The halotolerant rizhobacterium Glutamicibacter sp. alleviates salt impact on Phragmites australis by producing exopolysaccharides and limiting plant sodium uptake.

Salinity is a widespread abiotic stress, which has strong adverse effects on plant growth and crop productivity. Exopolysaccharides (EPS) play a crucial role in plant growth-promoting rhizobacteria (PGPR)-mediated improvement of plant stress tolerance. This study aimed to assess whether Glutamicibacter sp. strain producing large amounts of EPS may promote tolerance of common reed, Phragmites australis (Cav.) Trin. ex Steud., towards salt stress. This halotolerant rizhobacterium showed tolerance to salinity (up to 1 M NaCl) when cultivated on Luria-Bertani (LB) medium. Exposure to high salinity (300 mM NaCl) significantly impacted the plant growth parameters, but this adverse effect was mitigated following inoculation with Glutamicibacter sp., which triggered higher number of leaves and tillers, shoot fresh weight/dry weight, and root fresh weight as compared to non-inoculated plants. Salt stress increased the accumulation of malondialdehyde (MDA), polyphenols, total soluble sugars (TSSs), and free proline in shoots. In comparison, the inoculation with Glutamicibacter sp. further increased shoot polyphenol content, while decreasing MDA and free proline contents. Besides, this bacterial strain increased tissue Ca+ and K+ content concomitant to lower shoot Na+ and root Cl- accumulation, thus further highlighting the beneficial effect of Glutamicibacter sp. strain on the plant behavior under salinity. As a whole, our study provides strong arguments for a potential utilization of EPS-producing bacteria as a useful microbial inoculant to alleviate the deleterious effects of salinity on plants.

Seed priming mitigates high salinity impact on germination of bread wheat (Triticum aestivum L.) by improving carbohydrate and protein mobilization.

Salinity is increasingly considered as a major environmental issue, which threatens agricultural production by decreasing yield traits of crops. Seed priming is a useful and cost-effective technique to alleviate the negative effects of salinity and to enable a fast and uniform germination. In this context, we quantified the effects of priming with gibberellic acid (GP), calcium chloride (CP), and mannitol (MP) on seed germination of three bread wheat cultivars and investigated their response when grown at high salinity conditions (200 mM NaCl). Salt exposure strongly repressed seed imbibition and germination potential and extended germination time, whereas priming enhanced uniformity and seed vigor. Seed preconditioning alleviated the germination disruption caused by salt stress to varying degrees. Priming mitigating effect was agent-dependent with regard to water status (CP and MP), ionic imbalance (CP), and seed reserve mobilization (GP). Na+ accumulation in seedling tissues significantly impaired carbohydrate and protein mobilization by inhibiting amylase and proteases activities but had lesser effects on primed seeds. CP attenuated ionic imbalance by limiting sodium accumulation. Gibberellic acid was the most effective priming treatment for promoting the germination of wheat seeds under salt stress. Moreover, genotypic differences in wheat response to salinity stress were observed between varieties used in this study. Ardito, the oldest variety, seems to tolerate better salinity in priming-free conditions; Aubusson resulted the most salt-sensitive cultivar but showed a high germination recovery under priming conditions; Bologna showed an intermediate behavior.

Improving environmental stress resilience in crops by genome editing: insights from extremophile plants.

In basic and applied sciences, genome editing has become an indispensable tool, especially the versatile and adaptable CRISPR/Cas9 system. Using CRISPR/Cas9 in plants has enabled modifications of many valuable traits, including environmental stress tolerance, an essential aspect when it comes to ensuring food security under climate change pressure. The CRISPR toolbox enables faster and more precise plant breeding by facilitating: multiplex gene editing, gene pyramiding, and de novo domestication. In this paper, we discuss the most recent advances in CRISPR/Cas9 and alternative CRISPR-based systems, along with the technical challenges that remain to be overcome. A revision of the latest proof-of-concept and functional characterization studies has indeed provided more insight into the quantitative traits affecting crop yield and stress tolerance. Additionally, we focus on the applications of CRISPR/Cas9 technology in regard to extremophile plants, due to their significance on: industrial, ecological and economic levels. These still unexplored genetic resources could provide the means to harden our crops against the threat of climate change, thus ensuring food security over the next century.

