Differences In Osmoregulation Research Articles

Physiological responses of the invasive blue crabs Callinectes sapidus to salinity variations: Implications for adaptability and invasive success

This study provides a comprehensive analysis of the eco-physiological responses of the blue crab (Callinectes sapidus) to variations in salinity, shedding light on its adaptability and invasive success in aquatic environments. Gender-specific differences in osmoregulation and Electron Transport System (ETS) activity highlight the importance of considering sex-specific aspects when understanding the physiological responses of invasive species. Females exhibited increased ETS activity at lower salinities, potentially indicative of metabolic stress, while males displayed constant ETS activity across a range of salinities. Osmoregulatory capacity which depended on gender and salinity, was efficient within meso-polyhaline waters but decreased at higher salinities, particularly in males. These findings provide valuable understandings into how C. sapidus specimens in an invaded area responds to salinity changes, important for considerate its distribution through saline pathways during tidal cycle fluctuations. This study shows the importance of interdisciplinary research for effective management of invasive species and conservation of affected aquatic ecosystems.

Small Stomates and Xylem Vessels Associated With Freeze Tolerance in Winter Barley

ABSTRACTFreeze tolerance is a complex agronomic trait that is difficult to evaluate in the field because of year‐to‐year variation in weather. Discovering plant characteristics closely related to freeze tolerance would enable more effective selection for this important trait. To explore possible physiological mechanisms and search for useful characteristics related to freeze tolerance in winter barley, we conducted field and growth chamber experiments with seven freeze‐tolerant and seven freeze‐susceptible genotypes that exhibited contrasting winter survival in preliminary field screenings. In a 2‐year field experiment, malondialdehyde, proline and water‐soluble carbohydrate concentrations were measured during cold acclimation and deacclimation to investigate differences in osmoregulation and membrane stability between freeze‐tolerant and freeze‐sensitive genotypes. All parameters varied by sampling year, and significant differences between freeze tolerance groups were found mainly during cold deacclimation in the spring. In growth chamber experiments, the size of xylem vessels and stomates was measured with and without cold acclimation. Freeze‐tolerant genotypes had smaller xylem vessels and stomates than freeze‐sensitive genotypes with and without cold acclimation, and small stomatal length was associated with a small xylem vessel area. Thus, it may be possible to improve freeze tolerance in winter barley by selecting smaller xylem and stomate cells. This study also validated germplasms of winter barley with differential freeze tolerance for future projects on breeding for improving winter hardiness and on plant physiology and genetics in response to freezing stress.

A draft genome of the neritid snail Theodoxus fluviatilis.

The neritid snail Theodoxus fluviatilis is found across habitats differing in salinity, from shallow waters along the coast of the Baltic Sea to lakes throughout Europe. Living close to the water surface makes this species vulnerable to changes in salinity in their natural habitat, and the lack of a free-swimming larval stage limits this species' dispersal. Together, these factors have resulted in a patchy distribution of quite isolated populations differing in their salinity tolerances. In preparation for investigating the mechanisms underlying the physiological differences in osmoregulation between populations that cannot be explained solely by phenotypic plasticity, we present here an annotated draft genome assembly for T. fluviatilis, generated using PacBio long reads, Illumina short reads, and transcriptomic data. While the total assembly size (1045 kb) is similar to those of related species, it remains highly fragmented (N scaffolds = 35,695; N50 = 74 kb) though moderately high in complete gene content (BUSCO single copy complete: 74.3%, duplicate: 2.6%, fragmented: 10.6%, missing: 12.5% using metazoa n = 954). Nevertheless, we were able to generate gene annotations of 21,220 protein-coding genes (BUSCO single copy complete: 65.1%, duplicate: 16.7%, fragmented: 9.1%, missing: 9.1% using metazoa n = 954). Not only will this genome facilitate comparative evolutionary studies across Gastropoda, as this is the first genome assembly for the basal snail family Neritidae, it will also greatly facilitate the study of salinity tolerance in this species. Additionally, we discuss the challenges of working with a species where high molecular weight DNA isolation is very difficult.

