A reliable method for spectrophotometric determination of glycine betaine in cell suspension and other systems

Unravelling drought and salinity stress responses in barley genotypes: physiological, biochemical, and molecular insights

In the face of escalating environmental challenges, understanding crop responses to abiotic stress is pivotal for sustainable agriculture. The present study meticulously investigates the intricate interplay between drought and salinity stress in barley (Hordeum vulgare L.). Employing three distinct barley genotypes-Traveller, Prunella, and Zahna-we scrutinize their physiological, biochemical, and molecular adaptations under stress conditions. Our findings underscore genotype-specific responses, unravelling the multifaceted mechanisms that govern stress tolerance. Chlorophyll content, a vital indicator of photosynthetic efficiency, exhibits significant variations across genotypes. Salinity stress induces a decline in chlorophyll levels, while drought stress triggers a more nuanced response. Stomatal conductance, a key regulator of water loss, also diverges among the genotypes. Traveller displays remarkable stomatal closure under drought, conserving water, whereas Prunella and Zahna exhibit contrasting patterns. Antioxidant enzyme activities, crucial for combating oxidative stress, fluctuate significantly. Activities of superoxide dismutase (SOD) and catalase (CAT) surge under salinity stress, while drought predominantly impacts SOD. Gene expression profiling reveals genotype-specific signatures, with stress-responsive genes modulating adaptive pathways. Correlation analyses revealed the intricate interplay of the physiological and biochemical parameters. Genotype-specific adaptations, coupled with dynamic physiological and molecular responses, underscore the plasticity of barley's stress tolerance mechanisms. Throughout the study, the Zahna genotype demonstrated notable tolerance in terms of performance. These insights hold promise for breeding resilient cultivars, bolstering food security in an increasingly unpredictable climate. By deciphering the barley stress symphony, we contribute to the harmonious orchestration of sustainable agricultural practices.

Ultrasensitive molecular imprinted electrochemical sensor for in vivo determination of glycine betaine in plants

Glycine betaine (GB) is a bioactive molecule protecting plants from abiotic stress. This study fabricated an ultrasensitive molecular imprinted polymer (MIP) electrochemical sensor to perform in vivo measurements of GB. Polydopamine (PDA) was formed on the carboxylated multi-walled carbon nanotubes (COOH-MWCNTs) by spontaneous polymerisation of dopamine (DA). Then MIP-coated MWCNTs were fabricated on a Au nanoparticles (NP) and thionine (Thi) modified screen-printed electrode (SPE). The MIP-COOH-MWCNTs/pThi/AuNPs/SPE exhibited an ultrasensitive GB detection response between 1 fmol/L and 10 mmol/L (R2 = 0.996) with a low detection limit (0.707 fmol/L, S/N = 3). In vivo measurement of GB in cucumber seedling leaves under different salinity stress conditions confirmed the practical applicability of the MIP sensor. Thus, this study proposed a novel and promising fabrication method for an electrochemical MIP sensor that has broad application prospects in precision agriculture.

Salt Tolerance of Sea Flax (Linum maritimum L.), a Rare Species with Conservation Interest in Eastern Spain

Seldom found in saltmarshes, Linum maritimum is a halophyte of great conservation interest in the eastern Iberian Peninsula. Although the species has been reported in different plant communities, there is no information on its range of salinity tolerance or mechanisms of response to environmental stress factors. In this study, L. maritimum plants were subjected to increasing salt concentrations in controlled conditions in a greenhouse. After six months of watering with salt solutions, only plants from the control, 50 mM and 100 mM NaCl treatment groups survived, but seeds were produced only in the first two. Significant differences were found between the plants from the various treatment groups in terms of their growth parameters, such as plant height, fresh weight, and the quantity of flowers and fruits. The main mechanism of salt tolerance is probably related to the species' ability to activate K+ uptake and transport to shoots to partly counteract the accumulation of toxic Na+ ions. A biochemical analysis showed significant increases in glycine betaine, flavonoids and total phenolic compounds, highlighting the importance of osmotic regulation and antioxidant compounds in the salt tolerance of Linum maritimum. These findings have implications for the conservation of the species, especially under changing climatic conditions that may lead to increased soil salinity in its Mediterranean distribution area.

