The water flow in plant serves as the transport of nutrients and other substances and is done in a peculiar way different from animals.
The water circulates through plants from root to the vessel leaves lenosos.Es absorbed by the root, at the level of root hairs doing so the plants are nourished and physiological degradation more delay in time while without one.
Process by which water moves.
The water moves within the plant following the water potential differences. The water potential consists of several components:
- osmotic potential: is related to the osmolarity of the aqueous solution. Osmolytes depends dissolved in water.
Thus the water travels from areas with higher water potential to areas with lower potential. A plant in an optimal soil (water potential close to 0 kPa) water absorbed by the roots, traveling from the xylem to the leaves where it would evaporate and pass into the atmosphere, which has a really low water potential (from tens of kPa negative). The process described is called transpiration. Thus most of the water absorbed by plants is evaporated in the leaves. These forces of evaporation from the lives of all create a negative voltage is one that "pulls" the water into the upper branches and that the process of capillary action is not enough to carry water several feet high. Finally there is another force that raises the water in the xylem of the plant, is a positive pressure exerted by the root that absorbs water actively (by the absorption of osmolytes).
water potential
The liquid water is a fluid whose molecules are in constant motion. The ability of water molecules to move in a particular system depends on its free energy. The scale most commonly used to express and measure the state of free energy of water is the water potential Ψ. Water potential can be expressed in units of energy per unit mass or volume, the unit most commonly used the MPa (MPa = 10 bars), although in the recent past have also used the atmosphere and the bar (1 bar = 0.987 atm .) . Water movement in soil and plants occurs spontaneously along gradients of free energy from regions where water is abundant, and therefore has high energy freedom per unit volume (higher Ψ), to areas where the free energy of water is low (less Ψ). Pure water has a high free energy because the molecules can move freely. This is the reference state of water potential, to a mass of pure water, free, without interactions with other bodies, and normal pressure, corresponds to a Ψ 0. The Ψ is primarily determined by the osmotic effect associated with the presence of solutes by matric forces which adsorb or retain water in solid or colloidal arrays on the effect of altitude and positive or negative pressures or tensions in vessels or ducts where found. . These factors have an additive effect, which typically reduces the potential soil or ground water on the potential of pure water. Thus, in a particular system, the water potential is the sum total of four components:
Ψm Ψh = Ψo + + + Ψp Ψg
where Ψ mean potential, and the subscripts h, o, m , gyp, meaning water, osmotic, matric, gravitational, and pressure, respectively. The Ψo represents the component determined by the presence of dissolved solutes, decreases the free energy of water and can be zero or take on negative values. As solute concentration (ie, the number of solute particles per unit volume of solution) increases, the Ψo becomes more negative. Without the presence of other factors that alter the water potential, water molecules move solutions from places with low solute concentration to areas with higher concentrations of solute. The Ψo is treated as 0 for pure water. The Ψm represents the degree of water retention due to interactions with solids or colloidal arrays. Such matrices constitute the soil colloidal material and the cell walls. You can have zero or negative values. Finally the influence is Ψg gravitational field and is usually positive, although this depends on the position for the reference state. Ψp represents the hydrostatic pressure and can assume positive or negative values \u200b\u200bas the water is under pressure or tension. For example, Ψp pressure potential in the cells is positive and represents the pressure exerted by the protoplast against the cell wall, while the xylem is negative due to the tension developed by differences in water potential caused sweating. In the soil-plant-atmosphere water potential can be measured at various points in the path of movement of water from the soil through the plant to the atmosphere. Along the route, vary the contributions of the different components in determining the water potential.
