A thin layer of fresh water from summer monsoon rain and river runoff in the Bay of Bengal (BoB) has profound influence on air‐sea interaction across the south Asian region, but the mechanisms that ...sustain the low‐salinity layer are as yet unknown. Using the first long time series of high‐frequency observations from a mooring in the north BoB and satellite salinity data, we show that fresh water from major rivers is transported by large‐scale flow and eddies, and shallow salinity stratification persists from summer through the following winter. The moored observations show frequent 0.2–1.2 psu salinity jumps with time scales of 10 min to days, due to O(1–10) km submesoscale salinity fronts moving past the mooring. In winter, satellite sea surface temperature shows 10 km wide filaments of cool water, in line with moored data. Rapid salinity and temperature changes at the mooring are highly coherent, suggesting slumping of salinity‐dominated fronts. Based on these observations, we propose that submesoscale fronts may be one of the important drivers for the persistent fresh layer in the north BoB.
Key Points
Persistence of shallow stratification and river water from moored data in the north Bay of Bengal
First evidence of submesoscale (order 1–10 km) salinity fronts in the Bay of Bengal
Slumping of submesoscale fronts may sustain shallow stratification
The adaptability to wide salinities remains a big challenge for artificial nanofluidic systems, which plays a vital role in water–energy nexus science. Here, inspired by euryhaline fish, ...sandwich‐structured nanochannel systems are constructed to realize salinity self‐adaptive nanofluidic diodes, which lead to high‐performance salinity‐gradient power generators with low internal resistance. Adaptive to changing salinity, the pore morphology of one side of the nanochannel system switches from a 1D straight nanochannel (45 nm) to 3D network pores (1.9 nm pore size and ≈1013 pore density), along with three orders of magnitude change for charge density. Thus, the abundant surface charges and narrow pores render the membrane‐based osmotic power generator with power density up to 26.22 Wm−2. The salinity‐adaptive membrane solves the surface charge‐shielding problem caused by abundant mobile ions in high salinity and increases the overlapping degree of the electric double layer. The dynamic adaption process of the membrane to the hypersaline environment endows it with good salt endurance and stability. New routes for designing nanofluidic devices functionally adaptable to different salinities and building power generators with excellent salt endurance are demonstrated.
A sandwich‐structured nanochannel system is constructed to realize salinity self‐adaptive nanofluidic diodes, which lead to a high‐performance salinity‐gradient power generator with low internal resistance. Adaptive to changing salinity, the pore morphology of one side of the nanochannel system switches from a 1D straight nanochannel to 3D network pores, along with three orders of magnitude change for charge density.
Summary
Soil salinity is a major constraint for the global agricultural production. For many decades, Na+ exclusion from uptake has been the key trait targeted in breeding programs; yet, no major ...breakthrough in creating salt‐tolerant germplasm was achieved. In this work, we have combined the microelectrode ion flux estimation (MIFE) technique for non‐invasive ion flux measurements with confocal fluorescence dye imaging technique to screen 45 accessions of barley to reveal the relative contribution of Na+ exclusion from the cytosol to the apoplast and its vacuolar sequestration in the root apex, for the overall salinity stress tolerance. We show that Na+/H+ antiporter‐mediated Na+ extrusion from the root plays a minor role in the overall salt tolerance in barley. At the same time, a strong and positive correlation was found between root vacuolar Na+ sequestration ability and the overall salt tolerance. The inability of salt‐sensitive genotypes to sequester Na+ in root vacuoles was in contrast to significantly higher expression levels of both HvNHX1 tonoplast Na+/H+ antiporters and HvVP1 H+‐pumps compared with tolerant genotypes. These data are interpreted as a failure of sensitive varieties to prevent Na+ back‐leak into the cytosol and existence of a futile Na+ cycle at the tonoplast. Taken together, our results demonstrated that root vacuolar Na+ sequestration but not exclusion from uptake played the main role in barley salinity tolerance, and suggested that the focus of the breeding programs should be shifted from targeting genes mediating Na+ exclusion from uptake by roots to more efficient root vacuolar Na+ sequestration.
