The development of halophyte-based agriculture: past and present

Effects of Temperature and Packaging Atmosphere on Shelf Life, Biochemical, and Sensory Attributes of Glasswort (Salicornia europaea L.) Grown Hydroponically at Different Salinity Levels

Halophytes, such as Salicornia species, are promising new foods and are consumed for their pleasant salty taste and nutritional value. Since Salicornia is perishable, modified atmospheric packaging (MAP) can be a useful tool, in combination with proper temperature, to halt further quality degradation in this type of product. The purpose of this study was to investigate the effect of MAP, with or without refrigeration, to extend the shelf life of glasswort (Salicornia europaea L.) grown hydroponically (floating raft system) in a greenhouse with a nutrient solution containing 0 g/L (C) or 12.5 g/L of NaCl (T). The dry matter content, weight loss, respiration rate, biochemical composition, color, antioxidant capacity, and sensorial attributes were determined in shoots after harvest and during storage in plastic bags filled with technical air or with MAP at 4 or 20 °C for 120 h. At harvest, plants supplied with salt-enriched solution (T) showed a significant improvement in nutritional value and sensory profile. Storage in air at room temperature (20 °C) accelerated weight loss and diminished color stability, particularly in non-salinity samples (C), while MAP extended the shelf life of all the samples regardless of the storage temperature adopted. Optimal storage conditions were observed when MAP was combined with refrigeration, which allowed to effectively preserve shoots sensory acceptability for a period of about seven days. Future research could further explore the long-term effects on the nutritional value and sensory quality of S. europaea under various combinations of MAP and different storage temperatures ranging between 4 °C and 20 °C.

Diagnostic species are crucial for the functioning of plant associations in inland salt marshes

Salt marsh vegetation is considered unique and valuable and has been legally protected in Europe for years but is still declining. Its protection is related to vegetation syntaxonomical units. The characteristic combination of diagnostic species is used to create this syntaxonomical system. The aim of our novel study was to assess whether diagnostic species are sufficient for characterising vegetation functioning. Moreover, we included biochemical traits not considered to date in vegetation ecology. We hypothesised that (1) diagnostic species are crucial for the functioning of inland salt marsh vegetation and (2) their morphological and biochemical traits define the functioning of typical salt marsh associations. We chose three typical inland associations to test our hypotheses and measured the morphological and biochemical functional traits of their diagnostic plant species. Our research has shown that diagnostic species play a crucial role not only in distinguishing typical inland salt marsh associations but also in determining their functioning. Among the analysed associations, Salicornietum ramosissimae was the most adaptable to osmotic and oxidative stress under soil salinity. Triglochino maritimae-Glaucetum maritimae showed the lowest salt resistance, as indicated by the highest osmotic and oxidative stress and stress responses. Our findings may facilitate the practical application of new approaches and protection strategies for inland salt marsh habitats.

The Sustainable Use of Halophytes in Salt-Affected Land: State-of-the-Art and Next Steps in a Saltier World

Salinization is a major cause of soil degradation that affects several million hectares of agricultural land, threatening food security and the sustainability of agricultural systems worldwide. Nevertheless, despite the negative impact of salinity, salt-affected land also provides several important ecosystem services, from providing habitats and nurseries for numerous species to sustainable food production. This opinion paper, written in the framework of the EU COST Action CA22144 SUSTAIN on the sustainable use of salt-affected land, therefore, focuses on the potential of halophytes and saline agriculture to transform and restore key functions of these salt-affected and marginal lands. As the current knowledge on sustainable saline agriculture upscaling is fragmented, we highlight (i) the research gaps in halophyte and salinity research and (ii) the main barriers and potentials of saline agriculture for addressing food security and environmental sustainability in terms of population growth and climate change.

An updated phylogeny and adaptive evolution within Amaranthaceae s.l. inferred from multiple phylogenomic datasets

Amaranthaceae s.l. is a widely distributed family consisting of over 170 genera and 2000 species. Previous molecular phylogenetic studies have shown that Amaranthaceae s.s. and traditional Chenopodiaceae form a monophyletic group (Amaranthaceae s.l.), however, the relationships within this evolutionary branch have yet to be fully resolved. In this study, we assembled the complete plastomes and full-length ITS of 21 Amaranthaceae s.l. individuals and compared them with 38 species of Amaranthaceae s.l. Through plastome structure and sequence alignment analysis, we identified a reverse complementary region approximately 5200 bp long in the genera Atriplex and Chenopodium. Adaptive evolution analysis revealed significant positive selection in eight genes, which likely played a driving role in the evolution of Amaranthaceae s.l., as demonstrated by partitioned evolutionary analysis. Furthermore, we found that about two-thirds of the examined species lack the ycf15 gene, potentially associated with natural selection pressures from their adapted habitats. The phylogenetic tree indicated that some genera (Chenopodium, Halogeton, and Subtr. Salsolinae) are paraphyletic lineages. Our results strongly support the clustering of Amaranthaceae s.l. with monophyletic traditional Chenopodiaceae (Clades I and II) and Amaranthaceae s.s. After a comprehensive analysis, we determined that cytonuclear conflict, gene selection by adapted habitats, and incomplete lineage sorting (ILS) events were the primary reasons for the inconsistent phylogeny of Amaranthaceae s.l. During the last glacial period, certain species within Amaranthaceae s.l. underwent adaptations to different environments and began to differentiate rapidly. Since then, these species may have experienced morphological and genetic changes distinct from those of other genera due to intense selection pressure.

Modulation of physio-biochemical and photosynthesis parameters by overexpressing SbPIP2 gene improved abiotic stress tolerance of transgenic tobacco

The present study aims to explore the potential of a plasma-membrane localized PIP2-type aquaporin protein sourced from the halophyte Salicornia brachiata to alleviate salinity and water deficit stress tolerance in a model plant through transgenic intervention. Transgenic plants overexpressing SbPIP2 gene showed improved physio-biochemical parameters like increased osmolytes (proline, total sugar, and amino acids), antioxidants (polyphenols), pigments and membrane stability under salinity and drought stresses compared to control plants [wild type (WT) and vector control (VC) plants]. Multivariate statistical analysis showed that, under water and salinity stresses, osmolytes, antioxidants and pigments were correlated with SbPIP2-overexpressing (SbPIP2-OE) plants treated with salinity and water deficit stress, suggesting their involvement in stress tolerance. As aquaporins are also involved in CO2 transport, SbPIP2-OE plants showed enhanced photosynthesis performance than wild type upon salinity and drought stresses. Photosynthetic gas exchange (net CO2 assimilation rate, PSII efficiency, ETR, and non-photochemical quenching) were significantly higher in SbPIP2-OE plants compared to control plants (wild type and vector control plants) under both unstressed and stressed conditions. The higher quantum yield for reduction of end electron acceptors at the PSI acceptor side [Φ( R0 )] in SbPIP2-OE plants compared to control plants under abiotic stresses indicates a continued PSI functioning, leading to retained electron transport rate, higher carbon assimilation, and less ROS-mediated injuries. In conclusion, the SbPIP2 gene functionally validated in the present study could be a potential candidate for engineering abiotic stress resilience in important crops.

Influence of dietary Salicornia europaea L. extract supplementation on feed efficiency of Altay sheep by modifying their gastrointestinal bacteria communities

This experiment aimed to examine the impact of Salicornia europaea L. extract on sheep growth performance, rumen fermentation variables, nutrient apparent digestibility, and gastrointestinal microbial diversity. Forty-eight male Altay sheep, weighing 32.5 ± 2.8 kg and approximately 3.5 months old, were chosen. Four dietary treatments, each consisting of four replicates and three sheep per replicate, were distributed randomly to the sheep. The pelleted total mixed ration containing Salicornia europaea L. extract at 0.0, 0.2, 0.4, and 0.6% DM was freely available to the sheep in the four treatment groups. The 56-day experiment consisted of 45 days of measurements followed by 11 days of adaptation. The growth performance was not affected by nutrition Salicornia europaea L. extract (p ≤ 0.05), but the feed-to-gain ratio was reduced when the extract was given at 0.4% DM (p ≤ 0.05). Compared to the 0 and 0.2% treatments, the apparent digestibility of DM, OM, NDF, and ADF was substantially greater in the 0.4, and 0.6% treatments. Furthermore, compared to sheep in the 0 and 0.2% groups, sheep in the 0.6% group had a noticeably higher apparent digestibility of CP. As the amount of Salicornia europaea L. extract added to the rumen fluid rose, the molar ratio of acetic acid increased. In contrast, the molar ratio of propionic acid gradually decreased, and the total volatile fatty acid content gradually reduced. Thus, adding a suitable quantity of Salicornia europaea L. extract to the sheep ration is natural and secure, which may improve the environmental sustainability of small ruminant production systems.

