Diffusion pressure deficit

The original proposal concerning the mode of action of auxin stated that auxin made cell walls more plastic, thus inducing a water-diffusion-pressure deficit and causing the cells to expand (7). Much evidence has since been gathered in support of this hypothesis. For example, in Avena coleoptiles it has been established that the auxin-induced increase in plasticity precedes, or coincides with, the... 

Pfeifer s system involved separation of the sucrose solution from water (the solvent) by a membrane allowing diffusion of water molecules but not of sucrose and a membrane of this type was described as semipermeable. Further, the movement of water into the sucrose solution was prevented hy a hydrostatic pressure applied to the solution the osmotic pressure was revealed as a deficit of hydrostatic pressure, as a diffusion pressure deficit DPD) of water in the sucrose solution. The osmotic pressure of the solution was the excess hydrostatic pressure which when applied to the solution prevented osmosis (the net diffusion of water across the membrane) by raising the chemical potential (activity) of the water in the solution to that of pure water at the same temperature. This reduction of... 

Fig. 2.S. Relationship between change in tissue or cell volume or weight from its initial (natural) value and the osmotic potential of the solution in which it is immersed. The osmotic potential in which there is no change in volume or weight gives the (water potential of protoplast) of the cell or tissue. Pp is equal but opposite in sign to the DPD (diffusion pressure deficit) or SF (suction force). (From T. A. Rennet-Clark, in Plant Physiology, vol. 2, pp. 105-192, edited by F. C. Steward, Academic Press, New York, 1959.)...

Conde,L.F., Kramer, P.J. The effect of vapor pressure deficit and diffusion resistance in Opuntia compressa. Can. J. Bot. 53,2923-2926 (1975)... 

An important feature of salts with diffuse dissolution regime is their capability to dissolve quickly at the excess of moisture and precipitate easily at its deficit. In conditions humid climate these salts are easily removed from the surface. An exception is salt karst associated with young diapirs in Rumania. On the surface and outside water bodies they are preserved only in conditions of arid climate (Iran, Israel, Chile). Their main mass is associated with evaporite sequences in the subsurface. In conditions of high pressure and temperature halite, sylvinite and some other soluble salts acquire plasticity and because of this become impermeable. That is why at depth they play role of a aquifuge and are subject to diapirism. 

Deviations from stoichiometry and chemical diffusion in metal-deficit samples were studied at 973 to 1273K, for S activities of 0.1 to lOOOOPa, by using a microthermogravimetric technique. It was found that the non-stoichiometry was a function of temperature and the equilibrium S pressure thus indicating that the cation vacancies did not interact, were fully ionized and were randomly distributed throughout the crystal lattice. Re-equilibration-rate measurements of nonstoichiometry showed that the vacancy diffusivity (a direct measure of defect mobility) did not depend upon their concentration and could be described by ... 

Many explosives, which have solid carbon as a detonation product, exhibit behavior that is not described adequately without including some time-dependent phenomenon, such as diffusion-controlled carbon deposition or some other kinetic behavior of the detonation products. A time-dependent carbon deposition is the only process known that could account for the large energy deficits required by the build-up model. The observed velocity constancy and large C-J pressure variations can be reproduced by the time-dependent carbon deposition mechanism. 

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