Mineral Nutrients Research Articles

Bacterial community present in the earthworm’s gut and its role in soil biology and health

Earthworms are known as ecological engineers due to their significant role in enhancing soil health and productivity. Various factors such as temperature, moisture, acidity, pH, sunlight and the availability of organic matter influence their presence in soil. Earthworms exhibit diverse feeding and burrowing behaviors, which lead to crucial ecological processes within terrestrial ecosystems. Their interactions with soil result in the colonization of their gut and surrounding soil by diverse bacterial communities, including key species such as Escherichia coli, Streptomyces, Bacillus and Pseudomonas. These bacteria aid in the digestion of organic and inorganic matter, thereby altering soil physio-chemical properties and enhancing nutrient mineralization, which promotes plant growth. Additionally, earthworms influence nutrient cycling by modifying microbial soil populations and the bacterial communities in their gut and adjacent soil contribute to phytoremediation. This review delves into the types of bacterial populations found in the earthworm’s gut and surrounding soil, elucidating their specific roles and contributions to the terrestrial ecosystem. By understanding these complex interactions, we can better appreciate the vital role earthworms and their associated bacterial communities play in soil biology. This knowledge is essential for developing sustainable agricultural practices and improving soil management strategies, ultimately contributing to healthier and more productive ecosystems.

Comprehensively assessing the effects of exogenous proline on nutritional and flavour quality of celery (Apium graveolens L.) under salt stress

Salt stress is one of the constraints limiting high-yield and high-quality cultivation of vegetables, currently, the effect of exogenous proline on the quality of celery under salt stress is rarely reported. The study aimed to explore the comprehensive effects of exogenous proline application on the quality of celery (Apium graveolens L.) under salt stress. The affiliation function method was used to comprehensively analyze the effects of foliar application of 0.3 mM proline on celery mineral nutrients, amino acids, organic acids, nitrate, dietary fiber, and volatile components under 100 mM NaCl stress. Results showed that exogenous proline application inhibited Na content and nitrate enrichment in celery, and promoted the accumulation of other mineral elements (N, P, K, Ca, Mg, Cu, Fe, Mn and Zn), glycine, oxalic acid, malic acid, citric acid, lignin, dietary fiber, and aromatic compounds in leaves and petioles under salt stress. In addition, the results of a comprehensive evaluation analysis of the affiliation function indicated that the application of exogenous proline to salt-stressed seedlings was an effective treatment which significantly mitigated the salt-induced detrimental effects. Overall, exogenous proline played a positive role in regulating the balance of mineral elements, accumulation of glycine, accumulation of organic acids, and enrichment of aromatic substances in celery under salt stress. Results from this study provides a theoretical basis for cultivating cultivation of high quality celery under saline conditions.

Spatial-spectral feature mining in hyperspectral corn leaf venation structure and its application in nitrogen content estimation

The growth of corn plants requires a significant amount of nitrogen nutrient supply to ensure the yield. Meanwhile, overfertilization could result in adverse environmental impacts, making it crucial to monitor the nitrogen supply condition in corn plants precisely. Hyperspectral imaging (HSI) could be the solution to this challenge, as HSI plant phenotyping technology has been widely utilized to nondestructively identify plant traits, such as mineral nutrient deficiencies in corn plants. However, limitations persist where the conventional HSI nitrogen prediction models mainly relied on the overall colors of the plant tissue extracted from the spectral domain but rarely included the spatially distributed information on the leaf level. This study aimed to examine if including new information from the spatial domain could potentially improve the performance of HSI models. Because the venation structure plays a crucial role in the distribution of various nutrients across the leaf, a series of physiological responses caused by nitrogen deficiency could result in non-uniform color patterns related to the veins. The recent advancement of HSI techniques such as LeafSpec, whose imaging quality and spatial-spectral resolution have been significantly improved, made it possible to extract the venation structure together with high-resolution spatial-spectral features. In this study, the hypothesis was that utilizing high-resolution spatial-spectral features extracted based on the venation structure could yield a better-performed nitrogen content prediction model compared to the averaged spectrum of the corn leaf. First, a venation structure segmentation algorithm was developed using the Local Binary Patterns (LBP) method for hyperspectral corn leaf images scanned with LeafSpec. Second, for every hyperspectral leaf image, 131 spectral index heatmaps were generated, and 30 leaf regions were picked based on the venation structure, resulting in 3930 spatial-spectral features. Third, the features were picked using the Least Absolute Shrinkage and Selection Operator (LASSO) regression. As the results tested with a field assay involving two different corn genotypes and two nitrogen treatments, the Partial Least Square Regression (PLS-R) model built with selected spatial-spectral features outperformed the model built with the averaged leaf spectra in terms of the Root Mean Squared Error (RMSE) of predictions. The results provided encouraging proof and guidance for the potential benefit of using high-resolution spatial-spectral features derived from hyperspectral leaf images to improve the accuracy and robustness of the nitrogen content prediction models for corn plants.