Trichoderma asperellum boosts nitrogen accumulation and photosynthetic capacity of wolfberry (Lycium chinense) under saline soil stress

Trichoderma can promote plant growth under saline stress, but the mechanisms remain to be revealed. In this study, we investigate photosynthetic gas exchange, photosystem II (PSII) performance, nitrogen absorption and accumulation in a medicinal plant wolfberry (Lycium chinense) in saline soil supplemented with Trichoderma biofertilizer (TF). Larger nitrogen and biomass accumulation were found in plants supplemented with TF than with organic fertilizer (OF), suggesting that Trichoderma asperellum promoted plant growth and nitrogen accumulation under saline stress. T. asperellum strengthened root nitrogen (N) absorption according to greater increased root NH4+ and NO3- influxes under supplement with TF than OF, while nitrogen assimilative enzymes such as nitrate reductase, nitrite reductase and glutamine synthetase activities in roots and leaves were also stimulated. Thus, the elevated N accumulation derived from the induction of T. asperellum on nitrogen absorption and assimilation. Greater increased photosynthetic rate (Pn) and photosynthetic N-use efficiency under supplement with TF than OF illustrated that T. asperellum enhanced photosynthetic capacity and N utilization under saline stress. Although increased leaf stomatal conductance contributed to carbon (C) isotope fractionation under TF supplement, leaf 13C abundance was significantly increased by supplement with TF rather than OF, indicating that T. asperellum raised CO2 assimilation to a greater extent, reducing C isotope preference. Trichoderma asperellum optimized electron transport at PSII donor and acceptor sides under saline stress because of lower K and J steps in chlorophyll fluorescence transients under supplement with TF than OF. The amount of PSII active reaction centers was also increased by T. asperellum. Thus, PSII performance was upgraded, consistent with greater heightened delayed chlorophyll fluorescence transients and I1 peak under supplement with TF than OF. In summary, TF acted to increase N nutrient acquisition and photosynthetic C fixation resulting in enhanced wolfberry growth under saline soil stress.

Insight into bacterial and archaeal community structure of Suaeda altissima and Suaeda dendroides rhizosphere in response to different salinity level

IMPORTANCE

Suaeda play an important ecological role in reclamation and improvement of agricultural saline soil due to strong salt tolerance. At present, research on Suaeda salt tolerance mainly focuses on the physiological and molecular regulation. However, the important role played by microbial communities in the high-salinity tolerance of Suaeda is poorly studied. Our findings have important implications for understanding the distribution patterns and the driving mechanisms of different Suaeda species and soil salinity levels. In addition, we explored the key microorganisms that played an important ecological role in Suaeda rhizosphere. We provide a basis for biological improvement and ecological restoration of salinity-affected areas.

Exploring the Antioxidant and Genoprotective Potential of Salicornia ramosissima Incorporation in the Diet of the European Seabass (Dicentrarchus labrax)

The identification of novel feed materials as a source of functional ingredients is a topical priority in the finfish aquaculture sector. Due to the agrotechnical practices associated and phytochemical profiling, halophytes emerge as a new source of feedstuff for aquafeeds, with the potential to boost productivity and environmental sustainability. Therefore, the present study aimed to assess the potential of Salicornia ramosissima incorporation (2.5, 5, and 10%), for 2 months, in the diet of juvenile European seabass, seeking antioxidant (in the liver, gills, and blood) and genoprotective (DNA and chromosomal integrity in blood) benefits. Halophyte inclusion showed no impairments on growth performance. Moreover, a tissue-specific antioxidant improvement was apparent, namely through the GSH-related defense subsystem, but revealing multiple and complex mechanisms. A genotoxic trigger (regarded as a pro-genoprotective mechanism) was identified in the first month of supplementation. A clear protection of DNA integrity was detected in the second month, for all the supplementation levels (and the most prominent melioration at 10%). Overall, these results pointed out a functionality of S. ramosissima-supplemented diets and a promising way to improve aquaculture practices, also unraveling a complementary novel, low-value raw material, and a path to its valorization.

Phytoremediation of chloride from marine dredged sediments: A new model based on a natural vegetation recolonization

Phytoremediation is a type of bioremediation process that involves the use of plants to remove or degrade contaminants from soil, water, or air. In most of the observed phytoremediation models, plants are introduced and planted on a polluted site to take up, absorb, or transform contaminants. This study aims to explore a new mixed phytoremediation approach that involves natural recolonization of a contaminated substrate, by identifying the species growing naturally, their bioaccumulation capacity, and by modeling annual mowing cycles of their aerial parts. This approach aims to evaluate the phytoremediation potential of such a model. Both natural and human interventions are involved in this approach, which is referred to as a mixed phytoremediation process. The study focuses on chloride phytoremediation from a chloride-rich and regulated substrate that is marine dredged sediments abandoned for 12 years and recolonized for 4 years. The sediments are colonized by a Suaeda vera dominated vegetation and possess heterogeneity in lixiviate chloride and conductivity. The study found that despite Suaeda vera is the well adapted species for this environment, it is not an effective species for phytoremediation as it has low bioaccumulation and translocation rates (9.3 and 2.6 respectively), and disturbs chloride leaching below in the substrate. Other identified species, such as Salicornia sp., Suaeda maritima, and Halimione portulacoides, have better phytoaccumulation (respectively 39.8, 40.1, 34.8) and translocation rates (respectively 7.0, 4.5, 5.6) and can successfully remediate the sediment in 2-9 years. The following species have been found to bioaccumulate chloride in aboveground biomass at the following rates: Salicornia sp. (181 g/kg DW), Suaeda maritima (160 g/kg DW), Sarcocornia perennis (150 g/kg DW), Halimione portulacoides (111 g/kg DW) and Suaeda vera (40 g/kg DW).

Leaf nitrogen and phosphorus stoichiometry of the halophytes across China

Halophytes play a crucial role in the ecological restoration of saline and alkaline land and hold promising benefits to food security in China. Although a variety of aspects of halophytes have been extensively addressed, there is still a lack of overall understanding of the leaf nitrogen (N) and phosphorus (P) stoichiometric characteristics, especially at a national scale. We compiled a national dataset of 311 observations from 113 sampling sites across China to explore the changing trends and influencing factors on leaf N and P concentrations, and N:P ratio of halophytes. The results showed that leaf N concentration decreased significantly with increasing latitude (LAT), which was mainly driven by the mean annual temperature (MAT) and mean annual precipitation (MAP). The leaf P concentration increased remarkably with increasing longitude (LON), which was induced by the variation in soil total P (TP) content. The leaf N:P ratio increased as LAT increased and LON decreased, which was potentially regulated by the MAT, MAP, and soil TP content. The scaling exponents of the N-P relationship differed significantly among halophyte types and were 0.40, 0.87, and 1.39 for euhalophyte, pseudohalophyte, and recretohalophyte, respectively. The leaf N concentration exhibited significant differences among ecosystem types and halophyte types, whereas the leaf P concentration and N:P ratio remained relatively stable. In summary, the leaf N concentration and N-P scaling exponent might be the classification criteria for halophyte types from the perspective of plant nutrient resource allocation. Moreover, this study characterized the spatial distribution and allocation strategy of leaf N and P stoichiometry in halophytes by data integration analysis, providing the basic information for nutrient management in the processes of the future domestication and introduction of halophytes.

