Seed priming to optimize germination in Arthrocnemum Moq.

BACKGROUND: Seed germination and seedling growth constitute the first stage of a plant's life cycle for crop establishment. Arthrocnemum Moq. is a halophyte of the subfamily Salicornioideae (Amaranthaceae), which could be recognized in the foreseeable future as an emerging candidate in applied biosaline agricultural programs, mainly due to the large biomass it represents in coastal and inland saltmarshes, in addition to its interesting nutritional and pharmacological properties. However, to ensure their subsequent use as a crop, it is necessary to optimize their germination through appropriate seed priming treatments. The main goal of this work was to seek the optimization of Arthrocnemum germination process using different pretreatments: exposure to sodium chloride (100 to 1200 mM) in the dark and its subsequent transferred to distilled water separately and together with the combination of pH (5, 7, 9), salinity (0, 100, 200 mM NaCl), and iron conditions (0, 200, 400 µM FeSO4). The experiments were tested on six samples of two different species: A. meridionale (from Tunisia) and A. macrostachyum (from Spain). RESULTS: Salinity priming of seeds for 15 days in darkness improved germination percentages by almost 25% at 600 mM NaCl, in both Tunisian and Spanish species. However, keeping seeds at different salt concentrations for 30 days produced higher improvement percentages at lower concentrations in A. meridionale (100-200 mM NaCl), while in A. macrostachyum the highest improvement percentages were obtained at 600 mM NaCl (percentage improvement of 47%). When the dark time period is reduced to 5 days at higher salt concentrations, the greater germination percentages were reached in all the samples at the concentration of 800 mM NaCl, increasing the improvement of germination between 17 and 50%. Finally, the conditions of pH = 7, pretreatment in darkness at 800 mM NaCl and 400 µM or iron, turned out to be an effective medium for seed germination. CONCLUSIONS: Therefore, before using Arthrocnemum seeds in applied biotechnological programs, a seed priming treatment based on prior exposure to high salt concentrations (600-1000 mM NaCl) is recommended in order to maximize germination percentages.

Microbial diversity associated with the anaerobic sediments of a soda lake (Mono Lake, California, USA).

Soda lakes are inhabited by important haloalkaliphilic microbial communities that are well adapted to these extreme characteristics. The surface waters of the haloalkaline Mono Lake (California, USA) are alkaline but, in contrast to its bottom waters, do not present high salinity. We have studied the microbiota present in the shoreline sediments of Mono Lake using next-generation sequencing techniques. The statistical indexes showed that Bacteria had a higher richness, diversity, and evenness than Archaea. Seventeen phyla and 8 "candidate divisions" were identified among the Bacteria, with a predominance of the phyla Firmicutes, Proteobacteria, and Bacteroidetes. Among the Proteobacteria, there was a notable presence of Rhodoplanes and a high diversity of sulfate-reducing Deltaproteobacteria, in accordance with the high sulfate-reducing activity detected in soda lakes. Numerous families of bacterial fermenters were identified among the Firmicutes. The Bacteroides were represented by several environmental groups that have not yet been isolated. Since final organic matter in anaerobic environments with high sulfate contents is mineralized mainly by sulfate-reducing bacteria, very little methanogenic archaeal biodiversity was detected. Only 2 genera, Methanocalculus and Methanosarcina, were retrieved. The species similarities described indicate that a significant number of the operational taxonomic units identified may represent new species.

Arthrocnemum Moq.: Unlocking Opportunities for Biosaline Agriculture and Improved Human Nutrition.

(1) Background: This study provides novel insights into the elemental content and biomineralization processes of two halophytic species of the genus Arthrocnemum Moq. (A. macrostachyum and A. meridionale). (2) Methods: Elemental content was analyzed using ICP-MS, while biominerals were detected through electron microscopy (SEM and TEM) and X-ray diffraction. (3) Results: The elemental content showed significant concentrations of macronutrients (sodium, potassium, magnesium, and calcium) and micronutrients, especially iron. Iron was consistently found as ferritin in A. macrostachyum chloroplasts. Notably, A. macrostachyum populations from the Center of the Iberian Peninsula exhibited exceptionally high magnesium content, with values that exceeded 40,000 mg/kg d.w. Succulent stems showed elemental content consistent with the minerals identified through X-ray diffraction analysis (halite, sylvite, natroxalate, and glushinskite). Seed analysis revealed elevated levels of macro- and micronutrients and the absence of heavy metals. Additionally, the presence of reduced sodium chloride crystals in the seed edges suggested a mechanism to mitigate potential sodium toxicity. (4) Conclusions: These findings highlight the potential of Arthrocnemum species as emerging edible halophytes with nutritional properties, particularly in Western European Mediterranean territories and North Africa. They offer promising prospects for biosaline agriculture and biotechnology applications.