From intercropping to monocropping: the effects of Pseudomonas strain to facilitate nutrient efficiency in peanut and soil

As an oilseed crop, the yield and quality of peanuts are severely constrained by nutrient deficiencies, particularly in calcareous soils in northern China. Maize-peanut intercropping is an effective strategy to enhance mineral nutrient efficiency in peanuts via plant-microbe interaction, but the underlying mechanisms remain elusive. Here, we conducted experiments using a Pseudomonas strain (Pse.IP6) with diverse beneficial characteristics, which was isolated from the rhizosphere of intercropped peanuts. Additionally, Pse.IP6 exhibits high phylogenetic similarity with the Amplicon Sequence Variants 48 (ASV48) which belongs to Pseudomonas and is positively correlated with Fe in plants and soil in intercropping. To confirm the plant growth-promoting potential of Pse.IP6 and its role in intercropping advantage, we constructed pot experiments. Results revealed that Pse.IP6 promoted shoot growth and root development, as well significantly enhanced SPAD value, net photosynthetic rate, stomatal conductance, and transpiration rate of peanut leaves. Moreover, the application of Pse.IP6 resulted in a notable accumulation of nitrogen (N), phosphorus (P), and potassium (K) in shoot and active iron (Fe) in leaves, accompanied by an increased K-N ratio. The primary reason for the nutrient promotion is the enhancement of the bioavailability of nitrate, ammonium, P, K, and Fe in the rhizosphere. Collectively, our findings demonstrate that Pse.IP6, enriched in intercropping peanut, is a plant growth-promoting bacteria, represented by transferring the intercropping advantage on nutrients activation to monocropping peanuts. Our results offer insights into plant-rhizobacteria interaction mechanisms and therefore provide a rhizobacteria-based pathway to improve nutrient efficiency and productivity of crops.

Nutrient-dependent regulation of symbiotic nitrogen fixation in legumes

Abstract Mineral nutrients are essential for plant growth and development, playing a critical role in the mutualistic symbiosis between legumes and rhizobia. Legumes have evolved intricate signaling pathways that respond to various mineral nutrients, selectively activating genes involved in nodulation and nutrient uptake during symbiotic nitrogen fixation (SNF). Key minerals, including nitrogen (N), calcium (Ca), and phosphorus (P), are vital throughout the SNF process, influencing signal recognition, nodule formation, the regulation of nodule numbers, and the prevention of nodule early senescence. Here we review recent advancements in nutrient-dependent regulation of root nodule symbiosis, focusing on the systemic autoregulation of nodulation (AON) in nitrate-dependent symbiosis, the roles of NIN-like proteins (NLPs), and the function of essential nutrients and their associated transporters in legume symbiosis. Additionally, we discuss several key research areas that require further exploration to deepen our understanding of nutrient-dependent mechanisms in SNF.

