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At least 649 records · Page 36Linked to original sources
PubMed2001

Relationships between growth and gas exchange characteristics in some salt-tolerant amphidiploid Brassica species in relation to their diploid parents.

Relationships between growth and different gas exchange characteristics of two amphidiploid salt tolerant species, Brassica napus, and B. carinata with respect to their salt sensitive parents, B. oleracea, and B. nigra were investigated. Twenty three-day old plants of these four species along with those of another amphidiploid moderately salt tolerant B. juncea (developed by hybridization of diploids, B. campestris and B. nigra), and a diploid moderately salt tolerant, B. campestris, were subjected for 28 days to salinized sand culture containing 0, 100 or 200 mol NaCl m(-3) in Hoagland's nutrient solution. The species B. napus and B. carinata produced significantly greater shoot fresh and dry matters than their parents under saline conditions. A close association was found between growth, and assimilation rate for all species differing in degree of salt tolerance. Stomatal conductance (g(s)) was reduced due to salt stress in all species but this variable had no significant correlation with assimilation rate (A). However, the amphidiploid salt tolerant species, B. napus and B. carinata had significantly greater photosynthetic rate, water use efficiency (A/E), intrinsic water use efficiency (A/g(s)) than those of their diploid parents. In conclusion, high salt tolerance of the two amphidiploid species, B. napus and B. carinata was associated with a high assimilation rate, water use efficiency and intrinsic water use efficiency but there was little association of the tolerance of these species with stomatal conductance, leaf water potential or transpiration rate (E).

Journal Article↗
PubMed1992

Oxytocin blocks the environmentally conditioned compensatory response present after tolerance to ethanol-induced hypothermia in mice.

The present study tested the hypothesis that the attenuation by oxytocin of tolerance to ethanol-induced hypothermia relies upon an impairment of the putative conditioning processes underlying environment-specific tolerance. According to the conditioning model of tolerance, such tolerance occurs because an opposite compensatory response conditioned to ethanol-paired cues attenuates ethanol's effects. Tolerance to ethanol-induced hypothermia was established to a particular environment over 4 days by injecting mice (daily) with oxytocin 2 h before ethanol, outside the colony room. As controls, other mice were injected similarly but following testing in the animal room. We found that oxytocin suppressed the conditioned compensatory response, revealed by injecting saline to every group in the tolerance-associated environment. These results suggest that oxytocin acted, at least partly, via an inhibition of the associative learning processes that facilitate tolerance development.

Animals↗
PubMed2006

Ultrastructure, osmotic tolerance, glycerol toxicity and cryopreservation of caput and cauda epididymidal kangaroo spermatozoa.

The aim of the present study was to compare cryopreservation, osmotic tolerance and glycerol toxicity between mature and immature epididymal kangaroo spermatozoa to investigate whether the lack of cryopreservation success of cauda epididymidal spermatozoa may be related to the increased complexity of the sperm ultrastructure acquired during epididymal transit. Caput and cauda epididymidal spermatozoa were recovered from red-necked wallabies (RNW; Macropus rufogriseus) and eastern grey kangaroos (EGK; M. giganteus). In Experiment 1, caput and cauda epididymidal spermatozoa were frozen and thawed using a standard cryopreservation procedure in Tris-citrate buffer with or without 20% glycerol. Although cryopreservation of caput epididymidal spermatozoa resulted in a significant increase in sperm plasma membrane damage, they were more tolerant of the procedure than spermatozoa recovered from the cauda epididymidis (P < 0.05). In Experiment 2, caput and cauda epididymidal EGK spermatozoa were diluted into phosphate-buffered saline media of varying osmolarity and their osmotic tolerance determined. Plasma membranes of caput epididymidal spermatozoa were more tolerant of hypo-osmotic media than were cauda epididymidal spermatozoa (P < 0.05). In Experiment 3, caput and cauda epididymidal RNW spermatozoa were incubated in Tris-citrate buffer with and without 20% glycerol at 35 and 4 degrees C to examine the cytotoxic effects of glycerol. At both temperatures, caput epididymidal spermatozoa showed less plasma membrane damage compared with cauda epididymidal spermatozoa when exposed to 20% glycerol (P < 0.05). These experiments clearly indicate that epididymal maturation of kangaroo spermatozoa results in a decreased ability to withstand the physiological stresses associated with cryopreservation.

Animals↗
PubMed1995

Tolerance to the anticonvulsant and ataxic effects of pentobarbital: effect of an ascending-dose regimen.

