Accumulation Of Mineral Elements Research Articles

Genetic background influences mineral accumulation in rice straw and grains under different soil pH conditions

Mineral element accumulation in plants is influenced by soil conditions and varietal factors. We investigated the dynamic accumulation of 12 elements in straw at the flowering stage and in grains at the mature stage in eight rice varieties with different genetic backgrounds (Japonica, Indica, and admixture) and flowering times (early, middle, and late) grown in soil with various pH levels. In straw, Cd, As, Mn, Zn, Ca, Mg, and Cu accumulation was influenced by both soil pH and varietal factors, whereas P, Mo, and K accumulation was influenced by pH, and Fe and Ni accumulation was affected by varietal factors. In grains, Cd, As, Mn, Cu, Ni, Mo, Ca, and Mg accumulation was influenced by both pH and varietal factors, whereas Zn, Fe, and P accumulation was affected by varietal factors, and K accumulation was not altered. Only As, Mn, Ca and Mg showed similar trends in the straw and grains, whereas the pH responses of Zn, P, K, and Ni differed between them. pH and flowering time had synergistic effects on Cd, Zn, and Mn in straw and on Cd, Ni, Mo, and Mn in grains. Soil pH is a major factor influencing mineral uptake in rice straw and grains, and genetic factors, flowering stage factors, and their interaction with soil pH contribute in a combined manner.

The Physiological Response Mechanism of Peanut Leaves under Al Stress.

Aluminum (Al) toxicity in acidic soils can significantly reduce peanut yield. The physiological response of peanut leaves to Al poisoning stress still has not been fully explored. This research examined the influences of Al toxicity on peanut leaves by observing the leaf phenotype, scanning the leaf area and perimeter, and by measuring photosynthetic pigment content, physiological response indices, leaf hormone levels, and mineral element accumulation. Fluorescence quantitative RT-PCR (qPCR) was utilized to determine the relative transcript level of specific genes. The results indicated that Al toxicity hindered peanut leaf development, reducing their biomass, surface area, and perimeter, although the decrease in photosynthetic pigment content was minimal. Al toxicity notably affected the activity of antioxidative enzymes, proline content, and MDA (malondialdehyde) levels in the leaves. Additionally, Al poisoning resulted in the increased accumulation of iron (Fe), potassium (K), and Al in peanut leaves but reduced the levels of calcium (Ca), manganese (Mn), copper (Cu), zinc (Zn), and magnesium (Mg). There were significant changes in the content of hormones and the expression level of genes connected with hormones in peanut leaves. High Al concentrations may activate cellular defense mechanisms, enhancing antioxidative activity to mitigate excess reactive oxygen species (ROS) and affecting hormone-related gene expression, which may impede leaf biomass and development. This research aimed to elucidate the physiological response mechanisms of peanut leaves to Al poisoning stress, providing insights for breeding new varieties resistant to Al poisoning.

Comparative impact of Arbuscular Mycorrhizal fungi from Moroccan soils and commercial inoculum on potato yield and nutrient composition

Potato (Solanum tuberosum L.) is a widely grown crop in Morocco. Mycorrhiza fertilization of potatoes needs to be monitored in order to observe their effects on the growth of potatoes. The aim of this study was therefore to test the effect of fungal strains on potato yield and tuber quality. The inoculation treatments included a commercial inoculum (T2), a natural inoculum (T3), represented by leek roots fragments, obtained after trapping by this host plant of AMF spores naturally present in the soil of the region of Guercif-Morocco, and a control treatment consisting of a sterile substrate. Our results showed significant differences in the frequency and intensity of mycorrhization between the T3 inoculum and the T2 inoculum, while control plants showed no AMF infection. Compared to the T1 control (non-inoculated plants), the gains in number of tubers/plant was 24% and 39% higher, whereas gains in yield was 34% and 48% higher for potato plants inoculated with T2 and T3 inocula, respectively. Furthermore, chemical analyses showed the important role of controlled mycorrhization in the accumulation of mineral elements; N, P, K, Zn, Cu and Fe in potato tubers. The T3 inoculum obtained from the soil of Guercif-Morocco allowed to obtain the best value of dry matter (16.82 g/100 g fM) and the best contents in Zn; K and P and the tubers.