Salinity and nitrogen source affect productivity and nutritional value of edible halophytes

Saline agriculture may contribute to food production in the face of the declining availability of fresh water and an expanding area of salinized soils worldwide. However, there is currently little known about the biomass and nutrient/antinutrient accumulation response of many edible halophytes to increasing levels of salinity and nitrogen source. To address this, two glass house experiments were carried out. The first to study the shoot biomass, and nutrient accumulation response, measured by ICP-MS analysis, of edible halophyte species, including Mesembryanthemum crystallinum (ice plant), Salsola komarovii (Land seaweed), Enchylaena tomentosa (Ruby Saltbush), Crithmum maritimum (Rock Samphire), Crambe maritima (Sea Kale) and Mertensia maritima (Oyster Plant), under increasing levels of salinity (0 to 800 mM). The second experiment studied the effects of nitrogen source combined with salinity, on levels of oxalate, measured by HPLC, in ice plant and ruby saltbush. Species differences for biomass and sodium (Na), potassium (K), chloride (Cl), nitrogen (N) and phosphorus (P) accumulation were observed across the range of salt treatments (0 to 800mM). Shoot concentrations of the anti-nutrient oxalate decreased significantly in ice plant and ruby saltbush with an increase in the proportion of N provided as NH4+ (up to 100%), while shoot oxalate concentrations in ice plant and ruby saltbush grown in the absence of NaCl were not significantly different to oxalate concentrations in plants treated with 200 mM or 400 mM NaCl. However, the lower shoot oxalate concentrations observed with the increase in NH4+ came with concurrent reductions in shoot biomass. Results suggest that there will need to be a calculated tradeoff between oxalate levels and biomass when growing these plants for commercial purposes.

Harnessing the Value of Tripolium pannonicum and Crithmum maritimum Halophyte Biomass through Integrated Green Biorefinery

Bioactive extracts are often the target fractions in bioprospecting, and halophyte plants could provide a potential source of feedstock for high-value applications as a part of integrated biorefineries. Tripolium pannonicum (Jacq.) Dobrocz. (sea aster) and Crithmum maritimum L. (sea fennel) are edible plants suggested for biosaline halophyte-based agriculture. After food production and harvesting of fresh leaves for food, the inedible plant fractions could be utilized to produce extracts rich in bioactive phytochemicals to maximize feedstock application and increase the economic feasibility of biomass processing to bioenergy. This study analyzed fresh juice and extracts from screw-pressed sea aster and sea fennel for their different phenolic compounds and pigment concentrations. Antioxidant and enzyme inhibition activities were also tested in vitro. Extracts from sea aster and sea fennel had phenolic contents up to 45.2 mgGAE/gDM and 64.7 mgGAE/gDM, respectively, and exhibited >70% antioxidant activity in several assays. Ethanol extracts also showed >70% inhibition activity against acetylcholinesterase and >50% inhibition of tyrosinase and α-glucosidase. Therefore, these species can be seen as potential feedstocks for further investigations.

Soilless Cultivated Halophyte Plants: Volatile, Nutritional, Phytochemical, and Biological Differences

The use of halophyte plants appears as a potential solution for degraded soil, food safety, freshwater scarcity, and coastal area utilization. These plants have been considered an alternative crop soilless agriculture for sustainable use of natural resources. There are few studies carried out with cultivated halophytes using a soilless cultivation system (SCS) that report their nutraceutical value, as well as their benefits on human health. The objective of this study was to evaluate and correlate the nutritional composition, volatile profile, phytochemical content, and biological activities of seven halophyte species cultivated using a SCS (Disphyma crassifolium L., Crithmum maritimum L., Inula crithmoides L., Mesembryanthemum crystallinum L., Mesembryanthemum nodiflorum L., Salicornia ramosissima J. Woods, and Sarcocornia fruticosa (Mill.) A. J. Scott.). Among these species, results showed that S. fruticosa had a higher content in protein (4.44 g/100 g FW), ash (5.70 g/100 g FW), salt (2.80 g/100 g FW), chloride (4.84 g/100 g FW), minerals (Na, K, Fe, Mg, Mn, Zn, Cu), total phenolics (0.33 mg GAE/g FW), and antioxidant activity (8.17 µmol TEAC/g FW). Regarding the phenolic classes, S. fruticosa and M. nodiflorum were predominant in the flavonoids, while M. crystallinum, C. maritimum, and S. ramosissima were in the phenolic acids. Moreover, S. fruticosa, S. ramosissima, M. nodiflorum, M. crystallinum, and I. crithmoides showed ACE-inhibitory activity, an important target control for hypertension. Concerning the volatile profile, C. maritimum, I. crithmoides, and D. crassifolium were abundant in terpenes and esters, while M. nodiflorum, S. fruticosa, and M. crystallinum were richer in alcohols and aldehydes, and S. ramosissima was richer in aldehydes. Considering the environmental and sustainable roles of cultivated halophytes using a SCS, these results indicate that these species could be considered an alternative to conventional table salt, due to their added nutritional and phytochemical composition, with potential contribution for the antioxidant and anti-hypertensive effects.

Genome-Wide Analysis of MYB Transcription Factors in the Wheat Genome and Their Roles in Salt Stress Response

Large and rapidly increasing areas of salt-affected soils are posing major challenges for the agricultural sector. Most fields used for the important food crop Triticum aestivum (wheat) are expected to be salt-affected within 50 years. To counter the associated problems, it is essential to understand the molecular mechanisms involved in salt stress responses and tolerance, thereby enabling their exploitation in the development of salt-tolerant varieties. The myeloblastosis (MYB) family of transcription factors are key regulators of responses to both biotic and abiotic stress, including salt stress. Thus, we used the Chinese spring wheat genome assembled by the International Wheat Genome Sequencing Consortium to identify putative MYB proteins (719 in total). Protein families (PFAM) analysis of the MYB sequences identified 28 combinations of 16 domains in the encoded proteins. The most common consisted of MYB_DNA-binding and MYB-DNA-bind_6 domains, and five highly conserved tryptophans were located in the aligned MYB protein sequence. Interestingly, we found and characterized a novel 5R-MYB group in the wheat genome. In silico studies showed that MYB transcription factors MYB3, MYB4, MYB13 and MYB59 are involved in salt stress responses. qPCR analysis confirmed upregulation of the expression of all these MYBs in both roots and shoots of the wheat variety BARI Gom-25 (except MYB4, which was downregulated in roots) under salt stress. Moreover, we identified nine target genes involved in salt stress that are regulated by the four MYB proteins, most of which have cellular locations and are involved in catalytic and binding activities associated with various cellular and metabolic processes.

Halophytes as new model plant species for salt tolerance strategies

Soil salinity is becoming a growing issue nowadays, severely affecting the world's most productive agricultural landscapes. With intersecting and competitive challenges of shrinking agricultural lands and increasing demand for food, there is an emerging need to build resilience for adaptation to anticipated climate change and land degradation. This necessitates the deep decoding of a gene pool of crop plant wild relatives which can be accomplished through salt-tolerant species, such as halophytes, in order to reveal the underlying regulatory mechanisms. Halophytes are generally defined as plants able to survive and complete their life cycle in highly saline environments of at least 200-500 mM of salt solution. The primary criterion for identifying salt-tolerant grasses (STGs) includes the presence of salt glands on the leaf surface and the Na⁺ exclusion mechanism since the interaction and replacement of Na⁺ and K⁺ greatly determines the survivability of STGs in saline environments. During the last decades or so, various salt-tolerant grasses/halophytes have been explored for the mining of salt-tolerant genes and testing their efficacy to improve the limit of salt tolerance in crop plants. Still, the utility of halophytes is limited due to the non-availability of any model halophytic plant system as well as the lack of complete genomic information. To date, although Arabidopsis (Arabidopsis thaliana) and salt cress (Thellungiella halophila) are being used as model plants in most salt tolerance studies, these plants are short-lived and can tolerate salinity for a shorter duration only. Thus, identifying the unique genes for salt tolerance pathways in halophytes and their introgression in a related cereal genome for better tolerance to salinity is the need of the hour. Modern technologies including RNA sequencing and genome-wide mapping along with advanced bioinformatics programs have advanced the decoding of the whole genetic information of plants and the development of probable algorithms to correlate stress tolerance limit and yield potential. Hence, this article has been compiled to explore the naturally occurring halophytes as potential model plant species for abiotic stress tolerance and to further breed crop plants to enhance salt tolerance through genomic and molecular tools.

