Accumulation of Solutes in Leaves of Sorghum and Sunflower in Response to Water Deficits

187

107

Osmotic adjustment was studied in cultured cells of tomato (Lycopersicon esculentum Mill cv VFNT-Cherry) adapted to different levels of external water potential ranging from -4 bar to -28 bar. The intracellular concentrations of reducing sugars, total free amino acids, proline, malate, citrate, quaternary ammonium compounds, K@, NO3-, Na', and Cl1 increased with decreasing external water potential. At any given level of adaptation, the maximum contribution to osmotic potential was from reducing sugars followed by potassium ions. The sucrose levels in the cells were 3-to 8-fold lower than reducing sugar levels and did not increase beyond those observed in cells adapted to -16 bar water potential. Concentrations of total free amino acids were 4-to 5-fold higher in adapted cells. Soluble protein levels declined in the adapted cell lines, but the total reduced nitrogen was not significantly different after adaptation. Uptake of nitrogen (as NH4' or NO3-) from the media was similar for adapted and unadapted cells. Although the level of quaternary ammonium compounds was higher in the nonadapted cells than that of free proline, free proline increased as much as 500-fold compared to only a 2-to 3-fold increase observed for quaternary ammonium compounds. Although osmotic adjustment after adaptation was substantial (up to -36 bar), fresh weight (volume increase) was restricted by as much as 50% in the adapted cells. Altered metabolite partitioning was evidenced by an increase in the soluble sugars and soluble nitrogen in adapted cells which occurred at the expense of incorporation of sugar into cell walls and nitrogen into protein. Data indicate that the relative importance of a given solute to osmotic adjustment may change depending on the level of adaptation.

Section: Discussionmentioning

confidence: 99%

Solutes Contributing to Osmotic Adjustment in Cultured Plant Cells Adapted to Water Stress

Handa¹,

Bressan²,

Handa³

et al. 1983

187

107

“…Sulfates were measured turbidometrically according to the method of DeJorge et al (5), and phosphates by the procedures of Fiske and Subbarow (7). Total carboxylic acids were separated and determined by titration to pH 7.0 with standard KOH (22). Qualitative analysis of the carboxylic acid extract by paper chromatography revealed that malate and soluble oxalate were most abundant; consequently, total organic acids were calculated as dicarboxylates.…”

Section: Methodsmentioning

confidence: 99%

“…Qualitative analysis of the carboxylic acid extract by paper chromatography revealed that malate and soluble oxalate were most abundant; consequently, total organic acids were calculated as dicarboxylates. Total amino acids were separated as described by Jones, Osmond, and Turner (22), evaporated to dryness, dissolved in water, and titrated with standard NaOH. Total free sugar analyses also followed the procedure of Jones, Osmond, and Turner (22).…”

Section: Methodsmentioning

confidence: 99%

“…Total amino acids were separated as described by Jones, Osmond, and Turner (22), evaporated to dryness, dissolved in water, and titrated with standard NaOH. Total free sugar analyses also followed the procedure of Jones, Osmond, and Turner (22). Proline was measured according to the procedure of Bates et al (3), and betaine according to the procedure of Storey and Wyn-Jones (26).…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Rapid Osmotic Adjustment by a Succulent Halophyte to Saline Shock

Mcnulty¹

1985

The objective of this research was to measure the short term osmotic adjustment of Saticornia europaea L. ssp. rubra (A. Nels) Breitung when suddenly exposed to 100 millimolar NaCl. Plants were grown hydroponically, shocked with 100 millimolar NaCI added to the culture solution, and stem tips analyzed for free inorganic ions and small organic molecules at intervals up to 72 hours. In the first 2 hours, the calculated leaf osmoticum showed a net increase of 158.8 millimolar most (16,18,20,28,32). Compartmentation of extraneous ions in the vacuole would necessitate an equal amount of compatible solutes in the cytoplasm to balance the water potential. Small organic molecules that could act alone as osmotica in the cytoplasm without disruption of metabolic reactions have been reported (4,10,21,24,26,27 possible mechanism for cytoplasmic osmotic adjustment is a general increase in osmotica as suggested by Greenway and Sims (15) or an increase in two or more organic solutes together (10, 24).The experimental design used by most investigators of salt tolerance mechanisms in terrestrial halophytes has been to grow them in ranges of salinity, followed by analyses of potential osmotica. There is little experimental evidence for the changes that occur in the leaves of halophytes when subject to salinity shock, i.e. a sudden increase in exogenous salt concentration (13). The objective of this study was to investigate the short term osmotic adjustment by a succulent, C3, salt-accumulating halophyte when subjected to a saline shock, measuring the degree of osmotic adjustment achieved, and ascertaining which solutes might be responsible. MATERIALS AND METHODSSeeds of Salicornia europaea L. ssp. rubra (A. Nels.) Breitung were collected locally and germinated in vermiculite wet with Hoagland solution. When about 2 cm high, the seedlings were transferred to large hydroponic tanks containing Hoagland solution plus 10 mM NaCl. The tanks were continuously aerated and the culture solution was changed at 2-week intervals. Sixty d after transplanting, the plants were still vegetative, profusely branched, and about 30 cm tall. At this time (time 0), 4 h after sunrise, 1-to 2-cm samples were taken from the terminal ends of the succulent stems. NaCl was then added to the culture solution to bring it to 100 mm NaCl, and samples were again taken at 2,4,6,8,12,16,20,24, 48, and 72 h after the addition of salt. Sampling was terminated at 72 h, because previous experiments indicated that 96% of the osmotic adjustment had occurred by this time, complete adjustment required 195 h. The samples were all taken from the terminal ends of the stems to insure similar ages and stages ofdevelopment ofthe tissues. They were rapidly rinsed in distilled H20, damp dried, sealed in bottles, and frozen in liquid N2.Extraction and Analysis. Osmotic potential of the terminal shoots was measured cryoscopically with an osmometer. Pressure extraction of the frozen and thawed shoots did not provide satisfactory reproducible results, so the following proce...

“…Free amino acids can also act as osmotically active solutes and have been linked to osmotic adjustment during water stress (5). A possible role of free amino acids in the development of freezing resistance in strawberry leaves was therefore examined.…”

Section: Methodsmentioning

confidence: 99%

Osmotic Adjustment and the Development of Freezing Resistance in Fragaria virginiana

O’Neill¹

1983