Integrated transcriptomics and proteomics analysis reveals muscle metabolism effects of dietary Ulva lactuca and ulvan lyase supplementation in weaned piglets

Seaweeds, including the green Ulva lactuca, can potentially reduce competition between feed, food, and fuel. They can also contribute to the improved development of weaned piglets. However, their indigestible polysaccharides of the cell wall pose a challenge. This can be addressed through carbohydrase supplementation, such as the recombinant ulvan lyase. The objective of our study was to assess the muscle metabolism of weaned piglets fed with 7% U. lactuca and 0.01% ulvan lyase supplementation, using an integrated transcriptomics (RNA-seq) and proteomics (LC–MS) approach. Feeding piglets with seaweed and enzyme supplementation resulted in reduced macronutrient availability, leading to protein degradation through the proteasome (PSMD2), with resulting amino acids being utilized as an energy source (GOT2, IDH3B). Moreover, mineral element accumulation may have contributed to increased oxidative stress, evident from elevated levels of antioxidant proteins like catalase, as a response to maintaining tissue homeostasis. The upregulation of the gene AQP7, associated with the osmotic stress response, further supports these findings. Consequently, an increase in chaperone activity, including HSP90, was required to repair damaged proteins. Our results suggest that enzymatic supplementation may exacerbate the effects observed from feeding U. lactuca alone, potentially due to side effects of cell wall degradation during digestion.

Physiological responses of low- and high-cadmium accumulating Robinia pseudoacacia-rhizobium symbioses to cadmium stress

The role of rhizobia in alleviating cadmium (Cd) stress in woody legumes is still unclear. Therefore, two types of black locust (Robinia pseudoacacia L.) with high and low Cd accumulation abilities were selected from 11 genotypes in China, and the effects of rhizobium (Mesorhizobium huakuii GP1T11) inoculation on the growth, CO2 and H2O gas exchange parameters, Cd accumulation, and the absorption of mineral elements of the high (SX) and low Cd-accumulator (HB) were compared. The results showed that rhizobium-inoculation significantly increased biomass, shoot Cd contents, Cd accumulation, root-to-shoot translocation factor (TF) and the absorption and accumulation of mineral elements in both SX and HB. Rhizobium-inoculation increased chlorophyll a and carotenoid contents, and the intercellular carbon dioxide concentrations in HB plants. Under Cd exposure, the high-accumulator SX exhibited a significant decrease in photosynthetic CO2 fixation (Pn) and an enhanced accumulation of Cd in leaves, but coped with Cd exposure by increasing chlorophyll synthesis, regulating stomatal aperture (Gs), controlling transpiration (Tr), and increasing the absorption and accumulation of mineral elements. In contrast, the low-accumulator HB was more sensitive to Cd exposure despite preferential accumulation of Cd in roots, with decreased chlorophyll and carotenoid contents, but significantly increased root biomass. Compared to the low-accumulator HB, non-inoculated Cd-exposed SX plants had higher chlorophyll contents, and rhizobium-inoculated Cd-exposed SX plants had higher Pn, Tr, and Gs as well as higher levels of P, K, Fe, Ca, Zn, and Cu. In conclusion, the high- and low-Cd-accumulator exhibited different physiological responses to Cd exposure. Overall, rhizobium-inoculation of black locust promoted the growth and heavy metal absorption, providing an effective strategy for the phytoremediation of heavy metal-contaminated soils by this woody legume.

Identification of novel germplasm and genetic loci for enhancing mineral element uptake in soybean