Characteristics and acidic soil amelioration effects of biochar derived from a typical halophyte Salicornia europaea L. (common glasswort)

Glycophyte biomass - derived biochars have proven to be effective in the amelioration of acidic soil. However, there is scarce information on the characteristics and soil amelioration effects of halophyte-derived biochars. In this study, a typical halophyte Salicornia europaea, which is mainly distributed in the saline soils and salt-lake shores of China, and a glycophyte Zea mays, which is widely planted in the north of China, were selected to produce biochars with a pyrolysis process at 500 °C for 2 h. S. europaea-derived and Z. mays-derived biochars were characterized in elemental content, pores, surface area, and surface functional groups, and then by using a pot experiment their potential utilizable value as acidic soil conditioner was evaluated. The results showed that compared with Z. mays-derived biochar, S. europaea-derived biochar displayed higher pH, ash contents, base cations (K⁺, Ca²⁺, Na⁺, and Mg²⁺) contents and exhibited more larger surface area and pore volume than Z. mays-derived biochar. Both biochars had abundant oxygen-containing functional groups. Upon treating the acidic soil, the pH of acidic soil was increased by 0.98, 2.76, and 3.36 units after the addition of 1%, 2%, and 4% S. europaea-derived biochar, while it was increased only by 0.10, 0.22, and 0.56 units at 1%, 2%, and 4% Z. mays-derived biochar. High alkalinity in S. europaea-derived biochar was the main reason for the increase of pH value and base cations in acidic soil. Thus, application of halophyte biochar such as S. europaea-derived biochar is an alternative method for the amelioration of acidic soils.

Stimulation of PGP Bacteria on the Development of Seeds, Plants and Cuttings of the Obligate Halophyte Arthrocaulon (Arthrocnemum) macrostachyum (Moric.) Piirainen & G. Kadereit

The Earth is undergoing alterations at a high speed, which causes problems such as environmental pollution and difficulty in food production. This is where halophytes are interesting, due to their high potential in different fields, such as remediation of the environment and agriculture. For this reason, it is necessary to deepen the knowledge of the development of halophytes and how plant growth-promoting bacteria (PGP) can play a fundamental role in this process. Therefore, in this work were tested the effects of five PGP bacteria on its rhizosphere and other endophytic bacteria at different concentrations of NaCl on seed germination, plant growth (0 and 171 mM) and cutting growth (0 mM) of Arthrocaulon macrostachyum. The growth promotion in this strict halophyte is highlighted due to the presence of PGP bacteria and the fact that no salt is needed. Thus, without salt, the bacterial strains Kocuria polaris Hv16, Pseudarthrobacter psychrotolerans C58, and Rahnella aceris RTE9 enhanced the biomass production by more than 60% in both stems and roots. Furthermore, germination was encouraged by more than 30% in the presence of both R. aceris RTE9 and K. polaris Hv16 at 171 mM NaCl; the latter also had a biocontrol effect on the fungi that grew on the seeds. Additionally, for the first time in cuttings of this perennial species, the root biomass was improved thanks to the consortium of K. polaris Hv16 and P. psychrotolerans C58. Finally, this study demonstrates the potential of PGPs for optimising the development of halophytes, either for environmental or agronomic purposes.

Interactive Temperature and CO2 Rise, Salinity, Drought, and Bacterial Inoculation Alter the Content of Fatty Acids, Total Phenols, and Oxalates in the Edible Halophyte Salicornia ramosissima

In this work, we studied the combined effect of increased temperature and atmospheric CO₂, salt and drought stress, and inoculation with plant-growth-promoting rhizobacteria (PGPR) on the growth and some nutritional parameters of the edible halophyte Salicornia ramosissima. We found that the increase in temperature and atmospheric CO₂, combined with salt and drought stresses, led to important changes in S. ramosissima fatty acids (FA), phenols, and oxalate contents, which are compounds of great importance for human health. Our results suggest that the S. ramosissima lipid profile will change in a future climate change scenario, and that levels of oxalate and phenolic compounds may change in response to salt and drought stress. The effect of inoculation with PGPR depended on the strains used. Some strains induced the accumulation of phenols in S. ramosissima leaves at higher temperature and CO₂ while not altering FA profile but also led to an accumulation of oxalate under salt stress. In a climate change scenario, a combination of stressors (temperature, salinity, drought) and environmental conditions (atmospheric CO_2, PGPR) will lead to important changes in the nutritional profiles of edible plants. These results may open new perspectives for the nutritional and economical valorization of S. ramosissima.

Towards the Sustainable Exploitation of Salt-Tolerant Plants: Nutritional Characterisation, Phenolics Composition, and Potential Contaminants Analysis of Salicornia ramosissima and Sarcocornia perennis alpini

Increasing soil salinisation represents a serious threat to food security, and therefore the exploitation of high-yielding halophytes, such as Salicornia and Sarcocornia, needs to be considered not merely in arid regions but worldwide. In this study, Salicornia ramosissima and Sarcocornia perennis alpini were evaluated for nutrients, bioactive compounds, antioxidant capacity, and contaminants. Both were shown to be nutritionally relevant, exhibiting notable levels of crude fibre and ash, i.e., 11.26-15.34 and 39.46-40.41% dry weight (dw), respectively, and the major minerals were Na, K, and Mg. Total phenolics thereof were 67.05 and 38.20 mg of gallic acid equivalents/g extract dw, respectively, mainly p-coumaric acid and quercetin. Both species displayed antioxidant capacity, but S. ramossima was prominent in both the DPPH and ß-carotene bleaching assays. Aflatoxin B1 was detected in S. ramosissima, at 5.21 µg/Kg dw, which may pose a health threat. The Cd and Pb levels in both were low, but the 0.01 mg/Kg Hg in S. perennis alpini met the maximum legal limit established for marine species including algae. Both species exhibit high potential for use in the agro-food, cosmetics, and pharmaceutical sectors, but specific regulations and careful cultivation strategies need to be implemented, in order to minimise contamination risks by mycotoxins and heavy metals.

Deciphering salt tolerance in tetraploid honeysuckle (Lonicera japonica Thunb.) from ion homeostasis, water balance and antioxidant defense

Polyploid plants are usually salt tolerant, but the underlying mechanisms remain fragmental. This study aimed to dissect salt resistance of tetraploid honeysuckle (Lonicera japonica Thunb.) from ion balance, osmotic adjustment and antioxidant defense by contrasting with its autodiploid through pot experiments. Less salt-induced reduction in leaf and root biomass confirmed higher tolerance in tetraploid honeysuckle, and moreover, its greater stability of photosynthetic apparatus was verified by mild influence on delayed chlorophyll fluorescence transients. Compared with the diploid, greater root Na⁺ exclusion helped alleviate salt-induced decrease in leaf K⁺/Na⁺ for maintaining ion balance in tetraploid honeysuckle, and relied on Na⁺/H⁺ antiporter activity, because their difference of root Na⁺ exclusion disappeared after applying a specific inhibitor of Na⁺/H⁺ antiporter. Lower reduction in leaf relative water content suggested higher tolerance to osmotic pressure in tetraploid honeysuckle under salt stress, which hardly resulted from osmotic adjustment given the similar decrease extent of leaf osmotic potential with that in the diploid. In contrast to significant elevated leaf lipid peroxidation and superoxide dismutase and ascorbate peroxidase activities in the diploid, no obvious changes in them suggested that tetraploid honeysuckle never suffered salt-induced oxidative stress. According to more accumulated leaf chlorogenic acid and phenolics and greater elevated leaf phenylalanine ammonia-lyase activity and transcription, leaf phenolic synthesis was enhanced greater in tetraploid honeysuckle upon salt stress, which might serve to prevent oxidative threat by consuming reducing power. In conclusion, polyploidy enhanced salt tolerance in honeysuckle by maintaining ion homeostasis and water balance and preventing oxidative stress.

Edible Halophytes and Halo-Tolerant Species in Apulia Region (Southeastern Italy): Biogeography, Traditional Food Use and Potential Sustainable Crops

The Mediterranean basin is rich in wild edible species which have been used for food and medicinal purposes by humans throughout the centuries. Many of these species can be found near coastal areas and usually grow under saline conditions, while others can adapt in various harsh conditions including high salinity. Many of these species have a long history of gathering from the wild as a source of food. The aim of this contribution is an overview on the most important halophyte species (Salicornia sp. pl., Arthrocaulon macrostachyum (Moric.) Piirainen & G. Kadereit, Soda inermis Fourr., Cakile maritima Scop., Crithmum maritimum L., Reichardia picroides (L.) Roth., Silene vulgaris (Moench) Garcke subsp. tenoreana (Colla) Soldano & F. Conti, Allium commutatum Guss., Beta vulgaris L. subsp. maritima (L.) Arcang., Capparis spinosa L.) that traditionally have been gathered by rural communities in southern Italy, with special interest on their ecology and distribution, traditional uses, medicinal properties, marketing and early attempts of cultivation. It is worth noting that these species have an attractive new cash crop for marsh marginal lands.

