Physiological Essence of Magnesium in Plants and Its Widespread Deficiency in the Farming System of China

Nano-sized metal oxide fertilizers for sustainable agriculture: balancing benefits, risks, and risk management strategies

This critical review comprehensively analyses nano-sized metal oxide fertilizers (NMOFs) and their transformative potential in sustainable agriculture. It examines the characteristics and benefits of different NMOFs, such as zinc, copper, iron, magnesium, manganese, nickel, calcium, titanium, cerium, and silicon oxide nanoparticles. NMOFs offer unique advantages such as increased reactivity, controlled-release mechanisms, and targeted nutrient delivery to address micronutrient deficiencies, enhance crop resilience, and improve nutrient efficiency. The review underscores the essential role of micronutrients in plant metabolism, crop growth, and ecosystem health, highlighting their importance alongside macronutrients. NMOFs present significant benefits over traditional fertilizers, including enhanced plant uptake, reduced nutrient losses, and decreased environmental impact. However, the review also critically examines potential risks associated with NMOFs, such as nanoparticle toxicity and environmental persistence. A comparative analysis of different metal types used in nanofertilizers is provided, detailing their primary advantages and potential drawbacks. The review emphasizes the need for cautious management of NMOFs to ensure their safe and effective use in agriculture. It calls for comprehensive research to understand the long-term effects of NMOFs on plant health, soil ecosystems, and human health. By integrating insights from material science, plant biology, and environmental science, this review offers a holistic perspective on the potential of NMOFs to address global food security challenges amid resource constraints and climate change. The study concludes by outlining future research directions and advocating for interdisciplinary collaboration to advance sustainable agricultural practices and optimize the benefits of NMOFs.

Nanocarrier foliar uptake pathways affect delivery of active agents and plant physiological response

Layered double hydroxide (LDH) nanoparticles enable foliar delivery of genetic material, herbicides, and nutrients to promote plant growth and yield. Understanding the foliar uptake route of nanoparticles is needed to maximize their effectiveness and avoid unwanted negative effects. In this study, we investigated how delivering layered double hydroxide (d = 37 ± 1.5 nm) through the adaxial (upper) or abaxial (lower) side of leaves affects particle uptake, nutrient delivery, and photosynthesis in tomato plants. LDH applied on the adaxial side was embedded in the cuticle and accumulated at the anticlinal pegs between epidermal cells. On the abaxial side, LDH particles penetrated the cuticle less, but the presence of the stomata enables penetration to deeper leaf layers. Accordingly, the average penetration levels of LDH relative to the cuticle were 2.47 ± 0.07, 1.25 ± 0.13, and 0.75 ± 0.1 μm for adaxial, abaxial with stomata, and abaxial without stomata leaf segments, respectively. In addition, the colocalization of LDH with the cuticle was ∼2.3 times lower for the adaxial application, indicating the ability to penetrate the cuticle. Despite the low adaxial stomata density, LDH-mediated delivery of magnesium (Mg) from leaves to roots was 46% higher for the adaxial than abaxial application. In addition, adaxial application leads to ∼24% higher leaf CO2 assimilation rate and higher biomass accumulation. The lower efficiency from the abaxial side was, at least partially, a result of interference with the stomata functionality which reduced stomatal conductance and evapotranspiration by 28% and 25%, respectively, limiting plant photosynthesis. This study elucidates how foliar delivery pathways through different sides of the leaves affect their ability to deliver active agents into plants and consequently affect the plants' physiological response. That knowledge enables a more efficient use of nanocarriers for agricultural applications.

Effects of the combination of biochar and organic fertilizer on soil properties and agronomic attributes of soybean (Glycine max L.)

This research aimed to investigate the impacts of a combination of rice husk biochar and organic fertilizer on the physical and chemical properties of soil, the population of soil bacteria, the relative chlorophyll content of leaves, the development of soybean root nodules, and yield components under strongly acid soil conditions. A greenhouse and pot experiment was designed using a randomize complete block design with factorial 2 × 3 treatments and three replications. The experimental treatments comprised two rates of biochar (35 and 70 g/pot) and three rates of organic fertilizer (70, 105, and 140 g/pot). After 100 days of amendment of strongly acidic soils, the results showed that application of treatments B35F70 and B70F140 increased soil pH by 16.80% compared to the control group (CK). On the other hand, treatments B35F140 and B70F105 resulted in an increase of soil electrical conductivity by 66.67% compared to CK. In addition, after 100 days of amendment with treatments B35F105, B35F105, B35F140, B70F105, B70F70, B70F70, and B35F140, organic matter, available phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), and zinc (Zn), organic matter, available phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), and zinc (Zn), significantly increased when compared to the control group (CK). Treatment B35F140 increased relative leaf chlorophyll content and soybean seed weight per plant by 60.76% and 100.56%, respectively when compared to the CK. Furthermore, treatment B35F70 produced 125% more root nodules than CK. Moreover, each amended strongly acid soil resulted with a significant upsurge in total soil bacteria compared to the CK. Overall, statistics proved that a combination of biochar and organic fertilizer improved soil properties and soybean agronomic attributes.

Modulation of Cd carriers by innovative nanocomposite (Ca+Mg) and Cd-resistance microbes (Bacillus pumilus): a mechanistic approach to enhance growth and yield of rice (Oryza sativa L.)

Cadmium (Cd) is a well-known pollutant in agricultural soil, affecting human health through the food chain. To combat this issue, Ca + Mg (25 mg L-1) nanocomposite and Bacillus pumilus, either alone or combined, were applied to rice plants under Cd (5 mg kg-1, 10 mg kg-1) contamination. In our study, growth and yield traits demonstrated the beneficial influence of Ca + Mg and B. pumilus application in improving rice defense mechanism by reducing Cd stress. Combined Ca + Mg and B. pumilus application increased SPAD (15), total chlorophyll (18), chlorophyll a (11), chlorophyll b (22), and carotenoids (21%) with Cd (10 mg kg-1), compared to the application alone. Combined Ca + Mg and B. pumilus application significantly regulated MDA (15), H2O2 (13), EL (10), and O2 •- (24%) in shoots under Cd (10 mg kg-1), compared to the application alone. Cd (10 mg kg-1) increased the POD (22), SOD (21), APX (12), and CAT (13%) in shoots with combined Ca + Mg and B. pumilus application, compared to the application alone. Combined Ca + Mg and B. pumilus application significantly reduced Cd accumulation in roots (22), shoots (13), and grains (20%) under Cd (10 mg kg-1), compared to the application alone. Consequently, the combined application of Ca + Mg and B. pumilus is a sustainable solution to enhance crop production under Cd stress.