We assessed the effect of an ascending-dose regimen on the development of tolerance to the anticonvulsant and ataxic effects of pentobarbital in four groups of amygdala-kindled rats. Each rat received 20 bidaily (one every 48 h) trials in which an intraperitoneal (IP) pentobarbital or vehicle injection was delivered 1 h before a convulsive amygdala stimulation. On each trial, the rats in the three pentobarbital groups received either a high dose (50 mg/kg), a low dose (10mg/kg), or ascending doses of pentobarbital that began at 10 mg/kg and increased to as high as 26 mg/kg by 1 mg/kg increments as tolerance developed to its anticonvulsant effect; the rats in the vehicle group received saline. The rats in the ascending-dose condition displayed significantly more tolerance to the anticonvulsant effect of pentobarbital than did the other rats; in contrast, the high-dose rats displayed more tolerance to the ataxic effect of pentobarbital than did the other rats. These findings extend previous reports of the facilitatory effect of ascending-dose regimens on the development of tolerance to the anticonvulsant effect of benzodiazepines, and show that the facilitatory effect of ascending-dose regimens does not extend to all drug effects.

Animals↗
PubMed2006

Genome-wide transcriptional analysis of salinity stressed japonica and indica rice genotypes during panicle initiation stage.

Rice yield is most sensitive to salinity stress imposed during the panicle initiation (PI) stage. In this study, we have focused on physiological and transcriptional responses of four rice genotypes exposed to salinity stress during PI. The genotypes selected included a pair of indicas (IR63731 and IR29) and a pair of japonica (Agami and M103) rice subspecies with contrasting salt tolerance. Physiological characterization showed that tolerant genotypes maintained a much lower shoot Na+ concentration relative to sensitive genotypes under salinity stress. Global gene expression analysis revealed a strikingly large number of genes which are induced by salinity stress in sensitive genotypes, IR29 and M103 relative to tolerant lines. We found 19 probe sets to be commonly induced in all four genotypes. We found several salinity modulated, ion homeostasis related genes from our analysis. We also studied the expression of SKC1, a cation transporter reported by others as a major source of variation in salt tolerance in rice. The transcript abundance of SKC1 did not change in response to salinity stress at PI stage in the shoot tissue of all four genotypes. However, we found the transcript abundance of SKC1 to be significantly higher in tolerant japonica Agami relative to sensitive japonica M103 under control and stressed conditions during PI stage.

DNA Primers↗
PubMed2005

Recent advances in engineering plant tolerance to abiotic stress: achievements and limitations.

Abiotic stresses, especially salinity and drought, are the primary causes of crop loss worldwide. Plant adaptation to environmental stresses is dependent upon the activation of cascades of molecular networks involved in stress perception, signal transduction, and the expression of specific stress-related genes and metabolites. Consequently, engineering genes that protect and maintain the function and structure of cellular components can enhance tolerance to stress. Our limited knowledge of stress-associated metabolism remains a major gap in our understanding; therefore, comprehensive profiling of stress-associated metabolites is most relevant to the successful molecular breeding of stress-tolerant crop plants. Unraveling additional stress-associated gene resources, from both crop plants and highly salt- and drought-tolerant model plants, will enable future molecular dissection of salt-tolerance mechanisms in important crop plants.

Adaptation, Physiological↗
PubMed2001

Fosphenytoin: pharmacokinetics and tolerance of intramuscular loading doses.

PURPOSE: Fosphenytoin (FPHT; Cerebyx) is well absorbed when given intramuscularly (IM). All prior pharmacokinetic studies had the first plasma sample obtained 30 min after IM administration. The objectives of this study were to determine the rate and extent of FPHT absorption and to evaluate the tolerability of IM FPHT compared with IM saline. METHODS: This was an open-label, double-blinded study in which patients received 10 mg/kg dose of IM FPHT in one gluteus and IM saline in the other gluteus. Half the patients received saline injection of equal volume to FPHT (up to 19.5 mL); the other half received 2 mL of saline. Neurologic examination, vital signs, PHT blood samples, injection site examination, and subjective pain scores at injection site were obtained before and at timed intervals for 6 h. RESULTS: Total PHT serum concentrations 10 microg/mL were obtained in 5 min in 14.3% of patients and in 26.3% after 10 min. More than half the patients had therapeutic serum concentrations at 30 min; 45.8% of patients reported no pain at either the FPHT or saline injection site. No significant difference in pain was noted between FPHT and saline injection sites at 60 min and thereafter. Early decrease in blood pressure occurred but was not clinically significant. Classic PHT-induced central nervous system (CNS) side effects were evident in one third of patients within 1 h after injection. CONCLUSIONS: (a) IM FPHT is rapidly absorbed (therapeutic levels achieved as early as 5-20 min). (b) IM FPHT is well tolerated by most patients irrespective of injection volume.

