Osmotic, adjustment

Rower, D.J. Ludlow, M.M. (1986). Contribution of osmotic adjustment to the dehydration tolerance of water-stressed pigeon pea (Cajanus cajan (L.) Millsp.) leaves. Plant, Cell and Environment, 9, 33-40. 

Matsuda, K. Riazi, A. (1981). Stress-induced osmotic adjustment in growing regions of barley leaves. Plant Physiology, 68, 571-6. 

Sharp, R.E., Hsiao, T.C. Silk, W.K. (1988). Growth of the maize primary root at low water potentials. II. Spatial distribution of osmotic adjustment in the growing zone. Plant Physiology, (in press). 

Shone, M.G.T. Flood, A.V. (1983). Effects of periods of localised water stress on subsequent nutrient uptake by barley roots and their adaptation by osmotic adjustment. New Phytologist, 94, 561-72. 

Steponkus, P.L., Shahan, K. W. Cutler, J.M. (1982). Osmotic adjustment in rice. In Drought Resistance in Crops with Emphasis on Rice, pp. 181-94. Los Banos, Philippines International Rice Research Institute. 

Turner, N.C. Jones, M.M. (1980). Turgor maintenance by osmotic adjustment A review and evaluation. In Adaptation of Plants to Water and High Temperature Stress, ed. N.C. Turner and P.J. Kramer, pp. 87-103. New York Academic Press. 

Westgate, M.E. Boyer, J.S. (1985 ). Osmotic adjustment and the inhibition of leaf, root, stem and silk growth at low water potentials in maize. Planta, 164, 540-9. 

Fig. 4. Whole-plant fresh weight and leaf osmotic adjustment of Thino-pyrum bessarabicum as a function of time following the gradual addition of 250 mol m NaCl to the culture solution. Fresh weight = control, O = 250 mol m NaCl. Leaf sap osmotic pressure = 250molm NaCl.

When data on the amphidiploid and the hexaploid wheats are considered (Table 5), the former being substantially more salt tolerant in hydroponic culture, then again several points are noted. First, the sap osmotic pressure in the young leaves is least in the tolerant amphidiploid. Secondly, Na" and Cl levels are also lower in the juvenile amphidiploid leaves. These data imply that minimal osmotic adjustment is more beneficial than apparently complete osmotic adjustment. 

Accumulation of compatible solutes (glycine betaine, proline and polyols such as mannitol, sorbitol and pinitol) occurs in many droughted plants and they act as cytoplasmic osmotica for osmotic adjustment. However, they may have other functions which include enhancing the stability of macromolecules and membranes (Paleg, Stewart Starr, 1985 Smirnoff Stewart, 1985 Chapter 7). 

Osmotic adjustment Cell expansion and Morgan Condon,... 

Some wild species have larger capacities for osmotic adjustment, a trait which may improve yield during drought (Table 3, Turner, 1986). Interesting examples of this are Dubautia species from Hawaii which differ in osmotic adjustment mainly as a result of differences in cell wall elasticity. Interspecific hybrids can be made which have intermediate properties (Robichaux, Holsinger Morse, 1986). Material such as this could make a basis for the molecular study of differences in cell wall elasticity. 

La Rosa, P.C., Hasegawa, P.M., Rhodes, D., Clithero, J.M., Watas, A.A. Bressan, R.A. (1987). Abscisic acid stimulated osmotic adjustment and its involvement in adaptation of tobacco cells to NaCl. Plant Physiology, 85, 174-81. 

Cells selected for tolerance to water stress have been demonstrated in a number of plant species (Handa et al., 1983 Heyser Nabors, 1981 Stavarek Rains, 1984b). High molecular weight PEG is commonly used to induce water deficits (Hasegawa et al., 1984). This provides an opportunity to evaluate intracellular osmotic adjustment of plants exposed to water stress. If information is desired on the effect of specific osmotic substances on cellular adjustment to osmotic stress PEG can be used as an independent osmotic regulator and/or in combination with an absorbable osmoticum. In these situations the interaction of osmoticum produced by the cell with the osmoticum absorbed by the cell can be evaluated. 

The common response of both cultured cells and cells comprising the body of a plant when these two systems are exposed to water stress is the requirement for osmotic adjustment. It seems reasonable then to expect that information obtained at the cellular level should enhance our understanding of the biochemical and physiological response of plants exposed to water stress. 

Osmotic adjustment by plant cells in response to an increasing saline environment can be mediated by an alteration in intracellular concentrations of both inorganic and organic ions (Wyn Jones, 1980,1984 Aspinall, 1986 Flowers Yeo, 1986 Grumet Hanson, 1986 Moftah Michel, 1987). 

A number of chapters in this volume (especially Chapters 5 and 6) provide a more thorough discussion of osmotic adjustment by intact plants and tissues in response to environmental stress and the role of osmotically active solutes in this response. The following section focuses on the role of organic osmotica in the response of plant cells to salt stress. Cultured plant cells offer the opportunity to evaluate the effect of both internally synthesised and externally administered organic osmotica. 

Brassica napus cells have been selected for tolerance to Na2S04 (Chandler Thorpe, 1987). When selected cells were compared with non-selected cells in response to Na2S04 salinity the selected cells grew better and showed less negative cell water potential than the non-selected cells. Both cell lines showed osmotic adjustment and proline accumulation. However, proline accumulation was related to inhibition of growth and did not play a significant role in osmotic adjustment. 

Handa, S., Bressan, R.A., Handa, A.K., Carpita, N.C. Hcisegawa, P.M. (1983). Solutes contributing to osmotic adjustment in cultured plant cells adapted to water stress. Plant Physiology, 73, 834-43. 

Hsiao, T.C., O Toole, J.C., Yambao, E.B. Turner, N.C. (1984). Influence of osmotic adjustment on leaf rolling and tissue death in rice Oryza sativa L.). Plant Physiology, 75, 338-41. 

McCree, K.J., Kallsen, C.E. Richardson, S.G. (1984). Carbon balance of sorghum plants during osmotic adjustment to water stress. Plant Physiology, 76, 898-902. 

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