Habitat-specific allocations of elements in Atriplex lentiformis seeds indicate adaptation to metal toxicity

Self-sustaining vegetation in metal-contaminated areas is essential for rebuilding ecological resilience and community stability in degraded lands. Metal-tolerant plants originating from contaminated post-mining areas may hold the key to successful plant establishment and growth. Yet, little is known about the impact of metal toxicity on reproductive strategies, metal accumulation, and allocation patterns at the seed stage. Our research focused on the metal tolerant Atriplex lentiformis. Specifically, we examined the effects of toxic metal(loid) concentration in soils on variability in its reproductive strategies, including germination patterns, elemental uptake, and allocation within the seeds. We employed advanced imaging techniques like synchrotron X-ray fluorescence microscopy (2D scans and 3D tomograms) combined with inductively coupled plasma mass spectrometry to reveal significant differences in metal(loid) concentration and distribution within the seed structures of A. lentiformis from contrasting habitats. Exclusive Zn hotspots of high concentrations were found in the seeds of the metallicolous accession, primarily in the sensitive tissues of shoot apical meristems and root zones of the seed embryos. Our findings offer novel insights into phenotypic variability and metal tolerance and accumulation in plants from extreme environments. This knowledge can be applied to enhance plant survival and performance in land restoration efforts.

Forage yields and nutritive values of oat and triticale pastures for grazing sheep in early spring

Background

Small-grain winter cereals can be utilized as early spring pastures in temperate climates to relieve grazing pressure and potentially mitigate feed shortages. This study was conducted to determine the effects of triticale and oat cereal pastures grazed by sheep during early spring on forage yields, nutritive values, and nutritional requirements of sheep.

Methods

The research was carried out over three consecutive years, from 2015 to 2017, at the Sheep Research Institute in Bandırma-Balıkesir, located in the Marmara region of Türkiye. The treatments were arranged in a completely randomized block design, with the two forage species, triticale and oat, randomized within each of three blocks. The animal material for the study consisted of 24 Karacabey Merino sheep, each 2 years old, with an average live weight of 57.6 ± 0.5 kg, all in the late lactation stage. In each replication, four sheep were included, resulting in a total of 12 sheep grazing in each of the triticale and oat pastures. The sheep grazed exclusively on the cereal pastures without any additional feed, and had unrestricted access to water throughout the entire period of the experiment. The dry matter yields (DMY), dry matter intakes (DMI), nutritive values, and mineral contents of the cereal species were determined.

Results

The DMY showed significant differences over the years (P < 0.05). No differences in DMY were observed between pastures, with oats yielding 11.99 t ha-1 and triticale yielding 11.08 t ha-1. During the grazing period, the change in DMY was significant in all years (P < 0.05). The average DMI of the sheep was 2,003.5 g d-1 for triticale and 2,156.6 g d-1 for oat, respectively, and DMI exhibited no significant differences across pastures. Although there was no difference in DMI between 2015 and 2016, the lowest consumption occurred in 2017 (P < 0.05). Additionally, while DMI showed different trends each year based on the periods, it generally decreased by the end of the grazing period. While both pastures provided similar nutritive values, significant differences were observed in the crude protein (CP), acid detergent fiber (ADF), in vitro true DM digestibility (DDM), and metabolisable energy (ME) values across the years. Over the years, as the grazing period progressed, CP levels decreased while neutral detergent fiber (NDF), ADF, and acid detergent lignin (ADL) increased, resulting in reduced DDM and ME values. The phosphorus (P) content in triticale was higher than in oats, but there were no differences in the content of other minerals between them. Between the years, significant differences were observed in the levels of phosphorus (P) and iron (Fe), while changes in other elements were insignificant. The variation in mineral content during the grazing process differed over the three years. Study results indicated that the nutritional values of triticale and oat pastures are similar, and both can effectively be used to provide sufficient feed to meet the early spring forage requirements for sheep.

Euglena mutabilis exists in a FAB consortium with microbes that enhance cadmium tolerance

BACKGROUND

Synthetic algal-fungal and algal-bacterial cultures have been investigated as a means to enhance the technological applications of the algae. This inclusion of other microbes has enhanced growth and improved stress tolerance of the algal culture. The goal of the current study was to investigate natural microbial consortia to gain an understanding of the occurrence and benefits of these associations in nature. The photosynthetic protist Euglena mutabilis is often found in association with other microbes in acidic environments with high heavy metal (HM) concentrations. This may suggest that microbial interactions are essential for the protist's ability to tolerate these extreme environments. Our study assessed the Cd tolerance of a natural fungal-algal-bacterial (FAB) association whereby the algae is E. mutabilis.

RESULTS

This study provides the first assessment of antibiotic and antimycotic agents on an E. mutabilis culture. The results indicate that antibiotic and antimycotic applications significantly decreased the viability of E. mutabilis cells when they were also exposed to Cd. Similar antibiotic treatments of E. gracilis cultures had variable or non-significant impacts on Cd tolerance. E. gracilis also recovered better after pre-treatment with antibiotics and Cd than did E. mutabilis. The recoveries were assessed by heterotrophic growth without antibiotics or Cd. In contrast, both Euglena species displayed increased chlorophyll production upon Cd exposure. PacBio full-length amplicon sequencing and targeted Sanger sequencing identified the microbial species present in the E. mutabilis culture to be the fungus Talaromyces sp. and the bacterium Acidiphilium acidophilum.

CONCLUSION

This study uncovers a possible fungal, algal, and bacterial relationship, what we refer to as a FAB consortium. The members of this consortium interact to enhance the response to Cd exposure. This results in a E. mutabilis culture that has a higher tolerance to Cd than the axenic E. gracilis. The description of this interaction provides a basis for explore the benefits of natural interactions. This will provide knowledge and direction for use when creating or maintaining FAB interactions for biotechnological purposes, including bioremediation.

Biochar-based nanoparticles mitigated arsenic toxicity and improved physiological performance of basil via enhancing cation exchange capacity and ferric chelate reductase activity

The modified biochars have positive effects in reducing heavy metal toxicity for plants. However, the mechanism and extent of these effects on mitigating arsenic toxicity and plant performance are not clear. Thus, a pot experiment was conducted as factorial to evaluate the potential of fresh and enriched biochars with potassium and magnesium nano-sulfates [potassium-enriched biochar (K-BC), magnesium-enriched biochar (Mg-BC) in individual and combined forms] on reducing arsenic toxicity (non-contamination, 50, and 100 mg NaAsO2 kg-1 soil) in basil plants. Biochar-related treatments reduced plant arsenic absorption rate (up to 24%), arsenic content of root (up to 38%) and shoot (up to 21%) and root tonoplast H+-ATPase activity (up to 30%). The fresh and particularly enriched biochars improved soil properties (pH, CEC, and available iron content), ferric chelate reductase activity, iron, potassium and magnesium contents of plant tissues, chlorophyll content index, photochemical efficiency of photosystem II, relative electron transport rate, leaf area, and basil growth (shoot and root dry weight). These results revealed that enriched biochars are useful soil amendments for improving physiological performance of plants via reducing heavy metal toxicity and enhancing cation exchange capacity, nutrient availability and ferric chelate reductase activity. Therefore, soil amendment by enriched biochars could be a sustainable solution for enhancing plant productivity in contaminated soils via mitigating environmental impacts. This is an environmentally friendly method for using the natural wastes to overcome the adverse effects of soil pollutants on medicinal plants.

