The spermatozoon of the African catfish: fine structure, motility, viability and its behaviour in seminal vesicle secretion

The spermatozoon of the African catfish Clarias gariepinus is a simple organized aquasperm although it reveals very unique characteristics: the cytoplasmic channel is lacking, the mitochondria form a complex structure and the arrangement of the centriolar complex is species specific. Semen has high initial motility rates ( c. 70–90%) and swimming velocities ( c. 120–140 μm s⁻¹), the main swimming type is linear. Motility duration in water is 30 s and is prolonged only to 40 s in NaCl solutions or more complex bu ered motility activating saline solutions. A pH between 7.0 and 9.0 has no e ect on the sperm motility parameters. Motility is completely and reversibly suppressed in electrolyte and non-electrolyte solutions with an osmolality of 200 mosmol kg⁻¹. During immotile storage the sperm viability is influenced by the osmolality and the potassium levels of the storage medium, by the temperature and by the dilution. At optimal conditions (bu ered sperm motility inhibiting saline solution: 150 mmol l⁻¹ NaCl, 2.5 mmol l⁻¹ KCl, 1 mmol l⁻¹ CaCl₂, 1 mmol l⁻¹ MgSO₄, 20 mmol l⁻¹ Tris solution, pH 8.5; dilution rate 1: 5; storage temperature, 4°C) sperm viability persists for >7 days. High viscosity of the pure seminal vesicle secretion completely inhibits the sperm motility. When the seminal vesicle secretion is diluted in water the viscosity decreases and the motility suppressing e ect is neutralized. When semen is mixed with seminal vesicle secretion the sperm viability decreases to zero within 10 min.     

Some aspects of osmoregulation in a stenohaline freshwater catfish, Heteropneustes fossilis (Bloch), in different salinities

Transfer of the catfish, Heteropneustes fossilis , to 10% sea water (101 mosmol l⁻¹) or to 0·4% NaCl (140 mosmol l⁻¹) does not evoke any change in plasma osmolarity from the normal freshwater values. There is, however, a reduction in urine flow rate (UFR) and increase in urine osmolarity without any change in the rate of osmolar clearance. In isosmotic (25% sea water or 0·7% NaCl) and in hyperosmotic (30% sea water or 1·1% NaCl) media there is a significant increase in plasma osmolarity accompanied by marked reduction in glomerular filtration rate (GFR), UFR and free water clearance. The results suggest that the catfish cannot effectively osmoregulate in isosmotic or hyperosmotic media and that the inability of the renal tubules to increase reabsorption of water and to reduce free water clearance may account for the restricted range of salinity tolerance of this catfish. Also, in the hyperosmotic media, plasma levels of cortisol are lowered while in the proximal pars distalis the corticotrophs appear active, suggesting increased utilization and clearance of cortisol. Prolactin-secreting cells, however, are degranulated and chromophobic in catfish maintained in hyperosmotic environment.     

Batch marking of otoliths and fin spines to assess the stock enhancement of Argyrosomus japonicus

Juvenile mulloway Argyrosomus japonicus (54·6 ± 4·6 mm total length, mean ±  s . e .) were immersed in a range of oxytetracycline (OTC) solutions ranging between 0–600 mg l⁻¹ in salinities of 5 (diluted sea water) and 35 (undiluted sea water), and alizarin complexone (ALC) solutions ranging between 0–60 mg l⁻¹ in undiluted sea water, for 6, 12 and 24 h. Optimal marking conditions were 600 mg l⁻¹ OTC for 24 h in a salinity of 5, and 30 mg l⁻¹ ALC for 12 h respectively. Mark quality (MQ) was assessed using a score of 0–3 in both otoliths and anal fin spines, with a score >2 found to be acceptable for adequate mark identification. Acceptable marks were not produced using OTC in undiluted sea water. Immersion in OTC or ALC, or reduced salinity had no effect on survival relative to controls. Transverse sections of vertebrae from the ALC and OTC treatments with the highest otolith mark quality showed no discrete marks. Optimal marking techniques were used to produce double marks with a 3 day interval between marking, and marking techniques were applied to 130 000 juvenile mulloway in batch mode with minimal mortality. A numerical model of the chemical behaviour of OTC in sea water describes the decline of available OTC in increasing salinity, so that a species' salinity tolerance and successful marking can be optimized.     

