Time‐dependent kinetics of xylem Na+ loading was investigated using a large number of barley genotypes contrasting in their salinity tolerance. Salt‐sensitive varieties were less efficient in ...controlling xylem Na+ loading and showed a gradual increase in the xylem Na+ content over the time. To understand underlying ionic and molecular mechanisms, net fluxes of Ca2+, K+ and Na+ were measured from the xylem parenchyma tissue in response to H2O2 and ABA; both of them associated with salinity stress signalling. Our results indicate that NADPH oxidase‐mediated apoplastic H2O2 production acts upstream of the xylem Na+ loading and is causally related to ROS‐inducible Ca2+ uptake systems in the root stelar tissue. It was also found that ABA regulates (directly or indirectly) the process of Na+ retrieval from the xylem and the significant reduction of Na+ and K+ fluxes induced by bumetanide are indicative of a major role of chloride cation co‐transporter (CCC) on xylem ion loading. Transcript levels of HvHKT1;5_like and HvSOS1_like genes in the root stele were observed to decrease after salt stress, while there was an increase in HvSKOR_like gene, indicating that these ion transporters are involved in primary Na+/K+ movement into/out of xylem.
This work analyzes the economic cost of global climate changes on crop productivity and argues for a broader use of wild relatives to improve crop stress resilience lost during domestication.
...Abstract
To match predicted population growth, annual food production should be doubled by 2050. This is not achievable by current agronomical and breeding practices, due to the impact of climate changes and associated abiotic stresses on agricultural production systems. Here, we analyze the impact of global climate trends on crop productivity and show that the overall loss in crop production from climate-driven abiotic stresses may exceed US$170 billion year–1 and represents a major threat to global food security. We also show that abiotic stress tolerance had been present in wild progenitors of modern crops but was lost during their domestication. We argue for a major shift in our paradigm of crop breeding, focusing on climate resilience, and call for a broader use of wild relatives as a major tool in this process. We argue that, while molecular tools are currently in place to harness the potential of climate-resilient genes present in wild relatives, the complex polygenic nature of tolerance traits remains a major bottleneck in this process. Future research efforts should be focused not only on finding appropriate wild relatives but also on development of efficient cell-based high-throughput phenotyping platforms allowing assessment of the in planta operation of key genes.
Plant salinity tolerance is a physiologically complex trait, with numerous mechanisms contributing to it. In this work, we show that the ability of leaf mesophyll to retain K＋ represents an important ...and essentially overlooked component of a salinity tolerance mechanism. The strong positive correlation between mesophyll K＋ retention ability under saline conditions （quantified by the magnitude of NaCl-induced K＋ efflux from mesophyll） and the overall salinity tolerance （relative fresh weight and/or survival or damage under salinity stress） was found while screening 46 barley （Hordeum vulgare L.） genotypes contrasting in their salinity tolerance. Genotypes with intrinsically higher leaf K＋ content under control conditions were found to possess better K＋ retention ability under salinity and, hence, overall higher tolerance. Contrary to previous reports for barley roots, K＋ retention in mesophyll was not associated with an increased H＋-pumping in tolerant varieties but instead correlated negatively with this trait. These findings are explained by the fact that increased H＋ extrusion may be needed to charge balance the activity and provide the driving force for the high affinity HAK/KUP K＋ transporters required to restore cytosolic K＋ homeostasis in salt-sensitive genotypes.