Valorization of Salicornia patula Duval-Jouve Young Shoots in Healthy and Sustainable Diets.

The revalorization of natural resources in food production is increasing, and the effect of climate change is negatively affecting the production of conventional crops. In recent years, edible halophytes have received more attention due to their ability to tolerate a wide range of salinities. Thus, the use of halophytes that require less water and are strongly adapted to high-salinity soil and coastal areas can provide sustainable agriculture in certain areas. In addition, there is growing interest in the study of the possibilities that these species offer as foods due to their excellent nutritional profile and antioxidant properties. For that reason, the exploitation of plants adapted to these areas is nowadays even more important than in the past to guarantee food security in arid or semiarid salinized territories. The available data about the nutrients and bioactive compounds composition of many non-cultivated edible vegetables traditionally used in the Mediterranean area, such as Salicornia edible young shoots, are still scarce. With the aim of improving the knowledge on their nutritional value, the present study provides new data about the content of some compounds with biological activity, such as fiber and organic acids, in eight samples of young shoots of S. patula Duval-Jouve gathered in great mainland and coastal salt marshes in Southwest and Central Spain. Results showed that this vegetable can be considered a healthy food and a very good source of dietary fiber (4.81-6.30 g/100 g fw total fiber). Its organic acid profile showed oxalic, malic, citric and succinic acids. Oxalic acid was the major one, with mean values of 0.151-1.691 g/100 g fw. From the results obtained in this study, S. patula shoots could be recommended as an alternative source of fiber for healthy and sustainable diets in the general adult population with no risk of renal disease.

On the elemental composition of the Mediterranean euhalophyte Salicornia patula Duval-Jouve (Chenopodiaceae) from saline habitats in Spain (Huelva, Toledo and Zamora).

A complete survey is presented on the inorganic composition of the euhalophyte annual succulent species Salicornia patula (Chenopodiaceae), including materials from the Iberian Peninsula, littoral-coastal Tinto River basin areas (SW Spain: Huelva province), and mainland territories (NW and central Spain: Zamora and Toledo provinces). The aim of this contribution is to characterize the elemental composition of the selected populations and their soils and compare the relationship between them and the macro- and micronutrient plant intake; all these nutrients may allow this species to be considered an edible plant. Using analytical techniques such as ICP-MS (inductively coupled plasma mass spectrometry), our results revealed high values of Na and K followed by Ca, Mg, Fe and Sr in stems. These data demonstrate the importance of annual halophytic species as edible plants and their potential uses in phytoremediation procedures involving soils with certain heavy metals (Pb, Sr, As, Cu, Zn).

Bioactive Compounds in Salicornia patula Duval-Jouve: A Mediterranean Edible Euhalophyte.

Many halophytes have great nutritional and functional potential, providing chemical compounds with biological properties. Salicornia patula Duval-Jouve is a common euhalophyte from saline Mediterranean territories (Spain, Portugal, France, and Italy). In the present work we quantified for the first time the bioactive compounds in S. patula (total phenolic compounds and fatty acids), from Iberian Peninsula localities: littoral-coastal Tinto River basin areas (southwest Spain, the Huelva province), and mainland continental territories (northwest and central Spain, the Valladolid and Madrid provinces). Five phenolic acids including caffeic, coumaric, veratric, salicylic, and transcinnamic have been found with differences between mainland and coastal saltmarshes. S. patula contain four flavonoids: quercetin-3-O-rutinoside, kaempferol/luteolin, apigenin 7-glucoside, and pelargonidin-3-O-rutinoside. These last two glycosylated compounds are described for the first time in this genus of Chenopodiaceae. The fatty acid profile described in S. patula stems contains palmitic, oleic, and linoleic acids in high concentrations, while stearic and long-chain fatty acids were detected in low amounts. These new findings confirm that S. patula is a valuable source of bioactive compounds from Mediterranean area.

Silicon induced Fe deficiency affects Fe, Mn, Cu and Zn distribution in rice (Oryza sativa L.) growth in calcareous conditions.

A protective effect by silicon in the amelioration of iron chlorosis has recently been proved for Strategy 1 species, at acidic pH. However in calcareous conditions, the Si effect on Fe acquisition and distribution is still unknown. In this work, the effect of Si on Fe, Mn, Cu and Zn distribution was studied in rice (Strategy 2 species) under Fe sufficiency and deficiency. Plants (+Si or-Si) were grown initially with Fe, and then Fe was removed from the nutrient solution. The plants were then analysed using a combined approach including LA-ICP-MS images for each element of interest, the analysis of the Fe and Si concentration at different cell layers of root and leaf cross sections by SEM-EDX, and determining the apoplastic Fe, total micronutrient concentration and oxidative stress indexes. A different Si effect was observed depending on plant Fe status. Under Fe sufficiency, Si supply increased Fe root plaque formation, decreasing Fe concentration inside the root and increasing the oxidative stress in the plants. Therefore, Fe acquisition strategies were activated, and Fe translocation rate to the aerial parts was increased, even under an optimal Fe supply. Under Fe deficiency, +Si plants absorbed Fe from the plaque more rapidly than -Si plants, due to the previous activation of Fe deficiency strategies during the growing period (+Fe + Si). Higher Fe plaque formation due to Si supply during the growing period reduced Fe uptake and could activate Fe deficiency strategies in rice, making it more efficient against Fe chlorosis alterations. Silicon influenced Mn and Cu distribution in root.