Influence of Salinity on Copper Toxicity in Paracentrotus lividus and Arbacia lixula Embryos

The sea urchins Paracentrotus lividus and Arbacia lixula have a key role in benthic dynamics and they are often used to assess the toxicity of environmental contaminants. The aim of this research was to investigate the influence of salinity on copper toxicity on P. lividus and A. lixula embryos, evaluating the impact of future ocean salinity variations and estimating an optimum range for embryos. For this purpose, sea urchin embryos were exposed to different copper concentrations under varying salinity regimes, estimating the toxic effects with the percentage of abnormal embryos and the Integrative Toxicity Index (ITI). Results revealed acceptable levels of anomalies in a salinity range of 33–36‰ for A. lixula and 33–39‰ for P. lividus. The effect concentrations (EC50) of copper reveals increasing toxicity at increasing salinity for both sea urchin species, but between 33–36‰ (A. lixula) and 36–39‰ (P. lividus) the toxicity appear inversely related with salinity. This study illustrates the difficulty in relating a biological response to bioavailability, because the uptake and the sensitivity to copper across salinities is influenced by differences in osmoregulation, enhancing our knowledge about optimal salinity ranges and the potential impact of climate change on sea urchin embryo development.

Osmoregulation in Hypogean Populations of the Freshwater Amphipod, Gammarus pulex (L.)

Abstract The freshwater amphipod Gammarus pulex is widely distributed in freshwater streams and rivers of Europe. This amphipod also has isolated hypogean populations, which are transparent in appearance, suggestive of adaptation to their cave environment. Since cave habitats are often food limited, physiological adaptations have been observed that reduce the energy expenditure of cave organisms. Osmoregulation is an energetically expensive mechanism that allows gammarids to survive in fresh water. This study tested the hypothesis that differences in osmoregulation existed between hypogean and epigean populations of G. pulex. The osmoregulatory parameters measured were haemolymph cation concentrations, water and sodium fluxes and gill Na+/K+-ATPase activity. The hypogean G. pulex had significantly lower haemolymph sodium and potassium concentrations, but had a significantly higher haemolymph ammonium concentration than the epigean G. pulex. The low food availability in the hypogean environment was conside...

Evaluation in barley lines of a simple pollen method for breeding for drought tolerance in wheat

A pollen test, which is used in wheat to detect an osmoregulation gene, was evaluated in 16 barley doubled-haploid lines. In the presence of water stress, created using a 40% polyethylene glycol 6000 solution on microscope slides, the application of a low concentration of KCl produced a size response in approximately 50% of lines. Visual selection was confirmed by quantification in 8 lines, with significant responses in 5. The lines were then evaluated in the field in low and high soil-water deficit sites. Water deficit was produced by exclusion of rain after initially wetting up the soil profile. The group selected for a pollen response showed significantly lower leaf zero turgor water potentials (ie. greater turgor maintenance). This was, in turn, due to differences in osmoregulation. At ear emergence, mean turgor pressures at low deficit and mean relative water contents at high deficit were higher in lines with high pollen osmoregulation. There was also a separate effect due to differences in maturity between the lines. Higher turgor maintenance and osmoregulation occurred in lines with faster maturity. Because lines were dissimilar, accurate dry weight and yield comparisons between osmoregulation groups were not feasible. A drought susceptibility index was used to accommodate variation in low stress growth and yield, and to allow comparisons with wheat experiments. In all experiments high osmoregulation groups had lower mean values than low groups. Indices calculated for osmoregulation groups in barley were not significantly different to those from similar wheat experiments conducted over 4 seasons with differing evaporative demand, suggesting operation of a similar process or gene. Further confirmatory work is needed using more closely related lines.