Nitrogen, phosphorus and potassium budget in crop production in South-Asia: regional and country trends during the last five decades

Nutrient budgeting for cropland is a crucial tool for assessing nutrient mining or excess application. We estimated the nutrient budget of nitrogen (N), phosphorus (P), and potassium (K) in cropland for South Asia during the last five decades (from 1970 to 2018) using equation-based empirical methods. Nutrient budget for the last five decades shows a negative balance of N (3.94 million tons, Mt), P (23.87 Mt), and K (247.23 Mt). Inorganic fertilizer remained the major input source for N and P, and its decadal average share increased for N (from 27.9% to 72.8%) and P (from 72.1% to 94.5%) from 1970 to 2010s and the share of manure, deposition, and crop residue to N, P and K input decreased. Deposition remained a major source of K input and its share decreased from 64.0% to 35.5% during the period. The share of crop removal to the decadal output of N (58.6% to 53.4%) and P (49.0% to 23.1%) decreased, and K (72.5% to 76.0%) increased from 1970 to 2010s. The higher losses of fertilizer N, and accumulation of P and K fertilizers in soils, resulted in decreasing partial factor productivity of N (from 72.2% to 16.9%), P (from 217.0% to 42.2%), and K (from 480.3% to 113.8%) from 1970 to 2018. Nutrient budget helps in identifying the regional imbalance (mining/accumulation) of the major nutrients, it will provide valuable information on the present status of country-level nutrient use for reorientation of their nutrient/fertilizer use policies.

Sulfur redirects carbon metabolism to optimize nitrogen utilization and promote andrographolide biosynthesis in Andrographis paniculata seedlings

Sulfur (S) is an important mineral nutrient element that improves plant growth and secondary metabolism. S affects the biosynthesis of andrographolide in medicinal plant Androgaphis paniculata by regulating nitrogen (N) metabolism. However, its specific role in N utilization and the connection with andrographolide biosynthesis have not yet been thoroughly understood. Here, a soilless cultivation experiment with low S (LS, 0.1 mM) and high S (HS, 2.4 mM) was conducted to investigate how S influences carbon (C) metabolism and N utilization to promote andographolide biosynthesis in Andrographis paniculata. The results showed that HS significantly increased plant biomass and N use efficiency (NUE), accompanying with remarkable enhanced andrographolide content. HS promoted the expression of photosynthetic genes, and redirected C metabolism towards to sugars accumulation by enhancing the activities of NAD-dependent glutamate dehydrogenase (NAD-GDH), malic enzyme (ME) and phosphoenolpyruvate carboxykinase (PEPCK) (P < 0.05). On the other hand, HS reduced N and S assimilation, and stimulated a greater N allocation in photosynthesis. Accordingly, NUE was increased and andrographolided biosynthesis could profit from the shift of C resource reallocation. Additionally, the significantly increased activities of ME, glucose 6-phosphate dehydrogenase (G6PDH) and isocitrate dehydrogenase (ICDH) provided reductants for secondary metabolism. HS also considerably upregulated the expression of genes in andrographolide biosynthetic pathway, including ApDXS, ApDXR, ApHDS and ApHDR in the MEP pathway, and ApGGPS. Transcription factors in the families of MYB, WRKY, ERF and bHLH, and plant hormones ABA and JA were in response to HS. Our results revealed that S synergistically promotes NUE and andrographolide biosynthesis via remodeling of C metabolism in A. paniculata.

Soil organic matter interactions along the elevation gradient of the James Ross Island (Antarctica)