Salt-Tolerant Plants as Sources of Antiparasitic Agents for Human Use: A Comprehensive Review

Parasitic diseases, especially those caused by protozoans and helminths, such as malaria, trypanosomiasis, leishmaniasis, Chagas disease, schistosomiasis, onchocerciasis, and lymphatic filariasis, are the cause of millions of morbidities and deaths every year, mainly in tropical regions. Nature has always provided valuable antiparasitic agents, and efforts targeting the identification of antiparasitic drugs from plants have mainly focused on glycophytes. However, salt-tolerant plants (halophytes) have lately attracted the interest of the scientific community due to their medicinal assets, which include antiparasitic properties. This review paper gathers the most relevant information on antiparasitic properties of halophyte plants, targeting human uses. It includes an introduction section containing a summary of some of the most pertinent characteristics of halophytes, followed by information regarding the ethnomedicinal uses of several species towards human parasitic diseases. Then, information is provided related to the antiprotozoal and anthelmintic properties of halophytes, determined by in vitro and in vivo methods, and with the bioactive metabolites that may be related to such properties. Finally, a conclusion section is presented, addressing perspectives for the sustainable exploitation of selected species.

The interactions of Cr (VI) concentrations and amendments (biochar and manure) on growth and metal accumulation of two species of Salicornia in contaminated soil

Heavy metals are among the most dangerous contaminants in the environment. Organic components and plant species that can accumulate and stabilize heavy metals in their organs are a good option for soil remediation of these elements. Therefore, this study aimed to investigate the effects of manure and biochar on the accumulation of heavy metals by Salicornia species. Salicornia persica Akhani and Salicornia perspolitana Akhani were cultivated outdoor in experimental pots. The effects of experimental treatments, including Cr (VI) concentrations, manure, and biochar on the two studied species, were investigated. The results indicated a significant effect (p < 0.05) of biochar on the accumulation of heavy metals by two species, S. persica and S. perspolitana, so that Cr concentrations in the roots and shoots were 258 and 5.41 mg/kg, respectively. In addition, Cr accumulations under manure treatments in the roots and shoots were 334.34 and 9.79 mg/kg, respectively. The content of photosynthetic pigments in both S. persica and S. perspolitana species under biochar treatment was higher than in control and manure treatments. In general, one can conclude that the accumulation of Cr in S. perspolitana was higher than in S. persica. Applying biochar and manure amendments could stabilize Cr in soil and reduce Cr accumulation in both S. persica and S. perspolitana species.

Application of In Vitro Plant Tissue Culture Techniques to Halophyte Species: A Review

Halophytes are plants able to thrive in environments characterized by severe abiotic conditions, including high salinity and high light intensity, drought/flooding, and temperature fluctuations. Several species have ethnomedicinal uses, and some are currently explored as sources of food and cosmetic ingredients. Halophytes are considered important alternative cash crops to be used in sustainable saline production systems, due to their ability to grow in saline conditions where conventional glycophyte crops cannot, such as salt-affected soils and saline irrigation water. In vitro plant tissue culture (PTC) techniques have greatly contributed to industry and agriculture in the last century by exploiting the economic potential of several commercial crop plants. The application of PTC to selected halophyte species can thus contribute for developing innovative production systems and obtaining halophyte-based bioactive products. This work aimed to put together and review for the first time the most relevant information on the application of PTC to halophytes. Several protocols were established for the micropropagation of different species. Various explant types have been used as starting materials (e.g., basal shoots and nodes, cotyledons, epicotyls, inflorescence, internodal segments, leaves, roots, rhizomes, stems, shoot tips, or zygotic embryos), involving different micropropagation techniques (e.g., node culture, direct or indirect shoot neoformation, caulogenesis, somatic embryogenesis, rooting, acclimatization, germplasm conservation and cryopreservation, and callogenesis and cell suspension cultures). In vitro systems were also used to study physiological, biochemical, and molecular processes in halophytes, such as functional and salt-tolerance studies. Thus, the application of PTC to halophytes may be used to improve their controlled multiplication and the selection of desired traits for the in vitro production of plants enriched in nutritional and functional components, as well as for the study of their resistance to salt stress.

Effects of Vertically Heterogeneous Soil Salinity on Genetic Polymorphism and Productivity of the Widespread Halophyte Bassia prostrata

Salinity is one of the environmental factors that affects both productivity and genetic diversity in plant species. Within the soil profile, salinity is a dynamic indicator and significantly changes with depth. The present study examined the effects of the vertical heterogeneity of soil salinity chemistry on the plant height, fresh and dry biomass accumulation, water content, level of genetic polymorphism, and observed and expected heterozygosity in seven populations of halophyte Bassia prostrata in natural habitats. Soil salinity ranged from slight (Ssalts = 0.11-0.25%) to extreme (Ssalts = 1.35-2.57%). The main contributors to salinity were Na+, Ca2+, and Mg2+. Multivariate analysis revealed that biomass accumulation is positively affected by moderate/high salinity in 20-60 cm soil layers, which may be associated with the salt required for the optimal growth of the halophyte B. prostrata. The formation of seed genetic diversity is negatively affected by slight/moderate salinity in the 0-40 cm layers. An increase in divalent ion content can reduce genetic diversity and increase the local adaptation of B. prostrata to magnesium-calcium sulfate salinity. The effect of the in-depth distribution of soil salinity on productivity and genetic diversity may be related to seasonal variables during biomass accumulation (summer) and seed formation (autumn).

Transcriptome-wide identification of NAC (no apical meristem/Arabidopsis transcription activation factor/cup-shaped cotyledon) transcription factors potentially involved in salt stress response in garlic

Soil salinity has been an increasing problem worldwide endangering crop production and human food security. It is an ideal strategy to excavate stress resistant genes and develop salt tolerant crops. NAC (no apical meristem/Arabidopsis transcription activation factor/cup-shaped cotyledon) transcription factors have been demonstrated to be involved in salt stress response. However, relevant studies have not been observed in garlic, an important vegetable consumed in the world. In this study, a total of 46 AsNAC genes encoding NAC proteins were identified in garlic plant by transcriptome data. Phylogenetic analysis showed that the examined AsNAC proteins were clustered into 14 subgroups. Motif discovery revealed that the conserved domain region was mainly composed of five conserved subdomains. Most of the genes selected could be induced by salt stress in different tissues, indicating a potential role in salt stress response. Further studies may focus on the molecular mechanisms of the AsNAC genes in salt stress response. The results of the current work provided valuable resources for researchers aimed at developing salt tolerant crops.

Composite materials for innovative urban farming of alternative food sources (macroalgae and crickets)

Facing an inexorable growth of the human population along with substantial environmental changes, the assurance of food security is a major challenge of the present century. To ensure responsible food consumption and production (SDG 12), new approaches in the food system are required. Thus, environmentally controlled, sustainable production of alternative food sources are of key interest for both urban agriculture and food research. To face the current challenge of integrating food production systems within existing structures, multidisciplinary discourses are required. Here, we bring together novel technologies and indoor farming techniques with the aim of supporting the development of sustainable food production systems. For this purpose, we investigated the feasibility of 10 composite materials for their innovative use as structural support in macroalgal cultivation (settlement substrates) and cricket rearing (housing). Considering material resistance, rigidity, and direct material-organism interactions, the bio-based composite polylactic acid (PLA) was identified as a suitable material for joint farming. For macroalgae cultivation, PLA sustained the corrosive cultivation conditions and provided a suitable substrate without affecting the macroalgal physiology or nutritional composition (carotenoids and chlorophylls). For cricket rearing, PLA provided a suitable and recyclable shelter, which was quickly accepted by the animals without any observed harm. In contrast, other common composite components like phenolic resin or aramid were found to be unsuitable due to being harmful for the cultivated organisms or instable toward the applied sterilization procedure. This multidisciplinary study not only provides profound insights in the developing field of urban indoor food production from a new perspective, but also bridges material science and farming approaches to develop new sustainable and resilient food production systems.

