Insoluble Oxalate Research Articles

Efficient Quantification of Soluble and Insoluble Oxalates in Clay Mineral Mixtures

ABSTRACT Quantification of oxalate salts in soil clay minerals is necessary to study oxalate biogeochemistry, but existing analytical techniques are expensive and time-consuming. We aim to develop an efficient attenuated total reflectance mid-infrared (MIR) spectroscopic technique to quantify oxalate salts in a clay mineral matrix. We calibrated MIR models for analysis of oxalate anion concentrations in standard solutions (0–0.01 M) by using a partial least-squares regression algorithm. MIR models were also developed for analysis of sodium oxalate (NaOx) and calcium oxalate (CaOx) content in clay mineral mixtures with composition like soils of a semi-arid region and with contrasting concentrations (0–1.0 g g−1 for both oxalate salts) to test sensitivity of analyses. Validation plots (true vs predicted values) showed excellent model fit (R2 ≥ 0.96) and accuracy (normalized root mean squared error of prediction ≤ 0.06) for CaOx, NaOx and oxalic acid components. Once predictive models are stored in analytical software, MIR spectroscopic analyses of samples are much more efficient than chemical techniques. Our MIR spectral-based models are suitable for direct quantification of oxalate salts in clay mineral mixtures for samples like those used for model calibration.

Nutritional evaluation of Colocasia esculenta (L.) Schott leaves and corms from KwaZulu-Natal, South Africa

Green leafy vegetables (GLVs) are good sources of vital nutrients for human health sustenance. In this study, the nutrient compositions of Colocasia esculenta L. (Schott) leaves and corms from both Southern and Northern locations of KwaZulu-Natal province were investigated. Total, soluble, and insoluble oxalates and soil minerals were analysed to establish nutrient-plant organ correlations. Substantial variations were observed in nutrient contents among plant parts and locations. Young leaves in both locations showed higher phosphorus content and the northern location had the highest potassium levels in both young and mature leaves. Zinc and copper contents of leaf tissues were relatively low, ranging from 1.9 to 4.7 mg/100 g and 0.48–1.46 mg/100 g FW, respectively, whereas manganese (2–64 mg/100 g FW) and iron (13 – 88 mg/100 g FW) showed higher variability. While oxalate levels showed minimal location effects, corms had more than double the total oxalate content (35–39 g/100 g FW) of leaf tissues. Despite variations in mineral profile, Colocasia esculenta leaves can serve as a valuable source of essential micronutrients to address micronutrient needs in vulnerable communities.

Quantitative Determination of Oxalic and Phytic Acids of Lippia Multiflora Moldenke (Verbenaceae) Leaves and In Silico Study of Their Interaction with Haemoglobin S and 2,3-DPG-Mutase

The aim of this study is to measure oxalic and phytic acids from the leaves of Lippia multiflora and to evaluate their anti-sickle cell activity in silico. The histological characterization of the leaves of L. multiflora was performed by optical micrography. Theseanti-nutritional factors oxalic acid and phytic acid were determined by the standard method. Discovery Studio, ChemDraw and Autodock Vina software were used in molecular modeling. The pharmacokinetic and toxicological profile was evaluated using the bioinformatics descriptor SWISSADME. Histological analysis shows that fibres, sclerites and suber fragments are characteristic tissues of L. multiflora leaves. These leaves contain oxalic acid (insoluble oxalates: 51.457±27.653 mg/100 g DM; total oxalates: 59.483±0.704 mg/100 g MS; calcium oxalates: 0.216±0.0021 mg/100 g MS) and phytic acid (18.400±5.062 mg/100 g MS). Oxalic acid interacts more effectively with 2,3-diphospgoglycerate mutase (ΔG=-5.30±0.03 kcal/mol) while phytic acid interacts more strongly with deoxyhemoglobin S (ΔG=-9.30±0.01 kcal/mol) in silico. Phytic acid interacts with deoxyhemoglobin S by two hydrogen bonds (Arginine 31 and Lysine 120) while oxalic acid forms five hydrogen bonds with 2,3-DPG mutase (Arginine 10, Asparagine 17; Arginine 62; Histidine 188 and Glycine 189). The pharmacopharmacokinetic profile shows that these compounds do not inhibit cytochrome P450 complex enzymes and are not toxic. Both compounds represent added value for L. multiflora in the symptomatic treatment of sickle cell disease. In addition to attenuating hypersideremia, they can inhibit erythrocyte sickle formation via interaction with both protein receptors.