Significance Statement
Our results demonstrated that root vacuolar Na+ sequestration but not exclusion from uptake plays the main role in barley salinity tolerance, and suggest that the focus of the breeding programs should be shifted from targeting genes mediating Na+ exclusion from uptake by roots to more efficient root vacuolar Na+ sequestration.
Global sea surface salinity (SSS) has been obtained from space since 2009 by the Soil Moisture and Ocean Salinity (SMOS) mission and has been further enhanced by Aquarius in 2011 and Soil Moisture ...Active‐Passive (SMAP) missions in 2015. Due to the differences between SMOS, Aquarius, and SMAP in the instruments used, retrieval algorithms, and error correction strategies, the quality of their gridded products are different. In this paper, we have assessed the accuracy of three satellite products using in situ gridded data and buoy data. Compared with gridded in situ salinity measurements, the monthly Aquarius data are of the best quality, reaching the mission target accuracy (0.2 PSU) in the open ocean. SMOS and SMAP agree well with in situ data in the open ocean between 40°S and 40°N (root‐mean‐square deviation RMSD: SMOS 0.211 PSU, SMAP 0.233 PSU). The RMSD of SMAP is lower than that of SMOS at high latitudes, which may due to the fact that the roughness correction of SMAP is based on the Aquarius geophysical model function. Meanwhile, time series comparison of salinity measured at 1 m by moored buoys indicates that satellite SSS captures variability of SSS at weekly time scales with reasonably good accuracy (RMSD: SMOS 0.25 PSU, SMAP 0.26 PSU), when excluding suspicious buoy data. Synergetic analysis of satellite SSS and Argo data indicates that satellite SSS can be applied as real‐time quality control of buoy 1‐m salinity data.
Plain Language Summary
It is important to analyze salinity variations and understand their relationship with the global hydrological cycle and climate changes. The performance of different sea surface salinity products from three salinity satellites is evaluated based on in situ salinity measurements in this study. The results show that the satellite salinity products agree well with in situ data in the open ocean and can be used as real‐time quality control of buoy sea surface salinity data. However, large discrepancies can be found in high latitudes and in the regions along the coast.
Key Points
Satellite‐derived sea surface salinity (SSS) products from SMOS, Aquarius, and SMAP are compared with in situ data
Aquarius data are of best quality between 40°S–40°N, and the root‐mean‐square deviations of SMOS and SMAP are close
Satellite SSS can be applied as real‐time quality control (QC) of buoy data
Main conclusion
There is a need to integrate conceptual framework based on the current understanding of salt stress responses with different approaches for manipulating and improving salt tolerance ...in crop plants.
Soil salinity exerts significant constraints on global crop production, posing a serious challenge for plant breeders and biotechnologists. The classical transgenic approach for enhancing salinity tolerance in plants revolves by boosting endogenous defence mechanisms, often via a single-gene approach, and usually involves the enhanced synthesis of compatible osmolytes, antioxidants, polyamines, maintenance of hormone homeostasis, modification of transporters and/or regulatory proteins, including transcription factors and alternative splicing events. Occasionally, genetic manipulation of regulatory proteins or phytohormone levels confers salinity tolerance, but all these may cause undesired reduction in plant growth and/or yields. In this review, we present and evaluate novel and cutting-edge approaches for engineering salt tolerance in crop plants. First, we cover recent findings regarding the importance of regulatory proteins and transporters, and how they can be used to enhance salt tolerance in crop plants. We also evaluate the importance of halobiomes as a reservoir of genes that can be used for engineering salt tolerance in glycophytic crops. Additionally, the role of microRNAs as critical post-transcriptional regulators in plant adaptive responses to salt stress is reviewed and their use for engineering salt-tolerant crop plants is critically assessed. The potentials of alternative splicing mechanisms and targeted gene-editing technologies in understanding plant salt stress responses and developing salt-tolerant crop plants are also discussed.