Salinity adaptation in the snakehead, Ophiocephalus maculatus Lacépède: changes in oxygen consumption, branchial Na+-K+-ATPase and body composition

Snakeheads were adapted to fresh water (1 mOsm kg⁻¹), 25% sea water (230 mOsm kg⁻¹), 33% sea water (320 mOsm kg⁻¹) and 40% sea water (380 mOsm kg⁻¹) for 20 days. Exposure to salt water resulted in tissue dehydration, elevations of plasma osmolality, Na⁺, Mg²⁺, Cl⁻and protein concentrations and stimulation of branchial Na⁺-K⁺-ATPase activity. These changes were accompanied by concomitant decline of the hepatosomatic index and liver glycogen concentration. The routine rate of oxygen consumption was increased in snake-heads adapted to 33% sea water. These data were taken to indicate a stressful effect of salinity to the snakehead despite documentation of its ability to penetrate into brackish waters.     

The effects of acid and acid/aluminum exposure on circulating plasma cortisol levels and other blood parameters in the rainbow trout, Salmo gairdneri

Softwater (Ca²⁺=50, Na⁺= 50(μequiv. l⁻¹) acclimated rainbow trout were fitted with chronic arterial catheters to allow for repetitive blood sampling. After 48 h recovery they were then exposed to either control (pH 6.5, Al = 0μg l⁻¹), acid (pH 4.8, Al = 0μg l⁻¹) or acid plus aluminum (pH 4.8, A1 = 112 μg l⁻¹) conditions for 72 h. Parameters measured included blood glucose, lactate, haemoglobin, haematocrit and plasma Na⁺, Cl⁻, protein and cortisol.
Exposure to pH 4'8 alone caused no mortality, a moderate ionoregulatory disturbance and a transient elevation in plasma cortisol. All other parameters were not significantly different from controls. Addition of aluminum to this exposure caused 100% mortality with a mean survival time of only 27.0 h. There was a marked decrease in plasma ions, hyperglycemia, lactate accumulation, haemoconcentration, red cell swelling, and a sharp rise in plasma cortisol becoming greatly increased as the fish neared death. The mechanism of toxicity of acute acid/aluminum exposure, the role for cortisol under such conditions, and the validity of cortisol and glucose as indicators of stress in fish are discussed.     

Extracellular ionic and acid-base adjustments of Atlantic salmon presmolts and smolts in fresh water and after transfer to sea water: the effects of ovine growth hormone on the acquisition of euryhalinity

In order to better understand the basis for the acquisition of euryhalinity by juvenile salmon and the role of endogeneous stimuli, experiments have been carried out to examine the dynamics of ionic and acid-base adjustments in fresh water (FW) and after direct transfer to full salinity (32 g l⁻¹) sea water (SW) (1) on Atlantic salmon smolt during the natural period of smoltification in spring, (2) on presmolt salmon in autumn, after intraperitoneal implantation of pellets containing ovine growth hormone (oGH). During parr-smolt transformation in FW, gill Na⁺/K⁺ ATPase activity gradually rises, the plasma osmolality (Posm) is unaffected and the total CO₂ of the plasma decreases significantly while whole blood pH fluctuates slightly. Direct transfer of smolt from FW to SW provokes only a slight increase in Posm and emphasizes the acid-base balance disruptions shown in FW. An oGHimplant in a presmolt stimulates gill Na⁺/K⁺ ATPase activity in FW, and affects the acid-base balance. After SW transfer (12 days after implantation), oGH treatment prevents the increase of osmotic pressure and the restoration of the acid-base, ionic equilibrium was faster for oGH-implanted fish than for sham-operated fish. These observations show that in FW smelting salmon develop most of the systems they need for migration and growth in SW and that oGH implants induce the development of physiological characteristics of smolts in a non-natural period of smolting.     

Changes in serum cortisol, metabolites, osmotic pressure and electrolytes in response to different blood sampling procedures in cultured sea bass (Dicentrarchus labrax L.)

This study investigated the effect of five sampling procedures on serum cortisol, glucose, total protein, osmolality, Na⁺, Cl^–, K⁺ and Ca⁺⁺ concentrations in 2-year-old cultured sea bass ( Dicentrarchus labrax L).
Mild disturbance caused by rapid removal of fish and brief handling did not induce significant variation in any of the blood parameters investigated. Confinement and crowding elicited a high and significant increase in serum cortisol, glucose, osmolality, Na⁺, Cl^–, and Ca⁺⁺ concentrations. Exposure to MS 222 (140 mg L^–1) significantly increased osmolality, but not ionic concentration. Site of blood withdrawal (cardiac sinuses/caudal vein) had no effect on the concentration of analysed blood constituents, except for K⁺ levels. Scattered literature of sea bass blood chemistry is reviewed and compared with 'normal' ranges of blood constituents measured in this study. We conclude that it is necessary to select and rigorously execute an opportune blood sampling procedure whenever blood constituents are used as indicators of fish functional state.     