Integrative analysis of transcriptome and metabolome provides insights into the mechanisms of leaf variegation in Heliopsis helianthoides

BACKGROUND

In the field of ornamental horticulture, phenotypic mutations, particularly in leaf color, are of great interest due to their potential in developing new plant varieties. The introduction of variegated leaf traits in plants like Heliopsis helianthoides, a perennial herbaceous species with ecological adaptability, provides a rich resource for molecular breeding and research on pigment metabolism and photosynthesis. We aimed to explore the mechanism of leaf variegation of Heliopsis helianthoides (using HY2021F1-0915 variegated mutant named HY, and green-leaf control check named CK in 2020 April, May and June) by analyzing the transcriptome and metabolome.

RESULTS

Leaf color and physiological parameters were found to be significantly different between HY and CK types. Chlorophyll content of HY was lower than that of CK samples. Combined with the result of Weighted Gene Co-expression Network Analysis (WGCNA), 26 consistently downregulated differentially expressed genes (DEGs) were screened in HY compared to CK subtypes. Among the DEGs, 9 genes were verified to be downregulated in HY than CK by qRT-PCR. The reduction of chlorophyll content in HY might be due to the downregulation of FSD2. Low expression level of PFE2, annotated as ferritin-4, might also contribute to the interveinal chlorosis of HY. Based on metabolome data, differential metabolites (DEMs) between HY and CK samples were significantly enriched on ABC transporters in three months. By integrating DEGs and DEMs, they were enriched on carotenoids pathway. Downregulation of four carotenoid pigments might be one of the reasons for HY's light color.

CONCLUSION

FSD2 and PFE2 (ferritin-4) were identified as key genes which likely contribute to the reduced chlorophyll content and interveinal chlorosis observed in HY. The differential metabolites were significantly enriched in ABC transporters. Carotenoid biosynthesis pathway was highlighted with decreased pigments in HY individuals. These findings not only enhance our understanding of leaf variegation mechanisms but also offer valuable insights for future plant breeding strategies aimed at preserving and enhancing variegated-leaf traits in ornamental plants.

Comparing the Effects of Lime Soil and Yellow Soil on Cadmium Accumulation in Rice during Grain-Filling and Maturation Periods

The karst area has become a high-risk area for Cadmium (Cd) exposure. Interestingly, the high levels of Cd in soils do not result in an excessive bioaccumulation of Cd in rice. Carbonate rock dissolution ions (CRIs) could limit the accumulation and translocation of Cd in rice. CRIs can become a major bottleneck in the remediation and management of farmlands in karst areas. However, there is limited research on the effects of CRIs in soils on Cd accumulation in rice. The karst area of lime soil (LS) and the non-karst areas of yellow soil (YS) were collected, and an external Cd was added to conduct rice cultivation experiments. Cd and CRIs (Ca2+, Mg2+, CO32-/HCO3-, and OH-) in the rice-soil system were investigated from the grain-filling to maturity periods. The results showed that CRIs of LS were significantly higher than that of YS in different treatments. CRIs of LS were 2.05 mg·kg-1 for Ca2+, 0.90 mg·kg-1 for Mg2+, and 42.29 mg·kg-1 for CO32- in LS. CRIs could influence DTPA Cd, resulting in DTPA Cd of LS being lower than that of YS. DTPA Cd of YS was one to three times larger than that of YS. Cd content in different parts of rice in YS was higher than that of LS. Cd in rice grains of YS was one to six times larger than that of LS. The uptake of Cd from the soil during Filling III was critical in determining rice Cd accumulation. CRIs in the soil could affect Cd accumulation in rice. Ca2+ and Mg2+ had significant negative effects on Cd accumulation of rice at maturity and filling, respectively. CO32-/HCO3- and OH- had significant negative effects on DTPA Cd in soil.

Receptor-like cytoplasmic kinase 58 reduces tolerance of maize seedlings to low magnesium via promoting H2O2 over-accumulation

KEY MESSAGE

ZmRLCK58, a negative growth regulator, reduces tolerance of maize seedlings to low Mg via enhancing H2O2 accumulation in the shoot. Magnesium (Mg) deficiency is one of critical limiting factors for crop production in widespread acidic soils worldwide. However, the molecular mechanism of crop response to Mg deficiency is still largely unclear. Here, we found higher concentrations of H2O2, soluble sugars, and starch (1.5-, 1.9-, and 1.4-fold, respectively) in the shoot of low-Mg-treated maize seedlings, compared with Mg sufficient plants under hydroponic culture. Consistent with over-accumulation of H2O2, transcriptome profiling revealed significant enrichment of 175 differentially expressed genes (DEGs) in "response to oxygen-containing compound" out of 641 DEGs in the shoot under low Mg. Among 175 DEGs, a down-regulated receptor-like cytoplasmic kinase ZmRLCK58 underwent a recent duplication event before Poaceae divergence and was highly expressed in the maize shoot. ZmRLCK58 overexpression enhanced H2O2 accumulation in shoots by 21.3% and 29.8% under control and low-Mg conditions, respectively, while reducing biomass accumulation compared with wild-type plants. Low Mg further led to 39.7% less starch accumulation in the ZmRLCK58 overexpression shoot and lower Mg utilization efficiency. Compared with wild-type plants, overall down-regulated expression of genes related to response to carbohydrate, photosynthesis, H2O2 metabolic, oxidation-reduction, and ROS metabolic processes in ZmRLCK58 overexpression lines preconditioned aforementioned physiological alterations. Together, ZmRLCK58, as a negative growth regulator, reduces tolerance of maize seedlings to low Mg via enhancing H2O2 accumulation.

Trace and essential elements as vital components to improve the performance of the male reproductive system: Implications in cell signaling pathways

Successful male fertilization requires the main processes such as normal spermatogenesis, sperm capacitation, hyperactivation, and acrosome reaction. The progress of these processes depends on some endogenous and exogenous factors. So, the optimal level of ions and essential and rare elements such as selenium, zinc, copper, iron, manganese, calcium, and so on in various types of cells of the reproductive system could affect conception and male fertility rates. The function of trace elements in the male reproductive system could be exerted through some cellular and molecular processes, such as the management of active oxygen species, involvement in the action of membrane channels, regulation of enzyme activity, regulation of gene expression and hormone levels, and modulation of signaling cascades. In this review, we aim to summarize the available evidence on the role of trace elements in improving male reproductive performance. Also, special attention is paid to the cellular aspects and the involved molecular signaling cascades.

