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An urgent challenge within crop production is to maintain productivity in a world plagued by climate change and its associated plant stresses, such as heat, drought and salinity. A key factor in this endeavor is to understand the dynamics of root suberization, and its role in plant‐water relations and nutrient transport. This study focuses on the hypothesis that endodermal suberin, acts as a physical barrier preventing radial potassium (K) movement out of the vascular tissues during translocation. Previous attempts to experimentally support this idea have produced inconsistent results. We developed a Laser Ablation‐Inductively Coupled Plasma‐Mass Spectrometry (LA‐ICP‐MS) method, allowing us to visualize the distribution of mineral elements and track K movement. Cesium (Cs), dosed in optimized concentrations, was found to be an ideal tracer for K, due to its low background and similar chemical/biological properties. In suberin mutants of Arabidopsis thaliana, we observed a positive correlation between suberin levels and K translocation efficiency, indicating that suberin enhances the plant's ability to retain K within the vascular tissues during translocation from root to shoot. In barley (Hordeum vulgare), fully suberized seminal roots maintained higher K concentrations in the stele compared to younger, less suberized root zones. This suggests that suberization increases with root maturity, enhancing the barrier against K leakage. In nodal roots, suberin was scattered towards the phloem in mature root zones. Despite this incomplete suberization, nodal roots still restrict outward K movement, demonstrating that even partial suberin barriers can significantly reduce K loss. Our findings provide evidence that suberin is a barrier to K leakage during root‐to‐shoot translocation. This understanding is crucial to maintain crop productivity in the face of climate change. [ABSTRACT FROM AUTHOR]

Manganese (Mn) toxicity is a major problem for plant growth, often caused by acidic soils leading to an excessive plant availability of Mn2+. However, Mn deficiency is also a major nutritional disorder, commonly observed on slightly alkaline soils, which are favoring oxidation of soluble Mn2+ to the plant unavailable form MnO2. The work reported here was initiated with the aim of identifying and characterizing barley Mn2+ transport proteins. Using yeast as a model system we have identified and characterized barley genes encoding Mn2+ transport proteins. The plasma membrane localized HvIRT1 protein is a broad range metal ion transporter. The HvIRT1 transcript expression was induced under Mn and Fe deficiency and the expression level was correlated with the Mn2+ uptake capacity, suggesting an important role of HvIRT1 in Mn2+ acquisition. Two additional genes encoding Mn2+ transport proteins were identified in a Mn2+ tolerance yeast assay; one belonging to the CDF family designated HvMTP8.1 and one homologous gene to the yeast CCC1, named HvVIT1. It is proposed that HvMTP8.1 has a role in Mn2+ efflux mechanisms into the apoplast whereas HvVIT1 are involved in Mn2+ sequestration into internal cellular compartments. The results presented provide the basis for an improved understanding of the mechanisms involved in Mn2+ acquisition and homeostasis in crop plants. This information will facilitate engineering of genotypes able to grow efficiently on marginal soils.

Manganese (Mn) deficiency is a major plant nutritional problem in many parts of the world. Most frequently Mn deficiency occurs as a hidden nutritional disorder without displaying any visual leaf symptoms and there is an urgent need for fast and specific method to diagnose the disorder. In this study two barley genotypes displaying a marked difference in their ability to tolerate growth at low Mn concentrations, a phenomenon designated as differential Mn efficiency, were used. Induction of Mn deficiency in the genotypes led to a decline in the quantum yield efficiency of PSII for both, however, faster in the Mn-inefficient genotype. Leaf tissue and thylakoid Mn concentrations were reduced under Mn deficiency, but no difference between genotypes was observed and no visual Mn deficiency symptoms were developed during the experiment. However, analysis of the fast fluorescence induction kinetics (FIK) revealed that in addition to the usual O-J-I-P steps, clear K- and D-steps were developed in the Mn-inefficient genotype under Mn deficiency. These marked changes indicated damages to photosystem II (PSII). This was further substantiated by state transition measurements, indicating that the ability of plants to redistribute excitation energy was reduced. The percent change in state transitions for control plants with normal Mn supply of both genotypes were 9-11%. However, in Mn deficient leaves of the Mn inefficient genotypes, state transitions were reduced to less than 1%, whereas no change was observed for the Mn-efficient genotypes. Comparison of plants with deficiencies of other relevant nutrients (Mg, S, Fe, Cu and Mn) revealed that fluorescence spectroscopy based leaf measurements constitute a highly specific and promising tool to accurately diagnose Mn deficiency in cereals. These data will be presented at the conference.