Bioavailability, uptake, and spatial distribution of essential and toxic mineral elements are pivotal factors that govern crop growth, development, and productivity. Soybean is a major leguminous crop globally, and yield losses are commonly attributed to various abiotic factors, including nutrient deficiencies or the influence of toxic minerals in the soil. Therefore, understanding the molecular basis of differential mineral element uptake, translocation, and accumulation in soybean is vital for developing improved cultivars. Here, we used portable X-ray fluorescence (p-XRF) for rapid and high-throughput mineral element profiling of a diverse set of soybean germplasm using leaves, stem, root, and seed tissues. Genome-wide association (GWAS) was performed on the element profiles of 219 soybean accessions, revealing lines with notable two to tenfold difference in various mineral nutrient uptake. These identified lines represent valuable genetic resources for germplasm development and gene discovery. The GWAS analysis pinpointed significant genomic loci and haplotypes associated with accumulation of aluminum (Al), silicon (Si), iron (Fe), and manganese (Mn). Remarkably, genes associated with the transport of solutes, metals, and ions have been pinpointed, indicating their potential involvement in the nutrient uptake and soybean improvement. To gain functional insights, Si deposition, allelic variants and expression of three Si transporter genes was studied in greater details. The high Si accumulating line PI548452 showed 12-fold increase in leaf Si content compared to low Si lines. Expression of HiSil2b and HiSil2c effluxer genes showed root and leaf specific expression, respectively, providing evidence for tissue specific Si transport and the basis for precise management of Si uptake to improve abiotic and biotic stresses. In summary, this study uncovered the novel accessions, haplotypes, allelic diversity, and the potential candidate genes underpinning the mineral nutrient accumulation in soybean.

Agronomic and Genetic Strategies to Enhance Selenium Accumulation in Crops and Their Influence on Quality.

Selenium (Se) is an essential trace element that plays a crucial role in maintaining the health of humans, animals, and certain plants. It is extensively present throughout the Earth's crust and is absorbed by crops in the form of selenates and selenite, eventually entering the food chain. Se biofortification is an agricultural process that employs agronomic and genetic strategies. Its goal is to enhance the mechanisms of crop uptake and the accumulation of exogenous Se, resulting in the production of crops enriched with Se. This process ultimately contributes to promoting human health. Agronomic strategies in Se biofortification aim to enhance the availability of exogenous Se in crops. Concurrently, genetic strategies focus on improving a crop's capacity to uptake, transport, and accumulate Se. Early research primarily concentrated on optimizing Se biofortification methods, improving Se fertilizer efficiency, and enhancing Se content in crops. In recent years, there has been a growing realization that Se can effectively enhance crop growth and increase crop yield, thereby contributing to alleviating food shortages. Additionally, Se has been found to promote the accumulation of macro-nutrients, antioxidants, and beneficial mineral elements in crops. The supplementation of Se biofortified foods is gradually emerging as an effective approach for promoting human dietary health and alleviating hidden hunger. Therefore, in this paper, we provide a comprehensive summary of the Se biofortification conducted over the past decade, mainly focusing on Se accumulation in crops and its impact on crop quality. We discuss various Se biofortification strategies, with an emphasis on the impact of Se fertilizer strategies on crop Se accumulation and their underlying mechanisms. Furthermore, we highlight Se's role in enhancing crop quality and offer perspective on Se biofortification in crop improvement, guiding future mechanistic explorations and applications of Se biofortification.

Altitudinal Variation on Metabolites, Elements, and Antioxidant Activities of Medicinal Plant Asarum.

Asarum (Asarum sieboldii Miq. f. seoulense (Nakai) C. Y. Cheng et C. S. Yang) is a medicinal plant that contains asarinin and sesamin, which possess extensive medicinal value. The adaptation and distribution of Asarum's plant growth are significantly affected by altitude. Although most studies on Asarum have concentrated on its pharmacological activities, little is known about its growth and metabolites with respect to altitude. In this study, the physiology, ionomics, and metabolomics were investigated and conducted on the leaves and roots of Asarum along an altitude gradient, and the content of its medicinal components was determined. The results showed that soil pH and temperature both decreased along the altitude, which restricts the growth of Asarum. The accumulation of TOC, Cu, Mg, and other mineral elements enhanced the photosynthetic capacity and leaf plasticity of Asarum in high-altitude areas. A metabolomics analysis revealed that, at high altitude, nitrogen metabolism in leaves was enhanced, while carbon metabolism in roots was enhanced. Furthermore, the metabolic pathways of some phenolic substances, including syringic acid, vanillic acid, and ferulic acid, were altered to enhance the metabolism of organic acids. The study uncovered the growth and metabolic responses of Asarum to varying altitudes, providing a theoretical foundation for the utilization and cultivation of Asarum.