Transcription-related metabolic regulation in grafted lemon seedlings under magnesium deficiency stress

Magnesium is one of the essential nutrients for plant growth, and plays a pivotal role in plant development and metabolism. Soil magnesium deficiency is evident in citrus production, which ultimately leads to failure of normal plant growth and development, as well as decreased productivity. Citrus is mainly propagated by grafting, so it is necessary to fully understand the different regulatory mechanisms of rootstock and scion response to magnesium deficiency. Here, we characterized the differences in morphological alterations, physiological metabolism and differential gene expression between trifoliate orange rootstocks and lemon scions under normal and magnesium-deficient conditions, revealing the different responses of rootstocks and scions to magnesium deficiency. The transcriptomic data showed that differentially expressed genes were enriched in 14 and 4 metabolic pathways in leaves and roots, respectively, after magnesium deficiency treatment. And the magnesium transport-related genes MHX and MRS2 may respond to magnesium deficiency stress. In addition, magnesium deficiency may affect plant growth by affecting POD, SOD, and CAT enzyme activity, as well as altering the levels of hormones such as IAA, ABA, GA3, JA, and SA, and the expression of related responsive genes. In conclusion, our research suggests that the leaves of lemon grafted onto trifoliate orange were more significantly affected than the roots under magnesium-deficient conditions, further indicating that the metabolic imbalance of scion lemon leaves was more severe.

Comparative Physio-Biochemical and Transcriptome Analyses Reveal Contrasting Responses to Magnesium Imbalances in Leaves of Mulberry (Morus alba L.) Plants

Magnesium (Mg) deficiency is a major factor limiting the growth and development of plants. Mulberry (Morus alba L.) is an important fruit tree crop that requires Mg for optimal growth and yield, especially in acid soils. However, the molecular mechanism of Mg stress tolerance in mulberry plants remains unknown. In this study, we used next-generation sequencing technology and biochemical analysis to profile the transcriptome and physiological changes of mulberry leaves under different Mg treatments (deficiency: 0 mM, low: 1 mM, moderate low: 2 mM, sufficiency: 3 mM, toxicity: 6 mM, higher toxicity: 9 mM) as T1, T2, T3, CK, T4, T5 treatments, respectively, for 20 days. The results showed that Mg imbalance altered the antioxidant enzymatic activities, such as catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD), and non-enzymatic, including soluble protein, soluble sugar, malondialdehyde (MDA), and proline (PRO), contents of the plant. The Mg imbalances disrupted the ultrastructures of the vital components of chloroplast and mitochondria relative to the control. The transcriptome data reveal that 11,030 genes were differentially expressed (DEGs). Genes related to the photosynthetic processes (CAB40, CAB7, CAB6A, CAB-151, CAP10A) and chlorophyll degradation (PAO, CHLASE1, SGR) were altered. Antioxidant genes such as PER42, PER21, and PER47 were downregulated, but DFR was upregulated. The carbohydrate metabolism pathway was significantly altered, while those involved in energy metabolism processes were perturbed under high Mg treatment compared with control. We also identified several candidate genes associated with magnesium homeostasis via RT-qPCR validation analysis, which provided valuable information for further functional characterization studies such as promoter activity assay or gene overexpression experiments using transient expression systems.

Assessment of potentially toxic and mineral elements in paddy soils and their uptake by rice (Oryza sativa L.) with associated health hazards in district Malakand, Pakistan

Rice, a primary food source in many countries of the world accumulate potentially harmful elements which pose a significant health hazard to consumers. The current study aimed to evaluate potentially toxic and mineral elements in both paddy soils and rice grains associated with allied health risks in Malakand, Pakistan. Rice plants with intact root soil were randomly collected from paddy fields and analyzed for mineral and potentially toxic elements (PTEs) through inductively coupled plasma optical emission spectrometry (ICP‒OES). Through deterministic and probabilistic risk assessment models, the daily intake of PTEs with allied health risks from consumption of rice were estimated for children and adults. The results of soil pH (< 8.5) and electrical conductivity (EC > 400 μs/cm), indicated slightly saline nature. The mean phosphorus concentration of 291.50 (mg/kg) in soil samples exceeded FAO/WHO permissible limits. The normalized variation matrix of soil pH with respect to Ni (0.05), Ca (0.05), EC (0.08), and Mg (0.09), indicated significant influence of pH on PTEs mobility. In rice grains, the mean concentrations (mg/kg) of Mg (463.81), Al (70.40), As (1.23), Cr (12.53), Cu (36.07), Fe (144.32), Mn (13.89), and Ni (1.60) exceeded FAO/WHO safety limits. The transfer factor >1 for K, Cu, P and Zn indicated bioavailability and transfer of these elements from soil to rice grains. Monte Carlo simulations of hazard index >1 for Cr, Zn, As, and Cu with certainties of 89.93% and 90.17%, indicated significant noncarcinogenic risks for children and adults from rice consumption. The total carcinogenic risk (TCR) for adults and children exceeded the USEPA acceptable limits of 1×10-6 to 1×10-4, respectively. The sensitivity analysis showed that the ingestion rate was a key risk factor. Arsenic (As) primarily influenced total cancer risk (TCR) in children, while chromium (Cr) significantly impacted adults. Deterministic cancer risk values slightly exceeded probabilistic values due to inherent uncertainties in deterministic analysis. Rice consumption poses health risks, mainly from exposure to Cr, Ni and As in the investigated area.

Monitoring plant responses in field-grown peanuts exposed to exogenously applied chitosan under full and limited irrigation levels

In recent decades, numerous studies have examined the effects of climate change on the responses of plants. These studies have primarily examined the effects of solitary stress on plants, neglecting the simultaneous effects of mixed stress, which are anticipated to transpire frequently as a result of the extreme climatic fluctuations. Therefore, this study investigated the impact of applied chitosan on boosting the resistance responses of peanuts to alkali and mixed drought-alkali stresses. Peanuts were grown in mid-alkaline soil and irrigated with full irrigation water requirements (100%IR), represented alkali condition (100% IR × alkali soil) and stress conditions (70% IR × alkali soil-represented mixed drought-alkali conditions). Additionally, the plants were either untreated or treated with foliar chitosan. The study evaluated various plant physio-chemical characteristics, including element contents (leaves and roots), seed yield, and irrigation water use efficiency (IWUE). Plants that experienced solitary alkali stress were found to be more vulnerable. However, chitosan applications were effective for reducing (soil pH and sodium absorption), alongside promoting examined physio-chemical measurements, yield traits, and IWUE. Importantly, when chitosan was applied under alkali conditions, the accumulations of (phosphorus, calcium, iron, manganese, zinc, and copper) in leaves and roots were maximized. Under mixed drought-alkali stresses, the results revealed a reduction in yield, reaching about 5.1 and 5.8% lower than under (100% IR × alkali), in the first and second seasons, respectively. Interestingly, treated plants under mixed drought-alkali stresses with chitosan recorded highest values of relative water content, proline, yield, IWUE, and nutrient uptake of (nitrogen, potassium, and magnesium) as well as the lowest sodium content in leaves and roots. Enhances the accumulation of (N, K, and Mg) instead of (phosphorus, calcium, iron, manganese, zinc, and copper) was the primary plant response to chitosan applications, which averted severe damage caused by mixed drought-alkali conditions, over time. These findings provide a framework of the nutrient homeostasis changes induced by chitosan under mixed stresses. Based on the findings, it is recommended under mixed drought-alkali conditions to treat plants with chitosan. This approach offers a promising perspective for achieving optimal yield with reduced water usage.