Plant Growth-Promoting Rhizobacteria Alleviate High Salinity Impact on the Halophyte Suaeda fruticosa by Modulating Antioxidant Defense and Soil Biological Activity.

Plant growth-promoting rhizobacteria (PGPR) are considered as bio-ameliorators that confer better salt resistance to host plants while improving soil biological activity. Despite their importance, data about the likely synergisms between PGPR and halophytes in their native environments are scarce. The objective of this study was to assess the effect of PGPR (Glutamicibacter sp. and Pseudomonas sp.) inoculation on biomass, nutrient uptake, and antioxidant enzymes of Suaeda fruticosa, an obligate halophyte native in salt marshes and arid areas in Tunisia. Besides, the activity of rhizospheric soil enzyme activities upon plant inoculation was determined. Plants were grown in pots filled with soil and irrigated with 600 mM NaCl for 1 month. Inoculation (either with Pseudomonas sp. or Glutamicibacter sp.) resulted in significantly higher shoot dry weight and less accumulation of Na+ and Cl- in shoots of salt-treated plants. Glutamicibacter sp. inoculation significantly reduced malondialdehyde (MDA) concentration, while increasing the activity of antioxidant enzymes (superoxide dismutase; catalase; ascorbate peroxidase; and glutathione reductase) by up to 100%. This provides strong arguments in favor of a boosting effect of this strain on S. fruticosa challenged with high salinity. Pseudomonas sp. inoculation increased shoot K+ and Ca2+ content and lowered shoot MDA concentration. Regarding the soil biological activity, Pseudomonas sp. significantly enhanced the activities of three rhizospheric soil enzymes (urease, ß-glucosidase, and dehydrogenase) as compared to their respective non-inoculated saline treatment. Hence, Pseudomonas sp. could have a great potential to be used as bio-inoculants in order to improve plant growth and soil nutrient uptake under salt stress. Indole-3-acetic acid concentration in the soil increased in both bacterial treatments under saline conditions, especially with Glutamicibacter sp. (up to +214%). As a whole, Glutamicibacter sp. and Pseudomonas sp. strains are promising candidates as part of biological solutions aiming at the phytoremediation and reclamation of saline-degraded areas.

Potassium (K+) Starvation-Induced Oxidative Stress Triggers a General Boost of Antioxidant and NADPH-Generating Systems in the Halophyte Cakile maritima.

Potassium (K+) is an essential macro-element for plant growth and development given its implication in major processes such as photosynthesis, osmoregulation, protein synthesis, and enzyme function. Using 30-day-old Cakile maritima plants as halophyte model grown under K+ deprivation for 15 days, it was analyzed at the biochemical level to determine the metabolism of reactive oxygen species (ROS), key photorespiratory enzymes, and the main NADPH-generating systems. K+ starvation-induced oxidative stress was noticed by high malondialdehyde (MDA) content associated with an increase of superoxide radical (O2•-) in leaves from K+-deficient plants. K+ shortage led to an overall increase in the activity of hydroxypyruvate reductase (HPR) and glycolate oxidase (GOX), as well as of antioxidant enzymes catalase (CAT), those of the ascorbate-glutathione cycle, peroxidase (POX), and superoxide dismutase (SOD), and the main enzymes involved in the NADPH generation in both leaves and roots. Especially remarkable was the induction of up to seven CuZn-SOD isozymes in leaves due to K+ deficiency. As a whole, data show that the K+ starvation has associated oxidative stress that boosts a biochemical response leading to a general increase of the antioxidant and NADPH-generating systems that allow the survival of the halophyte Cakile maritima.

Changes in leaf ecophysiological traits and proteome profile provide new insights into variability of salt response in the succulent halophyte Cakile maritima.