Salt stress is one of the major environmental stresses limiting plant growth and productivity. To adapt to salt stress, plants have developed various strategies to integrate exogenous salinity stress ...signals with endogenous developmental cues to optimize the balance of growth and stress responses. Accumulating evidence indicates that phytohormones, besides controlling plant growth and development under normal conditions, also mediate various environmental stresses, including salt stress, and thus regulate plant growth adaptation. In this review, we mainly discuss and summarize how plant hormones mediate salinity signals to regulate plant growth adaptation. We also highlight how, in response to salt stress, plants build a defense system by orchestrating the synthesis, signaling, and metabolism of various hormones via multiple crosstalks.
Both stress hormones and growth hormones are important in the mediation of plant salinity stress responses.Sophisticated crosstalk occurs among the different hormones in plant growth adaptation under salinity stress.The cooperation or antagonism among different plant hormones is dependent on growth stages.Plants adapt to salinity stress through flexible regulation of hormone levels and/or signaling.Glycosyl inositol phosphorylceramide (GIPC) sphingolipids in the plasma membrane act as Na+ receptors for sensing Na+ in the apoplastic space and then gate Ca2+ influx channels in plants.
Soil salinity reduces crop yield. The extent and severity of salt-affected agricultural land is predicted to worsen as a result of inadequate drainage of irrigated land, rising water tables and ...global warming. The growth and yield of most plant species are adversely affected by soil salinity, but varied adaptations can allow some crop cultivars to continue to grow and produce a harvestable yield under moderate soil salinity. Significant costs are associated with saline soils: the economic costs to the farming community and the energy costs of plant adaptations. We briefly consider mechanisms of adaptation and highlight recent research examples through a lens of their applicability to improving the energy efficiency of crops under saline field conditions.
Soil salinization is a major threat to global food security and the biodiversity of natural ecosystems. To adapt to salt stress, plants rely on ROS‐mediated signalling networks that operate upstream ...of a broad array of physiological and genetic processes. A key player in ROS signalling is NADPH oxidase, a plasma‐membrane‐bound enzyme encoded by RBOH genes. In this study, we have conducted a comprehensive bioinformatic analysis of over 50 halophytic and glycophytic species to link the difference in the kinetics of ROS signalling between contrasting species with the abundance and/or structure of NADPH oxidases. The RBOH proteins were predicted in all the tested plant lineages except some algae species from the Rhodophyta, Chlorophyta and Streptophyta. Within the glycophytic group, the number of RBOH copies correlated negatively with salinity stress tolerance, suggesting that a reduction in the number of RBOH isoforms may be potentially related to the evolution of plant salinity tolerance. While halophytes did not develop unique protein families during evolution, they evolved additional phosphorylation target sites at the N‐termini of NADPH oxidases, potentially modulating enzyme activity and allowing more control over their function, resulting in more efficient ROS signalling and adaptation to saline conditions.
Halophytes evolved additional phosphorylation target sites at N‐terminus of NADPH oxidase, potentially modulating enzyme activity and allowing more control over its function needed for more efficient ROS signalling and adaptation to conditions of high salinity.
Soil salinisation is one of the major soil degradation threats occurring in Europe. The effects of salinisation can be observed in numerous vital ecological and non-ecological soil functions. Drivers ...of salinisation can be detected both in the natural and man-made environment, with climate and the foreseen climate change also playing an important role. This review outlines the state of the art concerning drivers and pressures, key indicators as well as monitoring, modeling and mapping methods for soil salinity. Furthermore, an overview of the effect of salinisation on soil functions and the respective mechanism is presented. Finally, the state of salinisation in Europe is presented according to the most recent literature and a synthesis of consistent datasets. We conclude that future research in the field of soil salinisation should be focused on among others carbon dynamics of saline soil, further exploration of remote sensing of soil properties and the harmonization and enrichment of soil salinity maps across Europe within a general context of a soil threat monitoring system to support policies and strategies for the protection of European soils.
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•State of the art regarding drivers, effects, indicators, monitoring, modeling and management of soil salinity at European scale is presented.•Current state of soil salinity in Europe is introduced by compiling a variety of sources.•Knowledge gaps and aspects beyond the state of the art regarding the soil threat of salinisation are highlighted.
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