Phytic acid and proteins are believed to be important for the distribution and bio-availability of zinc and iron in the cereal grain, but little quantitative information is available on the relative importance of different organic ligands. We have used several chromatographic techniques including size exclusion chromatography (SEC) hyphenated to ICP-MS to analyse the molecular speciation of Fe and Zn in tissues of barley and rice seeds. The majority of Fe in barley embryos co-eluted with P as a species with the apparent mass of 12.3 kDa, whereas the majority of Zn co-eluted with S as a 3 kDa species, devoid of any co-eluting P. Subsequent ion pairing chromatography of the Fe/P peak showed that phytic acid (myo-inositol 1, 2, 3, 4, 5, 6-hexakisphosphate: IP6) was the main Fe binding ligand, with the stoichiometry Fe4(IP6)18. When incubating the embryo tissue with phytase, the enzyme responsible for degradation of phytic acid, the extraction efficiency of both Fe and P was doubled, whereas that of Zn and S was unaffected. Protein degradation on the other hand, using protease XIV, boosted the extraction of Zn and S, but not that of Fe and P. Similar observations were made for the endosperm of rice grains. It is concluded that Fe and Zn have a different molecular speciation in cereal grain tissues; Zn appears mainly bound to peptides, while Fe is mainly associated with phytic acid.

Problems with Mn deficiency are significant in global crop production. Attempts to assess the plant availability of Mn have been impeded as it is highly redox sensitive and can be present in soil in a variety of chemical species having very different plant availability depending on the soil conditions. The Diffusive Gradients in Thin-films (DGT) technique is one of the most promising techniques for assessing plant nutrient and contaminant availability in soils. We tested the possibility of using DGT to assess Mn availability in soils under different conditions relevant to agricultural crops. It was found that it worked perfectly at pH 4 to 6 in model solutions with Mn concentrations relevant to agricultural soils. When different concentrations of competing cations (Ca, Mg, and Fe) were added at pH 6.5 the DGT still worked satisfactorily, but there were some indications that the highest concentrations influenced the DGT adsorbtion of Mn. Synchrotron analysis showed that Mn(II), which is the most prevalent oxidation state of Mn, was depleted in the soil when exposed to the DGT. Different soil deployment time showed that the DGT was able to register differences in plant availability caused by redox changes. Thus, our results suggest that the DGT technique may represent an efficient and reliable way of getting information on the plant availability of Mn in agricultural soils. Furthermore, the DGT technique appears to be a strong tool to assess the mechanisms controlling Mn availability in soil, including the redox potential and availability of carbon.

One of the most acute challenges in agriculture is to improve the efficiency of fertilisation to increase crop yields per unit area and simultaneously reduce climate and environmental footprints. Most soil based fertilisation strategies are remarkably inefficient due to chemical fixation, microbial immobilisation and leaching of nutrients to aqueous ecosystems. Nanofertilisation offers an attractive supplementary strategy as it allow us to manipulate the basic physico-chemical properties of mineral elements contained in nanoparticles and thereby bypass a range of those processes currently hampering an efficient uptake. Thus, bio-nanotechnology displays a range of emerging and fascinating possibilities, which pave the road to markedly improve nutrient use efficiency of both soil and foliar fertilisation. Here, we review how nanoparticles can be tailored with smart properties to better interact with root and leaf tissue for timely delivery of nutrients. Phosphorus fertilisation is used as a timely case to demonstrate how nanofertilisation can be developed to a stage where it can improve the poor phosphorus use efficiencies currently challenging modern agriculture on a global scale. [ABSTRACT FROM AUTHOR]

Phosphorus (P) deficiency is a global issue which can severely impact the yield of crops, including the P demanding and important food crop potato. Diagnosis of P status directly in the field can be used to adapt P fertilization strategies to the needs of the evolving crop during the growing season and is often estimated by analyzing P concentrations in leaf tissue. In this study, we investigate how diagnosis of P status in field grown potato plants is affected by leaf position and time of measurement in a randomized block experiment. The concentrations of many essential plant nutrients are highly dynamic, and large differences in nutrient concentrations were found in potato leaves depending on leaf age and time of sampling. During tuber initiation, P concentrations decreased in a steep gradient from the youngest leaves (0.8%) towards the oldest leaves (0.2%). The P concentrations in the youngest fully expanded leaf decreased by 25-33% within just 7 days, due to a high remobilization of P from source to sink tissue during crop development. 40 days later P concentrations in all leaves were near or below the established critical P concentration of 0.22%. The P concentration in leaf tissue thus depends on sampling time and leaf position on the plant, which in a practical setting might prevent a meaningful interpretation in terms of fertilizer recommendation. The chlorophyll a fluorescence parameter "P-predict", derived from the fluorescence transients, is an alternative to the classical chemical analysis of nutrient concentrations in leaf tissue. P-predict values serve as a proxy for the bioavailable P pool in the leaf and can be measured directly in the field using handheld technology. However, in conditions of high solar irradiation, the P-predict values of the most lightexposed leaf positions, i.e. the younger leaves, were found to be severely impacted by photoinhibition, preventing accurate characterization of the P status in potatoes. Shading the plants can reverse or prevent photoinhibition and restore the diagnostic capabilities of the P-predict approach. [ABSTRACT FROM AUTHOR]