An α/β hydrolase family member negatively regulates salt tolerance but promotes flowering through three distinct functions in rice

Ongoing soil salinization drastically threatens crop growth, development, and yield worldwide. It is therefore crucial that we improve salt tolerance in rice by exploiting natural genetic variation. However, many salt-responsive genes confer undesirable phenotypes and therefore cannot be effectively applied to practical agricultural production. In this study, we identified a quantitative trait locus for salt tolerance from the African rice species Oryza glaberrima and named it as Salt Tolerance and Heading Date 1 (STH1). We found that STH1 regulates fatty acid metabolic homeostasis, probably by catalyzing the hydrolytic degradation of fatty acids, which contributes to salt tolerance. Meanwhile, we demonstrated that STH1 forms a protein complex with D3 and a vital regulatory factor in salt tolerance, OsHAL3, to regulate the protein abundance of OsHAL3 via the 26S proteasome pathway. Furthermore, we revealed that STH1 also serves as a co-activator with the floral integrator gene Heading date 1 to balance the expression of the florigen gene Heading date 3a under different circumstances, thus coordinating the regulation of salt tolerance and heading date. Notably, the allele of STH1 associated with enhanced salt tolerance and high yield is found in some African rice accessions but barely in Asian cultivars. Introgression of the STH1^HP46 allele from African rice into modern rice cultivars is a desirable approach for boosting grain yield under salt stress. Collectively, our discoveries not only provide conceptual advances on the mechanisms of salt tolerance and synergetic regulation between salt tolerance and flowering time but also offer potential strategies to overcome the challenges resulted from increasingly serious soil salinization that many crops are facing.

Cultivation and characterisation of Salicornia europaea, Tripolium pannonicum and Crithmum maritimum biomass for green biorefinery applications

Salt-tolerant halophytes have shown potential for biorefinery and agricultural use in salt-affected soils, increasing the value of marginal lands. They could provide a bio-based source for compounds obtained from the petrochemical industry or an alternative for biomass currently imported overseas. Salicornia europaea, Tripolium pannonicum and Crithmum maritimum were cultivated in hydroponic systems under various salinity conditions, harvested green but not food-grade, and fractionated to green juice and fibre residue. Obtained fractions were characterised for contents of carbohydrates, Klason lignin, crude protein, organic acids, lipids, and minerals to evaluate the biomass' suitability for biorefinery. Significant differences were observed in the biomass yield and the composition of the biomass fractions from different cultivation salinities. High concentrations of crude protein were found. Thus, these species could have the potential for green protein production. Fractions rich in carbohydrates could be used for lignocellulose processing and processes utilising micro-organisms.

Salicornia bigelovii, S. brachiata and S. herbacea: Their Nutritional Characteristics and an Evaluation of Their Potential as Salt Substitutes

Excessive sodium (salt) intake in our diet is a main contributor to hypertension and a major risk factor for cardiovascular illnesses. As a result, research has made great efforts to develop salt alternatives, and Salicornia spp. offers a very high potential in the food industry for its promising functional characteristics. This review focuses on the nutritional profile, health effects and commercial potential of three specific species of the Salicornia genus: S. bigelovii, S. brachiata and S. herbacea. It also addresses the methods that are used to produce them as salt substitutes. Owing to the antinutritional and anti-inflammatory effects of its bioactive compounds, Salicornia spp. can serve as an organic biological preservative in foods with better consumer appeal when compared with chemical preservatives that are common in the food industry. Overall, the commercial use of these underutilized species will help to improve food security.

Sensory Evaluation of Common Ice Plant (Mesembryanthemum crystallinum L.) in Response to Sodium Chloride Concentration in Hydroponic Nutrient Solution

Common ice plant (Mesembryanthemum crystallinum L.) is a novel edible plant with a succulent and savory flavor. The plants display prominent epidermal bladder cells (EBCs) on the surface of the leaves that store water and sodium chloride (NaCl). The plants have high nutritional value and are adapted to saline soils. Previous research has determined the impact of NaCl on the growth and mineral content of ice plant, but as NaCl has an impact on a food's sensory properties, an interesting question is whether saline growth media can affect the plant's taste and texture, and if this alters consumers' sensory response to ice plant. The objective of this study was to evaluate the sensory aspects of ice plant, as well as consumer liking in response to increasing NaCl concentration in hydroponic nutrient solution. Four-week-old seedlings of ice plant were transplanted into deep water culture (DWC) hydroponic systems and treated with five NaCl concentrations (0 M [control], 0.05 M, 0.10 M, 0.20 M, and 0.40 M NaCl). Eight-week-old plants (after four weeks of NaCl treatment) were harvested, and the middle leaves of each plant were sampled for consumer testing. A total of 115 participants evaluated various flavor, texture, and appearance aspects of ice plant and provided their liking ratings. The consumers were able to discriminate differences in salt intensity from the plants based on NaCl treatment in the hydroponic nutrient solution. Low NaCl concentrations (0.05-0.10 M) did not have obvious adverse effect on consumer liking, which aligns with the result of previous research that 0.05-0.10 M NaCl could largely stimulate the growth of ice plant. NaCl concentrations higher than 0.20 M are not recommended from both a production and consumer perspective. With increased NaCl level in plant samples, the consumers detected more saltiness, sourness, and fishiness, less green flavor, and similar levels of bitterness and sweetness. NaCl treatment had no effects on leaf appearance and texture, and the consumers' overall liking was mainly determined by flavor. Overall, ice plant presents some unique attributes (salty and juicy) compared to other edible salad greens; however, consumer awareness of ice plant is very low, and purchase intent is relatively low as well. Consumers picture ice plant being used mainly in salads and in restaurants.

Enhancing quinoa growth under severe saline-alkali stress by phosphate solubilizing microorganism Penicillium funicuiosum P1

Promoting the growth of plants and improving plant stress-resistance by plant growth-promoting microorganism increasingly become a hotpot. While, most researchers focus on their supply role of nutrition or plant hormone. In this study, a novel mechanism that phosphate solubilizing microorganisms promoted plant growth under saline-alkali stress through secretion of organic acids, was proposed. The effects of desulfurization gypsum, humic acid, organic fertilizer and phosphate-solubilizing microorganism Penicillium funicuiosum P1 (KX400570) on the growth of quinoa (Chenopodium quinoa cv. Longli 1), showed that the survival rate, stem length and dry weight of quinoa treated with P1 were 2.5, 1.5, 1 and 1.5 times higher than those of sterile water (CK) under severe saline-alkali stress. The growth-promoting effect of P1 on quinoa was much better than that of other treatment groups. In addition, P1 promoted the growth of quinoa because the organic acids (malic acid, citric acid, succinic acid, etc.) from P1 stimulated the antioxidant system and promote the photosynthesis of quinoa, further promote quinoa growth.

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.

The Lack of Alternative Oxidase 1a Restricts in vivo Respiratory Activity and Stress-Related Metabolism for Leaf Osmoprotection and Redox Balancing Under Sudden Acute Water and Salt Stress in Arabidopsis thaliana

In plants salt and water stress result in an induction of respiration and accumulation of stress-related metabolites (SRMs) with osmoregulation and osmoprotection functions that benefit photosynthesis. The synthesis of SRMs may depend on an active respiratory metabolism, which can be restricted under stress by the inhibition of the cytochrome oxidase pathway (COP), thus causing an increase in the reduction level of the ubiquinone pool. However, the activity of the alternative oxidase pathway (AOP) is thought to prevent this from occurring while at the same time, dissipates excess of reducing power from the chloroplast and thereby improves photosynthetic performance. The present research is based on the hypothesis that the accumulation of SRMs under osmotic stress will be affected by changes in folial AOP activity. To test this, the oxygen isotope-fractionation technique was used to study the in vivo respiratory activities of COP and AOP in leaves of wild-type Arabidopsis thaliana plants and of aox1a mutants under sudden acute stress conditions induced by mannitol and salt treatments. Levels of leaf primary metabolites and transcripts of respiratory-related proteins were also determined in parallel to photosynthetic analyses. The lack of in vivo AOP response in the aox1a mutants coincided with a lower leaf relative water content and a decreased accumulation of crucial osmoregulators. Additionally, levels of oxidative stress-related metabolites and transcripts encoding alternative respiratory components were increased. Coordinated changes in metabolite levels, respiratory activities and photosynthetic performance highlight the contribution of the AOP in providing flexibility to carbon metabolism for the accumulation of SRMs.

Recent Trends in Microbial Approaches for Soil Desalination

Soil salinization has become a major problem for agriculture worldwide, especially because this phenomenon is continuously expanding in different regions of the world. Salinity is a complex mechanism, and in the soil ecosystem, it affects both microorganisms and plants, some of which have developed efficient strategies to alleviate salt stress conditions. Currently, various methods can be used to reduce the negative effects of this problem. However, the use of biological methods, such as plant-growth-promoting bacteria (PGPB), phytoremediation, and amendment, seems to be very advantageous and promising as a remedy for sustainable and ecological agriculture. Other approaches aim to combine different techniques, as well as the utilization of genetic engineering methods. These techniques alone or combined can effectively contribute to the development of sustainable and eco-friendly agriculture.

