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An urgent challenge within agriculture is to improve fertilizer efficiency in order to reduce the environmental footprint associated with an increased production of crops on existing farmland. Standard soil fertilization strategies are often not very efficient due to immobilization in the soil and losses of nutrients by leaching or volatilization. Foliar fertilization offers an attractive supplementary strategy as it bypasses the adverse soil processes, but implementation is often hampered by a poor penetration through leaf barriers, leaf damage, and a limited ability of nutrients to translocate. Recent advances within bionanotechnology offer a range of emerging possibilities to overcome these challenges. Here we review how nanoparticles can be tailored with smart properties to interact with plant tissue for a more efficient delivery of nutrients. Recent advances within bionanotechnology pave the way for development of biocompatible foliar nanofertilizers with superior nutrient use efficiency. Emerging evidence shows that nanoparticle physicochemical properties and formulation are key for effective penetration of all major plant barriers, including the cuticle, stomata, cell walls, and plasma membrane. Nanoparticles can be targeted to specific cell organelles and be programmed to release their nutrients in a time-dependent manner or as a response to cellular stimuli. Nanoparticles can translocate from exposed leaves to unexposed tissue. This highlights a clear potential for designing phloem-mobile nanofertilizers, containing nutrients that are currently immobile. Manipulating the phloem mobility of nutrients would constitute a major landmark within plant science. [ABSTRACT FROM AUTHOR]

Agronomic biofortification is one of the main strategies for alleviation of micronutrient deficiencies in food and feed. The objective of this study was to investigate the effect of N supply on total concentration of Zn and Fe and their chemical species in the soluble extracts of maize silage grown under field conditions. Total concentrations of Zn, Fe, Cu, Mn, S and P were measured by flow-injection inductive coupled plasma (ICP) – mass spectrometer (MS). Soluble Fe and Zn were extracted and analyzed by size exclusion−inductively coupled plasma mass spectrometry. Using the same set-up for total elemental and speciation analysis enabled direct quantitative comparison of the detected speciated molecules with the total element sample content. N or Zn treatment, except in control plots, did not significantly affect concentrations of Zn and Fe in the maize silage and grain samples. Significant positive correlation was observed between Zn and Fe maize silage (r = 0.64, p < 0.01) and maize grain (r = 0.85, p < 0.01) concentrations. N and Zn treatment did not affect solubility of Zn and Fe, while available Zn and Fe were affected by increase in Zn soil treatment. Soluble Zn was speciated in LMW complexes, while soluble Fe was speciated in MMW and LMW complexes. [ABSTRACT FROM AUTHOR]

Among the rare-earth elements, lanthanides constitute unique labels in bioanalytical assays and are detected with high sensitivity by inductively-coupled plasma mass spectrometry (ICP-MS). ICP-MS is a versatile technology that, based on coupling to various bioanalytical techniques, has facilitated multiplexed analysis of both proteins and nucleic acids. In this review, we present different types of bioanalytical applications used to detect these biomolecules. Moreover, we review common conjugation approaches and lanthanide-chelating tags used in these assays. Multiplexed lanthanide immunoassays have developed substantially over the past few years and, in the most recent applications, analysis of more than 30 proteins has been achieved. In parallel, methods using lanthanide-labelled DNA probes combined with ICP-MS detection have emerged and enabled multiplexed analysis of up to 15 different DNA sequences. We anticipate the further development of quantitative lanthanide-hybridization assays of hitherto unseen multiplexed character, with great potential for nucleic-acid research. [ABSTRACT FROM AUTHOR]

Abstract: Using two barley (Hordeum vulgare) cultivars (cvs. Tokak and Hamidiye) nutrient solution experiments were conducted in order to study the genotypic variation in tolerance to Cd toxicity based on (i) development of leaf symptoms, (ii) decreases in dry matter production, (iii) Cd concentration and (iv) changes in antioxidative defense system in leaves (i.e., superoxide dismutase, ascorbate peroxidase, glutathione reductase, catalase, ascorbic acid and non-protein SH-groups). Plants were grown in nutrient solution under controlled environmental conditions, and subjected to increasing concentrations of Cd (0, 15, 30, 60 and 120μmol/L Cd) for different time periods. Of the barley cultivars Hamidiye was particularly sensitive to Cd as judged by the severity and earlier development of Cd toxicity symptoms on leaves. Within 48h of Cd application Hamidiye rapidly developed severe leaf Cd toxicity symptoms whereas in Tokak the leaf symptoms appeared only slightly. Hamidiye also tended to show more decrease in growth caused by Cd supply when compared to Tokak. The differences in sensitivity to Cd between Tokak and Hamidiye were not related to Cd concentrations in roots and shoots or Cd accumulation per plant. With the exception of catalase, activities of the enzymes involved in detoxification of reactive oxygen species (ROS) were markedly enhanced in Hamidiye by increasing Cd supply. By contrast, in Tokak there was either only a slight increase or no change in the activities of the antioxidative enzymes. Similarly, levels of ascorbic acid and especially non-protein SH-groups were increased in Hamidiye by Cd supply, but not affected in Tokak. The results indicate the existence of a large genotypic variation between barley cultivars for Cd tolerance. The differential Cd tolerance found in the barley cultivars was not related to uptake or accumulation of Cd in plants, indicating importance of internal mechanisms in expression of differential Cd tolerance in barley. As a response to increasing Cd supply particular increases in antioxidative mechanisms in the Cd-sensitive barley cultivar Hamidiye suggest that the high Cd sensitivity of Hamidiye is related to enhanced production and oxidative damage of ROS. [Copyright &y& Elsevier]

