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It was previously reported that the p...
It was previously reported that the plant cytoplasm
membrane significantly differs in it’s water conducting
properties from the vacuole membrane.
In this short paper we’ll try to explain the functional logic behind this
difference, by building a mathematical model.
The model imitates cell submerged in a solution. As the outer osmolarity changes, water flux is created, until osmolarity in all the compartments reach equilibrium. During this process, the submerged cell changes it’s volume. The ratio in the volume between the cytoplasm and the vacuole may change as well.
We’ll introduce a constant representing membrane’s maximum water conductance properties per unit of time (PP—Physical Permeability).
The water conducting properties of the both membranes (PP), affect the maximum rate of water flux between the cell compartments and the surroundings.
As experiments show, the difference in the PP of the Vacuole membrane can get 100 or more times larger than the Cytoplasm membrane.
What is the functional logic of such difference ?
To answer that, we’ll simulate cell swelling and monitor the osmolarity inside the cell compartments, at different possible values of PP.
Vacuole PP = 1 Cytoplasm PP = 1(Click to see the movie clip)
Vacuole PP = 10 Cytoplasm PP = 1 (Click to see the movie clip)
The results of both simulations are presented in the
following chart.
In conditions when the Vacuole membrane’s PP is larger than the Cytoplasm, we can see much more gradual osmolarity change inside the compartment where most of the enzymatic processes happen, the cytoplasm.
The final osmolarity of the compartments in both cases (when the PP ratio is 1 and 10) does not differ greatly.
The advantage of the large difference between the water conducting properties of the membranes, can be compensation of the larger osmotic potential across the cytoplasm membrane, exposed to the changes in surroundings osmolarity, allowing both compartments to change their volume in a similar rate.
More gradual changes in osmolarity in the cytoplasm may diminish possible damages caused by sudden changes the solute concentration.
Methodology
The experiments were simulated in Data-Light 0.1 platform. Featuring built-in configurable model simulations synchronized with custom graphics.
(c) L-Data Research Ltd, Israel
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