Interactive Effects between Zinc and Selenium on Mineral Element Accumulation and Fruit Quality of Strawberry

In this study, we evaluated zinc (Zn) and selenium (Se) biofortification in strawberry fruits under substrate and soil cultivation, along with their effects on mineral element accumulation and fruit quality. To achieve this, foliar Zn (0.1% and 0.2%) and Se (0.003% and 0.006%) fertilizers were applied separately or in combination at the initial flowering stage. The Zn and Se contents in strawberry fruits increased with the spraying dosage. Compared to the control, the Zn content in the first batch of Zn-treated strawberries increased by 36.9–109% and 27.1–102% under substrate and soil cultivation, respectively, while Se increased by 313–444% and 21.3–53.3%, respectively. However, foliar Zn application could not ensure long-term sustainability as Zn in strawberries gradually decreased in the two subsequent batches, while Se was more stable. Compared to the control, the Se content in the three batches of Se2 (0.006%)-treated strawberries grown in soil increased by 32.9%, 124%, and 109%, respectively. Meanwhile, compared to Se alone, the Zn–Se combined application decreased the Se content in strawberries by 61.2–77.6% and 24.9–45.7% under substrate and soil cultivation, respectively, while low doses of Se promoted Zn enrichment (by 8.62–40.9%) and high doses inhibited it (by 13.2–28.9%) under substrate cultivation. Moreover, the copper content in strawberries under substrate cultivation after the Se1 (0.003%) treatment was significantly higher (by 75.0%) than that in the control. A positive correlation was observed between Cu and Zn contents in strawberries under both substrate and soil cultivation. A consistent positive impact was also observed on fruit quality. The Se2 (0.006%) treatment caused an increase in ascorbic acid content (by 37.2%) in strawberry fruits. The soluble sugar content increased by 36.3% after the Zn1 (0.1%) treatment. The present study provides a practical basis for the biofortification of strawberries with Zn and Se.

Enhancing environmental monitoring: utilizing plant and soil assays to track pollution in a Turkish organized industrial zone

The aim of the current investigation was to determine the concentration of different metals in Mentha spicata L. subsp. tomentosa plants and soils in order to highlight the pollution level in a Turkish Organized Industrial Zone in Dilovasi District, in Kocaeli City. The concentration of metals in plant and soil samples were examined. When the soil values were examined, the highest cadmium, chromium, copper, iron, nickel, and lead levels were collected from the location which is hosting numerous industrial facilities. All elements except boron and copper, exceeded normal limits in the leaf samples while cadmium, chromium, iron, nickel, lead, and zinc reached “toxic levels” in leaf samples. Heavy metals were accumulated in leaves more than rhizomes. Mineral element uptake and accumulation were affected from heavy metal amounts, especially in rhizomes. Although washing procedure notably reduced the concentration of some heavy metals in leaves samples, the reduced values were higher than acceptable levels in some locations of the district. According to the data, it may be said that the region, especially its industrialized parts are heavily polluted by heavy metals. Moreover, in the accordance with the fact that, the highest values of elements were determined in regions having considerable industrial activity such as metal and plastic processing facilities. Additionally, Mentha spicata plants exhibited higher heavy metal values in areas with high heavy metal content in the soil, and lower heavy metal values in areas with low heavy metal concentration. These findings indicate that Mentha spicata, a plant known for its medicinal and culinary uses, can be considered as an effective biomonitor for heavy metal pollution in the region. Consequently, constant inspection is required to prevent the excessive buildup of metals in the region and similar areas with comparable characteristics in terms of human life.