Body temperature and seawater adaptation in farmed Atlantic salmon and rainbow trout during prolonged chilling

The core temperature of the rainbow trout Oncorhynchus mykiss (3·5 kg) dropped to 1·0° C during the first 6 h of chilling at 0·5° C, remained stable until 24 h, and dropped significantly to 0·7° C after 39 h. Blood plasma osmolality increased and muscle moisture content decreased gradually with increasing chilling time. After 39 h of chilling, the rainbow trout experienced 40 mosmol l^-1 higher blood plasma osmolality and 2·8% less muscle moisture content compared with initial values. In the Atlantic salmon Salmo salar (5·3 kg), core temperature dropped to 1·3° C and blood plasma osmolality increased significantly during the first 6 h of chilling at 0·5° C, but remained relatively stable throughout the rest of the experimental period. After 39 h of chilling, the salmon experienced 20 mosmol l^-1 higher blood plasma osmolality and 0·5% less muscle moisture content compared with initial values. In rainbow trout muscle moisture content was inversely related to blood plasma osmolality indicating reduced seawater adaptation with increasing hours of chilling. No such relationship was observed in the Atlantic salmon. Hence, changes in plasma osmolality and muscle moisture in the Atlantic salmon do not indicate osmoregulatory failure since the new levels, once established, were maintained throughout the chilling time.     

The dissolved oxygen and temperature requirements of Atlantic salmon, Salmo salar L., in the Thames Estuary

An improvement in water quality in the estuary of the River Thames in recent years, coupled with the return of adult Atlantic salmon following artificial stocking of the headwaters with parr and of the lower river with smolts, has provided an opportunity to define the dissolved oxygen requirements of adult fish ascending the estuary to reach fresh water. Between July and September 1984 the fish traversed a length of 30 km where the concentration of dissolved oxygen was at its lowest, the 5-percentile and median values being 1.6–2.6 and 3.5–5.9 mg l⁻¹, respectively, depending upon exact location. Within this zone there was a length of about 20 km in which the minimum at any one time during the period was always less than 5mg l⁻¹ and a shorter length of 15 km in which it was always less than 4.7 mg l⁻¹, and it is likely that some fish experienced even lower values during their upstream passage. Over lengths of 1, 10 and 30 km, for example, the 10-percentiles were 2, 2.2 and 2.8 mg l⁻¹, respectively, the medians were 3.6, 3.8 and 4.3 mg l⁻¹, respectively and the 90-percentiles were 4.8, 4.9 and 5.3 mg l⁻, respectively. The water temperature during August, when most of the fish were caught, was never lower than 19°C and there was a length of estuary of at least 20 km where it exceeded 22°C.     

Intracellular ion levels in erythrocytes and hepatocytes isolated from three teleost species

Intracellular concentrations of Na⁺ and K⁺ were similar (∼75 mmol l⁻¹) in rainbow trout Oncorhynchus mykiss hepatocytes directly following isolation by collagenase digestion, but partial recovery occurred over 6 h with K⁺ levels increasing to 110 mmol l⁻¹ and Na⁺ levels decreasing to 42 mmol l⁻¹. Black bullhead Ameiurus melas hepatocytes exhibited higher intracellular concentrations of K⁺ (90 mmol l⁻¹) than Na⁺ (55 mmol l⁻¹) with no recovery occurring over 6 h following cell isolation. Concentrations of Na⁺, K⁺ and Cl⁻ in eel Anguilla rostrata hepatocytes were similar (∼ 55 mmol l⁻¹) following isolation, with no recovery occurring over time. Erythrocytes from all species apparently did not experience an intracellular ion imbalance following isolation as indicated by high K⁺ levels (<140 mmol l⁻¹) and low Na⁺ levels (<40 mmol l⁻¹) during the entire 24-h monitoring period. Although hepatocytes from all species exhibited an ion imbalance post-isolation, comparison of their in vitro intracellular Na⁺ and K⁺ concentrations with those in plasma demonstrated that directionally correct ion gradients still exist across the cell membrane, albeit differing from those that would be found in the tissue in vivo .     