Effects of Exogenous Isosteviol on the Physiological Characteristics of Brassica napus Seedlings under Salt Stress

In this paper, the effect of isosteviol on the physiological metabolism of Brassica napus seedlings under salt stress is explored. Brassica napus seeds (Qinyou 2) were used as materials, and the seeds were soaked in different concentrations of isosteviol under salt stress. The fresh weight, dry weight, osmotic substance, absorption and distribution of Na+, K+, Cl-, and the content of reactive oxygen species (ROS) were measured, and these results were combined with the changes shown by Fourier transform infrared spectroscopy (FTIR). The results showed that isosteviol at an appropriate concentration could effectively increase the biomass and soluble protein content of Brassica napus seedlings and reduce the contents of proline, glycine betaine, and ROS in the seedlings. Isosteviol reduces the oxidative damage to Brassica napus seedlings caused by salt stress by regulating the production of osmotic substances and ROS. In addition, after seed soaking in isosteviol, the Na+ content in the shoots of the Brassica napus seedlings was always lower than that in the roots, while the opposite was true for the K+ content. This indicated that under salt stress the Na+ absorbed by the Brassica napus seedlings was mainly accumulated in the roots and that less Na+ was transported to the shoots, while more of the K+ absorbed by the Brassica napus seedlings was retained in the leaves. It is speculated that this may be an important mechanism for Brassica napus seedlings to relieve Na+ toxicity. The spectroscopy analysis showed that, compared with the control group (T1), salt stress increased the absorbance values of carbohydrates, proteins, lipids, nucleic acids, etc., indicating structural damage to the plasma membrane and cell wall. The spectra of the isosteviol seed soaking treatment group were nearly the same as those of the control group (T1). The correlation analysis shows that under salt stress the Brassica napus seedling tissues could absorb large amounts of Na+ and Cl- to induce oxidative stress and inhibit the growth of the plants. After the seed soaking treatment, isosteviol could significantly reduce the absorption of Na+ by the seedling tissues, increase the K+ content, and reduce the salt stress damage to the plant seedlings. Therefore, under salt stress, seed soaking with isosteviol at an appropriate concentration (10-9~10-8 M) can increase the salt resistance of Brassica napus seedlings by regulating their physiological and metabolic functions.

Physiological and Genetic Modifications Induced by Plant-Growth-Promoting Rhizobacteria (PGPR) in Tomato Plants under Moderate Water Stress

Physiological, metabolic, and genetic changes produced by two plant growth promoting rhizobacteria (PGPR) Pseudomonas sp. (internal code of the laboratory: N 5.12 and N 21.24) inoculated in tomato plants subjected to moderate water stress (10% polyethylene glycol-6000; PEG) were studied. Photosynthesis efficiency, photosynthetic pigments, compatible osmolytes, reactive oxygen species (ROS) scavenging enzymes activities, oxidative stress level and expression of genes related to abscisic acid synthesis (ABA; 9-cis-epoxycarotenoid dioxygenase NCDE1 gene), proline synthesis (Pyrroline-5-carboxylate synthase P5CS gene), and plasma membrane ATPase (PM ATPase gene) were measured. Photosynthetic efficiency was compromised by PEG, but bacterial-inoculated plants reversed the effects: while N5.12 increased carbon fixation (37.5%) maintaining transpiration, N21.24 increased both (14.2% and 31%), negatively affecting stomatal closure, despite the enhanced expression of NCDE1 and plasma membrane ATPase genes, evidencing the activation of different adaptive mechanisms. Among all parameters evaluated, photosynthetic pigments and antioxidant enzymes guaiacol peroxidase (GPX) and ascorbate peroxidase (APX) responded differently to both strains. N 5.12 increased photosynthetic pigments (70% chlorophyll a, 69% chlorophyll b, and 65% carotenoids), proline (33%), glycine betaine (4.3%), and phenolic compounds (21.5%) to a greater extent, thereby decreasing oxidative stress (12.5% in Malondialdehyde, MDA). Both bacteria have highly beneficial effects on tomato plants subjected to moderate water stress, improving their physiological state. The use of these bacteria in agricultural production systems could reduce the amount of water for agricultural irrigation without having a negative impact on food production.