Composition, speciation and distribution of iron minerals in Imperata cylindrica.

A comparative study of the roots, rhizomes and leaves of an iron hyperaccumulator plant, Imperata cylindrica, isolated from the banks of an extreme acidic environment, using complementary techniques: Mösbauer spectroscopy (MS), X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled to energy-dispersive X-ray microanalysis (EDAX) and transmission electron microscopy (TEM), has shown that two main biominerals, jarosite and ferrihydrate-ferritin, accumulate in the different tissues. Jarosite accumulates mainly in roots and rhizomes, while ferritin has been detected in all the structures. A model of iron management in I. cylindrica is presented.

Surface geochemistry of soils associated to the Tinto River (Huelva, Spain).

The Tinto River (Iberian Pyritic Belt) is a unique ecosystem characterized by extreme acidity and abnormally high concentrations of heavy metals in water, sediments and alluvium, with high microbial diversity and low plant diversity. The low pH value, a direct consequence of the high amount of Fe and S derived from the bedrock, promotes the dispersion of heavy metals. Less mobile elements (Fe, As, Pb, Ag and Ti) show the highest concentrations in the mid stretches of the river while easily mobile metals (Cu, Zn and Cd) accumulate in the estuarine sediments. Tinto River soils show a scarcity of nutrients (Ca, K, P, Mg and Na) due to the lack of lithologic sources and to loss by acid washing. Sea water and phospho-gypsum deposits near Huelva contribute to increase the Na, Mg and P concentrations in the estuarine soils. As a whole these features represent an extreme habitat to which plants must adapt.

Silicon in Imperata cylindrica (L.) P. Beauv: content, distribution, and ultrastructure.

Silicon concentration, distribution, and ultrastructure of silicon deposits in the Poaceae Imperata cylindrica (L.) P. Beauv. have been studied. This grass, known for its medicinal uses and also for Fe hyperaccumulation and biomineralization capacities, showed a concentration of silicon of 13,705 ± 9,607 mg/kg dry weight. Silicon was found as an important constituent of cell walls of the epidermis of the whole plant. Silica deposits were found in silica bodies, endodermis, and different cells with silicon-collapsed lumen as bulliforms, cortical, and sclerenchyma cells. Transmission electron microscope observations of these deposits revealed an amorphous material of an ultrastructure similar to that previously reported in silica bodies of other Poaceae.

Localization of nickel in tissues of Streptanthus polygaloides Gray (Cruciferae) and endemic nickel hyperaccumulators from California.

The genus Streptanthus Nutt. is one of the most important indicators of ultramafic floras in western North America. This genus contains taxa that are endemic or tolerant of ultramafic soils. Streptanthus polygaloides is an annual nickel hyperaccumulator strictly confined to ultramafic soils throughout the Californian Sierra Nevada foothills. Nickel concentration in S. polygaloides populations was evaluated by elemental microanalysis using inductively coupled plasma mass spectrometry (ICP-MS). Representative samples of S. polygaloides roots, stems, leaves, flowers, and fruits were studied by scanning electron microscopy (SEM) coupled to an energy-dispersive X-ray probe (SEM-EDX). Results show Ni accumulation values between 0.09 and 1.18 %, and a distribution pattern similar to that observed in other Ni hyperaccumulator taxa, with the leaf epidermis accumulating the largest concentrations.

Metal uptake and distribution in cultured seedlings of Nerium oleander L. (Apocynaceae) from the Río Tinto (Huelva, Spain).

