the Mechanism floemnogo transport. Sucrose deduction in sitovidnyh tubes ' in the course of transport

you are: the Mechanism floemnogo transport

During transport on floeme it is observed vysokoizbiratelnoe sucrose deduction in sitovidnyh tubes. The majority of other molecules can freely diffundirovat both in sitovidnye tubes, and from them; thus they are in an equilibrium state with surrounding molecules of the same type. Sucrose deduction in sitovidnyh tubes occurs against a considerable gradient of concentration and demands a constant expense of metabolic energy. Assume that sitovidnye tubes contain a considerable quantity ATR-ELEMENTS which, probably, participates in this process. recognising that kletkisputnitsy look very dense and abound mitohondrijami, it is possible to think that in them there are highly active metabolic processes. One of their functions, possibly, consists that they provide adjacent sitovidnye tubes with the energy necessary for maintenance of selective permeability of membranes.

Despite the fact that what for maintenance of the given system the energy considerable quantity, in itself transport in sitovidnyh tubes is required does not depend on a metabolism. speed of transport changes according to a consumption level. Thus, the metabolism provides only removal of sucrose from floemy. This process together with metabolic loading also delivers energy for continuous functioning of system. The overflowing of solutions of nutrients from their sources to consumption or storage places occurs on is pure-physical gradients.

Hence, the theory of an overflowing of solutions can explain the basic features floemnogo transport. The unique structure, which role is not understood yet, is a F-fiber. The assumption has been come out that mikrofilamenty F-fiber create a surface for transport of substances on border of section of two phases, promoting that to fast movement of a solution on floeme. But till now there is no experimental acknowledgement of this assumption. Though there are, apparently, any else additional mechanisms floemnogo transport and the theory of an overflowing of solutions, possibly, will change in the future a little, now it represents the best description of transport assimiljatov on sitovidnym to tubes floemy.