Inter- and intraspecific variation in the use of marine food resources by three Cinclodes (Furnariidae, Aves) species: carbon isotopes and osmoregulatory physiology

The avian genus Cinclodes (Furnariidae) includes species that inhabit both inland and marine shores. We compared the carbon isotopic composition and osmoregulatory capacities of field caught individuals of three Cinclodes species in Chile. Cinclodes nigrofumosus is a resident of coastal shores, whereas C. oustaleti and C. patagonicus inhabit both coastal and inland environments. The tissues of C. nigrofumosus exhibited distinctively marine delta(13)C values, whereas those of C. oustaleti and C. patagonicus were intermediate between marine and terrestrial values. The differences in carbon isotopic composition among these three species were paralleled by differences in osmoregulatory characteristics. The species that carbon isotopes revealed to be strictly marine, C. nigrofumosus, had relatively larger kidneys with a higher fraction of total renal tissue occupied by medullary cones than its congeners C. oustaleti and C. patagonicus. Cinclodes nigrofumosus individuals also produced more concentrated urine. In addition to interspecific differences in osmoregulation, we found intraspecific differences. Cinclodes nigrofumosus collected at an arid site with limited or no available fresh water exhibited larger kidneys and higher relative medullary thickness than individuals collected at a mesic site. Cinclodes nigrofumosus, like all passerines, lacks functional salt glands. This species appears to be unique among passerines in its ability to live in extreme arid coastal environments and to cope with a marine diet that imposes high osmotic loads.

Consistent differences among wheat cultivars in osmotic adjustment and their relationship to plant production

Osmotic adjustment (OA) is generally considered an important component of drought resistance. Several reports by J.M. Morgan [Morgan, J.M., 1983. Osmoregulation as a selection criterion for drought tolerance in wheat. Aust. J. Agric. Res. 34, 607–614; 1992. Osmotic components and properties associated with genotypic differences in osmoregulation in wheat. Aust. J. Plant Physiol. 19, 67–76; 1995. Growth and yield of wheat lines with differing osmoregulative capacity at high soil water deficit in seasons of varying evaporative demand. Field Crops Res. 40, 143–152; Morgan, J.M., Condon, A.G., 1986. Water-use, grain yield and osmoregulation in wheat. Aust. J. Plant Physiol. 13, 523–532] from Australia concluded that consistent genetic differences in OA existed among wheat cultivars and that high OA cultivars tended to yield better than low OA cultivars under drought stress. Our study was performed to assess his results with his and other genetic materials. Two of Morgan’s spring wheat lines with high OA (‘H.Osm-134’) and low OA (‘L.Osm-136’) capacity in addition to eight other diverse spring wheat cultivars were tested for OA and plant production when grown in small plots under a rain exclusion shelter at Bet Dagan, Israel in 1996. OA of five of these cultivars (including Morgan’s lines) was also measured in two independent greenhouse tests in 1997 (Israel) and 1998 (Texas). The five cultivars differed significantly and ranked consistently for OA in all tests. No significant cultivar by test interaction for OA was revealed. OA was well correlated across cultivars between tests. The significantly higher OA capacity of H.Osm-134 as compared with L.Osm-136 was repeated in all tests. OA of all ten cultivars was positively correlated with biomass ( r = 0.73; p = 0.02) and yield ( r = 0.55; p = 0.09) under pre-flowering drought stress in the rain exclusion shelter. H.Osm-134 line performed significantly ( p ≤ 0.05) better than L.Osm-136 line for both biomass and yield under drought stress. We therefore support Morgan’s results and conclude that consistent differences in OA exist among wheat cultivars and that these differences can be associated with plant production under pre-flowering drought stress.

Pollen grain expression of a gene controlling differences in osmoregulation in wheat leaves: a simple breeding method

The possibility that a gene conditioning differences in osmoregulation in wheat leaves (or) is also expressed in pollen grains was investigated in order to differentiate heterozygous and homozygous lines for use in backcross breeding. The difference in osmoregulation in leaves was expressed as a difference in solute accumulation which was calculated from responses of osmotic potential and relative water content to reductions in water potential caused by droughting plants in pots. A corresponding allelic difference was found in pollen grains. It was demonstrated by a difference in relative size, and solute accumulation, after stressing using polyethelene glycol solution. The response occurred only after addition of a small quantity of potassium chloride, and the maximum response occurred at concentrations of approximately ≥0.2 mM (at least to 10 mM). This suggests that or may condition high affinity potassium transport. Single-gene control was confirmed using pollen responses, and pollen grain expression was further demonstrated by the use of pollen responses, to identify alleles and thus manipulate leaf responses in a backcross breeding study. Because the differences in pollen grain size may be readily observed without measurement using a microscope with relatively low magnification, and because the pollen grains are easily sampled at flowering, the pollen response is suitable as a routine test in plant breeding involving pedigree or backcross methods.