Use of a Biostimulant to Mitigate the Effects of Excess Salinity in Soil and Irrigation Water in Tomato Plants

Global warming is linked to progressive soil salinisation, which reduces crop yields, especially in irrigated farmland on arid and semiarid regions. Therefore, it is necessary to apply sustainable and effective solutions that contribute to enhanced crop salt tolerance. In the present study, we tested the effects of a commercial biostimulant (BALOX^®) containing glycine betaine (GB) and polyphenols on the activation of salinity defense mechanisms in tomato. The evaluation of different biometric parameters and the quantification of biochemical markers related to particular stress responses (osmolytes, cations, anions, oxidative stress indicators, and antioxidant enzymes and compounds) was carried out at two phenological stages (vegetative growth and the beginning of reproductive development) and under different salinity conditions (saline and non-saline soil, and irrigation water), using two formulations (different GB concentrations) and two doses of the biostimulant. Once the experiments were completed, the statistical analysis revealed that both formulations and doses of the biostimulant produced very similar effects. The application of BALOX^® improved plant growth and photosynthesis and assisted osmotic adjustment in root and leaf cells. The biostimulant effects are mediated by the control of ion transport, reducing the uptake of toxic Na⁺ and Cl^- ions and favoring the accumulation of beneficial K⁺ and Ca²⁺ cations, and a significant increase in leaf sugar and GB contents. BALOX^® significantly reduced salt-induced oxidative stress and its harmful effects, as evidenced by a decrease in the concentration of oxidative stress biomarkers, such as malondialdehyde and oxygen peroxide, which was accompanied by the reduction of proline and antioxidant compound contents and the specific activity of antioxidant enzymes with respect to the non-treated plants.

Wheat variety carrying 2NvS chromosomal segment provides yield advantage through lowering terminal heat-induced oxidative stress

A 2N^vS chromosomal segment carrying bread wheat variety, BARI Gom 33 ('BG33'), showed tolerance to terminal heat stress and higher yield over a heat-tolerant non-2N^vS BARI Gom 26 ('BG26') and a heat-susceptible Pavon 76 ('Pavon'). This study aimed to ascertain the potential of the 2N^vS 'BG33' in terminal heat-induced oxidative stress tolerance compared to non-2N^vS 'BG26' and heat-susceptible 'Pavon' under two heat regimes at the reproductive stages viz. control (optimum sowing time) and heat stress (late sowing). We found that both 'BG26' and 'BG33' showed significantly higher tolerance to oxidative stress by limiting the generation of reactive oxygen species (ROS), methylglyoxal under heat stress. During terminal heat stress, both 'BG33' and 'BG26' exhibited greater cellular homeostasis than heat-susceptible 'Pavon', which was maintained by the increased accumulation of osmolytes, nonenzymatic antioxidants, and enzymes associated with ROS scavenging, ascorbate-glutathione cycle, and glyoxalase system. Lesser cellular damage in 'BG26' and 'BG33' was eventually imitated in a smaller reduction in grain yield (15 and 12%, respectively) than in 'Pavon', which had a 33% reduction owing to heat stress. Collectively, our findings revealed that the chromosomal segment 2N^vS provides yield advantage to 'BG33' under terminal heat stress by lowering oxidative damage. As 2N^vS translocation contains multiple nucleotide-binding domain leucine-rich repeat containing, cytochrome P450, and other gene families associated with plant stress tolerance, further studies are warranted to dissect the underlying molecular mechanisms associated with higher heat stress tolerance of 2N^vS carrying 'BG33'.

Recovery from Salinity and Drought Stress in the Perennial Sarcocornia fruticosa vs. the Annual Salicornia europaea and S. veneta