Extreme low-temperature events can alleviate micronutrient deficiencies while increasing potential health risks from heavy metals in rice

Despite global warming, extreme low-temperature stress (LTS) events pose a significant threat to rice production (especially in East Asia) that can significantly impact micronutrient and heavy metal elements in rice. With two billion people worldwide facing micronutrient deficiencies (MNDs) and widespread heavy metal pollution in rice, understanding these impacts is crucial. We conducted detailed extreme LTS experiments with two rice (Oryza sativa L.) cultivars (Huaidao 5 and Nanjing 46) grown under four temperature levels (from 21/27 °C to 6/12 °C) and three LTS durations (three, six, and nine days). We observed significant interaction effects for LTS at different growth stages, durations and temperature levels on the contents and accumulation of mineral elements. The contents of most mineral elements (such Fe, Zn, As, Cu, and Cd) increased significantly under severe LTS at flowering, but decreased under LTS at the grain-filling stage. The accumulations of all mineral elements decreased at the three growth stages under LTS due to decreased grain weight. The contents and accumulation of mineral elements were more sensitive to LTS at the peak flowering stage than at the other two stages. Furthermore, the contents of most mineral elements in Nanjing 46 show larger variation under LTS compared to Huaidao 5. Accumulated cold degree days (ACDD, °C·d) were found to be suitable for quantifying the effects of LTS on the relative contents and accumulations of mineral elements. LTS at the flowering stage will help alleviate MNDs, but may also increase potential health risks from heavy metals. These results provide valuable insights for evaluating future climate change impacts on rice grain quality and potential health risks from heavy metals.

Comparative effects of copper nanoparticles and copper oxide nanoparticles on physiological characteristics and mineral element accumulation in Brassica chinensis L

In this study, the short–term toxicity of Cu NPs, CuO NPs, and CuSO4 on bok choy (Brassica chinensis L.) under hydroponic conditions was evaluated using indicators such as biomass, net photosynthesis rate, root morphology, enzyme activity, and Cu accumulation and subcellular distribution. Results showed that CuO NPs exposure notably increased the biomass, root length, and root tip number by 22.0%, 22.7%, and 82.9%, respectively, whereas Cu NPs and CuSO4 significantly reduced root biomass, net photosynthetic rate (PN), and root length by 31.2% and 44.2%, 24.5% and 32.2%, and 43.4% and 40.6%, respectively. In addition, Cu NPs, CuO NPs and CuSO4 exposure increased the distribution of Cu in soluble component and cell wall. Moreover, short–term exposure to different Cu forms significantly affected mineral element accumulation in bok choy. For instance, Cu NPs exposure reduced the concentrations of Mg, Ca and Mn in edible part by 21.7%, 16.1% and 23.2%, respectively. CuSO4 exposure reduced the concentrations of Mg and Ca in edible part by 12.3% and 50.1%, respectively. CuO NPs caused a significant increase of 30.4% for Ca concentration in root, 34.5% and 34.5% for K and Mn concentration in edible part. Over all, CuO NPs exposure was beneficial for plant growth. These findings help understand the phytotoxic effect of different Cu forms on bok choy, and CuO NPs has the potential to be applied to improve nutrition and prompt growth in edible plants.

Effects of Mineral-Based Potassium Humate on Cadmium Accumulation in Rice (Oryza sativa L.) under Three Levels of Cadmium-Contaminated Alkaline Soils

Humic acid amendments in the remediation of soils contaminated with heavy metals have received widespread attention. However, the impacts and related mechanisms of mineral-based humate substances on the remediation of alkaline paddy soils with different levels of cadmium (Cd) contamination are still unclear. Pot trials with four mineral-based potassium humate (MBPH) doses (0, 0.25%, 0.5%, 1%, w/w) and three Cd rates (slightly, moderately, and highly, 1, 2, and 4 mg Cd kg−1) were conducted to evaluate the effects of MBPH on rice. Results showed that the application of MBPH effectively reduced brown rice Cd concentrations of all Cd rates by 46.82–65.04%, 44.02–59.21%, and 15.84–43.99%, such that Cd in brown rice fell within the safe edible standards in the highly contaminated soils with the 0.5% and 1% MBPH applications. The application of MBPH significantly alleviated Cd toxicity by increasing soil solution pH, dissolved organic carbon (DOC), and potassium (K) and decreasing free Cd and the bioavailability of rhizosphere soil Cd, as reflected by promoting rice plant growth, photosynthesis, Fv/Fm, and antioxidant enzymes activities. Additionally, high dose applications (0.5% and 1%) of MBPH significantly reduced the translocation factor of Cd from flag leaf to brown rice. Furthermore, the application of MBPH enhanced the accumulation of mineral elements (iron, manganese, copper, zinc, potassium) in brown rice. Stepwise regression analysis revealed that soil solution K at maturity stage and soil solution DOC at tillering and filling stages were the most important factors affecting Cd accumulation in brown rice under slightly, moderately, and highly Cd-contaminated soils, respectively. Therefore, MBPH application on slightly and moderately Cd-contaminated alkaline soils contributed to achieving rice grains rich with mineral elements but Cd free and Cd safe in highly Cd-contaminated soil.