Highlights • A method for oxygen isotope ratio analysis of plant-derived sulphate was developed. • Oxygen isotope ratio analysis of sulphate was used for organic authentication. • The novel method was compared to traditional isotope markers. • Oxygen isotope analysis of sulphate was superior for authentication of organic vegetables. Abstract Analytical methods for authenticity testing of organically grown vegetables are urgently needed. Here we present a novel method for organic authentication based on stable isotope ratio analysis of oxygen in plant-derived sulphate. We combined this method with stable isotope ratio analysis of bulk plant tissue and plant-derived nitrate to discriminate organic and conventional potato, carrot, and cabbage from rigidly controlled long-term field trials and from a case study using retail potatoes. It was shown that oxygen isotope ratios of sulphate from organic vegetables were significantly lower compared to their conventional counterparts and the values were directly linked to the fertilisation strategy. The classification power of sulphate isotope analysis was superior compared to known bulk tissue isotope markers and nitrate isotope values. In conclusion, oxygen isotope analysis of plant-derived sulphate represents a promising new method for authentication of organic vegetables. [ABSTRACT FROM AUTHOR]

Growers need to produce increased crop yield to use resources more effectively and be resilient to abiotic stress and changing climates; however, current approaches are leading to maladaptation to stress. Bottlenecks in the selection of barley varieties have resulted in a reduction of genetic diversity that is obstructive to climate-smart agriculture. To reverse genetic erosion and identify novel sources of variation, we are re-examining and reintroducing crop landraces. Landscape genomics can add a new dimension by modelling potential adaptive responses to a specific environment or global climate change. In a conceptual model, we outline a targeted breeding programme connecting old cultivar collections with state-of-the-art gene discovery and phenotyping, necessary to provide new resources for future needs. Future crops need to be sustainable in the face of climate change. Modern barley varieties have been bred for high productivity and quality; however, they have suffered considerable genetic erosion, losing crucial genetic diversity. This renders modern cultivars vulnerable to climate change and stressful environments. We highlight the potential to tailor crops to a specific environment by utilising diversity inherent in an adapted landrace population. Tapping into natural biodiversity, while incorporating information about local environmental and climatic conditions, allows targeting of key traits and genotypes, enabling crop production in marginal soils. We outline future directions for the utilisation of genetic resources maintained in landrace collections to support sustainable agriculture through germplasm development via the use of genomics technologies and big data. [ABSTRACT FROM AUTHOR]

