The Thermodynamics of Active (Non-osmotic) Water Absorption

Abstract

The equation S = 1.28 X 10-8p2A was developed to calculate the amt. of sugar that would have to be respired to maintain a negative diffusion gradient-of p atms. S = gm. glucose/gm. tissue/hr. and A = specific surface across which the gradient occurs. Using this equation it was found that respiratory energy is incapable of maintaining a negative gradient of >1 atm. between the osmotic pressures of the vacuole and cytoplasm of a cell. A critical evaluation of higher values obtained by other workers revealed that these are due to incorrect interpretations. The negative gradient of 1 atm. obtained by van Overbeek between the stele and the tissues external to it could be maintained by the energy released from the respiration of 0.3 micrograms sugar/100 gm. tissue/hr. This negative gradient is therefore thermodynamically possible.