Evaluating Yield, Nutritional Quality, and Environmental Impact of Quinoa Straws across Mediterranean Water Environments

Quinoa (Chenopodium quinoa Willd.) is a promising and versatile crop due to its remarkable adaptability to diverse environments and the exceptional nutritional value of its seeds. Nevertheless, despite the recent extensive research on quinoa seeds, the straw associated with this crop has received comparatively little attention. The valorisation of this by-product provides an opportunity to improve the overall outcomes of quinoa cultivation. In this work, three quinoa varieties were evaluated for two years (2019 and 2020) under three different Mediterranean water environments (irrigation, fresh rainfed, and hard rainfed), aiming to assess the straw yield and nutritional quality and to study the changes in the crop nutritional uptake associated with different water environmental conditions. The nutritional analysis included the quantification of the ash, crude protein, crude fat, minerals (P, K, Ca, Mg), and fibre (gross fibre (GF), acid detergent fibre (ADF), neutral detergent fibre (NDF), acid detergent lignin (ADL), hemicellulose, cellulose) contents. As the results reveal, most of the parameters evaluated were susceptible to change mainly with the water environment but also with the genotype (or their interaction), including the yield, crude protein, relative feed value (RFV), and mineral content, which generally decreased under water-limiting conditions. Moreover, a comparative analysis revealed that straw Ca, Mg, and K contents were generally higher than in seeds. Overall, this study demonstrates that quinoa straw quality is genotypic and environmentally dependent, and these factors should be considered when aiming at improving straw feed value for livestock nutrition.

Nutritional status of Zombi pea (Vigna vexillata) as influenced by plant density and deblossoming

Feeding billions, a healthy and nutritious diet in the era of climate change is a major challenge before plant breeders, geneticists and agronomist. In this context, the continuous search for adaptive and nutritious crops could be a better alternative to combat the problems of hunger and malnutrition. The zombi pea, a nutritious and underutilized leguminous vegetable, is one of such better alternatives to feed billions a nutritious food besides being a potential gene source for breeding abiotic stress resistant varieties. To evaluate its potential as a wonder crop in the tropical and subtropical regions of India, the nutritional status of tubers, pods and pericarp were investigated under different treatments of plant spacings and deblossoming. The experiment was conducted in split plot design with three replications and eight treatments during 2021-2022 in the coastal regions of India. The nutrient profiling in tubers and pericarp of pods in zombi pea revealed higher accumulation of nutrients viz. potassium (K), magnesium (Mg), iron (Fe), manganese (Mn) and zinc (Zn) with blossom retention. The zombi pea tubers reflected significantly high protein accumulation with the increase in plant spacing. The results pertaining to nutrient profiling in the pods of zombi pea indicated that the plant spacing has no significant effect on the accumulation of majority of nutrients under study. The above-mentioned findings are conspicuously novel and valuable. The present study would pave the way for understanding nutritional importance and breeding potential of this orphan crop. The blossom retention renders higher nutrient accumulation in tubers, pods and pericarp of zombi pea. Deblossoming has no significant influence on nutritional profile of this wonder crop but, wider spacing is effective in producing tubers with high protein content.

Foliar zinc spraying improves assimilative capacity of sugar beet leaves by promoting magnesium and calcium uptake and enhancing photochemical performance

Sugar beet, a zinc-loving crop, is increasingly limited by zinc deficiency worldwide. Foliar zinc application is an effective and convenient way to supplement zinc fertilizer. However, the regulatory mechanism of foliar zinc spraying on sugar beet leaf photosynthetic characteristics remains unclear. Therefore, we investigated the effects of foliar ZnSO4·7H2O application (0, 0.1%, 0.2%, and 0.4%) on the photosynthetic performance of sugar beet leaves under controlled hydroponic conditions. The results indicated that a foliar spray of 0.2% Zn fertilizer was optimal for promoting sugar beet leaf growth. This concentration significantly reduced the leaf shape index of sugar beet, notably increasing leaf area, leaf mass ratio, and specific leaf weight. Foliar spraying of Zn (0.2%) substantially elevated the Zn content in sugar beet leaves, along with calcium (Ca) and magnesium (Mg) contents. Consequently, this led to an increase in the potential photochemical activity of PSII (Fv/Fo) (by 6.74%), net photosynthetic rate (Pn) (11.39%), apparent electron transport rate (ETR) (11.43%), actual photochemical efficiency of PSⅡ (Y (Ⅱ)) (11.46%), photochemical quenching coefficient (qP) (15.49%), and total chlorophyll content (25.17%). Ultimately, this increased sugar beet leaf dry matter weight (11.30%). In the cultivation and management of sugar beet, the application of 0.2% Zn fertilizer (2.88 mg plant-1) exhibited the potential to enhance Zn and Mg contents in sugar beet, improve photochemical properties, stimulate leaf growth, and boost light assimilation capacity. Our result suggested the foliar application of Zn might be a useful strategy for sugar beet crop management.

Development and Application of an Atomic Absorption Spectrometry-Based Method to Quantify Magnesium in Leaves of Dioscorea polystachya

The Chinese yam (Dioscorea polystachya, DP) is known for the nutritional value of its tuber. Nevertheless, DP also has promising pharmacological properties. Compared with the tuber, the leaves of DP are still very little studied. However, it may be possible to draw conclusions about the plant quality based on the coloration of the leaves. Magnesium, as a component of chlorophyll, seems to play a role. Therefore, the aim of this research work was to develop an atomic absorption spectrometry-based method for the analysis of magnesium (285.2125 nm) in leaf extracts of DP following the graphite furnace sub-technique. The optimization of the pyrolysis and atomization temperatures resulted in 1500 °C and 1800 °C, respectively. The general presence of flavonoids in the extracts was detected and could explain the high pyrolysis temperature due to the potential complexation of magnesium. The elaborated method had linearity in a range of 1-10 µg L-1 (R2 = 0.9975). The limits of detection and quantification amounted to 0.23 µg L-1 and 2.00 µg L-1, respectively. The characteristic mass was 0.027 pg, and the recovery was 96.7-102.0%. Finally, the method was applied to extracts prepared from differently colored leaves of DP. Similar magnesium contents were obtained for extracts made of dried and fresh leaves. It is often assumed that the yellowing of the leaves is associated with reduced magnesium content. However, the results indicated that yellow leaves are not due to lower magnesium levels. This stimulates the future analysis of DP leaves considering other essential minerals such as molybdenum or manganese.

