Plants turgor pressure

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. 

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... 

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. 

Plant foods are an important component of the diet of humans. Since the cell wall makes up a large component of the dry weight of plant tissues, and because in a normal diet most of the dietary fiber comes from plant cell walls, it follows that there is a need to know the composition of the cell walls. Moreover, the cell wall contributes (along with turgor pressure and the cell contents) to the texture of plant foods, and since humans consider the texture of foods an important sensory attribute, again, understanding wall composition is important. 

The functions of potassium in the plant are manifold. This element serves to activate or catalyze a host of enzyme actions, to facilitate the transport of nutrients and assimilates in the xylem and phloem, to maintain the structural integrity of the plant cell, to regulate turgor pressure, to mediate the fixation of nitrogen in leguminous plant species, and to protect plants to some degree from certain plant diseases. 

Subsequent tests with velvetleaf, Kodkia, Jerusalem artichoke, and cocklebur showed that their allelopathic action altered water balance (55,94,95). Growth reductions in sorghum and soybean seedlings in nutrient solution amended with extracts from these weeds correlated with high diffusive resistances and low leaf water potentials. Stomatal closure occurred in plants treated with the more concentrated extracts. Depressions in water potential were due to a reduction in both turgor pressure and osmotic potential. A lower relative water content was also found in velvetleaf-treated plants. These impacts on water balance were not from osmotic factors. Allelochemicals from these weeds have not been thoroughly ascertained, but the present evidence shows that some contain phenolic inhibitors. Lodhi (96) reported that Kodkia contains ferulic acid, chlorogenic acid, caffeic acid, myricetin, and quercetin. As noted earlier, an effect on plant-water relationships is one mechanism associated with the action of ferulic acid. 

Plant cells are surrounded by rigid cellulose walls, (unlike animal cells), but plant cells still take in water by osmosis when placed in pure water. However, plant cells do not burst because their cellulose cell walls limit how much water can move in. The cell walls exert pressure, called turgor pressure, as the cells take up water. Turgor... 

The plasma membranes of growing plant cells select to incorporate sugars, amino adds, ions and other low molecular weight compounds from the apoplastic space, and then, the cells have a certain level of osmotic pressure. The difference between their osmotic pressure and their wall pressure (=turgor pressure) is due to motive power (suction force) to suck water from the apoplastic space (Figure 1). The plant hormone auxin, which decreases the wall pressure in a growing plant cell, therefore induces cell elongation or expansion. 

Plant cells contain one or more large vacuoles, which are storage sites for Ions and nutrients. Osmotic flow of water Into vacuoles generates turgor pressure that pushes the plasma membrane against the cell wall. 

The rigid cell wall surrounding plant cells prevents their swelling and leads to generation of turgor pressure in response to the osmotic Influx of water. 

Regulation of turgor pressure In plant tonoplast Plant plasma membrane Yeast plasma membrane... 

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