Osmoregulation

Hellebusi, J A

doi:10.1146/annurev.pp.27.060176.002413

Cited by 340 publications

(129 citation statements)

References 72 publications

Supporting

Mentioning

121

Contrasting

Unclassified

Order By: Relevance

“…Furthermore, the alga was able to grow well even with internal proline concentration of 1600 mM. These results, therefore, appear to support the role of proline as a compatible cytoplasmic solute in plant cells (2,3,7,9,15,27,28). In our present studies, the inhibition of growth in C. autotrophica at high salinities was found to be associated with a decline in the cells' apparent turgor pressure under these conditions.…”

Section: Resultssupporting

confidence: 63%

“…Algae living in marine environments such as estuaries, tide pools, and brackish water ponds can tolerate a wide range of external salinities (6,14,15). At least some of these euryhaline algae possess a proper cell wall, thus, so far as the solute and water relations are concerned, they should respond to salinity in a manner similar to cells of higher plant halophytes.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Osmoregulation in the Extremely Euryhaline Marine Micro-Alga Chlorella autotrophica

Ahmad¹,

Hellebust²

1984

Plant Physiol.

View full text Add to dashboard Cite

Chlorella autotrophica (Clone 580) grows over the external salinity range of I to 400% artificial sea water (ASW), can photosynthesize over the range from I to 600% ASW, and survives the complete evaporation of seawater. The alga grown at high salinities shows an increase in cell volume and a small decrease in cell water content. Measurements of ion content were made by neutron activation analysis on cells washed in isoosmotic sorbitol solutions which contained a few millimolar of major ions to prevent ion leakage. Cells grown at various ASW concentrations contain large quantities of sodium, potassium, and chloride ions. Measurements of cations associated with cell wall and intracellular macromolecules were made to determine intracellular concentration of free ions. The proline content of cells increases in response to increases in external

show abstract

Section: Resultssupporting

confidence: 63%

mentioning

confidence: 99%

Osmoregulation in the Extremely Euryhaline Marine Micro-Alga Chlorella autotrophica

Ahmad¹,

Hellebust²

1984

Plant Physiol.

View full text Add to dashboard Cite

show abstract

“…This conjecture was based on their observation that stylet exudation continued at a constant rate during reciprocal variations in sucrose and K content, on similar reciprocal variations in sucrose and total amino acid content observed in 1955 by Hill (cited by Peel and Hoad [13]), and on reversible changes in exudate concentration produced by varying the xylem water potential by pressurization and by osmotica (15). More recent work concerning the role of turgor pressure in osmoregulation, particularly in marine algae (reviewed by Hellebust [5]), emphasizes the potential importance that similar processes might play in sieve tube physiology.…”

mentioning

confidence: 76%

Direct Measurement of Sieve Tube Turgor Pressure Using Severed Aphid Stylets

Wright

Fisher²

1980

Plant Physiol.

View full text Add to dashboard Cite

Turgor pressure in individual sieve tubes was measured directly by gluing capillary micromanometers over exuding aphid stylets with cyanoacrylate adhesive. Pressures of up to 10 bars were measured in sieve tubes of Salix babylonica, with an estimated accuracy of ± 03 bars or better.For comparison with the direct measurements of sieve tube turgor, calculated values of turgor pressure were also obtained from the difference between leaf water potential and phloem exudate solute potential, estimated from its refractive index and sucrose content. In most cases the measured turgor pressure was greater than the calculated value. The discrepancy between the two values was most likely due to the presence of appreciable concentrations of potassium and amino acids in the phloem exudate.Sieve tube turgor plays a central role in the physiology of phloem transport. Movement of solutes along the sieve tubes is almost certainly driven by osmotically generated pressure flow (3,6,10). Measurements of the turgor pressure are needed to estimate this driving force and its variation under different conditions. Also, although the evidence is fragmentary, several observations support the suggestion by Peel and Hoad (13) proportional to the fourth power of its radius. In 1968, Hammel (4) introduced a "phloem needle" technique for the direct measurement of sieve tube turgor and found pressures ranging from 7 to 24 bars at various heights in a red oak tree. Sheikholeslam and Currier (17) used Hammel's technique to measure sieve tube turgors of 0.3-10 bars in the squirting cucumber, Ecballium.The above techniques suffer various shortcomings. The first two are indirect and may be fairly inaccurate, while the phloem needle technique destroys the sieve tubes, allowing only a single measurement. The method presented in this report allows the direct measurement of sieve tube turgor over extended periods of time in intact, functioning sieve tubes. MATERIALS AND METHODSColonies of the willow aphid (Tuberolachnus salignus Gmelin) were maintained on weeping willow saplings (Salix babylonica L.) in a growth chamber on a 17-h photoperiod with 340 ,tE m-2 s-1 illumination (400-700 nm). Day temperature was 25 C and night temperature was 20 C.Plants used for turgor measurements were well established saplings, 2-3 m in height, rooted in large pots of soil, and grown in a greenhouse under a natural photoperiod. Turgor measurements were made in the laboratory, during which time illumination was provided by normal fluorescent room lights (about 40 ,uE m-2 s-'). A number of aphids were transfered to the cutting and, after they had begun to produce honeydew several hours later, they were anesthetized with CO2 and their stylets were cut with a razor blade fragment. A water droplet was placed around the stylet to prevent the exudate from becoming too viscous.The micromanometers for pressure measurements were square glass capillaries (Vitro Dynamics, Inc.)