Characterization of acetylcholinesterase from Arthrobacter ilicis associated with the marine sponge (Spirastrella sp.)

The bacterium Arthrobacter ilicis isolated from the marine sponge Spirastrella sp. produces extracellular serine type acetylcholinesterase. The maximum enzyme activity was found at 45 °C and pH 8·0. The activation and deactivation energies, calculated from an Arrhenius plot, were 13·68 and 36·96 kcal mol⁻¹, respectively. The enzyme was not affected by the addition of the major cations of sea water, such as Ca²⁺ and Mg²⁺ at 25 mmol l⁻¹, and was strongly inhibited by EDTA and different organophosphorus and carbamate compounds at 5 mmol l^−1.     

The role of light and CO2 in optimising the conditions for shoot proliferation of Actinidia deliciosa in vitro

Proliferating cultures of Actinidia deliciosa A. Chev., C. F. Liang and A. R. Ferguson cv. Tomuri (♂) were grown under photosynthetic photon flux density (PPFD) rates ranging from 30 to 250 μmol m⁻² s⁻¹ in order to determine certain physiological parameters in vitro: CO₂ evolution, photosynthesis at three CO₂ atmospheric concentrations (330, 1450 and 4500 μl l⁻¹), fresh and dry matter accumulation and proliferation rate.
A proportional response in dry weight, dry/fresh weight ratios and PPFD was found. The proliferation rate increased up to 120 μmol m⁻² s⁻¹ but decreased at higher rates. At the highest PPFD, the CO² released from cultures and accumulated in the vessels reached 200 μl l⁻¹ of; at the lowest rate the CO₂ concentration reached 10500 μl l⁻¹ after 28 days of culture. The photosynthetic rate at 1450 and 4500 μl l⁻¹ of CO₂ was nearly 4 times higher than at the lowest concentration tested.     

Effect of decreased environmental salinity on growth hormone cells in the gilthead sea bream (Sparus aurata)

The effect of decreased environmental salinity on growth hormone producing cells (GH cells) of the adenohypophysial proximal pars distalis has been studied in the gilthead sea bream ( Sparus aurata L.) adapted to sea water (SW, 980 mosmol kg ⁻¹) and brackish water (BW, 200 mosmol kg ⁻¹). A combined immunocytochemical, morphometric and electron microscopic study was carried out. GH cells offish adapted to BW occupied a greater hypophysial volume (about 21% of the total hypophysial volume in BW, 17% in SW) and had a larger nuclear area (mean 16 μm² in BW, 13 μm² in SW) than GH cells of SW-adapted fish. The immunoreactivity against a salmon GH-antiserum was lower in BW (mean optical density 142 in BW, 159 in SW). Ultrastructural characteristics of GH cells of BW-adapted fish were distended rough endo-plasmatic reticulum and large secretory granules (about 216 nm in diameter for BW, 209 nm in SW). Volumetric, densitometric and ultrastructural evidence suggested that the synthesis and release of GH were activated in S. aurata adapted to hypo-osmotic environment.     

Effect of acute and chronic ammonia and nitrite exposure on oxygen consumption and growth of juvenile big bellied seahorse

Juvenile big bellied seahorse Hippocampus abdominalis were exposed acutely and chronically to elevated ammonia and nitrite {24 h exposure: 0·01, 5·0, 10·1, 14·8 and 19·9 mg l⁻¹ total ammonia-nitrogen [TA-N] and <0·001, 74·4, 99·2 and 123·6 mg l⁻¹ [NO₂-N] nitrite-nitrogen and 35 days exposure: 0·11, 0·55, 1·67 and 3·07 mg l⁻¹ TAN and <0·001, 0·92, 4·67 and 9·10 mg NO₂-N l⁻¹}. Significant ( P <0·001) increases in oxygen consumption rate and ventilation frequency occurred at 14·8, 19·9 mg l⁻¹ TA-N and 99·2, 123·6 mg l⁻¹ NO₂-N for acutely exposed fish. Oxygen consumption rate was significantly ( P <0·05) elevated at 1·67 and 3·07 mg l⁻¹ TA-N in chronically treated fish and ventilation frequency increased significantly ( P <0·05) at 0·55, 1·67, 3·07 mg l⁻¹ TA-N and 4·59, 9·10 mg l⁻¹ NO₂-N. There were no significant differences in growth between controls and ammonia exposed fish. Mortalities occurred at 14·8, 19·9 mg l⁻¹ TA-N.     