Adolescent↗
PubMed2001

Quantitative trait loci for component physiological traits determining salt tolerance in rice.

Rice (Oryza sativa) is sensitive to salinity, which affects one-fifth of irrigated land worldwide. Reducing sodium and chloride uptake into rice while maintaining potassium uptake are characteristics that would aid growth under saline conditions. We describe genetic determinants of the net quantity of ions transported to the shoot, clearly distinguishing between quantitative trait loci (QTL) for the quantity of ions in a shoot and for those that affect the concentration of an ion in the shoot. The latter coincide with QTL for vegetative growth (vigor) and their interpretation is therefore ambiguous. We distinguished those QTL that are independent of vigor and thus directly indicate quantitative variation in the underlying mechanisms of ion uptake. These QTL independently govern sodium uptake, potassium uptake, and sodium:potassium selectivity. The QTL for sodium and potassium uptake are on different linkage groups (chromosomes). This is consistent with the independent inheritance of sodium and potassium uptake in the mapping population and with the mechanistically different uptake pathways for sodium and potassium in rice under saline conditions (apoplastic leakage and membrane transport, respectively). We report the chromosomal location of ion transport and selectivity traits that are compatible with agronomic needs and we indicate markers to assist selection in a breeding program. Based upon knowledge of the underlying mechanisms of ion uptake in rice, we argue that QTL for sodium transport are likely to act through the control of root development, whereas QTL for potassium uptake are likely to act through the structure or regulation of membrane-sited transport components.

Analysis of Variance↗
PubMed1999

Mechanism of tolerance development to 2,5-dimethoxy-4-iodoamphetamine in rats: down-regulation of the 5-HT2A, but not 5-HT2C, receptor.

RATIONALE: Defining the mechanism of tolerance development to hallucinogenic drugs will help to explain their mechanism of action. OBJECTIVES: The present study was conducted to determine first, if tolerance develops to the discriminative stimulus (DS) properties of the hallucinogen, 2,5 dimethoxy-4-iodo-amphetamine (DOI) and second, the mechanism mediating tolerance. METHODS: Rats were trained to discriminate 0.75 mg/kg DOI from saline on a concurrent VI-30-min schedule of reinforcement with a 15-min time-out for incorrect responses. To evaluate tolerance development, rats were assigned to one of four groups and treated with either chronic saline or chronic DOI. Prior to chronic treatment, two groups were tested for choice behavior following vehicle administration while the remaining two groups were tested following the administration of 0.375 mg/kg DOI. One group from each pre-test condition was injected with either saline or DOI (1 mg/kg) for 8 days. Twenty-four hours after the last chronic injection the pre-test treatments were replicated. Using receptor autoradiography, the density of 5-HT2A and 5-HT2C receptors was measured in independent groups of rats that had received identical treatment conditions. RESULTS: Animals receiving chronic DOI showed a 60% decrease in DOI lever responding (from 100% to 40%) when tested on 0.375 mg/kg DOI, while animals receiving chronic saline showed no change in percent choice (100%) on the DOI lever. Significant changes in binding were observed in 5-HT2A receptors but not 5-HT2C receptors. The results of tests with antagonists were consistent with the changes in binding. CONCLUSIONS: These results suggest that behavioral tolerance to DOI reflects neuroadaptive changes in 5-HT2A receptors.

Amphetamines↗
PubMed1989

The contribution of environmental cues to cross-tolerance between ethanol and pentobarbital.

The contribution of Pavlovian conditioning of environmental cues has been studied in relation to tolerance to ethanol-induced hypothermia and cross-tolerance to pentobarbital. Two groups of 12 male Sprague-Dawley rats were exposed every other day to a distinctive set of environmental cues paired with an IP injection of either ethanol 2.5 g/kg or an equivalent volume of isotonic saline. On alternating non-drug days, both groups received saline in the animal room. When they were tested for tolerance to the hypothermic effect of ethanol 2.5 g/kg and cross-tolerance to pentobarbital 25 mg/kg in each environment, tolerance and cross-tolerance in the ethanol-treated group were significantly more pronounced in the ethanol-paired environment than in the saline-paired environment. This indicates the importance of a conditional factor in tolerance and cross-tolerance in this paradigm. Determination of blood levels of ethanol and pentobarbital at various times after injection indicated that conditioned tolerance and cross-tolerance can be explained in part by dispositional factors.