In order to utilize the limited phosphorus (P) resources most efficiently, it is crucial to limit over- and under-fertilization in plant production. In this study we evaluated the Diffusive Gradients in Thin films (DGT) technique as a method to determine plant P availability in agricultural soils. DGT measurements were compared to a range of well-established and frequently used soil extraction methods. In order to select P responsive soils for field trials in multiple locations, a spring barley ( Hordeum vulgare ) pot experiment, with 34 soils from different locations in Denmark, Sweden, Norway and Finland was designed and plants were grown with or without P fertilization. The soils were analyzed for P availability with DGT and three soil extraction methods using the following extractants: sodium-bicarbonate (Olsen-P), ammonium lactate (P AL ), and ammonium acetate (P AAC ). When the plants were harvested after 6 weeks, it was observed that most plants had responded to P fertilization with increased leaf tissue P concentrations and DM, but with poor or no correlations to the P levels measured in soil extracts or with the DGT technique. This observation highlighted the importance of pot size relative to the produced biomass in order to avoid the development of extensive P depletion zones surrounding the roots, as it prevented extrapolation of results to the field scale. Consequently, based on interviews with farmers, nine soils which in previous seasons responded to P fertilization, were selected in Denmark (7) and Norway (2). On each location spring barley was cultivated either with or without P fertilization, and soil analyses were regularly compared with the composition of essential plant nutrients in leaf tissue and with the final grain yields. In the field experiments, 30 days after establishment (DAE), all four methods could predict P concentrations in the youngest fully emerged leaf (YFEL) of unfertilized plants. Using a Mitscherlich equation on these data, coefficients of determination (R 2 ) ranged from 0.46 to 0.83. The Olsen-P method performed poorest while the DGT method showed the best correlation. However, three weeks later (56 DAE) the soil tests failed to reflect plant available P, as the correlation with leaf P concentrations had disappeared. At harvest, only plants with a leaf P concentration below 2000 μg P g −1 DM during early vegetative growth (30 DAE) responded to P fertilization by increasing the grain yield. In summary, these observations suggested that a number of significant external factors, which cannot be reflected by DGT or any soil extraction methodology, inherently limit the validity of soils test in predicting the plant availability of P. This includes the inability of soil test to measure P availability in deeper soil layers and physiochemical parameters limiting P diffusion and uptake such as low soil moisture and temperature. [ABSTRACT FROM AUTHOR]

Manganese (Mn) is an essential plant micronutrient with an indispensable function as a catalyst in the oxygen-evolving complex (OEC) of photosystem II (PSII). Even so, Mn deficiency frequently occurs without visual leaf symptoms, thereby masking the distribution and dimension of the problem restricting crop productivity in many places of the world. Hence, timely alleviation of latent Mn deficiency is a challenge in promoting plant growth and quality. We describe here the key mechanisms of Mn deficiency in plants by focusing on the impact of Mn on PSII stability and functionality. We also address the mechanisms underlying the differential tolerance towards Mn deficiency observed among plant genotypes, which enable Mn-efficient plants to grow on marginal land with poor Mn availability. [ABSTRACT FROM AUTHOR]

Abstract: The aims were to bio-fortify onions by foliar application of selenium (Se) and to intrinsically label bioactive Se-metabolites in onion and carrot by enriched, stable 77Se for use in human physiological studies. Onion bulbs and leaves were enriched in Se by repeated foliar spraying of 10 or 100μgSeml−1 solutions of sodium selenite (Se(IV)) or sodium selenate (Se(VI)). ICP-MS analysis of onion leaves and bulbs showed that the Se concentration was enhanced by up to a factor of approximately 50 and 200 in bulbs and leaves, respectively. HPLC–ICP-MS analysis of proteolytic plant extracts showed that foliar application of Se(IV) gave rise to bio-synthesis of a higher fraction of the desired organic Se species and was better tolerated by the plants than Se(VI). Based on these findings onions and carrots were bio-fortified by foliar application of a solution of 77Se(IV) that was enriched to 99.7% as 77Se. The 77Se- labelled metabolites in onions were predominantly γ-glutamyl-77Se-selenomethyl-selenocysteine (γ-glu-Me77SeCys), 77Se-methylselenocysteine (Me77SeCys) and 77Se-selenomethionine (77SeMet). Furthermore, we report here for the first time the finding in carrots of the bioactive Me77SeCys, the identity of which was verified by HPLC–ESI-MS/MS. [Copyright &y& Elsevier]

Abstract: Zinc (Zn) is an essential element for plants but limited information is currently available on the molecular basis for Zn2+ transport in crop species. To expand the knowledge on Zn2+ transport in barley (Hordeum vulgare L.), a cDNA library prepared from barley roots was expressed in the yeast (Saccharomyces cerevisiae) mutant strain Δzrt1/Δzrt2, defective in Zn2+ uptake. This strategy resulted in isolation and identification of three new Zn2+ transporters from barley. All of the predicted proteins have a high similarity to the ZIP protein family, and are designated HvZIP3, HvZIP5 and HvZIP8, respectively. Complementation studies in Δzrt1/Δzrt2 showed restored growth of the yeast cells transformed with the different HvZIPs, although with different efficiency. Transformation into Fe2+ and Mn2+ uptake defective yeast mutants showed that the HvZIPs were unable to restore the growth on Fe2+ and Mn2+ limited media, respectively, indicating a specific role in Zn2+ transport. In intact barley roots, HvZIP8 was constitutively expressed whereas HvZIP3 and HvZIP5 were mainly expressed in −Zn plants. These results suggest that HvZIP3, HvZIP5 and HvZIP8 are Zn2+ transporters involved in Zn2+ homeostasis in barley roots. The new transporters may facilitate breeding of barley genotypes with improved Zn efficiency and Zn content. [Copyright &y& Elsevier]