Current agricultural problems, such as the decline of freshwater and fertile land, foster saline agriculture development. Salicornia and Sarcocornia species, with a long history of human consumption, are ideal models for developing halophyte crops. A greenhouse experiment was set up to compare the response of the perennial Sarcocornia fruticosa and the two annual Salicornia europaea and S. veneta to 30 days of salt stress (watering with 700 mM NaCl) and water deficit (complete withholding of irrigation) separate treatments, followed by 15 days of recovery. The three species showed high tolerance to salt stress, based on the accumulation of ions (Na+, Cl-, Ca2+) in the shoots and the synthesis of organic osmolytes. These defence mechanisms were partly constitutive, as active ion transport to the shoots and high levels of glycine betaine were also observed in non-stressed plants. The three halophytes were sensitive to water stress, albeit S. fruticosa to a lesser extent. In fact, S. fruticosa showed a lower reduction in shoot fresh weight than S. europaea or S. veneta, no degradation of photosynthetic pigments, a significant increase in glycine betaine contents, and full recovery after the water stress treatment. The observed differences could be due to a better adaptation of S. fruticosa to a drier natural habitat, as compared to the two Salicornia species. However, a more gradual stress-induced senescence in the perennial S. fruticosa may contribute to greater drought tolerance in this species.

PGPR-Mediated Salt Tolerance in Maize by Modulating Plant Physiology, Antioxidant Defense, Compatible Solutes Accumulation and Bio-Surfactant Producing Genes

Salinity stress is a barrier to crop production, quality yield, and sustainable agriculture. The current study investigated the plant growth promotion, biochemical and molecular characterization of bacterial strain Enterobacter cloacae PM23 under salinity stress (i.e., 0, 300, 600, and 900 mM). E. cloacae PM23 showed tolerance of up to 3 M NaCl when subjected to salinity stress. Antibiotic-resistant Iturin C (ItuC) and bio-surfactant-producing genes (sfp and srfAA) were amplified in E. cloacae PM23, indicating its multi-stress resistance potential under biotic and abiotic stresses. Moreover, the upregulation of stress-related genes (APX and SOD) helped to mitigate salinity stress and improved plant growth. Inoculation of E. cloacae PM23 enhanced plant growth, biomass, and photosynthetic pigments under salinity stress. Bacterial strain E. cloacae PM23 showed distinctive salinity tolerance and plant growth-promoting traits such as indole-3-acetic acid (IAA), siderophore, ACC deaminase, and exopolysaccharides production under salinity stress. To alleviate salinity stress, E. cloacae PM23 inoculation enhanced radical scavenging capacity, relative water content, soluble sugars, proteins, total phenolic, and flavonoid content in maize compared to uninoculated (control) plants. Moreover, elevated levels of antioxidant enzymes and osmoprotectants (Free amino acids, glycine betaine, and proline) were noticed in E. cloacae PM23 inoculated plants compared to control plants. The inoculation of E. cloacae PM23 significantly reduced oxidative stress markers under salinity stress. These findings suggest that multi-stress tolerant E. cloacae PM23 could enhance plant growth by mitigating salt stress and provide a baseline and ecofriendly approach to address salinity stress for sustainable agriculture.

Seed osmopriming with Ca2+ and K+ improves salt tolerance in quinoa seeds and seedlings by amplifying antioxidant defense and ameliorating the osmotic adjustment process

Salinity restricts seed germination and seedling growth through induction of osmotic and oxidative stresses. Therefore, this study aimed to enhance salinity tolerance in quinoa seed by pre-optimized osmo-priming treatments of CaCl₂ (10 mM, 10 °C, 10 h) and KNO₃ (150 mM, 5 °C, 24 h). The results showed that these treatments developed the cellular defense mechanisms in seeds as 'priming memory' that could improve the physiological and biochemical responses to salinity in post-priming stages. The germination capacity and seedling growth decreased with increasing salinity that was accompanied with a higher content of MDA and H₂O₂. However, the improvement of primed seed vigor against high salinity was explained by increasing the biological defense mechanisms including antioxidant enzymes (CAT, APX, SOD, GPX and PPO) and antioxidant metabolites (DPPH antioxidant activity, phenolics, flavonoids, ascorbic acid), particularly in presence of salt stress. In addition, Ca²⁺ and K⁺ priming acquired salinity tolerance in post-priming stages through a significant increase in the accumulation of proline, glycine-betaine, soluble carbohydrate. Improvement in homeostasis of K⁺/Na⁺ ratio by promoting K⁺ maintenance and Na⁺ exclusion was also found in post-priming stages. These observations may be utilized as effective methods in improving salinity tolerance of quinoa seed germination in saline agriculture by improving the antioxidant system, osmolyte accumulation and mineral nutrient homeostasis.