Natural variability of stress tolerance in halophytic plants is of significance both ecologically and in view of identifying molecular traits for salt tolerance in plants. Using ecophysiological and proteomic analyses, we address these phenomena in two Tunisian accessions of the oilseed halophyte, Cakile maritima Scop., thriving on arid and semi-arid Mediterranean bioclimatic stages (Djerba and Raoued, respectively), with a special emphasis on the leaves. Changes in biomass, photosynthetic gas exchange and pigment concentrations in C. maritima plants treated with three salinity levels (0, 100 and 300mM NaCl) were monitored for 1month. Comparative two-dimensional gel electrophoresis (2-DE) revealed 94 and 56 proteins of differential abundance in Raoued and Djerba accessions, respectively. These salinity-responsive proteins were mainly related to photosynthesis and oxidative phosphorylation (OXPHOS). Although Djerba accession showed a lower biomass productivity, it showed a slightly higher CO2 assimilation rate than Raoued accession when salt-treated. Photosynthesis impairment in both accessions under salinity was also suggested by the lower abundance of proteins involved in Calvin cycle and electron transfer. A significant increase of protein spots involved in the OXPHOS system was found in Djerba accession, suggesting an increase in mitochondrial respiration for increased ATP production under saline conditions, whereas a lesser pronounced trend was observed for Raoued accession. The latter showed in addition higher abundance of proteins involved in photorespiration. Salt-challenged plants of Djerba also likely developed mechanisms for scavenging ROS in leaves as shown by the increase in superoxide dismutase and thioredoxin, while an opposite trend was found in Raoued.

Nitric oxide donor, sodium nitroprusside modulates hydrogen sulfide metabolism and cysteine homeostasis to aid the alleviation of chromium toxicity in maize seedlings (Zea mays L.).

The current research aimed to assess the protective role of nitric oxide (NO) against chromium (Cr) toxicity in maize seedlings. Chromium (200 µM) lowered osmotic potential in epicotyls and mostly in radicles (by 38% and 63%, respectively) as compared to the control. Sodium nitroprusside (SNP, NO donor) restored seedling biomass (+90% for both organs) and water potential, whereas application of Nω-nitro-L-arginine methylester (L-NAME, a NOS inhibitor) increased sensitivity to Cr. SNP suppressed Cr-triggered proline accumulation by inhibiting Δ1-pyrroline-5-carboxylate synthetase activity and stimulating proline dehydrogenase activity, leading to glutamate over-accumulation (~30% for both organs). Cr stimulated cysteine metabolism and this was further enhanced by SNP which stimulated serine acetyl-transferase and O-acetylserine (thiol) lyase activities. This was followed by an increase in endogenous hydrogen sulfide (H2S) generation by up-regulating L-cysteine desulfhydrase (+205%), D-cysteine desulfhydrase (+150%) and cyanoalanine synthase (+65%) activities in radicles compared to Cr-treatments plants. These positive effects were reduced in L-NAME compared to control. Combined Cr+SNP affected the levels of compounds involved in glutathione metabolism (γ-glutamyl-cysteinyl, γ-glutamyl-cysteinyl-clycine, γ-cysteinyl-glycine, and glycine.). All together, our findings indicate that NO and elicited cellular H2S act synergistically to alleviate Cr stress in maize seedlings by influencing a metabolic interplay between cysteine, proline, and glutathione.

Stability of thylakoid protein complexes and preserving photosynthetic efficiency are crucial for the successful recovery of the halophyte Cakile maritima from high salinity.

Plants native to extreme habitats often face changes in environmental conditions such as salinity level and water availability. In response, plants have evolved efficient mechanisms allowing them to survive or recover. In the present work, effects of high salinity and salt-stress release were studied on the halophyte Cakile maritima. Four week-old plants were either cultivated at 0 mM NaCl or 200 mM NaCl. After one month of treatment, plants were further irrigated at either 0 mM NaCl, 200 mM NaCl, or rewatered to 0 mM NaCl (stress release). Upon salt stress, C. maritima plants exhibited reduced biomass production and shoot hydration which were associated with a decrease in the amount of chlorophyll a and b. However, under the same stressful conditions a significant increase of anthocyanin and malonyldialdehyde concentrations was noticed. Salt-stressed plants were able to maintain stable protein complexes of thylakoid membranes. Measurement of chlorophyll fluorescence and P700 redox state showed that PSI was more susceptible for damage by salinity than PSII. PSII machinery was significantly enhanced under saline conditions. All measured parameters were partially restored under salt-stress release conditions. Photoinhibition of PSI was also reversible and C. maritima was able to successfully re-establish PSI machinery indicating the high contribution of chloroplasts in salt tolerance mechanisms of C. maritima. Overall, to overcome high salinity stress, C. maritima sets a cascade of physio-biochemical and molecular pathways. Chloroplasts seem to act as metabolic centers as part of this adaptive process enabling growth restoration in this halophyte following salt stress release.