Comparative metabolomic profiling and nutritional chemistry of Chenopodium quinoa of diverse panicle architecture and agroecological zones

Chenopodium quinoa possesses remarkable nutritional value and adaptability to various agroecological conditions. Panicle architecture influences the number of spikelets and grains in a panicle, ultimately leading to productivity and yield. Therefore, this study aimed to investigate the metabolites, nutrients, and minerals in Chenopodium quinoa accessions of varying panicle architecture. Metabolic profiling using liquid chromatography-mass spectrometry (LC-MS) analysis identified seventeen metabolites, including flavonoids, phenolics, fatty acids, terpenoids, phenylbutenoid dimers, amino acids, and saccharides. Eight metabolic compounds were reported in this study for the first time in quinoa. Some metabolites were detected as differentially expressed. The compound (Z)-1-(2,4,5-trimethoxyphenyl) butadiene and chrysin were found only in SPrecm. Sodium ((2R,3S,4R,5R)-5-(6-amino-9H-purin-9-yl)-3,4-dihydroxtetrahydrofuran-2-yl) methyl hydrogen phosphate and elenolic acid were detected only in CHEN-33, and quercetin, 3-hydroxyphloretin-3'-C-glucoside, kurarinone, and rosmarinic acid were identified only in D-12175. Variable importance in projection (VIP) scores annotated ten metabolites contributing to variability. Mineral analysis using atomic absorption spectrophotometry indicated that the quantity of magnesium and calcium is high in D-12175. In comparison, SPrecm showed a high quantity of magnesium compared to CHEN-33, while CHEN-33 showed a high quantity of calcium compared to SPrecm. However, the proximate composition showed no significant difference among quinoa accessions.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-023-01398-2.

Regulation of magnesium and calcium homeostasis in citrus seedlings under varying magnesium supply

Magnesium (Mg) and calcium (Ca) are two essential macronutrients in plants; however, the characteristics of Mg and Ca concentrations in organ, subcellular and chemical forms and their relationships in citrus plants, especially under varying Mg supply, are not well understood. In this study, Citrus sinensis seedlings (cv. Xuegan) were cultivated in conditions of Mg deficiency (0 mmol Mg2+ L-1) and Mg sufficiency (2 mmol Mg2+ L-1) to investigate the responses of Mg and Ca homeostasis in different organs and fractions. Compared with Mg sufficiency, Mg deficiency significantly decreased root and shoot growth, with the shoot biomass reduction of branch organs was greater than that of parent organs. In addition to increasing the Ca concentration in the parent stem and lateral root organs, Mg deficiency significantly decreased the concentrations and accumulations of Mg and Ca in citrus seedlings, further altering their distribution in different organs. More than 50% of Ca and Mg were sequestrated in the cell wall and soluble fractions, respectively, with Mg concentration decreasing by 15.4% in roots and 46.9% in leaves under Mg deficiency, while Ca concentration decreased by 27.6% in roots and increased by 23.6% in parent leaves. Approximately 90% of Mg exists in inorganic, water-soluble, and pectate and protein-bound forms, and nearly 90% of Ca exists in water-soluble, pectate and protein-bound, phosphate and oxalate acid forms. Except for the decreased inorganic Mg in roots and water-soluble Mg and Ca in leaves, Mg deficiency increased the proportions of Mg and Ca in all chemical forms. However, Mg deficiency generally increased the Ca/Mg ratio in various organs, subcellular and chemical forms, with negative relationships between Mg concentration and Ca/Mg ratio, and the variations of Mg and Ca were highly separated between Mg supply and organs. In conclusion, our results provide insights into the effects of Mg supply on Mg and Ca homeostasis in citrus plants.

The power of magnesium: unlocking the potential for increased yield, quality, and stress tolerance of horticultural crops

Magnesium (Mg2+) is pivotal for the vitality, yield, and quality of horticultural crops. Central to plant physiology, Mg2+ powers photosynthesis as an integral component of chlorophyll, bolstering growth and biomass accumulation. Beyond basic growth, it critically affects crop quality factors, from chlorophyll synthesis to taste, texture, and shelf life. However, Mg2 + deficiency can cripple yields and impede plant development. Magnesium Transporters (MGTs) orchestrate Mg2+ dynamics, with notable variations observed in horticultural species such as Cucumis sativus, Citrullus lanatus, and Citrus sinensis. Furthermore, Mg2+ is key in fortifying plants against environmental stressors and diseases by reinforcing cell walls and spurring the synthesis of defense substances. A burgeoning area of research is the application of magnesium oxide nanoparticles (MgO-NPs), which, owing to their nanoscale size and high reactivity, optimize nutrient uptake, and enhance plant growth and stress resilience. Concurrently, modern breeding techniques provide insights into Mg2+ dynamics to develop crops with improved Mg2+ efficiency and resilience to deficiency. Effective Mg2+ management through soil tests, balanced fertilization, and pH adjustments holds promise for maximizing crop health, productivity, and sustainability. This review unravels the nuanced intricacies of Mg2+ in plant physiology and genetics, and its interplay with external factors, serving as a cornerstone for those keen on harnessing its potential for horticultural excellence.

Nutritional Content and Microbial Load of Fresh Liang, Gnetum gnemon var. tenerum Leaves

Liang (Gnetum gnemon var. tenerum) leaves are widely consumed as a green vegetable in Southern Thailand, and the plant is valued for its nutritional benefits. However, like other leafy greens, liang is vulnerable to microbial contamination, generating foodborne illnesses. This study examined the nutritional content and microbial load of liang leaves at different maturity stages and the effects of washing with chlorinated water. Various growth stages were analysed for proximate composition, amino acids, vitamins, and minerals. Results revealed distinct nutritional profiles, with tip leaves rich in protein and fat and intermediate leaves high in dietary fibre. Liang leaves are abundant in essential amino acids and proteins. Washing with chlorinated water increased leaf weight due to water retention but also caused physical damage, fostering microbial growth and spoilage. Microbiological analysis showed marginal reductions in total viable counts after washing with chlorinated water and significant decreases in coliform and Escherichia coli counts. However, stem detachment during washing increased the coliform and E. coli counts. Liang leaves exhibited favourable nutritional content, especially in the intermediate stage. Proper handling and storage of liang leaves are crucial to preventing physical damage and microbial contamination. Improved food safety measures, including appropriate post-harvest washing and handling of leafy vegetables, will ensure that consumers can safely enjoy the nutritional benefits of liang leaves.

