advantage and disadvantages of fensom and ner

Question

Advantage and disadvantages of Fensom and Spanner Electroosmotic Flow Hypothesis

The model has several advantages over Munch's model. The presence of P- proteins, and the occlusion of sieve plate pores by filaments bearing negative fixed charges are in favour of this model. While these filaments would greatly impede the flow of phloem sap under a pressure gradient, they would make electroosmotic flow more efficient. The negative aspects of this model are:

1. The apparent irrelevance of the source-sink long distance relationship .
2. Prohibitively large expenditure of energy (ATP) for K⁺ uptake and release by the companion cells and
3. Contradiction of the model in respect of anionic fluxes which would be excluded by electroosmosis across channels bearing negative fixed charges. So long the basic premises of this model are not established by experimental evidences; the model remains an interesting candidate for the mechanism of translocation in phloem.