Identifying the Genetic Basis of Mineral Elements in Rice Grain Using Genome-Wide Association Mapping.

Mineral malnutrition is a major problem in many rice-consuming countries. It is essential to know the genetic mechanisms of accumulation of mineral elements in the rice grain to provide future solutions for this issue. This study was conducted to identify the genetic basis of six mineral elements (Cu, Fe, K, Mg, Mn, and Zn) by using three models for single-locus and six models for multi-locus analysis of a genome-wide association study (GWAS) using 174 diverse rice accessions and 6565 SNP markers. To declare a SNP as significant, -log10(P) ≥ 3.0 and 15% FDR significance cut-off values were used for single-locus models, while LOD ≥ 3.0 was used for multi-locus models. Using these criteria, 147 SNPs were detected by one or two GWAS methods at -log10(P) ≥ 3.0, 48 of which met the 15% FDR significance cut-off value. Single-locus models outperformed multi-locus models before applying multi-test correction, but once applied, multi-locus models performed better. While 14 (~29%) of the identified quantitative trait loci (QTLs) after multiple test correction co-located with previously reported genes/QTLs and marker associations, another 34 trait-associated SNPs were novel. After mining genes within 250 kb of the 48 significant SNP loci, in silico and gene enrichment analyses were conducted to predict their potential functions. These shortlisted genes with their functions could guide future experimental validation, helping us to understand the complex molecular mechanisms controlling rice grain mineral elements.

Cultivar-specific response of rhizosphere bacterial community to uptake of cadmium and mineral elements in rice (Oryza sativa L.)

Toxic metal-contaminated farmland from Cadmium (Cd) can enhance the accumulation of Cd and impair the absorption of mineral elements in brown rice. Although several studies have been conducted on Cd exposure on rice, little has been reported on the relationship between Cd and mineral elements in brown rice and the regulatory mechanism of rhizosphere microorganisms during element uptake. Thus, a field study was undertaken to screen japonica rice cultivars with low Cd and high mineral elements levels, analyze the quantitative relationship between Cd and seven mineral elements, and investigate the cultivar-specific response of rice rhizosphere bacterial communities to differences in Cd and mineral uptake in japonica rice. Results showed that Huaidao-9 and Xudao-7 had low Cd absorption and high amounts of mineral nutrient elements (Fe, Zn, Mg, and Ca, LCHM group), whereas Zhongdao-1 and Xinkedao-31 showed opposite accumulation characteristics (HCLM group). Stepwise regression analysis showed that zinc, iron, and potassium are the key minerals that affect Cd accumulation in japonica rice and zinc was the most important factor, accounting for 68.99 %. The accumulation of Cd and mineral elements is potentially associated with rhizosphere soil bacteria. Taxa enriched in the LCHM rhizosphere (phyla Acidobacteriota and MBNT15) indicated the high nutrient characteristics of the soil and reduced activity of Cd in soil. The HCLM rhizosphere was highly colonized by metal-activating bacteria (Actinobacteria), lignin-degrading bacteria (Actinobacteria and Chlorofexi), and bacteria scavenging nutrients and trace elements (Anaerolinea and Ketobacter). Moreover, the differences in the uptake of Cd and mineral elements affected predicted functions of microbial communities, including sulfur oxidation and sulfur derivative formation, human or plant pathogen, and functions related to the iron oxidation and nitrate reduction. The results indicate a potential association of Cd and mineral elements uptake and accumulation with rhizosphere bacteria in rice, thus providing theoretical basis and a new perspective on the maintenance of rice security and high quality simultaneously.

Fast X-ray fluorescence microscopy provides high-throughput phenotyping of element distribution in seeds.

