyma cells sheathing the vascular bundles. 

This new theory has been extensively discussed in the review of Goldsmith in 1977 (see also Rubery 1980), and her introductory sentences (p 441) outline the basic concept. Cells, being more permeable to undissociated auxin molecules than to auxin anions, can accumulate auxin when the pH of the cytoplasm is above that of the walls... Carriers may be but are not necessarily involved in passage across the cell membrane... Unlike the conventional theory of polar secretion, which presumes active transport of auxin with direct coupling of energy to carriers in those cases when auxin transport appears to be uphill. 

3 Transport and Other Modes of Movement of Hormones (Mainly Auxins) 

according to this theory, polarity of transport is produced by an asymmetry in cellular permeability to the auxin anions (see also Sect. 3.2.3.3), but polar transport is basically an asymmetric diffusion (Goldsmith 1977, p 457). Therefore, the theory requires that profiles of the distribution of radioactivity in plant parts which had been supplied with a constant concentration of labeled auxin should fit to a solution of Pick s second law of diffusion, which relates the concentration to both the time of transport and the distance from the source, namely to error function curves. Such curves are constructed from 

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