Exogenous Glycine Betaine Application Improves Freezing Tolerance of Cabbage (Brassica oleracea L.) Leaves

Exogenous glycine betaine (GB) application has been reported to improve plant tolerance to various abiotic stresses, but its effect on freezing tolerance has not been well studied. We investigated the effect of exogenous GB on freezing tolerance of cabbage (Brassica oleracea L.) leaves. Seedlings fed with 30 mM GB via sub-irrigation showed effectively assimilated GB as evident by higher GB concentration. Exogenous GB did not retard leaf-growth (fresh weight, dry weight, and leaf area) rather slightly promoted it. Temperature controlled freeze-thaw tests proved GB-fed plants were more freeze-tolerant as indicated by lower electrolyte leakage (i.e., indication of less membrane damage) and alleviating oxidative stress (less accumulation of O₂^•- and H₂O₂, as well as of malondialdehyde (MDA)) following a relatively moderate or severe freeze-thaw stress, i.e., -2.5 and -3.5 °C. Improved freezing tolerance induced by exogenous GB application may be associated with accumulation of compatible solute (proline) and antioxidant (glutathione). GB-fed leaves also had higher activity of antioxidant enzymes, catalase (CAT), ascorbate peroxidase (APX), and superoxide dismutase (SOD). These changes, together, may improve freezing tolerance through membrane protection from freeze-desiccation and alleviation of freeze-induced oxidative stress.

Nanoencapsulation improves the protective effects of a nitric oxide donor on drought-stressed Heliocarpus popayanensis seedlings

Despite the important role played by nitric oxide (NO) in plants subjected to abiotic stress, NO donors application to induce drought tolerance in neotropical tree seedlings has not yet been tested. It is also worth investigating whether NO bioactivity in drought-stressed seedlings could be potentiated by NO donors nanoencapsulation. The aim of the current study is to evaluate the effects of chitosan nanoparticles (NPs) containing S-nitroso-mercaptosuccinic acid (S-nitroso-MSA) on drought-stressed seedlings of neotropical tree species Heliocarpus popayanensis Kunth in comparison to free NO donor and NPs loaded with non-nitrosated MSA. Nanoencapsulation slowed down NO release from S-nitroso-MSA, and nanoencapsulated S-nitroso-MSA yielded 2- and 1.6-fold higher S-nitrosothiol levels in H. popayanensis roots and leaves, respectively, than the free NO donor. S-nitroso-MSA has prevented drought-induced CO₂ assimilation inhibition, regardless of nanoencapsulation, but the nanoencapsulated NO donor has induced earlier ameliorative effect. Both NO and MSA have decreased oxidative stress in H. popayanensis roots, but this effect was not associated with antioxidant enzyme induction, with higher seedling biomass, or with proline and glycine betaine accumulation. Nanoencapsulated S-nitroso-MSA was the only formulation capable of increasing leaf relative water content in drought-stressed plants (from 32.3% to 60.5%). In addition, it induced root hair formation (increase by 36.6% in comparison to well-hydrated plants). Overall, results have evidenced that nanoencapsulation was capable of improving the protective effect of S-nitroso-MSA on H. popayanensis seedlings subjected to drought stress, a fact that highlighted the potential application of NO-releasing NPs to obtain drought-tolerant tree seedlings for reforestation programs.

Combined application of two Bacillus species enhance phytoremediation potential of Brassica napus in an industrial metal-contaminated soil