Ethylene-associated phase change from juvenile to mature phenotype of daylily (Hemerocallis) in vitro

Hemerocallis plantlets maintained in vitro for extended periods of time in tightly closed culture vessels frequently show a phenotype, albeit on a miniaturized scale, typical of more mature, field-grown plants. The positive relationship of elevated ethylene in the headspace of such vessels to the phase shift from juvenile to mature form is established. Rigorous restriction in air exchange with the external environment by means of silicone grease seals hastens the phase change and improves uniformity of response. Although some plantlets may take longer to accumulate enough ethylene in sealed jars to undergo change, added ethylene and ethylene-releasing agents promote it. Ethylene adsorbants (e.g. mercuric perchlorate) block the shift of juvenile to mature form. Critical ambient ethylene level for the shift is ca 1 μl l⁻¹. Levels up to 1000 μl l⁻¹ do not hasten the response but are not toxic. The phase change is fully reversible when air exchange permits ethylene to drop below 1 μl l⁻¹. At least 1 μl l⁻¹ ethylene is required to sustain the mature phenotype. The ethylene synthesis inhibitor aminoethoxyvinylglycine (AVG) prevents the phase change, while the ethylene biosynthesis intermediate 1-aminocyclopropanecarboxylic acid (ACC) improves it. KOH, as a CO₂ absorbant, does not prevent the phase change. Histology sections demonstrate subtle changes in the form of shoot tips of plantlets undergoing phase change.     

Effects of osmolality and ions on the motility of stripped and testicular sperm of freshwater-and seawater-acclimated tilapia, Oreochromis mossambicus

A significantly higher concentration of testicular spermatozoa was obtained from freshwater Oreochromis mossambicus (9·9×10⁹ spermatozoa ml⁻¹) than seawater O. mossambicus (4·6×10⁹ spermatozoa ml⁻¹). The mean osmolality of the urine of freshwater fish (78·5 mOsmol kg⁻¹) was significantly different from that of seawater fish (304·8 mOsmol kg⁻¹). The mean length of the mid-piece of the spermatozoa together with the tail was more variable in freshwater O. mossambicus (8·80±0·23μm) than in seawater specimens (8·27±0·18 μm). Stripped sperm of freshwater O. mossambicus was highly contaminated by urine which was a good activator of sperm motility in O. mossambicus held in both fresh and sea water. The osmolality for initiation of motility in freshwater O. mossambicus spermatozoa was from 0 to 333 mOsmol kg⁻¹ while for seawater O. mossambicus spermatozoa it was from 0 to 1022 mOsmol kg⁻¹. The optimum osmolality for motility was from 70 to 333 mOsmol kg⁻¹ for freshwater O. mossambicus spermatozoa and from 333 to 645 mOsmol kg⁻¹ for seawater fish. In freshwater O. mossambicus spermatozoa, the presence of 20 mM CaCl₂ increased the permissive osmolality of NaCl from 184 to 645 mOsmol kg⁻¹. For seawater O. mossambicus spermatozoa, solutions of NaCl devoid of CaCl₂ were unable initiate motility, but the addition of 1·5 to 30 mM CaCl₂ to the NaCl solution (0–934 mOsmol kg₁) had a full motility initiating effect.     

Isolation of a novel pentachlorophenol-degrading bacterium, Pseudomonas sp. Bu34

A pentachlorophenol (PCP)-degrading bacterium was isolated from possible PCP-contaminated soil from Pusan, Korea and identified as a member of the genus Pseudomonas. It used PCP as its sole source of carbon and energy. This micro-organism was capable of degrading PCP more effectively, certified by the increase in cell density and the decrease in PCP substrate. Pseudomonas sp. Bu34 was able to degrade a much higher concentration of PCP (4000 mg l⁻¹) than any previously reported PCP-degrading bacteria and fungi and to grow in mineral salts solution containing one of a variety of chlorophenols. In non-acclimated strain Bu34, the cell number decreased from 87 to 99·9% in 75–4000 mg l⁻¹ PCP at 24 h. In the acclimated strain the PCP toxic effect did not appear with 75 mg l⁻¹ PCP treatment, but 1000–4000 mg l⁻¹ PCP decreased the cell number of strain Bu34 by 25% to 24 h and then the cell number slightly increased at 48 h. Therefore, it suggested that the maximum resistance of acclimated strain Bu34 to PCP was 4000 mg l⁻¹ PCP. We suggest that strain Bu34 could be used as a micro-organism for the bioremediation of highly PCP-contaminated soils, water or wood products.     