Halophytes.tn: an innovative database for Tunisian halophyte plant identification, distribution and characterization

Halophytes.tn (http://halophytes.rnrt.tn/) is a web-based database of Tunisian halophyte species. Halophytes are salt-tolerant plants able to grow above 85 mM of salt, even up to 2 M as for Tecticornia spp. Tunisia, a North African country located on the Mediterranean border, covering ∼165 000 km², harbors several types of saline habitats and biotopes where halophytes preferably vegetate. With ∼6000 worldwide and over 420 Tunisian species, halophytes represent a huge potential in several fields, including desalination, phytoremediation, agrofarming, medicinal use, industrial applications, pharmacology and even nanotechnology. We describe the practical and technical steps followed and bioinformatics tools used to conceive and design the first Tunisian halophytes database, enabling species identification and characterization. As a first version, information about botany, morphology, ecophysiology and biochemistry were provided for the identified species with their sites of growing in Tunisia, first step of biodiversity conservation, management and valorization. The database will be regularly maintained, updated and enriched to achieve the goal of whole Tunisian halophyte species and fit the needs of scientists and all category of users.Database URL: http://halophytes.rnrt.tn/

Impact of Nanomaterials on the Regulation of Gene Expression and Metabolomics of Plants under Salt Stress

Plant salinity resistance results from a combination of responses at the physiological, molecular, cellular, and metabolic levels. This article focuses on plant stress tolerance mechanisms for controlling ion homeostasis, stress signaling, hormone metabolism, anti-oxidative enzymes, and osmotic balance after nanoparticle applications. Nanoparticles are used as an emerging tool to stimulate specific biochemical reactions related to plant ecophysiological output because of their small size, increased surface area and absorption rate, efficient catalysis of reactions, and adequate reactive sites. Regulated ecophysiological control in saline environments could play a crucial role in plant growth promotion and survival of plants under suboptimal conditions. Plant biologists are seeking to develop a broad profile of genes and proteins that contribute to plant salt resistance. These plant metabolic profiles can be developed due to advancements in genomic, proteomic, metabolomic, and transcriptomic techniques. In order to quantify plant stress responses, transmembrane ion transport, sensors and receptors in signaling transduction, and metabolites involved in the energy supply require thorough study. In addition, more research is needed on the plant salinity stress response based on molecular interactions in response to nanoparticle treatment. The application of nanoparticles as an aspect of genetic engineering for the generation of salt-tolerant plants is a promising area of research. This review article addresses the use of nanoparticles in plant breeding and genetic engineering techniques to develop salt-tolerant crops.

Integration of metabolomics and transcriptomics data to further characterize Gliricidia sepium (Jacq.) Kunth under high salinity stress

Soil salinity is one abiotic stress that threatens agriculture in more than 100 countries. Gliricidia [Gliricidia sepium (Jacq.) Kunth] is a multipurpose tree known for its ability to adapt to a wide range of soils; however, its tolerance limits and responses to salt stress are not yet well understood. In this study, after characterizing the morphophysiological responses of young gliricidia plants to salinity stress, leaf metabolic and transcription profiles were generated and submitted to single and integrated analyses. RNA from leaf samples were subjected to RNA sequencing using an Illumina HiSeq platform and the paired-end strategy. Polar and lipidic fractions from leaf samples were extracted and analyzed on an ultra-high-performance liquid chromatography (UHPLC) coupled with electrospray ionization quadrupole time-of-flight high-resolution mass spectrometry (MS) system. Acquired data were analyzed using the OmicsBox, XCMS Online, MetaboAnalyst, and Omics Fusion platforms. The substrate salinization protocol used allowed the identification of two distinct responses to salt stress: tolerance and adaptation. Single analysis on transcriptome and metabolome data sets led to a group of 5,672 transcripts and 107 metabolites differentially expressed in gliricidia leaves under salt stress. The phenylpropanoid biosynthesis was the most affected pathway, with 15 metabolites and three genes differentially expressed. Results showed that the differentially expressed metabolites and genes from this pathway affect mainly short-term salt stress (STS). The single analysis of the transcriptome identified 12 genes coding for proteins that might play a role in gliricidia response at both STS and long-term salt stress (LTS). Further studies are needed to reveal the mechanisms behind the adaptation response.

Biological and Agronomic Traits of the Main Halophytes Widespread in the Mediterranean Region as Potential New Vegetable Crops

Salinity is one of the oldest and most serious environmental problems in the world. The increasingly widespread salinization of soils and water resources represents a growing threat to agriculture around the world. A strategy to cope with this problem is to cultivate salt-tolerant crops and, therefore, it is necessary to identify plant species that are naturally adapted to high-salinity conditions. In this review, we focus our attention on some plant species that can be considered among the most representative halophytes of the Mediterranean region; they can be potential resources, such as new or relatively new vegetable crops, to produce raw or minimally processed (or ready-to-eat) products, considering their nutritional properties and nutraceuticals. The main biological and agronomic characteristics of these species and the potential health risks due to mycotoxigenic fungi have been analyzed and summarized in a dedicated section. The objective of this review is to illustrate the main biological and agronomical characteristics of the most common halophytic species in the Mediterranean area, which could expand the range of leafy vegetables on the market.

Physiological Responses to Drought, Salinity, and Heat Stress in Plants: A Review

On the world stage, the increase in temperatures due to global warming is already a reality that has become one of the main challenges faced by the scientific community. Since agriculture is highly dependent on climatic conditions, it may suffer a great impact in the short term if no measures are taken to adapt and mitigate the agricultural system. Plant responses to abiotic stresses have been the subject of research by numerous groups worldwide. Initially, these studies were concentrated on model plants, and, later, they expanded their studies in several economically important crops such as rice, corn, soybeans, coffee, and others. However, agronomic evaluations for the launching of cultivars and the classical genetic improvement process focus, above all, on productivity, historically leaving factors such as tolerance to abiotic stresses in the background. Considering the importance of the impact that abiotic stresses can have on agriculture in the short term, new strategies are currently being sought and adopted in breeding programs to understand the physiological, biochemical, and molecular responses to environmental disturbances in plants of agronomic interest, thus ensuring the world food security. Moreover, integration of these approaches is bringing new insights on breeding. We will discuss how water deficit, high temperatures, and salinity exert effects on plants.

Rock Samphire, a Candidate Crop for Saline Agriculture: Cropping Practices, Chemical Composition and Health Effects

The recent market trends for functional healthy foods have rekindled the interest in wild edible species and created a market niche for high added value products. The current supply, mainly supported by plants collected from the wild, cannot meet increasing market needs; therefore, it is of major importance to establish cropping protocols and further valorize wild plants for culinary and industrial applications. Sea fennel is a wild edible halophyte that is an important ingredient in local cuisines and is also used in folk medicine for its beneficial health effects. Its valorization has not been commercially explored on a great scale and more efforts are needed to integrate the species in farming systems. The present review compiles the most recent reports regarding the farming practices that could allow for the establishment of cultivation protocols for farmers, while the main constraints that hinder the further exploitation of the species are also presented. Moreover, this review presents the most up-to-date information regarding the chemical composition (e.g., chemical composition of the aerial parts and volatile compounds in essential oils) and the health-related effects of various plant parts (e.g., antimicrobial, insecticidal and anticholinesterase activities) aiming to reveal possible alternative uses that will increase the added value of the species and will contribute to its commercial exploitation. Finally, the future remarks and the guidelines that have to be followed are also discussed.