This work investigated the importance of the ability of leaf mesophyll cells to control K+ flux across the plasma membrane as a trait conferring tissue tolerance mechanism in plants grown under ...saline conditions. Four wheat (Triticum aestivum and Triticum turgidum) and four barley (Hordeum vulgare) genotypes contrasting in their salinity tolerance were grown under glasshouse conditions. Seven to 10‐day‐old leaves were excised, and net K+ and H+ fluxes were measured from either epidermal or mesophyll cells upon acute 100 mM treatment (mimicking plant failure to restrict Na+ delivery to the shoot) using non‐invasive microelectrode ion flux estimation (the MIFE) system. To enable net ion flux measurements from leaf epidermal cells, removal of epicuticular waxes was trialed with organic solvents. A series of methodological experiments was conducted to test the efficiency of different methods of wax removal, and the impact of experimental procedures on cell viability, in order to optimize the method. A strong positive correlation was found between plants' ability to retain K+ in salt‐treated leaves and their salinity tolerance, in both wheat and especially barley. The observed effects were related to the ionic but not osmotic component of salt stress. Pharmacological experiments have suggested that voltage‐gated K+‐permeable channels mediate K+ retention in leaf mesophyll upon elevated NaCl levels in the apoplast. It is concluded that MIFE measurements of NaCl‐induced K+ fluxes from leaf mesophyll may be used as an efficient screening tool for breeding in cereals for salinity tissue tolerance.
Salinity stress-induced production of reactive oxygen species (ROS) and associated oxidative damage is one of the major factors limiting crop production in saline soils. However, the causal link ...between ROS production and stress tolerance is not as straightforward as one may expect, as ROS may also play an important signaling role in plant adaptive responses. In this study, the causal relationship between salinity and oxidative stress tolerance in two cereal crops—barley (Hordeum vulgare) and wheat (Triticum aestivum)—was investigated by measuring the magnitude of ROS-induced net K+ and Ca2+ fluxes from various root tissues and correlating them with overall whole-plant responses to salinity. We have found that the association between flux responses to oxidative stress and salinity stress tolerance was highly tissue specific, and was also dependent on the type of ROS applied. No correlation was found between root responses to hydroxyl radicals and the salinity tolerance. However, when oxidative stress was administered via H2O2 treatment, a significant positive correlation was found for the magnitude of ROS-induced K+ efflux and Ca2+ uptake in barley and the overall salinity stress tolerance, but only for mature zone and not the root apex. The same trends were found for wheat. These results indicate high tissue specificity of root ion fluxes response to ROS and suggest that measuring the magnitude of H2O2-induced net K+ and Ca2+ fluxes from mature root zone may be used as a tool for cell-based phenotyping in breeding programs aimed to improve salinity stress tolerance in cereals.
Waterlogging remains a significant constraint to cereal production across the globe in areas with high rainfall and/or poor drainage. Improving tolerance of plants to waterlogging is the most ...economical way of tackling the problem. However, under severe waterlogging combined agronomic, engineering and genetic solutions will be more effective. A wide range of agronomic and engineering solutions are currently being used by grain growers to reduce losses from waterlogging. In this scoping study, we reviewed the effects of waterlogging on plant growth, and advantages and disadvantages of various agronomic and engineering solutions which are used to mitigate waterlogging damage. Further research should be focused on: cost/benefit analyses of different drainage strategies; understanding the mechanisms of nutrient loss during waterlogging and quantifying the benefits of nutrient application; increasing soil profile de-watering through soil improvement and agronomic strategies; revealing specificity of the interaction between different management practices and environment as well as among management practices; and more importantly, combined genetic, agronomic and engineering strategies for varying environments.
Extreme weather events threaten food security, yet global assessments of impacts caused by crop waterlogging are rare. Here we first develop a paradigm that distils common stress patterns across ...environments, genotypes and climate horizons. Second, we embed improved process-based understanding into a farming systems model to discern changes in global crop waterlogging under future climates. Third, we develop avenues for adapting cropping systems to waterlogging contextualised by environment. We find that yield penalties caused by waterlogging increase from 3-11% historically to 10-20% by 2080, with penalties reflecting a trade-off between the duration of waterlogging and the timing of waterlogging relative to crop stage. We document greater potential for waterlogging-tolerant genotypes in environments with longer temperate growing seasons (e.g., UK, France, Russia, China), compared with environments with higher annualised ratios of evapotranspiration to precipitation (e.g., Australia). Under future climates, altering sowing time and adoption of waterlogging-tolerant genotypes reduces yield penalties by 18%, while earlier sowing of winter genotypes alleviates waterlogging by 8%. We highlight the serendipitous outcome wherein waterlogging stress patterns under present conditions are likely to be similar to those in the future, suggesting that adaptations for future climates could be designed using stress patterns realised today.