Animals↗
PubMed1991

Acute tolerance to the locomotor stimulant effects of nicotine in the rat.

Studies of peripheral nicotinic receptors have revealed that, after an initial agonist action, the receptors remain inhibited either through continued depolarization blockade due to continued presence of the agonist or through a brief inactivation of the receptor following its activation. If a similar phenomenon occurs at central nervous system nicotinic receptors, then behavioral responses to nicotine should exhibit an acute tolerance (tachyphylaxis). Groups of rats were given either saline or 0.2 mg/kg nicotine injections at 20-min intervals in photocell activity cages. A progressive decline in the locomotor responsiveness to nicotine was observed. The time course of this acute tolerance was observed in other rats given initial 0.2 mg/kg nicotine injections followed at differing time intervals by second 0.2 mg/kg nicotine test injections. The secondary antagonism to nicotine's locomotor stimulant effects was maximal at 45-60 min and recovered by 90-120 min. The locomotor response to 0.2 mg/kg nicotine test injections was observed in other rats following exposure to 1.8 mg/kg nicotine, and the behavioral response was attenuated for more than 5 h.

Animals↗
PubMed1995

Alterations in hepatocyte insulin binding in chronic pancreatitis: effects of pancreatic polypeptide.

BACKGROUND: Hepatic insulin resistance has previously been demonstrated in chronic pancreatitis, and has been shown to be ameliorated by pancreatic polypeptide administration. Insulin binding was investigated in chronic pancreatitis induced by infusion of oleic acid into the pancreatic duct of rats. METHODS: Acute pancreatitis was induced in 12 200 to 225 g 8-week-old male Sprague-Dawley rats by intubation of the main bile duct at its junction with the duodenum through a small midline abdominal incision, and infusion of 99% oleic acid 0.015 mL/min for 4 minutes, with an additional 4 minutes dwell-time after infusion. Sham-operated animals served as controls. After 6 weeks, chronic pancreatitic and sham-operated animals received either intraperitoneal bovine pancreatic polypeptide or saline vehicle for 5 days. Intraduodenal glucose tolerance tests (GTT) were performed in fasted animals, after which tissues were procured. Insulin receptors were isolated from solubilized hepatocyte and rectus abdominus membranes and competitive-binding studies were performed by incubation with 125I-insulin. Dissociation coefficients (Kd) and maximum binding capacities (Bmax) for high-affinity receptors were derived from Scatchard analyses. RESULTS: Bmax and Kd in muscle were not altered in animals with chronic pancreatitis. In liver, Bmax was significantly less in rats with chronic pancreatitis given saline than in sham-operated rats given saline (17.0 +/- 6.3 versus 47.6 +/- 13.1 fmol/mg protein; data are mean +/- SEM). Pancreatic polypeptide administration increased hepatic Bmax in rats with chronic pancreatitis (to 47.2 +/- 9.8 fmol/mg protein), but had no significant effect in sham-operated rats. Receptor affinity was not significantly different in rats with chronic pancreatitis or rats who underwent sham operations and was unaltered by the administration of pancreatic polypeptide. The integrated plasma glucose response during the GTT was reduced by pancreatic polypeptide administration in rats with chronic pancreatitis (29.5 +/- 15.0 mg/dL per minute versus 69.0 +/- 21.8 in chronic pancreatitis without pancreatic polypeptide), but was not significantly altered in sham-operated animals. CONCLUSION: Diminished expression of high-affinity receptors on the hepatocyte membrane may contribute to hepatic insulin resistance in chronic pancreatitis. In this model, pancreatic polypeptide improved glucose tolerance and increased receptor capacity to the level observed in livers from nonpancreatitic animals.

Animals↗
PubMed2026

Sulfide-oxidizing potential and hypersalinity tolerance strategies in salt-crust covered coastal microbial mats.