Composition and Stability of the Oxidative Phosphorylation System in the Halophile Plant Cakile maritima.

Mitochondria play a central role in the energy metabolism of plants. At the same time, they provide energy for plant stress responses. We here report a first view on the mitochondrial Oxidative Phosphorylation (OXPHOS) system of the halophile (salt tolerant) plant Cakile maritima. Mitochondria were purified from suspension cultures of C. maritima and for comparison of Arabidopsis thaliana, a closely related glycophyte (salt sensitive) plant. Mitochondria were treated with digitonin and solubilized protein complexes were analyzed by 2D Blue native/SDS polyacrylamide gel electrophoresis. The OXPHOS systems of the two compared plants exhibit some distinct differences. C. maritima mitochondria include a very abundant respiratory supercomplex composed of monomeric complex I and dimeric complex III. At the same time the complexes II and IV are of reduced abundance. The stability of the OXPHOS complexes was investigated by combined salt and temperature treatments of isolated mitochondria. ATP synthase (complex V) is of increased stability in C. maritima. Also, the I + III2 supercomplex is present in high abundance during stress treatments. These results give insights into the mitochondrial contribution to the plant salt stress response.

Recovery aptitude of the halophyte Cakile maritima upon water deficit stress release is sustained by extensive modulation of the leaf proteome.

Among the most intriguing features characterizing extremophile plants is their ability to rapidly recover growth activity upon stress release. Here, we investigated the responses of the halophyte C. maritima to drought and recovery at both physiological and leaf proteome levels. Six week-old plants were either cultivated at 100% or at 25% field capacity. After 12 d of treatment, one lot of dehydrated plants was rewatered to 100% FC for 14 d (stress release). Drought stress impaired shoot hydration, photosynthetic activity and chlorophyll content compared to the control, resulting in severe plant growth restriction. This was concomitant with a marked increase in anthocyanin and proline concentrations. Upon stress release, C. maritima rapidly recovered with respect to all measured parameters. Two-dimensional gel-based proteome analysis of leaves revealed 84 protein spots with significantly changed volumes at the compared conditions: twenty-eight protein spots between normally watered plants and stressed plants but even 70 proteins between stressed and recovered plants. Proteins with higher abundance induced upon rewatering were mostly involved in photosynthesis, glycolytic pathway, TCA cycle, protein biosynthesis, and other metabolic pathways. Overall, C. maritima likely adopts a drought-avoidance strategy, involving efficient mechanisms specifically taking place upon stress release, leading to fast and strong recovery.

Comparative analysis of salt-induced changes in the root proteome of two accessions of the halophyte Cakile maritima.

NaCl stress is a major abiotic stress factor limiting the productivity and the geographical distribution of many plant species. Although halophytes are able to withstand and even to require salt in the rhizosphere, roots are the most sensitive organs to salinity. Here, we investigate the variability of salt tolerance in two Tunisian accessions of the halophyte Cakile maritima (Raoued and Djerba, harvested from the semi-arid and arid Mediterranean bioclimatic stages, respectively) with a special emphasis on the proteomic changes in roots. Seedlings were hydroponically grown for one month under salt-free conditions and subsequently at three salinities (0, 100, and 300 mM NaCl). Physiological parameters (plant growth, water content, Na+, K+ contents) and root protein profiles were analyzed. Plant biomass was higher in Raoued than in Djerba but the latter was impacted to a lesser extent by salinity, notably due to lower sodium accumulation and higher selectivity for K+. 121 and 97 salt-responsive proteins were identified in Djerba and Raoued accessions, respectively. These proteins can be assigned to several different functional categories: protein metabolism, nucleotide metabolism, amino acid metabolism, glutathione metabolism, translation and ribosome biogenesis, carbohydrate and energy metabolism, and reactive oxygen species regulation and detoxification. The comparative proteome analysis revealed that 33 proteins were salt-responsive in both accessions, while 88 and 64 proteins were salt-responsive only in the Djerba or Raoued accessions, respectively. Our results give deeper insights into the plasticity of salt-stress response of C. maritima in its native ecosystems.