Abstract. Around half of the Earth's soil organic carbon (SOC) is presently stored in the Northern Hemisphere permafrost region. In polar permafrost regions, low temperatures particularly inhibit both the production and biodegradation of organic matter. Under such conditions, abiotic factors such as mesoclimate, pedogenic substrate or altitude are thought to be more important for soil development than biological factors. In Antarctica, biological factors are generally underestimated in soil development due to the rare occurrence of higher plants and the short time since deglaciation. In this study, we aim to assess the relationship between SOC and other soil properties related to the pedogenic factors or properties. Nine plots were investigated along the altitudinal gradient from 10 to 320 m in the deglaciated area of James Ross Island (Ulu Peninsula) using a parallel tea-bag decomposition experiment. SOC contents showed a positive correlation with the content of easily extractable glomalin-related soil protein (EE-GRSP; Spearman r=0.733, P=0.031) and the soil buffering capacity (expressed as ΔpH; Spearman r=0.817, P=0.011). The soil-available P was negatively correlated with altitude (Spearman r=-0.711, P=0.032), and the exchangeable Mg was negatively correlated with the rock fragment content (Spearman r=-0.683, P=0.050). No correlation was found between the available mineral nutrients (P, K, Ca and Mg) and SOC or GRSP. This may be a consequence of the inhibition of biologically mediated nutrient cycling in the soil. Therefore, the main factor influencing nutrient availability in these soils does not seem to the biotic environment; rather, the main impact appears to stem from the abiotic environment influencing the mesoclimate (altitude) or the level of weathering (rock content). Incubation in tea bags for 45 d resulted in the consumption and translocation of more labile polyphenolic and water-extractable organic matter, along with changes in the C content (increase of up to +0.53 % or decrease of up to −1.31 % C) and a decrease in the C:N ratio (from 12.5 to 7.1–10.2), probably due to microbial respiration and an increase in the abundance of nitrogen-binding microorganisms. Our findings suggest that one of the main variables influencing the SOC/GRSP content is not the altitude or coarse-fraction content (for which a correlation with SOC/GRSP was not found); rather, we suspect effects from other factors that are difficult to quantify, such as the availability of liquid water.

Influence of Electrical Conductivity on Plant Growth, Nutritional Quality, and Phytochemical Properties of Kale (Brassica napus) and Collard (Brassica oleracea) Grown Using Hydroponics

Kale (Brassica napus) and collard (Brassica oleracea) are two leafy greens in the family Brassicaceae. The leaves are rich sources of numerous health-beneficial compounds and are commonly used either fresh or cooked. This study aimed to optimize the nutrient management of kale and collard in hydroponic production for greater yield and crop quality. ‘Red Russian’ kale and ‘Flash F1’ collard were grown for 4 weeks after transplanting in a double polyethylene-plastic-covered greenhouse using a nutrient film technique (NFT) system with 18 channels. Kale and collard were alternately grown in each channel at four different electrical conductivity (EC) levels (1.2, 1.5, 1.8, and 2.1 mS·cm−1). Fresh and dry yields of kale increased linearly with increasing EC levels, while those of collard did not increase when EC was higher than 1.8 mS·cm−1. Kale leaves had significantly higher P, K, Mn, Zn, Cu, and B than the collard at all EC levels. Additionally, mineral nutrients (except N and Zn) in leaf tissue were highest at EC 1.5 and EC 1.8 in both the kale and collard. However, the changing trend of the total N and NO3- of the leaves showed a linear trend; these levels were highest under EC 2.1, followed by EC 1.8 and EC 1.5. EC levels also affected phytochemical accumulation in leaf tissue. In general, the kale leaves had significantly higher total anthocyanin, vitamin C, phenolic compounds, and glucosinolates but lower total chlorophylls and carotenoids than the collard. In addition, although EC levels affected neither the total chlorophyll or carotenoid content in kale nor glucosinolate content in either kale or collard, other important health-beneficial compounds (especially vitamin C, anthocyanin, and phenolic compounds) in kale and collard leaves reduced with the increasing EC levels. In conclusion, the kale leaf had more nutritional and phytochemical compounds than the collard. An EC level of 1.8 mS·cm−1 was the optimum EC level for the collard, while the kale yielded more at 2.1 mS·cm−1. Further investigations are needed to optimize nitrogen nutrition for hydroponically grown kale.