show abstract

“…A number of species in the genus DunaZieIIa have been shown to use glycerol as the primary osmoregulatory solute (Craigie & McLachlan, 1964;Ben-Amotz & Avron, 1973;Borowitzka & Brown, 1974). Compounds which have been identified as osmoregulators in other species of algae include floridoside (Kauss, 1969), isofloridoside (Kauss, 1967), cyclohexanetetrol (Craigie, 1969), mannitol (Hellebust, 1976), mannisido-mannitol (Feige, 1972), sucrose (Wetherell, 1963), sorbitol and proline (Brown & Hellebust, 1978) and glucosylglycerol (Borowitzka et al, 1980;Mackay et al, 1983). The xerophilic yeast, Saccharomyces rouxii has been shown to accumulate glycerol efficiently in response to low external a, (Brown, 1978), but the highly salt-tolerant yeast Debaryomyces hansenii accumulates K + intracellularly, as well as glycerol, as the salinity of the culture medium increases (Gustafsson & Norkrans, 1976).…”

Section: Introductionmentioning

confidence: 99%

Natural-abundance 13C Nuclear Magnetic Resonance Studies on the Internal Solutes of Xerophilic Fungi

Hocking

Norton

1983

Microbiology

View full text Add to dashboard Cite

Natural-abundance 3C nuclear magnetic resonance spectroscopy was used to study the patterns of accumulation of osmotically active internal solutes in five different fungi. Four xerophilic fungi (Penicillium janczewskii, Eurotium chevalieri, Xeromyces bisporus and Wallemia sebi), and one non-xerophilic fungal species ( P . digitatum) were grown at three different water activities (a,) on media containing sorbitol, glucose/fructose or NaCl as the controlling solute. Under all conditions studied, the major internal solutes detected in aqueous ethanol extracts of these fungi were simple polyhydric alcohols : glycerol, erythritol, arabitol and mannitol. The most important osmoregulatory solute accumulated by all species was glycerol. On the sorbitol and the glucose/fructose media, all five fungi were able to accumulate glycerol. However, when NaCl was used to control a,, only one species, W. sebi, was able to accumulate glycerol below 0.92 a,, Significant quantities of the controlling solutes were also present in the extracts.When intact mycelia of P . janczewskii were examined by NMR, resonances of all the major internal solutes were clearly discernible, although they were not as well resolved as those from the fungal extracts. Relaxation measurements showed that the solutes were relatively mobile inside the cells.

show abstract

Osmoregulation

Cited by 340 publications

References 72 publications

Osmoregulation in the Extremely Euryhaline Marine Micro-Alga Chlorella autotrophica

Osmoregulation in the Extremely Euryhaline Marine Micro-Alga Chlorella autotrophica

Direct Measurement of Sieve Tube Turgor Pressure Using Severed Aphid Stylets

Natural-abundance 13C Nuclear Magnetic Resonance Studies on the Internal Solutes of Xerophilic Fungi

Contact Info

Product

Resources

About