Turgor Maintenance by Osmoregulation inBrassica napusandB. junceaunder Field Conditions

Indian mustard (Brassica juncea(L) Czernjacw) maintains higher leaf turgor than canola (B. napusL.) under water deficits and this is related to the greater yield of mustard under these conditions. The work reported in this paper was designed to study the way mustard maintains this turgor advantage. It was based on three field experiments that each used at least two cultivars or lines of each species. The leaf water potential at which leaves reached zero turgor was consistently lower in mustard than in canola (up to 1.1 MPa lower). This difference arose from a greater rate of decline in leaf osmotic potential with declining water potential in mustard rather than from any difference in the osmotic potential at full turgor. Calculations of solute accumulation showed that mustard had a greater capacity to osmoregulate than canola, with this capacity being the basis for its advantage in turgor maintenance. Other differences in plant water relations were consistent with the differences in osmoregulation, with the predicted relative water content of leaves at an osmotic potential of -2.5 MPa being 0.43 for canola and 0.61 for mustard. Mustard's greater capacity to accumulate solutes is concluded to be a major factor in its greater yield under water deficits.

Osmotic Components and Properties Associated With Genotypic Differences in Osmoregulation in Wheat

Solutes contributing to genotypic differences in osmoregulation in water-stressed wheat plants were investigated using samples of sap from expanded flag leaves of breeding lines with high and low osmoregulation. The sap samples were collected from leaves using a hand press after freezing and thawing. The leaves were sampled during a period of increasing stress created by withholding water from breeding lines growing in potting mix in the glasshouse. Measurements of potassium, free amino acids, proline, glucose, sucrose and fructose, as well as conductivity and refractive index, were made on the sap. The osmotic potential of the same sap samples was determined with a thermocouple psychrometer both before and after these measurements were made. Separate determinations of osmotic potential were also made on sections of frozen and thawed tissue from the same leaves used for sap samples, but without expressing the sap. The level of osmoregulation was expressed as the solute accumulation between full and zero turgor. The lines showed either very low (0.18 MPa) or very high (1.35 MPa) levels of solute accumulation. These levels were similar to a single gene effect observed in other lines. High osmoregulation was largely (78%) due to potassium accumulation, with amino acids the only other important contributor (22%). No sugar accumulation was found. The osmotic potential due to the solutes potassium, amino acids and sugars accounted for, on average, 90% of the sap osmotic potential measured with a thermocouple psychrometer. The major components were potassium (42-53%) and amino acids (35-43%). In high lines, increases in the proportion of potassium with increased stress were associated with changes in the relationship between sap osmotic potential and either tissue osmotic potential or that derived from the component solutes. The various methods of measuring osmotic potential and effects on the calculation of solute accumulation are discussed.

Adaptation to water-deficit in chickpea breeding lines by osmoregulation: relationship to grain-yields in the field

Differences in osmoregulation were found in the leaves of closely related breeding lines and cultivars of chickpea ( Cicer arietinum L.). Osmoregulation was determined from measurements of osmotic potentials (using thermocouple psychrometers) and relative water contents made on the leaves of plants grown in the glasshouse, and stressed by withholding water in a controlled-environment chamber. The controlled-environment measurements of osmoregulation were associated with increases in grain-yields in field experiments conducted at various sites in northern New South Wales in 1987 and 1988. The yield increases ranged from approximately zero in low-water-deficit environments (site mean yield, 3.5 t ha −1) to approximately 20% in high-water-deficit environments (site mean yield 1.3 t ha −1). These results suggest that osmoregulation may be a useful selection criterion in breeding for greater yields in water-limited environments.