Evaluating Leaf Wettability and Salt Hygroscopicity as Drivers for Foliar Absorption

The objective of this study was to evaluate the rate of foliar absorption of magnesium (Mg) salts with different deliquescence and efflorescence relative humidity values (DRH and ERH, also known as point of deliquescence (POD) and point of efflorescence (POE), respectively) when supplied to leaves of model plants with different wettability properties. For this purpose, a greenhouse pot experiment was conducted with lettuce (very wettable), broccoli (highly unwettable) and leek (highly unwettable). Foliar sprays contained 0.1% surfactant plus 100 mM Mg supplied as MgCl₂·6H₂O, Mg(NO₃)₂·6H₂O or MgSO₄·7H₂O. Leaf Mg concentrations were determined 1 and 7 days after foliar application. Anion concentrations were also measured in lettuce where a significant foliar Mg absorption was detected. Leaf wettability, leaf surface free energy and fertilizer drop deposit appearance onto the foliage were assessed. It is concluded that despite including a surfactant in the spray formulation, leaf wettability plays a major role in foliar Mg absorption.

Phytochemical Composition of Combretum molle (R. Br. ex G. Don.) Engl. & Diels Leaf and Stem Extracts

The demand for medicinal plants is on a rise due to their affordability, accessibility and relatively non-toxic nature. Combretum molle (Combretaceae) is used in African traditional medicine to treat a number of diseases. This study aimed to screen the phytochemical composition of the hexane, chloroform and methanol extracts of C. molle leaves and stems using qualitative phytochemical screening. Additionally, the study aimed to identify the functional phytochemical groups, determine the elemental composition and provide a fluorescence characterization of the powdered leaves and stems by performing Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray (EDX) microanalyses and fluorescence microscopy. Phytochemical screening revealed the presence of alkaloids, flavonoids, phenolic compounds, polyphenols, terpenoids, tannins, coumarins, saponins, phytosterols, gums, mucilage, carbohydrates, amino acids and proteins within all leaf and stem extracts. Lipids and fixed oils were additionally present within the methanol extracts. FTIR demonstrated significant peaks in absorption frequency in the leaf at wavelengths of 3283.18, 2917.81, 1617.72, 1318.83, 1233.97, 1032.32 and 521.38 cm^-1, and in the stem at 3318.91, 1619.25, 1317.13, 1032.68, 780.86 and 516.39 cm^-1. These corresponded to the functional groups of chemical compounds including alcohols, phenols, primary amines, alkyl halides, alkanes and alkyl aryl ethers, corroborating the presence of the detected phytochemicals within the plant. EDX microanalyses showed the elemental composition of the powdered leaves (68.44% C, 26.72% O, 1.87% Ca, 0.96% Cl, 0.93% Mg, 0.71% K, 0.13% Na, 0.12 % Mn and 0.10% Rb) and stems (54.92% C, 42.86% O, 1.7% Ca, 0.43% Mg and 0.09% Mn). Fluorescence microscopy provided a characteristic evaluation of the plant in its powdered form and revealed distinct colour changes in the material when treated with various reagents and viewed under ultraviolet light. In conclusion, the phytochemical constituents of the leaves and stems of C. molle confirm the suitability of this species for use in traditional medicine. The findings from this study suggest the need to validate the use of C. molle in the development of modern medicines.

Magnesium deficiency stress in rice can be alleviated by partial nitrate nutrition supply

The problem of nitrogen (N) excess and magnesium (Mg) deficiency in farmland is becoming more common, severe, and widespread in southern China. Magnesium is known to be an essential nutrient for higher plants; however, the physiological responses of field crops to Mg deficiency, particularly to its interaction with N forms, remain largely unknown. In this study, a hydroponic experiment was conducted using three Mg levels (0.01, 1.00, and 5.00 mM) and three nitrate/ammonium ratios (NO₃^-/NH₄⁺ of 0/100, 25/75, and 50/50) under greenhouse conditions. The results show that Mg deficiency (0.01 mM) could result in yellow leaves, dwarf plants, and fewer tillers during rice growth. Furthermore, Mg deficiency induced a major reduction in root morphology and activity, photosynthetic properties, and nutrient accumulation, while it resulted in a clear increase in malondialdehyde, superoxide dismutase, peroxidase, and catalase activities in rice. However, under Mg-deficiency stress, the supply of partial NO₃^- led to a significant drop in these antioxidant enzyme activities. Moreover, partial NO₃^- supply significantly improved the net photosynthetic rate, transpiration rate, stomatal conductance, and intercellular CO₂ concentrations under Mg-deficiency conditions. In particular, the supply of partial NO₃^- dramatically promoted the growth of the root system, boosted the occurrence of lateral roots, and enhanced root vitality under Mg-deficiency stress. Additionally, the supply of partial NO₃^- led to significant increases in dry weight and N and Mg contents under Mg deficiency. The results of this study suggest that the symptoms of Mg-deficiency stress in rice can be alleviated by partial NO₃^- supply.

A novel bud mutant of navel orange (Citrus sinensis) shows tolerance to chlorosis in acidic and magnesium-deficient soils

Interveinal chlorosis in old leaves is a common occurrence in citrus orchards in southern China. The present study investigates the 'Langfeng' navel orange (LF, Citrus sinensis) grafted onto a Trifoliate orange (TO, Poncirus trifoliata) rootstock, which exhibits healthy green leaves, and the 'Newhall' navel orange (NHE, C. sinensis) grafted onto TO, which has typical magnesium (Mg) deficiency-induced chlorosis. Chemical analysis of the rhizosphere soil revealed that the pH values were around 3.92 and that both Mg and calcium (Ca) were significantly deficient in the rhizosphere soil of both grafting combinations (LF/TO and NHE/TO). Furthermore, the chlorotic leaves of NHE/TO had significantly lower levels of Mg, Ca, and phosphorus (P), and the green leaves of NHE/TO had significantly lower levels of Mg and Ca compared to the green leaves of the LF/TO. This suggests that Mg deficiency may be the primary cause of chlorosis in NHE/TO. A greenhouse study using the same graft combinations showed that the LF/TO plants had better growth than the NHE/TO, possibly by promoting Mg uptake and/or improving Mg distribution to leaves, thereby increasing carbon dioxide (CO₂) assimilation and photosynthesis, optimizing carbohydrate distribution, and increasing plant biomass. This results in a phenotype that is tolerant to Mg deficiency. In conclusion, these findings suggest that the LF navel orange could be utilized in the development of new citrus varieties with improved Mg-use efficiency.