Hypersaline microbial mats are dense microbial ecosystems capable of performing nearly complete element cycling under harsh conditions including near-saturation salinity. Our previous study of salt-crust-covered microbial mats showed that oxygenic photosynthesis was inhibited at salt saturation, while phototrophic sulfide oxidation persisted despite well-known sulfide-oxidizing taxa being undetectable. In this study, we analyzed metagenome-assembled genomes (MAGs) from the same mats to identify sulfide-oxidizing taxa and adaptations enabling oxygenic phototrophs to survive salt saturation. We extended the dataset by including morphologically identical mats exposed to lower salinity regimes to identify metabolic capabilities specifically selected for by saturation-level salinity. The phototrophic sulfide oxidation capability was found in nearly all cyanobacterial MAGs, in some Chloroflexota, and in abundant Rhodovibrio populations previously not known to oxidize sulfide. Furthermore, we found clear indications of Haloarchaea-like potassium-based osmoregulation in Bradymonadaceae (Myxococcota) adding another taxon to the few known potassium-accumulating bacteria. Despite lower oxygen concentrations, salt-crust-covered mats showed smaller proportions of fermenters and higher proportions of aerobic microorganisms than lower-salinity mats. We compared the genetic signatures of hypersalinity and desiccation tolerance in cyanobacterial MAGs from this study to genomes from desiccation-prone environments such as desert soils and small freshwater streams. Genomes of hyperhalophilic cyanobacteria were characterized by lack of certain potassium transporters and catalase genes and presence of additional osmolyte transporter subunits and sulfide-oxidation genes. We hypothesize that during salt saturation the oxidative stress for mat dwelling cyanobacteria is lowered, while the ability to oxidize sulfide provides them with energy when oxygenic photosynthesis is inhibited.

Oxidation-Reduction↗
PubMed2025

Comparative genomic analysis of a novel heat-tolerant and euryhaline strain of unicellular marine cyanobacterium Cyanobacterium sp. DS4 from a high-temperature lagoon.

BACKGROUND: Cyanobacteria have diversified through their long evolutionary history and occupy a wide range of environments on Earth. To advance our understanding of their adaptation mechanisms in extreme environments, we performed stress tolerance characterizations, whole genome sequencing, and comparative genomic analyses of a novel heat-tolerant and euryhaline strain of the unicellular cyanobacterium Cyanobacterium sp. Dongsha4 (DS4). This strain was isolated from a lagoon on Dongsha Island in the South China Sea, a habitat with fluctuations in temperature, salinity, light intensity, and nutrient supply. RESULTS: DS4 cells can tolerate long-term high-temperature up to 50 &#x2103; and salinity from 0 to 6.6%, which is similar to the results previously obtained for Cyanobacterium aponinum. In contrast, most mesophilic cyanobacteria cannot survive under these extreme conditions. Based on the 16S rRNA gene phylogeny, DS4 is most closely related to Cyanobacterium sp. NBRC102756 isolated from Iwojima Island, Japan, and Cyanobacterium sp. MCCB114 isolated from Vypeen Island, India. For comparison with strains that have genomic information available, DS4 is most similar to Cyanobacterium aponinum strain PCC10605 (PCC10605), sharing 81.7% of the genomic segments and 92.9% average nucleotide identity (ANI). Gene content comparisons identified multiple distinct features of DS4. Unlike related strains, DS4 possesses the genes necessary for nitrogen fixation. Other notable genes include those involved in photosynthesis, central metabolisms, cyanobacterial starch metabolisms, stress tolerances, and biosynthesis of novel secondary metabolites. CONCLUSIONS: These findings promote our understanding of the physiology, ecology, evolution, and stress tolerance mechanisms of cyanobacteria. The information is valuable for future functional studies and biotechnology applications of heat-tolerant and euryhaline marine cyanobacteria.

Cyanobacteria↗
PubMed2005

Decolorization of azo dyes with high salt concentration by salt-tolerant mixed cultures under anaerobic conditions.

Because the lack of detailed study of biological decolorization in high salt dye wastewater, it is still difficult to evaluate the biological treatment on high-salinity dye wastewater. The experiments were carried out to study the salt-tolerant bacteria, which is useful in the treatment of high-salinity colored wastewater. Simulated wastewater containing 5-150 g/L salt (NaCl) and 50-2000 mg/L Reactive Brilliant Red K-2BP was treated with three salt-tolerant mixed cultures (CAS, TAS, DSAS), which were under a gradually acclimated procedure. With the increase of concentrations of salt and dye, the decolorization became low. The abilities of decolorization of dyes wastewater by three mixed cultures (CAS, TAS, DSAS) were studied, CAS and DSAS mixed cultures showed more active for the treatment of high-salinity colored wastewater than TAS mixed cultures. The results suggested that there might be a simple process for the high salt wastewater treatment, which could be incorporated into conventional activated sludge plants.