High salinity impacts germination of the halophyte Cakile maritima but primes seeds for rapid germination upon stress release.

Seed germination recovery aptitude is an adaptive trait of overriding significance for the successful establishment and dispersal of extremophile plants in their native ecosystems. Cakile maritima is an annual halophyte frequent on Mediterranean coasts, which produces transiently dormant seeds under high salinity, that germinate fast when soil salinity is lowered by rainfall. Here, we report ecophysiological and proteomic data about (1) the effect of high salt (200 mM NaCl) on the early developmental stages (germination and seedling) and (2) the seed germination recovery capacity of this species. Upon salt exposure, seed germination was severely inhibited and delayed and seedling length was restricted. Interestingly, non-germinated seeds remained viable, showing high germination percentage and faster germination than the control seeds after their transfer onto distilled water. The plant phenotypic plasticity during germination was better highlighted by the proteomic data. Salt exposure triggered (1) a marked slower degradation of seed storage reserves and (2) a significant lower abundance of proteins involved in several biological processes (primary metabolism, energy, stress-response, folding and stability). Yet, these proteins showed strong increased abundance early after stress release, thereby sustaining the faster seed storage proteins mobilization under recovery conditions compared to the control. Overall, as part of the plant survival strategy, C. maritima seems to avoid germination and establishment under high salinity. However, this harsh condition may have a priming-like effect, boosting seed germination and vigor under post-stress conditions, sustained by active metabolic machinery.

Facing the challenge of sustainable bioenergy production: Could halophytes be part of the solution?

Due to steadily growing population and economic transitions in the more populous countries, renewable sources of energy are needed more than ever. Plant biomass as a raw source of bioenergy and biofuel products may meet the demand for sustainable energy; however, such plants typically compete with food crops, which should not be wasted for producing energy and chemicals. Second-generation or advanced biofuels that are based on renewable and non-edible biomass resources are processed to produce cellulosic ethanol, which could be further used for producing energy, but also bio-based chemicals including higher alcohols, organic acids, and bulk chemicals. Halophytes do not compete with conventional crops for arable areas and freshwater resources, since they grow naturally in saline ecosystems, mostly in semi-arid and arid areas. Using halophytes for biofuel production may provide a mid-term economically feasible and environmentally sustainable solution to producing bioenergy, contributing, at the same time, to making saline areas - which have been considered unproductive for a long time - more valuable. This review emphasises on halophyte definition, global distribution, and environmental requirements. It also examines their enzymatic valorization, focusing on salt-tolerant enzymes from halophilic microbial species that may be deployed with greater advantage compared to their conventional mesophilic counterparts for faster degradation of halophyte biomass.

NADPH oxidase-dependent H2O2 production is required for salt-induced antioxidant defense in Arabidopsis thaliana.

The involvement of hydrogen peroxide (H2O2) generated by nicotinamide adenine dinucleotide phosphate-oxidase (NADPH oxidase) in the antioxidant defense system was assessed in salt-challenged Arabidopsis thaliana seedlings. In the wild-type, short-term salt exposure led to a transient and significant increase of H2O2 concentration, followed by a marked increase in catalase (CAT, EC 1.11.16), ascorbate peroxidase (APX, EC 1.11.1.11) and glutathione reductase (GR, EC 1.6.4.2) activities. Pre-treatment with either a chemical trap for H2O2 (dimethylthiourea) or two widely used NADPH oxidase inhibitors (imidazol and diphenylene iodonium) significantly decreased the above-mentioned enzyme activities under salinity. Double mutant atrbohd/f plants failed to induce the antioxidant response under the culture conditions. Under long-term salinity, the wild-type was more salt-tolerant than the mutant based on the plant biomass production. The better performance of the wild-type was related to a significantly higher photosynthetic activity, a more efficient K(+) selective uptake, and to the plants' ability to deal with the salt-induced oxidative stress as compared to atrbohd/f. Altogether, these data suggest that the early H2O2 generation by NADPH oxidase under salt stress could be the beginning of a reaction cascade that triggers the antioxidant response in A. thaliana in order to overcome the subsequent reactive oxygen species (ROS) production, thereby mitigating the salt stress-derived injuries.