Cardiovascular responses of eggs, embryos and alevins of Atlantic salmon and rainbow trout to nitric oxide donors, sodium nitroprusside and isosorbide dinitrate, and inhibitors of nitric oxide synthase, N-nitro-l-arginine methyl ester and aminoguanidine, following short- and long-term exposure

Atlantic salmon embryos and alevins Salmo salar that had been exposed to isosorbide dinitrate (ISDN) for 4 weeks, on transfer to fresh water, showed an increase in heart rate. Unexposed embryos and alevins showed a decrease in heart rate following transfer to 100 μmol l⁻¹ ISDN for 4 h. This is in contrast to adult rainbow trout and higher vertebrates where tachycardia occurred in response to nitric oxide (NO) donors. The decreased heart rate in response to ISDN was inhibited by 2 mg 1⁻¹ methylene blue, indicating that NO activates cardiovascular events via guanylyl cyclase and cyclic guanidine monophosphate. Heart rate of rainbow trout alevins Oncorhynchus mykiss exposed to 100 μmol l⁻¹ aminoguanidine responded with a slowly developed but significant bradycardia over 10 min as did those reared in aminoguanidine for 4 weeks then transferred to fresh water. A potentiated increase in heart rate on exposure to the NO donor sodium nitroprusside (SNP), occurred within 1 min in salmon alevins reared in l -nitro-arginine methyl ester ( l -NAME) for 4 weeks, indicating up-regulation of NO receptors. The evidence for down-regulation of SNP-reared alevins exposed to l -NAME was less well defined. The results suggest that both salmonid embryos and alevins have a functional l -arginine-NO pathway and that NO has a physiological role in control of cardiovascular events.     

Optimization of D-ribose production with a transketolase-affected Bacillussubtilis mutant strain in glucose and gluconic acid-based media

When the transketolase-deficient and D -ribose-producing Bacillus subtilis strain ATCC 21951 was grown in a glucose (200 g l⁻¹)-based medium (Kintaka et al. 1986), only 11 g l⁻¹ D -ribose was synthesized, in addition to acetic acid (12 g l⁻¹) and acetoin plus 2,3-butanediol (24 g l⁻¹), within 1 week of fermentation. After optimizing the process conditions at 2 l fermentor scale (simplified medium composition, pH 5·0 or 6·0, highly oxidative (1000 rev min⁻¹, 3 vvm)), 40 g l⁻¹ D -ribose was obtained from 200 g l⁻¹ D -glucose, in addition to 14·5 g l⁻¹ acetoin, during 1 week of fermentation. By partially substituting D -glucose with D -gluconic acid (100 g l⁻¹ D -glucose plus 50 g l⁻¹ D -gluconic acid) under highly oxidative (1000 rev min⁻¹, 3 vvm) and pH-controlled (pH 6·5) conditions, D -ribose productivity increased (45 g l⁻¹) and acetoin formation (7·5 g l⁻¹) dropped, as did the fermentation time (3·5 d). The mixed carbon substrate procedure here developed provides an excellent alternative to the less efficient glucose-based processes described so far.     

Salinity response of a freshwater charophyte, Chara vulgaris

Abstract. Chara vulgaris L. growing in an oligohaline lake was adapted to laboratory conditions and subjected to long-term salinity treatments ranging from 0 to 350 mol m ³ NaCl added to the lake water (40–680 mosmol kg ¹). Osmotic potential and concentration of the main osmotically active solutes (K⁺, Na⁺, Mg²⁺, Cl and sucrose) in the vacuolar sap of the central internodal cells were estimated. C. vulgaris did regulate turgor but incompletely. Turgor decreased from 335 mosmol kg ¹ under control conditions to 52–111 mosmol kg ¹ at 350 mol m ³ NaCl. The enhancement of πⁱ was achieved by increase in both ions and sucrose. Sterile and fertile plants differed in their response to osmotic stress. In sterile plants, the ions accounted for about 87% of the vacuolar osmotic potential. The increase of πⁱ under osmotic stress was exclusively due to an accumulation of Na⁺ and Cl^-. In fertile plants, sucrose accounted for about 35% of πⁱ and ions for about 51% Under osmotic stress, sucrose content increased together with the ionic content of Na⁺ and Cl^-.