This study aimed to assess the impact of individual as well as combined application of Lysinibacillus macroides and Bacillus safensis in phytoremediation potential of Brassica napus grown in soil contaminated by industrial effluents. In response to five metals; copper, chromium, nickel, lead, and cadmium, results revealed that germination percentage, fresh and dry weights, and photosynthetic pigments of B. napus decreased under contaminated soil. On the other hand, electrolyte leakage due to cellular injury, metabolites (proline and glycine betaine), antioxidant enzymes (superoxide dismutase, catalase, peroxidase, ascorbate peroxidase), accumulation of hydrogen peroxide and metals in plant's roots, shoots and leaves increased. Inoculation significantly reduced these effects as proved by the enhancement of germination percentage, fresh and dry biomass, and photosynthetic pigments. Simultaneously, the antioxidant enzymes, metabolites contents (proline and glycine betaine) and metal concentrations in plant's roots, shoots and leaves decreased. Combined application of both Bacilli strains was found more effective as compared to individual inoculation. It was concluded that metal resistant Bacillus species in combination had growth effects on B. napus and enhanced its phytoremediation efficiency in contaminated soil.Novelty statementBrassica napus; a hyper-accumulator of metals, loses phytoremediation potential with the passage of growth. Two Bacillus species (Lysinibacillus macroides and Bacillus safensis) having known bioremediation abilities were employed individually as well as in combination under metals contaminated soil to increase phytoremediation efficiency of B. napus. The metals containing soil used is a unique aspect in this study because selected soil, contaminated by industrial effluents, has not been evaluated or reported earlier. Combined application of Bacilli improved phytoremediation potential of B. napus more as compared to application of individual Bacillus strain which is yet another unique aspect of this investigation.

Physiological and Biochemical Dissection Reveals a Trade-off Between Antioxidant Capacity and Heat Tolerance in Bread Wheat (Triticum aestivum L.)

Heat stress alters photosynthetic components and the antioxidant scavenging system, negatively affecting plant growth and development. Plants overcome heat stress damage through an integrated network involving enzymatic and non-enzymatic antioxidants. This study aimed to assess physiological and biochemical responses in contrasting thermo-tolerant wheat varieties exposed to 25 °C (control) and 35 °C (heat stress), during the seedling stage. Our results revealed a substantial decrease in the photosynthetic pigments, carotenoids, anthocyanin content, and increased membrane injury index, malondialdehyde, methylglyoxal (MG), H₂O₂ contents and lipoxygenase activity compared to non-stress wheat seedlings. The heat-tolerant variety BARI Gom 26 ("BG26") maintained higher cellular homeostasis compared to the heat susceptible variety Pavon 76 ("Pavon"), perpetuated by higher accumulation of proline, glycine betaine, ascorbate-glutathione cycle associated enzymes, reduced glutathione and ascorbate concentration in plant cells. Significantly lower levels of MG detoxification and antioxidant activities and ascorbate-glutathione cycle-related enzymatic activities lead to increased susceptibility in variety "Pavon". Hierarchical clustering and principal component analysis revealed that variety "BG26" possess a combination of biochemical responses tailoring antioxidant activities that induced a higher level of tolerance. Taken together, our results provide a pipeline for establishing a trade-off between antioxidant capacity and heat tolerance to facilitate functional genomics and translational research to unravel underlying mechanisms to better adapt wheat to heat stress.

A potassium chloride to glycine betaine osmoprotectant switch in the extreme halophile Halorhodospira halophila

Halophiles utilize two distinct osmoprotection strategies. The accumulation of organic compatible solutes such as glycine betaine does not perturb the functioning of cytoplasmic components, but represents a large investment of energy and carbon. KCl is an energetically attractive alternative osmoprotectant, but requires genome-wide modifications to establish a highly acidic proteome. Most extreme halophiles are optimized for the use of one of these two strategies. Here we examine the extremely halophilic Proteobacterium Halorhodospira halophila and report that medium K⁺ concentration dramatically alters its osmoprotectant use. When grown in hypersaline media containing substantial K⁺ concentrations, H. halophila accumulates molar concentrations of KCl. However, at limiting K⁺ concentrations the organism switches to glycine betaine as its major osmoprotectant. In contrast, the closely related organism Halorhodospira halochloris is limited to using compatible solutes. H. halophila performs both de novo synthesis and uptake of glycine betaine, matching the biosynthesis and transport systems encoded in its genome. The medium K⁺ concentration (~10 mM) at which the KCl to glycine betaine osmoprotectant switch in H. halophila occurs is near the K⁺ content of the lake from which it was isolated, supporting an ecological relevance of this osmoprotectant strategy.