Advancements in Hydroponic Systems: A Comprehensive Review

Hydroponics, the practice of growing plants without soil using mineral nutrient solutions in water, represents a significant shift in agricultural methodologies. Modern hydroponic systems have evolved substantially since the early 20th century, with advancements in system design, automation, nutrient management, and environmental control enhancing efficiency, scalability, and applicability. This review examines recent innovations that have addressed traditional challenges and created new opportunities for hydroponic cultivation. Hydroponics offers advantages over traditional soil-based agriculture, including precise nutrient control, reduced water usage, and the elimination of soil-borne diseases and pests. These benefits are critical in addressing modern agricultural challenges such as soil degradation, water scarcity, and the need for increased food production for a growing global population. Hydroponic systems can be implemented in diverse environments, making them adaptable solutions for enhancing food security and sustainability. Key developments in various hydroponic systems are highlighted, including the Nutrient Film Technique (NFT), Deep Water Culture (DWC), Ebb and Flow, Aeroponics, Wick Systems, and Drip Systems. Innovations in these systems focus on optimizing nutrient delivery, oxygenation, and integrating sensors for precise control, improving overall performance and yield. Technological advancements, such as automation and control systems, sensors, and monitoring technologies, have revolutionized hydroponic farming by enabling real-time data collection and environmental management. The integration of the Internet of Things (IoT) and smart farming practices, combined with data analytics and machine learning, has further optimized system performance and decision-making. LED lighting and vertical farming techniques have maximized space utilization and improved crop yields, particularly in urban environments. Advances in nutrient solutions, disease management, and water quality have optimized plant health and resource efficiency. Economic and environmental considerations, including cost-benefit analyses and comparisons with traditional agriculture, highlight the potential for hydroponics to offer better returns on investment and reduce environmental impact. Despite the significant progress, challenges such as high initial setup costs and technical complexities remain. Future research opportunities and interdisciplinary collaborations are essential to address these challenges and drive further innovation in hydroponic farming.

Crucial role of fungi in environmentally sustainable agriculture

To produce more, better and safer food we must be able to do so while promoting the sustainable use of agricultural resources. The increase in agricultural production is currently through the use of pesticides, fertilizers, and developments in plant breeding and genetic skills. In naturally existing ecosystems, rhizospheric soils have biological living beings to favor the plant development, nutrient assimilation, stress tolerance, disease deterrence, carbon seizing and others. Fungi are among the most widely distributed organisms on Earth and are of great environmental importance. Mycorrhizal fungi, bacteria, actinomycetes, etc. solubilize nutrients and assist the plants in uptake by roots. Amongst them, vesicular/arbuscular mycorrhizal fungi (AMF) have key roles in the natural ecosystem, as the majority of the terrestrial plants form association with AMF. This symbiosis confers benefits directly to the host plant’s growth and development through the acquisition of phosphorus (P) and other mineral nutrients from the soil. They may also enhance the protection of plants against pathogens, increase plant diversity and have the potential to enhance plant growth under stressful environments. In this article, the sustainability and environmental aspects of agriculture, and the basic concepts of fungi will be reviewed to justify our point of view about the tremendous importance of fungi towards an environmentally sustainable agriculture.

Accumulation of mineral nutrients in fruit peel and pulp of loquat (Eriobotrya japonica) cultivars during fruit developmental stages

The experiment was conducted during 2023 at Punjab Agricultural University, Ludhiana, Punjab to assess the changes of mineral nutrients in peel and pulp of loquat cultivars at four developmental stages to explore its nutraceutical potential. During the development of loquat fruits, K and Zn content both in peel and pulp showed increasing trend from 60–92 DAFS. Similarly, Ca content in loquat peel, Fe and Mn content in pulp also exhibited increasing trend. While P, Cu and Mg content showed a decreasing trend in both peel and pulp. Likewise, Ca content in loquat pulp, Fe and Mn content in peel decreased from 60–92 DAFS. This study provides an insight regarding the accumulation of mineral nutrients in fruit peel and pulp in loquat cultivars during four fruit developmental stages which could be helpful for exploring its nutraceutical potential.

Cotton-mycorrhizal symbiosis: a comprehensive review of benefits for sustainable agriculture

Abstract Fertilizers and plant protection chemicals have played crucial role in modern agriculture. However, their excessive and imbalanced use over decades has resulted in the degradation and deterioration of soil health. The sustainability of agricultural systems largely depends on improving soil health. In this context, the arbuscular mycorrhizal fungi (AMF) association is a well-known interaction among plant microbial symbiotic associations that plays a multifunctional role in maintaining plant-soil health. More than 90% of terrestrial crop plants, including cultivated cotton, have a mutualistic symbiotic association with AMF. Symbiosis provides several benefits, such as the acquisition of mineral nutrients (primarily phosphorus), protection against biotic and abiotic stresses, and improved yield and fiber quality, contributing to the growth and development of the host plant. Under controlled conditions, the percent root length colonization of cotton was 50 to 70%, indicating the potential of AMF as a biological agent and plant growth promoter for sustainable cotton production. This review provides an updated and comprehensive overview of cotton-mycorrhizal symbiosis and its benefits.

