Turgor pressure

Cell enlargement occurs when a demand for water is created by relaxation of the cell walls under the influence of turgor pressure and wall-loosening factors. Water enters the cell down a water potential gradient, extending the cell walls (Lockhart, 1965 Boyer, 1985 Tomos, 1985). 

Table 3. Yield threshold and effective turgor pressure in growing tissues...

Table 4. Wheat root seedling elongation (30 replicates), tip turgor pressure (4 mm, >10 replicates) and tip tensiometric plasticity (2-7 mm, >10 replicates) following various growth altering treatments...

Munns, R., Greenway, H., Stelter, T.L. Kuo, J. (1983). Turgor pressure, volumetric elastic modulus, osmotic volume and ultrastructure of Chlorella emersoni grown at high and low external NaCl. Journal of Experimental Botany, 34,144-55. 

Zimmerman, U., Steudle, E. Lelkes, P.I. (1976). Turgor pressure regulation in Valonia utricularis. Effect of cell wall elasticity and auxin. Plant Physiology, 58, 608-13. 

Turgor pressure of single leaf cells was measured by an improved version of the cell pressure probe according to Husken et al. (7). Mikrocapillaries were pulled on a laser heated pulling device. 

Weed Extract in Nutrient Medium (g ml) Abaxial Leaf Resistance (sec/cm) Water Potential (bars) Osmotic Potential (bars) Turgor Pressure (bars)... 

Vacuoles (70-78) are membrane-bound regions of the cell filled with cell sap. Vacuoles are surrounded by a tonoplast (vacuolar membranes) and are diverse with distinct functions. Most investigators believe that lysosomes and the plant vacuoles are the same. Vacuoles develop turgor pressure and maintain tissue rigidity. They are storage components for various metabolites such as reserve proteins in seeds and malic acid in crassulacean acid metabolism (CAM) plants. Vacuoles canremove toxic secondary products and are the sites of pigment deposition. 

A decrease in firmness, linked to osmodehydration in both glucose and sucrose, was also observed in apple cylinders (Reppa et al., 1998). This could be due to loss of turgor pressure, which makes the cells of plant tissues less rigid, i.e., fracturability disappears while deformability increases (Aguilera... 

It has been suggested10 18 that the electroosmotic movement of water towards the cathode that causes oedema at the cathode site leads to increase of tissue turgor pressure there 18 it results in completely suspended circulation in the capillaries in the cathodic field leading thus to tissue death. 

These effects of ozone on the permeability of this algal system may be sximmed up as follows during exposure, K" " leaks out of the cell and cannot be pumped back in even when exposure is discontinued and the K" " leak has ceased, the cell is still unable to restore the lost K+ if a critical level of cellular K+ has been lost at this point, turgor pressure and water content become depressed, the metabolic control provided by ionic balance is lost and general metabolic alterations should be observed (17). 

Texture has been recognized as one of the most important quality attributes in dried potatoes which contribute to the consumer acceptance. Texture of potatoes is affected by drying processes and it is strongly associated with composition and stmcture of cells walls (Ramos et al., 2003). As previously stated, water loss is accompanied by loss of internal pressure cellular tissue shrinks and becomes soft. This pressure is known as turgor pressure and plays an important role in the rheological and textural properties of the potato tissue. 

Plants use osmotic pressure to achieve mechanical rigidity. The very high solute concentration in the plant cell vacuole draws water into the cell (Fig. 2-13). The resulting osmotic pressure against the cell wall (turgor pressure) stiffens the cell, the tissue, and the plant body. When the lettuce in your salad wilts, it is because loss of water has reduced turgor pressure. Sudden alterations in turgor pressure produce the movement of plant... 

The sensitive plant (Mimosa pudica) also undergoes a remarkable change in leaf shape triggered by mechanical touch (Fig. 2). A light touch or vibration produces a sudden drooping of the leaves, the result of a dramatic reduction in turgor pressure in cells at the base of each leaflet and leaf. As in the Venus flytrap, the drop in turgor pressure results from K+ release followed by the efflux of water. 

These cells reabsorb water during urine formation, a process for which water movement across membranes is essential (Box 11-3). The plant Arabidopsis thaliana has 38 genes that encode various types of aquaporins, reflecting the critical roles of water movement in plant physiology. Changes in turgor pressure, for example, require rapid movement of water across a membrane. 

---