Nerium oleander L. (Apocynaceae) is a micro-nano phanerophyte that grows in the riverbanks of the Río Tinto basin (Southwest Iberian Peninsula). The waters and soils of the Río Tinto area are highly acidic and have high concentrations of heavy metals. In this environment, N. oleander naturally grows in both extreme acidic (EA) and less extreme acidic (LEA) water courses, excluding, and bioindicating certain metals. In this work, we compared and evaluated the accumulation preferences and capacities, the distribution and processes of biomineralization of metals (Fe, Cu, Zn, Mn, Mg, Ca) in the first stages of growth of EA and LEA oleanders by means of inductively coupled plasma-mass spectrometry, scanning electron microscopy, and energy dispersive X-ray analyzer analysis. Seeds from both environments were grown and treated with a self-made solution simulating the most extreme red waters from the Río Tinto. LEA plants drastically reduces the metal uptake at the beginning, but later reactivates the uptake reaching concentration values in the same range as the EA plants. The results showed high Mn, Zn and Mg concentrations, accumulation of Fe and Cu in plants from both environments, differing from the metal concentrations of field-grown oleanders. Iron bioformations with traces of other metals were present inside and over epidermal cells and inside vascular cells of stems and roots. They were absent of leaves. The accumulation properties of N. oleander in its early stages of development make it a species to take in consideration in phytoremediation processes but optimized conditions are needed to ensure enough biomass production.

Immunocytochemical analysis of the subcellular distribution of ferritin in Imperata cylindrica (L.) Raeuschel, an iron hyperaccumulator plant.

Ferritin is of interest at the structural and functional level not only as storage for iron, a critical element, but also as a means to prevent cell damage produced by oxidative stress. The main objective of this work was to confirm by immunocytochemistry the presence and the subcellular distribution of the ferritin detected by Mösbauer spectroscopy in Imperata cylindrica, a plant which accumulates large amounts of iron. The localization of ferritin was performed in epidermal, parenchymal and vascular tissues of shoots and leaves of I. cylindrica. The highest density of immunolabeling in shoots appeared in the intracellular space of cell tissues, near the cell walls and in the cytoplasm. In leaves, ferritin was detected in the proximity of the dense network of the middle lamella of cell walls, following a similar path to that observed in shoots. Immunolabeling was also localized in chloroplasts. The abundance of immunogold labelling in mitochondria for I. cylindrica was rather low, probably because the study dealt with tissues from old plants. These results further expand the localization of ferritin in cell components other than chloroplasts and mitochondria in plants.

An improved semiquantitative method for elemental analysis of plants using inductive coupled plasma mass spectrometry.

A semiquantitative ICP-MS method suitable for evaluating metal content in plants exposed to high metal concentrations is described. The methodology which has been tested using different plant reference material is able, in only a few minutes, to obtain qualitative and quantitative information from the sample. Recoveries close to 100% were obtained for more than half of the referenced elements with an RSD <10%, thus avoiding the generation of a calibration line for each of the elements to be analyzed. The use of multi-standards improves the results obtained with conventional standards by a factor of two. In these conditions the semiquantitative multi-elemental analysis is a valid alternative for most of the analyzed elements with the exception of Si, Al, and P which requires the use of a quantitative ICP-MS analysis for its determination. Two different digestion protocols were tested, with and without the addition of HF to the HNO(3) + H(2)O(2) extraction mixture. Similar results were obtained for poplar and bush reference materials using the HNO(3) + H(2)O(2) mixture. The addition of HF did not improve the recovery of different elements, in general, but is critical for the quantitative measurements of Al and Si as its presence allows results to be obtained with an RDS <5%.

Metal accumulation screening of the Río Tinto flora (Huelva, Spain).

Río Tinto (Huelva, Spain) is located in one of the most important mining regions in the world. Its soils are characterized by their extreme acidity and elevated concentrations of heavy metals. Due to these characteristics, the Tinto ecosystem is considered unique and an ideal location to study biological adaptations to this type of habitat. Plant species that present these adaptations might be useful to mining and other metal pollution restoration programs. This study reports the results for the screening of Ca, Mg, Na, Mn, Fe, Ni, Cu, Zn, As, and Pb in aerial tissues of 97 plant species from the Tinto basin flora. In addition, plant-soil relationships were analyzed using the biological absorption coefficient (BAC) to detect the main plant adaptations in the Tinto flora. The species selected are representative of the biomass of the main dominant edaphophile and climatophile vegetation communities of the three river sections, forest, and subseral stages. Plant and soil elemental analyses were performed using inductively coupled plasma-mass spectrometry technique (ICP-MS). The results indicate that in general, Tinto flora shows a pattern of accumulation of the analyzed elements in aerial tissues which agrees with the nutritional requirements of vascular plants (macronutrients > micronutrients > indifferent or toxic elements). Among macronutrients, Ca seems to be an essential element in this habitat. This element accumulates in the aerial plant tissues. Basically, the Río Tinto flora is made of Fe, Cu, Zn, Ni, As, and Pb excluders, although some analyzed species of Erica, Quercus, Lavandula, Cistus, Genista, and Cytisus genera can be considered Mn accumulators. The results of this study make up a body of fundamental knowledge of the strategies used by plants to thrive in habitats with high concentrations of toxic heavy metals. This information is vital when it comes to planning a restoration program. Plants must be selected and used according to the requirements, always respecting the characteristics of the territory and facilitating the development of suitable vegetation.