The concentration, chemical speciation, and spatial distribution of essential and toxic mineral elements in cereal seeds have important implications for human health. To identify genes responsible for element uptake, translocation, and storage, high-throughput phenotyping methods are needed to visualize element distribution and concentration in seeds. Here, we used X-ray fluorescence microscopy (μ-XRF) as a method for rapid and high-throughput phenotyping of seed libraries and developed an ImageJ-based pipeline to analyze the spatial distribution of elements. Using this method, we nondestructively scanned 4,190 ethyl methanesulfonate (EMS)-mutagenized M1 rice (Oryza sativa) seeds and 533 diverse rice accessions in a genome-wide association study (GWAS) panel to simultaneously measure concentrations and spatial distribution of elements in the embryo, endosperm, and aleurone layer. A total of 692 putative mutants and 65 loci associated with the spatial distribution of elements in rice seed were identified. This powerful method provides a basis for investigating the genetics and molecular mechanisms controlling the accumulation and spatial variations of mineral elements in plant seeds.

Nutrient accumulation and transcriptome patterns during grain development in rice.

Rice is an important source of calories and mineral nutrients for more than half of the world's population. The accumulation of essential and toxic mineral elements in rice grain affects its nutritional quality and safety. However, the patterns and processes by which different elements progressively accumulate during grain filling remain largely unknown. In the present study, we investigated temporal changes in dry matter, elemental concentrations, and the transcriptome in the grain of field-grown rice. We also investigated the effects of seed setting rate and the position of the grain within the rice panicle on element accumulation. Three different patterns of accumulation were observed: (i) elements including K, Mn, B, and Ca showed an early accumulation pattern; (ii) dry matter and elements including N, P, S, Mg, Cu, Zn, Mo, As, and Cd showed a mid accumulation pattern; and (iii) elements such as Fe showed a gradual increase pattern. These different accumulation patterns can be explained by the differences in the biogeochemical behavior of the various elements in the soil, as well as differences in plant nutrient redistribution, gene expression, and the sink-source relationship. These results improve our knowledge of the dynamics of elemental accumulation in rice grain and are helpful for identification of functional genes mediating the translocation of elements to grain.

Nitric Oxide Is Essential for Melatonin to Enhance Nitrate Tolerance of Cucumber Seedlings

Melatonin (MT) and nitric oxide (NO) in plants can function cooperatively to alleviate salt stress, sodic alkaline stress and immune response, as well as adventitious root formation. The interaction of MT and NO on the nitrate stress tolerance of cucumber seedlings are not well understood. We investigated the effects of exogenous MT, NO donor (SNP) and NO scavenger (cPTIO) on the growth; photosynthesis; characteristics of root morphological; accumulation of mineral elements, endogenous NO, MT, IAA and ABA; and related genes expression in cucumber (Cucumis sativus L. “Jin You No. 1”) seedlings grown under high nitrate condition (HN). The results showed that MT and NO independently alleviated the inhibition of growth and photosynthesis capacity of cucumber seedlings under nitrate stress. NO was required for MT to enhance the root activity, root length, lateral root number and the accumulation of calcium, magnesium and iron in the roots of cucumber seedlings grown under nitrate stress. Consistently, the expression of adventitious rootless 1 gene (CsARL1) was modulated. Furthermore, exogenous MT induced accumulation of endogenous MT, NO, indole-3-acetic acid (IAA) and abscisic acid (ABA), mainly within 24 h after treatment, in which MT and NO were further increased at 48 h and 96 h, IAA and ABA were further increased at 16 h in the presence of SNP. In contrast, the accumulation of endogenous IAA, MT and ABA slightly decreased within 24 h, NO significantly decreased at 192 h in the presence of cPTIO. Correspondingly, the expression levels of genes involved in nitrogen metabolism (CsNR1 and CsNR2), MT metabolism (CsT5H, CsSNAT2 and Cs2-ODD33), auxin carriers and response factors (CsAUX1, CsGH3.5, CsARF17), ABA synthesis and catabolism (CsNCED1, CsNCED3 and CsCYP707A1) were upregulated by MT, in which CsNR1, CsNR2, CsAUX1, CsNCED3 and CsT5H were further induced in the presence of SNP in roots of cucumber seedlings. These observations indicated that NO act as a crucial factor in MT, alleviating nitrate stress through regulating the mechanism of root growth in cucumber seedlings.