A Gene Controlling Differences in Osmoregulation in Wheat

Evidence is presented for a single gene controlling differences in osmoregulation in wheat in response to water stress, confirming earlier results. Analyses of osmoregulation were made on the flag leaves of wheat plants which were grown in pots in the glasshouse and stressed in a controlled environment chamber by withholding water after the flag leaf had fully emerged. Osmoregulation was derived from responses of osmotic potential to relative water content or from responses of relative water content and osmotic potential to water potential. Usable estimates of osmoregulation were obtained for 67 F2 lines derived from contrasting parents, to test for gene number, and for one substitution series with contrasting parents, to determine chromosomal location. The F2 frequency response, which consisted of two overlapping distributions, was compatible with a single recessive gene, the estimated ratio being 2.79 : 1 (low: high osmoregulation). This confirmed previous measurements made on F1s and F4s Results for the substitution series were also compatible with these results in indicating a single chromosome, 7A, which had an identical response to the low osmoregulation parent, Red Egyptian. The effects of the gene were confined to solute accumulations at water potentials above, but not below, zero turgor.

Nonosmotic Stimuli Alter Osmoregulation in Patients with Spinal Cord Injury*

Studies on two quadriplegic patients who developed severe hyponatremia during episodes of acute respiratory distress were performed to determine whether differences in osmoregulation of vasopressin release could be identified in these patients compared to other quadriplegic subjects previously studied in a similar manner. Both patients were clinically stable and normonatremic, with no signs or symptoms of respiratory distress, when the studies were performed. However, both exhibited evidence of hemodynamic instability in the sitting posture. Linear regression analysis of the plasma vasopressin/plasma osmolality (Pavp:Posm) relationship during infusions of 0.85 M sodium chloride showed no significant differences in either the slope (sensitivity) or abscissal intercept (osmotic threshold) of this relationship compared to that of other quadriplegic subjects when the patients were supine. In contrast, when the patients were studied in the sitting posture there was a marked shift in the relationship of Pavp:Posm indicative of increased sensitivity and reduced osmotic threshold for vasopressin release. The slopes of the Pavp:Posm relationships were 0.249 and 0.178 for the two patients, respectively, compared to 0.092 +/- 0.03 ( +/- SD) for previously studied quadriplegic subjects. Oral water-loading studies performed on one patient revealed marked impairment of urine-diluting ability and free water clearance in the sitting posture compared with observations in similar studies performed when the patient was supine. Impairment of renal water excretion could not be attributed to an effect of vasopressin, which was reduced to unquantifiable levels by water loading. These studies have shown that hemodynamic stress related to autonomic dysfunction in quadriplegic patients may result in marked alteration of osmoregulation of vasopressin release in more severely affected individuals. Such altered osmoregulation, which may also be associated with vasopressin-independent impairment of renal water excretion in the sitting posture, may be a predisposing factor in the development of hyponatremia, especially in the presence of other potent nonosmotic stimuli.

The Use of Coleoptile Responses to Water Stress to Differentiate Wheat Genotypes for Osmoregulation, Growth and Yield

Differences in osmoregulation between genotypes of wheat (Triticum aestivum L.) were identified by measuring responses of coleoptiles to water stress. Seeds were germinated in Petri dishes on germination pads. Water stress was applied when coleoptiles were 1 cm long by either adding polyethylene glycol 6000 (20% w/w) or by removing the lids of the dishes and allowing the pads to dry by evaporation for a period of 2 d, or from the beginning of germination by varying the amount of water in the germination pads. Measurements of the water and osmotic potentials of shoots and roots (using thermocouple psychrometers) were used to estimate turgor pressures. Wheat genotypes showed the same segregation for shoot and root lengths and turgor pressures as they had done in previous studies for flag-leaf osmoregulation and yield. It was concluded that observations of the responses of coleoptile length to water stress could be used in plant-breeding applications to identify differences in osmoregulation between genotypes of wheat.