Alanine, proline and urea are major organic osmolytes in the snail Theodoxus fluviatilis under hyperosmotic stress

Hyperosmotic stress may result in osmotic volume loss from the body to the environment in animals that cannot control the water permeability of their integument. Euryhaline animals (which have a wide tolerance range of environmental salinities) have generally evolved the ability to counteract cell volume shrinkage by accumulating inorganic and organic osmolytes within their cells to balance internal and external osmolalities. Molluscs use very different combinations of amino acids and amino acid derivatives to achieve this goal. Theodoxus fluviatilis is a neritid gastropod that is distributed not only in limnic habitats in Europe but also in brackish waters (e.g. along the shoreline of the Baltic Sea). Animals from brackish sites survive better in high salinities than animals from freshwater locations. The results of the present study indicate that these differences in salinity tolerance cannot be explained by differences in the general ability to accumulate amino acids as organic osmolytes. Although there may be differences in the metabolic pathways involved in osmolyte accumulation in foot muscle tissue, the two groups of animals accumulate amino acid mixtures equally well when stepwise acclimated to their respective maximum tolerable salinity for extended periods. Among these amino acids, alanine and proline, as well as the osmolyte urea, hold a special importance for cell volume preservation in T. fluviatilis under hyperosmotic stress. It is possible that the accumulation of various amino acids during hyperosmotic stress occurs via hydrolysis of storage proteins, while alanine and proline are probably newly synthesised under conditions of hyperosmotic stress in the animals.

Nitric oxide and light co-regulate glycine betaine homeostasis in sunflower seedling cotyledons by modulating betaine aldehyde dehydrogenase transcript levels and activity

Glycine betaine (GB), an osmolyte, is produced in chloroplasts by the action of betaine aldehyde dehydrogenase (BADH) on its precursor betaine aldehyde. The present work highlights the significance of nitric oxide (NO) in GB homeostasis as a long-distance salt (120 mM NaCl) stress-elicited response. In light-grown seedling cotyledons, both the activity and transcript levels of BADH are much higher than in dark-grown seedlings irrespective of salt stress. Significantly high accumulation of GB in dark-grown seedling cotyledons indicates its preferential mobilization from cotyledons to other plant parts in light-grown seedlings. NO donor application (diethylenetriamine) maintains high BADH activity in light, although in dark it is brought down marginally. BADH levels are maintained high in light than in dark in respective treatments. Reversal of the effect of NO donor on age-dependent GB content, BADH activity, and transcript levels by NO scavenger (diethyldithiocarbamate) further demonstrates the impact of NO on GB homeostasis in light- and dark-grown seedlings in an age-dependent manner, major modulation being observed in 4-d-old seedlings. The present work, thus, provides new information on co-regulation of GB homeostasis by NO and light. It also puts forward new information of GB-NO crosstalk in maneuvering salt stress sensing as a long-distance response in seedlings.

Methodology of Drought Stress Research: Experimental Setup and Physiological Characterization

Drought is one of the major stress factors affecting the growth and development of plants. In this context, drought-related losses of crop plant productivity impede sustainable agriculture all over the world. In general, plants respond to water deficits by multiple physiological and metabolic adaptations at the molecular, cellular, and organism levels. To understand the underlying mechanisms of drought tolerance, adequate stress models and arrays of reliable stress markers are required. Therefore, in this review we comprehensively address currently available models of drought stress, based on culturing plants in soil, hydroponically, or in agar culture, and critically discuss advantages and limitations of each design. We also address the methodology of drought stress characterization and discuss it in the context of real experimental approaches. Further, we highlight the trends of methodological developments in drought stress research, i.e., complementing conventional tests with quantification of phytohormones and reactive oxygen species (ROS), measuring antioxidant enzyme activities, and comprehensively profiling transcriptome, proteome, and metabolome.

Salt resistant crop plants

Soil salinity is a major constraint to agriculture. To improve salinity tolerance of crops, various traits can be incorporated, including ion exclusion, osmotic tolerance and tissue tolerance. We review the roles of a range of genes involved in salt tolerance traits. Different tissues and cells are adapted for specific and often diverse function, so it is important to express the genes in specific cell-types and to pyramid a range of traits. Modern biotechnology (marker-assisted selection or genetic engineering) needs to be increasingly used to introduce the correct combination of genes into elite crop cultivars. Importantly, the effects of introduced genes need to be evaluated in the field to determine their effect on salinity tolerance and yield improvement.