Limoniastrum guyonianum behavior under seasonal conditions fluctuations of Sabkha Aïn Maïder (Tunisia)

In Sabkha biotope, several environmental factors (i.e., salinity, drought, temperature, etc.) especially during dry season affect halophytes developments. To cope with these harmful conditions, halophytes use multiple mechanisms of adaptations. In this study, we focused on the effect of environmental condition changes over a year in the Sabkha of Aïn Maïder (Medenine - Tunisia) on the physiological and biochemical behavior of Limoniastrum guyonianum using a modeling approach. Our study showed that the model depicted well (R² > 0.75) the monthly fluctuations of the studied parameters in this habitat. During the dry period (June to September), the salinity of the soil increased remarkably (high level of EC and Na⁺ content), resulting in high Na⁺ content in the aerial parts followed by a nutrient deficiency in K⁺, Ca²⁺, and Mg²⁺. As a result of this disruption, L. guyonianum decreased its water potential to more negative values to maintain osmotic potential using inorganic osmolytes (i.e., Na⁺) and organic osmolytes (i.e., sugars: sucrose, fructose, glucose, and xylitol, and organic acids: citric and malic acids). In addition, CO₂ assimilation rate, stomatal conductance, transpiration rate, and photosynthetic pigments decreased significantly with increasing salinity. The phenolic compounds contents and the antioxidant activity increased significantly in the dry period as a result of increased levels of H₂O₂ and lipid peroxidation. This increase was highly correlated with soil salinity and air temperature. The maintenance of tissue hydration (i.e., moderate decrease of relative water content), the accumulation of sugars and organic acids, the enhancement of phenolic compounds amounts, and the increase of antioxidant activity during the dry period suggest that L. guyonianum possesses an efficient tolerance mechanism that allows the plant to withstand the seasonal fluctuations of climatic conditions in its natural biotope.

De-novo Domestication for Improving Salt Tolerance in Crops

Global agriculture production is under serious threat from rapidly increasing population and adverse climate changes. Food security is currently a huge challenge to feed 10 billion people by 2050. Crop domestication through conventional approaches is not good enough to meet the food demands and unable to fast-track the crop yields. Also, intensive breeding and rigorous selection of superior traits causes genetic erosion and eliminates stress-responsive genes, which makes crops more prone to abiotic stresses. Salt stress is one of the most prevailing abiotic stresses that poses severe damages to crop yield around the globe. Recent innovations in state-of-the-art genomics and transcriptomics technologies have paved the way to develop salinity tolerant crops. De novo domestication is one of the promising strategies to produce superior new crop genotypes through exploiting the genetic diversity of crop wild relatives (CWRs). Next-generation sequencing (NGS) technologies open new avenues to identifying the unique salt-tolerant genes from the CWRs. It has also led to the assembly of highly annotated crop pan-genomes to snapshot the full landscape of genetic diversity and recapture the huge gene repertoire of a species. The identification of novel genes alongside the emergence of cutting-edge genome editing tools for targeted manipulation renders de novo domestication a way forward for developing salt-tolerance crops. However, some risk associated with gene-edited crops causes hurdles for its adoption worldwide. Halophytes-led breeding for salinity tolerance provides an alternative strategy to identify extremely salt tolerant varieties that can be used to develop new crops to mitigate salinity stress.

Nutritional and Functional Evaluation of Inula crithmoides and Mesembryanthemum nodiflorum Grown in Different Salinities for Human Consumption

The nutritional composition and productivity of halophytes is strongly related to the biotic/abiotic stress to which these extremophile salt tolerant plants are subjected during their cultivation cycle. In this study, two commercial halophyte species (Inula crithmoides and Mesembryanthemum nodiflorum) were cultivated at six levels of salinity using a soilless cultivation system. In this way, it was possible to understand the response mechanisms of these halophytes to salt stress. The relative productivity decreased from the salinities of 110 and 200 mmol L⁻¹ upwards for I. crithmoides and M. nodiflorum, respectively. Nonetheless, the nutritional profile for human consumption remained balanced. In general, I. crithmoides vitamin (B1 and B6) contents were significantly higher than those of M. nodiflorum. For both species, β-carotene and lutein were induced by salinity, possibly as a response to oxidative stress. Phenolic compounds were more abundant in plants cultivated at lower salinities, while the antioxidant activity increased as a response to salt stress. Sensory characteristics were evaluated by a panel of culinary chefs showing a preference for plants grown at the salt concentration of 350 mmol L⁻¹. In summary, salinity stress was effective in boosting important nutritional components in these species, and the soilless system promotes the sustainable and safe production of halophyte plants for human consumption.

Impacts of Reduced Nitrate Supply on Nitrogen Metabolism, Photosynthetic Light-Use Efficiency, and Nutritional Values of Edible Mesembryanthemum crystallinum

Mesembryanthemum crystallinum (common ice plant), as a nutritious ready-to-eat salad in Singapore, has become popular in recent years. However, basic data about the impacts of NO3 - supply on its NO3 - accumulation and nutritional quality are lacking. In this study, all plants were first grown indoor hydroponically in 10% artificial seawater (ASW) with modified full-strength Netherlands Standard Composition nutrient solution for 11 days, before transferring them to different reduced NO3 - solutions. All plants grew well and healthy after 7 days of treatment. However, plants grown with 3/4 N and 1/2 N were bigger with higher shoot and root fresh weight (FW), greater leaf number, and total leaf area (TLA) than those grown with full nitrogen (N), 1/4 N, and 0 N. Mesembryanthemum crystallinum grown with full N, 3/4 N, and 1/4 N had similar specific leaf area (SLA), while 0 N plants had significantly lower SLA. All plants had similar leaf succulence (LS). However, leaf water content (LWC) was lower, while leaf dry matter accumulation (LDMC) was higher in 0 N plants after 7 days of treatment. Compared with plants grown with full N, shoot NO3 - concentrations in 3/4 N, 1/2 N, and 1/4 N plants were constant or slightly increased during the treatments. For 0 N plants, shoot NO3 - concentration decreased significantly during the treatment compared with other plants. Shoot NO3 - accumulation was associated with nitrate reductase activity (NRA). For instance, after 7 days of treatment, shoot NO3 - concentration and NRA on a FW basis in 0 N plants were, respectively, 45 and 31% of full N plants. After transferring full N to 0 N for 7 days, all M. crystallinum had higher chlorophyll (Chl) content coupled with higher electron transport rate (ETR) and higher effective quantum yield of PSII, while full N plants had higher non-photochemical quenching (NPQ). The 0N plants had much higher concentrations of proline, total soluble sugar (TSS), and total ascorbic acid (ASC) than other plants. In conclusion, totally withdrawing NO3 - from the growth media prior to harvest could be one of the strategies to reduce shoot NO3 - concentration. Reduced NO3 - supply further enhanced nutritional values as concentrations of proline, TSS, and ASC were enhanced markedly in M. crystallinum plants after transferring them from full N to 0 N.

High Salinity Reduces Plant Growth and Photosynthetic Performance but Enhances Certain Nutritional Quality of C4 Halophyte Portulaca oleracea L. Grown Hydroponically Under LED Lighting

Portulaca oleracea L. (known as purslane) is one of the most nutritious leafy vegetables owing to its high content of antioxidants. In this study, all plants were grown indoors hydroponically with different NaCl salinities. Photosynthetic photo flux density (PPFD) at 200 μmol m^-2 s^-1 (12 h) was provided to all plants by LED with red:blue ratio of 2.2. Thirty days after transplanting, plants grown with100 mM NaCl had the highest productivity and the fastest leaf growth followed by those with 0, 200 and 300 mM NaCl. Grown with 300 mM NaCl, purslane had the lowest specific leaf area due to its highest leaf dry matter content and its lowest water content. All plants had similar values of leaf succulence except for those with 300 mM NaCl. Total chlorophyll and carotenoids contents were significantly higher in plants grown with 0 and 100 mM NaCl than with 200, and 300 mM NaCl. All plants had F_v/F_m ratios close to 0.8. However, electron transport rate and ΔF/F_m' were significantly higher in plants grown with 0 and 100 mM NaCl than with 200 and 300 mM NaCl. CAM-induced purslane with 300 mM NaCl had higher non-photochemical quenching. Maximum net photosynthetic O₂ evolution rate and Cyt b₆f concentration were significantly lower with 300 mM NaCl compared to all other plants while all plants had similar PS II concentration. Proline concentration increased with increasing salinities. All plants had similar levels of total soluble sugars. Plants grown with 0 and 100 mM NaCl had significantly higher concentrations of NO₃ ^-, total reduced nitrogen, total leaf soluble protein, Rubisco protein, total ascorbic acid, and total phenolic compounds than with 200 and 300 mM NaCl. The highest concentrations of K, Ca, and Mg were found in purslane grown under 0 mM NaCl. Statistically, no significant differences in Fe concentrations were observed among all plants. However, salinity seems to increase Fe concentration. In conclusion, it is feasible to grow purslane under 100 mM NaCl as it is the most optimal condition to achieve higher productivity and better quality. However, the production of antioxidants may depend on not only salinity but also other growth conditions.