Background and aims
Zinc (Zn) deficiency in humans is of worldwide concern and is primarily associated with a plant-based diet of crops grown in Zn-deficient soils. This work explores the effects of ...both soil factors and genotype on Zn accumulation in aboveground tissues in barley (
Hordeum vulgare
L.).
Methods
A meta-analysis was performed on collected articles data published between 1945-2020 describing Zn concentrations in barley shoots and grains in plants grown at different levels of Zn availability.
Results
Higher Zn levels in the growth substrate resulted in increased Zn concentrations in barley shoots and grains. Of note is that Zn concentrations were found to be highly cultivar specific, with a 3.5-fold (shoots) to 4.5-fold (grains) difference reported between high and low Zn accumulating cultivars under the same conditions. Additionally, the Zn translocation and remobilisation rate from shoots to grains were also 2-fold greater in Zn-efficient cultivars than others.
Conclusions
This meta-analysis is the first to collect all available data regarding Zn concentrations in barley. The findings demonstrate that Zn concentrations in aboveground parts of barley are highly cultivar-specific and change with substrate Zn. Target Zn concentrations in barley could be achieved through selective breeding and optimal Zn fertilisation. Further investigations revealing the major quantitative trait locus (QTLs) and candidate genes associated with desirable Zn phenotypes would allow better understanding of Zn use mechanisms in barley.
The Near East Fertile Crescent is well recognized as a primary center of barley origin, diversity, and domestication. A large number of wild barleys have been collected from the Tibetan Plateau, ...which is characterized by an extreme environment. We used genome-wide diversity array technology markers to analyze the genotypic division between wild barley from the Near East and Tibet. Our results confirmed the existence of Tibetan wild barley and suggested that the split between the wild barleys in the Near East and those in Tibet occurred around 2.76 million years ago (Mya). To test the concept of polyphyletic domestication of barley, we characterized a set of worldwide cultivated barley. Some Chinese hulless and six-rowed barleys showed a close relationship with Tibetan wild barley but showed no common ancestor with other cultivated barley. Our data support the concept of polyphyletic domestication of cultivated barley and indicate that the Tibetan Plateau and its vicinity is one of the centers of domestication of cultivated barley. The current results may be highly significant in exploring the elite germplasm for barley breeding, especially against cold and drought stresses.
While the importance of cell type specificity in plant adaptive responses is widely accepted, only a limited number of studies have addressed this issue at the functional level. We have combined ...electrophysiological, imaging, and biochemical techniques to reveal the physiological mechanisms conferring higher sensitivity of apical root cells to salinity in barley (Hordeum vulgare). We show that salinity application to the root apex arrests root growth in a highly tissue- and treatment-specific manner. Although salinity-induced transient net Na⁺ uptake was about 4-fold higher in the root apex compared with the mature zone, mature root cells accumulated more cytosolic and vacuolar Na⁺, suggesting that the higher sensitivity of apical cells to salt is not related to either enhanced Na⁺ exclusion or sequestration inside the root. Rather, the above differential sensitivity between the two zones originates from a 10-fold difference in K⁺ efflux between the mature zone and the apical region (much poorer in the root apex) of the root. Major factors contributing to this poor K⁺ retention ability are (1) an intrinsically lower H⁺-ATPase activity in the root apex, (2) greater salt-induced membrane depolarization, and (3) a higher reactive oxygen species production under NaCl and a larger density of reactive oxygen species-activated cation currents in the apex. Salinity treatment increased (2- to 5-fold) the content of 10 (out of 25 detected) amino acids in the root apex but not in the mature zone and changed the organic acid and sugar contents. The causal link between the observed changes in the root metabolic profile and the regulation of transporter activity is discussed.
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