Bacillus-Loaded Biochar as Soil Amendment for Improved Germination of Maize Seeds

Biochar is considered one of the most promising long-term solutions for soil quality improvement, representing an ideal environment for microorganisms' immobilization. Hence there is a possibility to design microbial products formulated using biochar as a solid carrier. The present study was aimed at development and characterization of Bacillus-loaded biochar to be applied as a soil amendment. The producing microorganism Bacillus sp. BioSol021 was evaluated in terms of plant growth promotion traits, indicating significant potential for production of hydrolytic enzymes, indole acetic acid (IAA) and surfactin and positive tests for ammonia and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase production. Soybean biochar was characterised in terms of physicochemical properties to evaluate its suitability for agricultural applications. The experimental plan for Bacillus sp. BioSol021 immobilisation to biochar included variation of biochar concentration in cultivation broth and adhesion time, while the soil amendment effectiveness was evaluated during maize germination. The best results in terms of maize seed germination and seedling growth promotion were achieved by applying 5% of biochar during the 48 h immobilisation procedure. Germination percentage, root and shoot length and seed vigour index were significantly improved when using Bacillus-biochar soil amendment compared to separate treatments including biochar and Bacillus sp. BioSol021 cultivation broth. The results indicated the synergistic effect of producing microorganism and biochar on maize seed germination and seedling growth promotion, pointing out the promising potential of this proposed multi-beneficial solution for application in agricultural practices.

Magnesium improved fruit quality by regulating photosynthetic nitrogen use efficiency, carbon-nitrogen metabolism, and anthocyanin biosynthesis in 'Red Fuji' apple

INTRODUCTION

Both nitrogen (N) and magnesium (Mg) play important roles in biochemical and physiological processes in plants. However, the application of excessive N and insufficient Mg may be the factor leading to low nitrogen utilization rate (NUE) and fruit quality degradation in apple production.

METHODS

In this study, we analyzed the effects of different application rates of Mg (0, 50, 100, 150, 200 kg/ha) on the photosynthetic nitrogen use efficiency (PNUE), the accumulation and distribution of carbon (C), N metabolism, anthocyanin biosynthesis and fruit quality of the 'Red Fuji' apple in 2018 and 2019.

RESULTS

The results showed that the application of Mg significantly increased the ¹⁵NUE and increased the allocation rate of ¹⁵N in the leaves whereas the ¹⁵N allocation rate in the perennial organs and fruits was decreased. With the increase in Mg supply, the activities of N metabolism enzymes (NiR, GS, and GOGAT) were significantly promoted and the content of intermediate products in N metabolism ( NO 2 - , NH 4 + , and free amino acid) was significantly decreased. Furthermore, an appropriate rate of Mg significantly promoted the net photosynthetic rate (P_n) and photosynthetic nitrogen use efficiency (PNUE), enhanced the enzyme activities of C metabolism (SS, SPS, S6PDH), and increased the contents of sorbitol and sucrose in leaves. In addition, Mg upregulated the gene expression of sugar transporters (MdSOT1, MdSOT3, MdSUT1, and MdSUT4) in fruit stalk and fruit fresh; ¹³C isotope tracer technology also showed that Mg significantly increased the ¹³C allocation in the fruits. Mg also significantly increased the expression of anthocyanin biosynthesis genes (MdCHS and MdF3H) and transcription factors (MdMYB1 and MdbZIP44) and the content of anthocyanin in apple peel.

CONCLUSION

The comprehensive analysis showed that the appropriate application of Mg (150 kg/ha) promoted PNUE, C-N metabolism, and anthocyanin biosynthesis in apple trees.

Inter- and Intra-Population Variation of Foliage Calcium and Magnesium in Two Chinese Pine Species

Calcium and magnesium are major nutrient elements of plants, and both play an important role in plant growth and development. Pinus massoniana and P. hwangshanensis are important afforestation tree species in barren mountains in China. However, observation and research on calcium and magnesium nutrition of dominant forest species in China are still limited. This study determined the concentration of calcium and magnesium in needles for two species from five sites in East China by inductively coupled plasma optical emission spectrometry (ICP-OES). We then explored the inter- and intra-population variation pattern of calcium and magnesium and their relationship with environmental factors. There were significant differences in traits among populations. The strongest factors, which impacted the variation of calcium and magnesium concentration, were elevation and individual differences, respectively. Element concentration was correlated to environmental factors such as longitude, latitude, elevation, and mean annual temperature. The results of this study can be helpful for a better understanding of tree growth, population survival, and forest succession.

Effect of Foliar Sodium Selenate and Nano Selenium Supply on Biochemical Characteristics, Essential Oil Accumulation and Mineral Composition of Artemisia annua L

Selenium (Se) biofortification of aromatic plants is a promising strategy to produce valuable functional food with high biological activity and enhanced essential oil yield. The experiment carried out in 2021 and 2022 on A. annua treated with sodium selenate or nano-Se sprayed on foliar apparatus demonstrated a significant increase in photosynthetic pigments, pectin, waxes, macro- and microelements and a decrease in malonic dialdehyde (MDA) accumulation. Contrary to literature reports, neither selenate nor nano-Se showed a beneficial effect on essential oil accumulation; the oil yield did not differ between the selenate treated and control plants but was halved by the nano-Se application. Extremely high variations in the number of essential oil components, as well as in the eucalyptol, artemisia ketone, camphor and germacrene D ratio in the 2021 and 2022 experiments were recorded. The analysis of the 2016-2022 data for oil yield and composition in the control plants revealed a direct correlation between the number of components and of solar flares, and a negative correlation between oil yield and the percentage of spotless days. Both control plants and plants fortified with selenium showed higher levels of germacrene D and lower levels of artemisia ketone in 2022, characterized by more remarkable solar activity compared to 2021. Nano-Se supply resulted in the highest percentage of germacrene D accumulation. The results of the present research highlight the importance of the solar activity effect on the essential oil yield and quality of aromatic plants.

Soil Treatment with Nitric Oxide-Releasing Chitosan Nanoparticles Protects the Root System and Promotes the Growth of Soybean Plants under Copper Stress

The nanoencapsulation of nitric oxide (NO) donors is an attractive technique to protect these molecules from rapid degradation, expanding, and enabling their use in agriculture. Here, we evaluated the effect of the soil application of chitosan nanoparticles containing S-nitroso-MSA (a S-nitrosothiol) on the protection of soybeans (Glycine max cv. BRS 257) against copper (Cu) stress. Soybeans were grown in a greenhouse in soil supplemented with 164 and 244 mg kg-1 Cu and treated with a free or nanoencapsulated NO donor at 1 mM, as well as with nanoparticles without NO. There were also soybean plants treated with distilled water and maintained in soil without Cu addition (control), and with Cu addition (water). The exogenous application of the nanoencapsulated and free S-nitroso-MSA improved the growth and promoted the maintenance of the photosynthetic activity in Cu-stressed plants. However, only the nanoencapsulated S-nitroso-MSA increased the bioavailability of NO in the roots, providing a more significant induction of the antioxidant activity, the attenuation of oxidative damage, and a greater capacity to mitigate the root nutritional imbalance triggered by Cu stress. The results suggest that the nanoencapsulation of the NO donors enables a more efficient delivery of NO for the protection of soybean plants under Cu stress.