Growth Disturbance, Mineral Nutrient Imbalance, Specific Symptoms and Leaf Characteristics Changes in Two Pomegranate Cultivars Induced by Deficiencies and Excess of Ca, Mg, Zn and Fe

Growth Disturbance, Mineral Nutrient Imbalance, Specific Symptoms and Leaf Characteristics Changes in Two Pomegranate Cultivars Induced by Deficiencies and Excess of Ca, Mg, Zn and Fe

Pre-Grafting Exposure to Root-Promoting Compounds Improves Top-Grafting Performance of Citrus Trees.

Top grafting is an efficient and practical technique for the renewal and rejuvenation of citrus trees in old orchards. However, root death after top grafting restricts plant growth and canopy reconstruction. Thus, applications of rooting promotion substances before citrus top grafting may increase the amount and activity of roots, thereby enhancing top-grafted plant performance. To test this assumption, four rooting promotion substances, i.e., rooting promotion powder, biochar, organic fertilizer, and potassium fulvic acid, were applied before top grafting, and the effects on biometric and physiological parameters were analyzed after top grafting. The results showed that the application of all rooting promotion substances before top grafting has a positive effect on growth and mineral nutrient acquisition, as well as on foliar C and N assimilates and the activity of anti-oxidative enzymes of top-grafted plants. Rooting promotion powder and biochar had the best effect on top-grafted tree performance in the short term. In conclusion, pre-grafting root promotion reduced root damage, enhanced nutrient acquisition, and improved the physiological performance of top-grafted plants. Therefore, this approach can play a crucial role in accelerating canopy reconstruction in old citrus orchards and in improving citrus plant development.

Mechanisms of calcium-induced protection against lead toxicity in Ulmus umbraculifera L.: a physiological and biochemical perspective.

Lead (Pb) is a toxic stressor in the soil, which affects plant morphological and physiological events differently. A pot study was initiated to characterize the effect of calcium (Ca) application (20 and 40 mM) on Ulmus umbraculifera L. under Pb treatment (200 and 400 µM). The results revealed that higher levels of Pb significantly reduced plant height (48.3%), total dry weight (44.7%), leaf area index (45%), chlorophyll a (53.7%), chlorophyll b (51.4%), carotenoids (37.8%), and Fv/Fm ratio (20.4%) compared to untreated plants. However, the Ca application improved the aforementioned physiological features. Additionally, Pb toxicity disrupted oxidative status in the plants by increasing malondialdehyde (MDA), methylglyoxal, superoxide anion, and H₂O₂, which also induced the activities of SOD, GR, APX, and CAT. In contrast, Ca decreased MDA, methylglyoxal, superoxide anion, and H₂O₂ by enhancing SOD, CAT, GR, and APX activities compared to the control. Notably, ascorbate (AsA), dehydroascorbic acid (DHA), glutathione (GSH), oxidized glutathione (GSSG) levels, and AsA-DHA and GSH-GSSG ratios changed significantly with Pb and Pb + Ca treatments. According to our findings, monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), glyoxalase (Gly) I, and Gly II activities increased with Pb treatment; however, Ca application further promoted their activities. Furthermore, Pb treatment significantly suppressed the uptake of mineral nutrients and increased Pb accumulation, whereas Ca application improved the uptake of these elements and lowered Pb content. These observations confirmed that the positive effects of Ca application on photosynthetic efficiency, nutrient absorption, and enzymatic and non-enzymatic antioxidants enhanced plant tolerance under Pb toxicity.

A plastidial lipoyl synthase LIP1p plays a crucial role in phosphate homeostasis in Arabidopsis.