Comparative Ni tolerance and accumulation potentials between Mesembryanthemum crystallinum (halophyte) and Brassica juncea: Metal accumulation, nutrient status and photosynthetic activity.

Saline soils often constitute sites of accumulation of industrial and urban wastes contaminated by heavy metals. Halophytes, i.e. native salt-tolerant species, could be more suitable for heavy metal phytoextraction from saline areas than glycophytes, most frequently used so far. In the framework of this approach, we assess here the Ni phytoextraction potential in the halophyte Mesembryanthemum crystallinum compared with the model species Brassica juncea. Plants were hydroponically maintained for 21 days at 0, 25, 50, and 100µM NiCl2. Nickel addition significantly restricted the growth activity of both species, and to a higher extent in M. crystallinum, which did not, however, show Ni-related toxicity symptoms on leaves. Interestingly, photosynthesis activity, chlorophyll content and photosystem II integrity assessed by chlorophyll fluorescence were less impacted in Ni-treated M. crystallinum as compared to B. juncea. The plant mineral nutrition was differently affected by NiCl2 exposure depending on the element, the species investigated and even the organ. In both species, roots were the preferential sites of Ni(2+) accumulation, but the fraction translocated to shoots was higher in B. juncea than in M. crystallinum. The relatively good tolerance of M. crystallinum to Ni suggests that this halophyte species could be used in the phytoextraction of moderately polluted saline soils.

The effect of hyper-osmotic salinity on protein pattern and enzyme activities of halophytes.

Studies of the convergence of the expression of enzymes and the physiology of salt resistance are rare, and give the general impression of a jigsaw puzzle with many missing pieces. To date, only minor responses of plasma membrane and tonoplast proteins of halophytes have been reported. Mostly, subunits of the catalytic portions of ATPases were found to change. In succulent plants such as Salicornia europea the abundance of V-type ATPase subunits has been correlated with growth performance. This stresses the physiological strategy to sequester incoming salt into vacuoles, which may also benefit osmotic regulation and further promote growth. A considerable amount of information is available on the responses of proteins involved in photosynthesis and detoxification of reactive oxygen species (ROS) under saline conditions. Two aspects deserve special attention: (i) salt responsive multiple spot patterns of individual proteins (due to protein modification, phosphorylation, for instance); and (ii) correlations between salt-mediated protein abundance and plant performance. Relevant observations underline that there exists a tightly knit metabolic network underlying physiological observations. Although the exact functioning of control and signalling sequences remains elusive, another aspect becomes very obvious from the publications analysed: stress responses of halophytes are multi-variant and include not only an increase in abundance of enzymes, but also of chaperones and proteins controlling organisation of the cytoplasm.

Proteomic and physiological responses of the halophyte Cakile maritima to moderate salinity at the germinative and vegetative stages.

Responses of the halophyte Cakile maritima to moderate salinity were addressed at germination and vegetative stages by bringing together proteomics and eco-physiological approaches. 75 mM NaCl-salinity delayed significantly the germination process and decreased slightly the seed germination percentage compared to salt-free conditions. Monitoring the proteome profile between 0 h and 120 h after seed sowing revealed a delay in the degradation of seed storage proteins when germination took place under salinity, which may explain the slower germination rate observed. Of the sixty-seven proteins identified by mass spectrometry, several proteins involved in glycolysis, amino acid metabolism, photosynthesis, and protein folding showed significantly increased abundance during germination. This pattern was less pronounced under salinity. At the vegetative stage, 100mM NaCl-salinity stimulated significantly the plant growth, which was sustained by enhanced leaf expansion, water content, and photosynthetic activity. Comparative proteome analyses of leaf tissue revealed 44 proteins with different abundance changes, most of which being involved in energy metabolism. A specific set of proteins predominantly involved in photosynthesis and respiration showed significantly higher abundance in salt-treated plants. Altogether, combining proteomics with eco-physiological tools provides valuable information, which contributes to improve our understanding in the salt-response of this halophyte during its life cycle.