DROUGHT EFFECTS ON MINERAL COMPOSITION OF THE LEAVES AND SEEDS OF AMARANTHUS TRICOLOR AND AMARANTHUS CRUENTUS

In global climate change, drought stress is one of the environmental restraining factors that can significantly influence the growth and development of crop plants. Drought stress conditions can also cause undesirable changes in plant physiological and metabolic processes. The influence of soil drought on the mineral composition of leaves and seeds of two species of amaranth (Amaranthus tricolor L. and Amaranthus cruentus L.) with С4-type of photosynthesis was studied through energy dispersive spectrometry (ESD). The recent investigations were carried out during the years 2020–2022 at the Department of Genofonde and Bioresources of Plants, Federal Scientific Center for Horticulture, Moscow, Russia. The research results showed the leaves of both amaranth with major elements, i.e., K (11.23–15.33), Ca (5.15–7.61), P (3.91–3.92), Mg (2.81–3.36), and Cl (1.86–2.29), whereas, relatively lower values were recorded for Fe (0.05–0.48), and Na (0.07–0.11) mass% respectively. Regarding amaranth plants seed composition, the major elements were K (13.86–13.97), P (7.02–9.76), Mg (3.78–5.64), Ca (3.31–4.78), Cl (2.81–5.30), and Mo (2.80–2.86) mass% respectively. In the species, A. tricolor, a strong correlation was observed between the elements, i.e., S-Cu, Mg-Si, Na-Cu, Na-S, Na-Ca, Na-Si, and Si-S in leaves, while in seeds, these were between Ca-Cu, Mg-Cl, Si-Mn, Ca-Mo, and Cl-Mn. In the other species of amaranth, A. cruentus, the elements viz., Mg-S, Mg-Mo, S-Mo, Mg-Cl, S-Cl, Cl-Mo, Cl-P, P-S, Si-Cl, Ca-Mo, S-Ca, Mg-Ca, Mg-P, P-Mo, and Mg-Si in leaves, while Ni-Cu, Mg-P, Si-P, and Si-Cl in seeds also showed strong relationship. Effects of drought led to a weakening of these ties and the formation of new ones. The accumulation of mineral elements in the leaves of amaranth plants varies from species to species under drought conditions, and A. tricolor cv. Valentina was found most resistant to drought conditions.

Effects of Mn2+ on Cd accumulation and ionome in rice and spinach.

Health risks caused by food containing Cd is a concern worldwide. Interaction between Mn and Cd has been widely studied in normal hydroponic solution with high ion activities (e.g., the study on sharing of transporter Natural Resistance-Associated Macrophage Protein 5 between Mn and Cd in rice [Oryza sativa L.]). However, interaction of Mn and Cd in crops like rice and spinach (Spinacia oleracea L.) at field ion activity level is still unknown. Thus, an ethyleneglycoltetraacetate-buffered solution experiment was conducted to explore the effect of Mn on the uptake and accumulation of Cd and other mineral elements in rice and spinach. In rice, antagonism of Mn and Cd was only observed in roots at deficient and toxic levels of external Mn2+ . Compared with those at Mn2+ sufficiency (pMn2+ 6.7-5.3), average root Cd levels were elevated significantly by 1.85-3.05 times at Mn2+ deficiency (pMn2+ 8.2) but decreased by 1.57-2.59 times at Mn2+ toxicity (pMn2+ 4.8). The antagonism between Mn and K/Mg in rice shoots might be caused by their common role in physiological processes in plants. Antagonism of Mn/Ni in spinach in this work was consistent with their shared transporters in dicots. Results about the antagonism of root Cd/Mn at Mn2+ deficiency suggest that sufficiently available Mn2+ is significant to reduce Cd uptake in rice under field levels of ion activity, but it was not for spinach because the change of tissue Cd was insignificant with the increase of Mn2+ activity from deficiency to toxicity.