Azo Compounds↗
PubMed2005

Morphological and biochemical alterations of oomycete fish pathogen Saprolegnia parasitica as affected by salinity, ascorbic acid and their synergistic action.

Vegetative growth of Saprolegnia parasitica decreased by increasing the concentration of NaCl and ascorbic acid. Under these conditions, the morphological features of the vegetative hyphae were distinguishable from those used as controls. NaCl and ascorbic acid in combination improved the tolerance of S. parasitica to high levels of salinity. Sporangial formation, release and proliferation were very sensitive to even lower levels of salinity. For instance, at 0.03 M NaCl sporangia formation was rarely observed. Ascorbic acid alone had a little effect on sporangial formation and release, but when combine with NaCl the developmental processes were improved. Reduction of numbers and plasmolysis of oogonia were found at various NaCl concentrations, whereas ascorbic acid stimulated the formation of these reproductive organs at low concentrations. The synergistic effect of NaCl and ascorbic acid improved and overcomed the symptoms of oogonial plasmolysis. Protease activity of S. parasitica was significantly reduced at all NaCl concentrations, whilst ascorbic acid significantly increased and inhibited it at low concentrations and at moderate and high concentrations, respectively. The combination of these compounds reduced protease activity at all tested concentrations with significant difference at the highest concentration. The total free amino-acids content of S. parasitica mycelia was significantly reduced at all the NaCl concentrations, whereas ascorbic acid significantly increased it at low but inhibited it at higher concentrations. The combination of NaCl and ascorbic acid significantly increased the accumulation of free amino-acids at low and moderate concentrations, but decreased them at high concentrations. Total protein content was reduced at all tested concentrations of NaCl and ascorbic acid had also similar effect. However, the combined effect of NaCl and ascorbic acid significantly enhanced and reduced total protein content at low and high concentrations, respectively. Treatments with NaCl induced proline accumulation in S. parasitica, which paralleled the salt concentration.

Animals↗
PubMed1983

Rapid development of tolerance to the behavioural actions of cholecystokinin.

Cholecystokinin (CCK) acts acutely to inhibit food consumption in fasted rats, mice, sheep, pigs, monkeys and humans. CCK has been proposed as a satiety signal, inducing the behavioural sequence of satiety, or as an aversive internal stimulus, which inhibits food intake by inducing malaise. Reductions in food intake and related exploratory behaviours are initiated by CCK at its peripheral receptor in the gut, which appears to transmit sensory feedback via the vagus nerve to brain regions mediating appetitive behaviours. The therapeutic potential of CCK as an appetite suppressant in obesity syndromes rests on the demonstration of significant, long-lasting body weight reduction. Chronic CCK administration by repeated injections is problematic, since this peptide is rapidly degraded in vivo. We chose the Alzet constant infusion osmotic minipump to investigate possible alterations in body weight and food intake during continuous infusion of CCK. We now report that no change was detected in either body weight or total daily food consumption at any time point during 2 weeks of intraperitoneally (i.p.) infused CCK. The mechanism underlying the lack of chronic CCK effects appears to be a rapid development of behavioural tolerance. Acute challenge doses of CCK which induced satiety-related behaviours in saline-infused rats were ineffective in CCK-infused rats. The behavioural tolerance was apparent within a few hours of minipump implantation. These results provide the first evidence that rapid and reversible tolerance develops to the actions of a gut peptide.

Animals↗
PubMedDate not supplied

Physiological basis of salt tolerance in plants.

For most plants, and under most field conditions, osmotic effects of salinity greatly predominate in restricting growth and yields. In certain cases, however, specific ion effects may be decisive. These may involve either nutrition, as in calcium deficiency in some lettuce varieties, tomato, and bell peppers, or direct toxicity (chloride or sodium toxicity, or both) in tree and vine crops. Rootstocks, or varieties that restrict the uptake of toxic ions, increase the salt tolerance of some susceptible fruit crops. Salinity-induced nutritional imbalance can, in some cases, be corrected by selecting better adapted varieties and in others by the use of foliar nutrient sprays. Recent evidence indicates simple single-gene control over uptakes of chloride and sodium, but the more general osmotic effects appear to be complex and under multigenic control.

Biological Transport↗