Medicinal halophytes: potent source of health promoting biomolecules with medical, nutraceutical and food applications.

Salt-tolerant plants grow in a wide variety of saline habitats, from coastal regions, salt marshes and mudflats to inland deserts, salt flats and steppes. Halophytes living in these extreme environments have to deal with frequent changes in salinity level. This can be done by developing adaptive responses including the synthesis of several bioactive molecules. Consequently, several salt marsh plants have traditionally been used for medical, nutritional, and even artisanal purposes. Currently, an increasing interest is granted to these species because of their high content in bioactive compounds (primary and secondary metabolites) such as polyunsaturated fatty acids, carotenoids, vitamins, sterols, essential oils (terpenes), polysaccharides, glycosides, and phenolic compounds. These bioactive substances display potent antioxidant, antimicrobial, anti-inflammatory, and anti-tumoral activities, and therefore represent key-compounds in preventing various diseases (e.g. cancer, chronic inflammation, atherosclerosis and cardiovascular disorder) and ageing processes. The ongoing research will lead to the utilisation of halophytes as a new source of healthy products as functional foods, nutraceuticals or active principles in several industries. This contribution focuses on the ethnopharmacological uses of halophytes in traditional medicine and reviews recent investigations on their biological activities and nutraceuticals. The work is distributed according to the different families of nutraceuticals (lipids, vitamins, proteins, glycosides, phenolic compounds, etc.) discussing the analytical techniques employed for their determination. Information about the claimed health promoting effects of the different families of nutraceuticals is also provided together with data on their application.

Municipal solid waste compost application improves productivity, polyphenol content, and antioxidant capacity of Mesembryanthemum edule.

Organic wastes were successfully used as soil amendment to improve agrosystems productivity. Yet, the effectiveness of this practice to enhance plant antioxidant capacities has received little attention. Here, we assess the effect of municipal solid waste (MSW) compost (at 40 t ha(-1)) on growth, polyphenol contents and antioxidant activities of Mesembryanthemum edule. MSW compost application significantly increased the soil contents of carbon, nitrogen, calcium, phosphorus and potassium. This was associated with higher nutrient (N, P, and K) uptake, which likely led to the significant improvement of the plant biomass and relative growth rate (RGR) (+93% on average) as compared to the control. In the same way, the fertilizing effect of the added organic matter significantly enhanced the antioxidant potential M. edule, assessed by radical scavenging activity, iron reducing power and ß-carotene bleaching capacity. This was associated with significantly higher antioxidant contents, mainly total phenols and flavonoids. Heavy metal (Pb, Cd, Cu, and Zn) concentrations were slightly increased upon compost application, but remained lower than phytotoxic values. Overall, our results point out that short-term MSW compost application at 40 t ha(-1) is efficient in enhancing the productivity together with the antioxidant potentiality of M. edule without any adverse environmental impact.

Effect of municipal solid waste compost and sewage sludge use on wheat (Triticum durum): growth, heavy metal accumulation, and antioxidant activity.

BACKGROUND: Inappropriate utilisation of biosolids may adversely impact agrosystem productivity. Here, we address the response of wheat (Triticum durum) to different doses (0, 40, 100, 200 and 300 t ha(-1)) of either municipal solid waste (MSW) compost or sewage sludge in a greenhouse pot experiment. Plant growth, heavy metal uptake, and antioxidant activity were considered. RESULTS: Biomass production of treated plants was significantly enhanced at 40 t ha(-1) and 100 t ha(-1) of MSW compost (+48% and +78% relative to the control, respectively). At the same doses of sewage sludge, the increase was only 18%. Higher doses of both biosolids restricted significantly the plant growth, in concomitance with the significant accumulation of heavy metals (Ni2+, Pb2+, Cu2+ and Zn2+), especially in leaves. Leaf activities of antioxidant enzymes (ascorbate peroxidase, glutathione reductase, catalase and superoxide dismutase) were unchanged at 40 t ha(-1) MSW compost or sewage sludge, but were significantly stimulated at higher doses (200-300 t ha(-1)), together with higher leaf concentration of reduced glutathione. CONCLUSION: This preliminary study suggests that a MSW supply at moderate doses (100 t ha(-1)) could be highly beneficial for wheat productivity.