Differences in Osmoregulation in Brassica species

Differences in Osmoregulation in Brassica species

Differences between two grain sorghum genotypes in adaptation to drought stress. III. Physiological responses

A sorghum hybrid (E-57) giving a higher yield under rain-fed systems of production was studied to examine the physiological basis of this effect. A comparison was made with another hybrid (TX-671) with similar maturity. E-57 was able to maintain stomatal opening to a lower leaf water potential than TX-671 because of its greater capacity to osmoregulate. In E-57 osmotic potential declined due to active solute accumulation, thus maintaining turgor as leaf water potential declined to - 2.0 MPa. In contrast, TX- 671 could only maintain this adjustment to - 1.4 MPa. The differences in osmoregulation were associated with maintenance of leaf area, water extraction and possibly root growth by E-57. This indicated that osmoregulation enabled photosynthesis to continue and that a significant amount of the resultant assimilate may have been diverted to root growth.

Growth and urine osmolarity in young Brattleboro rats.

Institute of Physiology, Czechoslovak Academy of Sciences, Prague, Czechoslovakia, 142 20 (Received 18 April 1977) If Brattleboro rats, homozygous (DI) and heterozygous (non-DI) for diabetes insipidus are deprived of water, no difference in urinary osmotic pressure can be detected between the two genotypes before 14 days of age Dlouhá, Křeček & Zicha, 1976). This may arise from a shortage of vasopressin in non-DI rats until week 3 after birth, as has been demonstrated in rats of the Wistar strain (Křeček, Dlouhá & Křečková, 1961). We have attempted to detect differences in osmoregulation in DI and non-DI rats before diabetes insipidus is manifest. Samples of urine were obtained from 147 young Brattleboro rats by perineal stimulation. In 10- and 14-day-old animals, all procedures were done at 30 °C. Dehydration was induced in 10-, 14-, 18- and 22-day-old rats by water deprivation for 6 h; water diuresis was induced in 14-, 19-

Differences in osmoregulation between wheat genotypes

SEVERAL recent experiments provide evidence to support the existence of osmoregulation in plants as a means of counteracting water stresses induced by changes in the soil or evaporative environment1–3. Viewed in terms of energy potentials, decreases in the water potential, Ψ, induced by changes in the environment, are immediately offset by decreases in the osmotic potential, π, through an increase in solute content. The turgor potential, P, is thereby maintained since Ψ = π+P+τ (assuming that the matric potential, τ, is small or constant). The importance of this response is that expansion growth, which is affected directly by the turgor potential, is maintained over a range of values of Ψ2. Despite this obvious significance, little is known of the extent of this phenomenon in crop plants in general and in particular of differences between genotypes in the same or closely related species. Here we present evidence indicating substantial differences between several genotypes of wheat; in some osmoregulation was marked, whereas in others it was virtually non-existent.

THE OSMOTIC ADAPTATION OF THE FAIRY SHRIMP BRANCHINECTA CAMPESTRIS LYNCH TO SALINE ASTATIC WATERS1

The fairy shrimp Branchinecta campestris was found in association with Artemia salina (L.) in four saline astatic lakes in Okanogan County, Washington, and in British Columbia. In all four lakes sulfate was the predominant ion making up in milliequivalence 48% of the total ions. The predominant cations sodium and magnesium occurred in varying proportions. The osmotic concentration of Penley Lake from hatching to death of the adult population of B. campestris increased progressively from 36 to 660 mOsm/liter. At concentrations of 286 mOsm/liter and less, B. campestris regulates hyperosmotically. However, from 451 to 660 mOsm/liter B. campestris is poikiloosmotic and not a hypoosmotic regulator like A. salina. Therefore, its ability to live in saline astatic waters can be partly attributed to tolerance of a high hemolymph concentration.Coexistence between A. salina and B. campestris is brief. B. campestris is restricted to the early phase of the saline astatic lake, characterized by low but increasing salinity and temperature, whereas A. salina appears a month later and is restricted to the high salinity‐temperature phase of the lake. Factors responsible for temporal separation of these two species appear to be differences in osmoregulation and in factors regulating development and hatching.