Abstract: A wealth of information on the different aspects of iron homeostasis in plants has been obtained during the last decade. However, there is no clear road-map integrating the relationships between the various components. The principal aim of the current review is to fill this gap. In this context we discuss the lack of low affinity iron uptake mechanisms in plants, the utilization of a different uptake mechanism by graminaceous plants compared to the others, as well as the roles of riboflavin, ferritin isoforms, nitric oxide, nitrosylation, heme, aconitase, and vacuolar pH. Cross-homeostasis between elements is also considered, with a specific emphasis on the relationship between iron homeostasis and phosphorus and copper deficiencies. As the environment is a crucial parameter for modulating plant responses, we also highlight how diurnal fluctuations govern iron metabolism. Evolutionary aspects of iron homeostasis have so far attracted little attention. Looking into the past can inform us on how long-term oxygen and iron-availability fluctuations have influenced the evolution of iron uptake mechanisms. Finally, we evaluate to what extent this homeostastic road map can be used for the development of novel biofortification strategies in order to alleviate iron deficiency in human. [Copyright &y& Elsevier]

Abstract: Carrot (Daucus carota) shoots were enriched by selenium using foliar application. Solutions of sodium selenite or sodium selenate at 10 and 100μgSeml−1, were sprayed on the carrot leaves and the selenium content and uptake rate of selenium were estimated by ICP–MS analysis. Anion and cation exchange HPLC were tailored to and applied for the separation of selenium species in proteolytic extracts of the biological tissues using detection by ICP–MS or ESI–MS/MS. Foliar application of solutions of selenite or selenate at 100μgSeml−1 resulted in a selenium concentration of up to 2μgSeg−1 (dry mass) in the carrot root whereas the selenium concentration in the controls was below the limit of detection at 0.045μgSeg−1 (dry mass). Selenate-enriched carrot leaves accumulated as much as 80μgSeg−1 (dry mass), while the selenite-enriched leaves contained approximately 50μgSeg−1 (dry mass). The speciation analyses showed that inorganic selenium was present in both roots and leaves. The predominant metabolised organic forms of selenium in the roots were selenomethionine and γ-glutamyl-selenomethyl-selenocysteine, regardless of which of the inorganic species were used for foliar application. Only selenomethionine was detected in the carrot leaves. The identity of selenomethionine contained in carrot roots and leaves was successfully confirmed by HPLC–ESI–MS/MS. [Copyright &y& Elsevier]

• Soils are under increasing stress to feed a rapidly growing human population. • We show that soils are a master variable regulating critical Earth-system processes. • Soils make major contributions to biogeochemical flows and land-system change. • Soils also contribute to climate change, ocean acidification, and ozone depletion. • Improving management of soils is critical to maintain Earth in a hospitable state. We use soils to provide 98.8% of our food, but we must ensure that the pressure we place on soils to provide this food in the short-term does not inadvertently push the Earth into a less hospitable state in the long-term. Using the planetary boundaries framework, we show that soils are a master variable for regulating critical Earth-system processes. Indeed, of the seven Earth-systems that have been quantified, soils play a critical and substantial role in changing the Earth-systems in at least two, either directly or indirectly, as well as smaller contributions for a further three. For the biogeochemical flows Earth-system process, soils contribute 66% of the total anthropogenic change for nitrogen and 38% for phosphorus, whilst for the land-system change Earth-system process, soils indirectly contribute 80% of global anthropogenic change. Furthermore, perturbations of soils contribute directly to 21% of climate change, 25% to ocean acidification, and 25% to stratospheric ozone depletion. We argue that urgent interventions are required to greatly improve soil management, especially for those Earth-system processes where the planetary boundary has already been exceeded and where soils make an important contribution, with this being for biogeochemical flows (both nitrogen and phosphorus), for climate change, and for land-system change. Of particular importance, it is noted that the highly inefficient use of N fertilizers results in release of excess N into the broader environment, contributes to climate change, and results in release of ozone-depleting substances. Furthermore, the use of soils for agricultural production results not only in land-system change, but also in the loss (mineralization) of organic matter with a concomitant release of CO 2 contributing to both climate change and ocean acidification. Thus, there is a need to markedly improve the efficiency of fertilizer applications and to intensify usage of our most fertile soils in order to allow the restoration of degraded soils and limit further areal expansion of agriculture. Understanding, and acting upon, the role of soils is critical in ensuring that planetary boundaries are not transgressed, with no other single variable playing such a strategic role across all of the planetary boundaries. [ABSTRACT FROM AUTHOR]