Phosphate (Pi) homeostasis is important for plant growth and adaptation to the dynamic environment, which requires the precise regulation of phosphate transporter (PHT) trafficking from the endoplasmic reticulum to the plasma membrane. LIPOYL SYNTHASE 1p (LIP1p) is known as a key enzyme in plastids to catalyze lipoylation of pyruvate dehydrogenase complex for de novo fatty acid synthesis. It is unknown whether this process is involved in regulating Pi homeostasis. Here, we demonstrate a new role of LIP1p in controlling Pi homeostasis by regulating PHT1 trafficking. We recovered a weak mutant allele of LIP1p in Arabidopsis that accumulates much less Pi and has enhanced expression of phosphate starvation-induced genes. LIP1p mutation alters the lipid profile and compromises vesicle trafficking of PHT1 to the plasma membrane to impair Pi uptake. Beside phosphorus, the homeostasis of a series of mineral nutrients was also perturbed in lip1p mutant. Our findings provide powerful genetic evidence to support the linkage between lipoylation and ion homeostasis in plants.

GmSTOP1-3 Increases Soybean Manganese Accumulation Under Phosphorus Deficiency by Regulating GmMATE2/13 and GmZIP6/GmIREG3.

Mineral nutrient deficiencies and metal ion toxicities coexist on acid soils. Phosphorus (P) deficiency in plants is generally accompanied with significant levels of leaf manganese (Mn) accumulation. However, the molecular regulatory mechanisms underpinning remain unclear. The present study found that P-deficient soybean plants accumulated more Mn compared to P-sufficient ones on acid soils in both field and greenhouse experiments. Meanwhile, both P deficiency and Mn toxicity enhanced the expression of GmSTOP1-3. Over-expressing GmSTOP1-3 enhanced Mn accumulation in transgenic soybean hairy roots, but RNA-interference did not show obvious differences. Moreover, transgenic soybeans with GmSTOP1-3-overexpression showed enhanced root citrate exudation and augmented Mn accumulation. RNA-sequence identified four downstream genes of GmSTOP1-3, including multidrug and toxic compound extrusion (GmMATE2/13) and metal transporter genes (GmZIP6/GmIREG3), which encode plasma membrane proteins. GmSTOP1-3 activated the transcription of these four genes by directly binding to their promoter regions. In addition, both GmZIP6 and GmIREG3 functioned in Mn uptake as manifested by the higher Mn concentration and decreased growth of soybean hairy roots with their overexpression. Taken together, it is suggested that upregulation of GmSTOP1-3 by low P stress on acid soils activates transcripts of GmMATE2/13 and GmZIP6/GmIREG3, which consequently result in enhanced Mn accumulation in soybean.

Unveiling the nutritional treasure trove: A comparative analysis of two Azolla species for potential food applications

The study investigates the nutritional potential of Azolla pinnata and Azolla caroliniana for its food applications. Nutritional evaluation revealed it as a valuable source of major and minor nutrients. Both species exhibited an abundance of vitamins as well as essential macro and micro mineral components. The essential amino acid profile ranged from 41.96% to 42.91%, and non-essential amino acids comprising of 57.1–58.02%. Fatty acid analysis indicated a significant amount of polyunsaturated fatty acids (26.96% - 28.06%) and Monounsaturated fatty acids were present in the range of 8.34–8.81%. The ω3:ω6 ratio favored a healthy balance in both species indicating a ratio of 4:1. Protein quality indices showed encouraging values with regard to Protein Efficiency Ratio (PER), Essential Amino Acid Index (EAAI), Nutritional Index (NI), Biological Value (BV), and Chemical Score (CS) for both species. Findings suggested Azolla species as promising candidate for its food applications. A balanced and varied diet is essential for human health, and to meet this, Azolla can be explored as a complementary source of nutrient along with other major dietary sources.

Seed priming with strigolactone GR24 develops tolerance toward salinity in ajwain (Trachyspermum ammi L.) by improving mineral nutrient contents and yield

Seed priming with strigolactone GR24 develops tolerance toward salinity in ajwain (Trachyspermum ammi L.) by improving mineral nutrient contents and yield