Crystal idioblasts are involved in the anther dehiscence of Nicotiana tabacum

In Nicotiana tabacum, the degeneration of connective tissue and stomium tissue (the stomium and circular cell cluster [CCC]) is essential for anther dehiscence. Both connective cells and CCC cells are crystal idioblasts, and these cells will undergo degeneration after accumulating calcium oxalate (CaOx) crystals. However, detailed data concerning this process are minimal. Therefore, this study used cellular biological and physiological methods to illustrate this relationship. Results demonstrated that tobacco anther dehiscence is a series of timed programmed cell death (PCD) processes that include the CCC, connective tissue, and stomium. The degenerating crystal idioblasts of the tobacco anther were found to possess two hallmark characteristics that distinguished them from normal PCD cells, namely dynamic changes in CaOx crystals and the appearance of numerous peroxisomes. The accumulation of CaOx and the production of H2 O2 occurred simultaneously or successively before PCD. The peak H2 O2 content was found to appear after the insoluble oxalate. Further, CeCl3 cytochemistry staining was used to detect subcellular H2 O2 , and the precipitate of H2 O2 was primarily present in peroxisomes and around CaOx crystals. These results show that anther dehiscence in N. tabacum is a PCD process in which crystal idioblasts play a vital role in CaOx degradation and H2 O2 production.

Do the Invasive Earthworms Amynthas agrestis (Oligochaeta: Megascolecidae) and Lumbricus rubellus (Oligochaeta: Lumbricidae) Stimulate Oxalate-Based Browser Defenses in Jack-in-the-Pulpit (Arisaema triphyllum) by Their Presence or Their Soil Biogeochemical Activity?

The introduction of invasive earthworms initiates physical and chemical alterations in previously earthworm-free forest soils, which triggers an ecological cascade. The most apparent step is the shift in the herbaceous plant community composition. However, some species, such as Arisaema triphyllum (jack-in-the-pulpit), persist where earthworms are present. It has been hypothesized that A. triphyllum produces insoluble oxalate, an herbivory deterrent, in the presence of earthworms. This study aimed to distinguish between the effects of earthworm-induced changes in soils and the physical presence of earthworms on oxalate production. As such, a two-way factorial greenhouse trial was conducted using uninvaded soils to test this hypothesis for two invasive earthworm species (Amynthas agrestis and Lumbricus rubellus). The sequential extraction of oxalates in A. triphyllum corms was performed with absolute ethanol, deionized water, acetic acid and HCl, representing fractions of decreasing solubility. Earthworm presence increased water-soluble (p = 0.002) and total oxalate (p = 0.022) significantly, but only marginally significantly for HCl-soluble oxalate (p = 0.065). The corms of plants grown in soils previously exposed to the two species did not differ in oxalate production when earthworms were not present. However, the data suggest that earthworms affect corm oxalate concentrations and that the sequence of invasion matters for oxalate production by A. triphyllum.

High and low oxalate content in spinach: an investigation of accumulation patterns.

Oxalic acid is a common antinutrient in the human diet, found in large quantities in spinach. However, spinach is highly regarded by vegetable producers because of its nutritional content and economic value. One of the primary purposes of spinach-breeding programs is to improve the nutritional value of spinach by adjusting oxalate accumulation. Knowledge of the biosynthetic patterns of oxalic acid, and its different forms, is important for a better understanding of this process. We found three biosynthetic patterns of accumulation and concentration of oxalates. Two of them are related to the maximum type and one is related to the minimum type. We also developed a general model of variations in these compounds in the genotypes that were studied. This study introduced a unique type of spinach with high oxalate accumulation, which could be particularly suitable for consumption. This had the highest ratio of insoluble oxalate to soluble oxalate. It also accumulated more ascorbic acid (AA) than other types. Our findings in this study also indicate a small role for AA as a precursor to oxalate production in spinach, possibly confirming the significant role of glyoxylate as the most critical precursor in this plant. © 2021 Society of Chemical Industry.

Antioxidants Capacity, Phenolic and Oxalate Content from Two Varieties of Solanum melongena at Different Maturity Stages

Aims: To investigate the antioxidant activities, total phenolic and oxalate contents in two varieties of eggplant (Solanum melongena) (terung telunjuk (TT) and terung rapuh (TR)) at different maturity stages.
 Study design: Each sample was extracted three times (n=3) for the antioxidant activities, total phenolic and oxalates content. All the data were analysed by using ANOVA and Tukey Pairwise tests.
 Place and duration of study: Malaysian Agricultural Research and Development Institute (MARDI), between December 2019 and October 2020.
 Methodology: Two varieties of eggplant (TT and TR) were cultivated and the samples were tagged and the fruits were harvested according to their maturity stages (stage 1 – stage 4). Samples were freeze dried and extracted to evaluate the antioxidant activities as well as the total phenolic and oxalate contents.
 Results: Total phenolic contents (TPC) in TR were lower from stage 1 to stage 3 but high at over mature stage (stage 4) meanwhile TPC in TT increased upon maturity. The DPPH assay from the fruit extracts of TT in all maturity stages showed a stronger antioxidant activity as compared to TR, in which fruit of TT from stage 3 was double in antioxidant activity as compared to TR. The FRAP assay of both eggplants showed extracts of TT having a higher ferric reduction power in all stages as compared to TR. Meanwhile, both eggplant varieties showed different total, soluble and insoluble oxalate contents in all maturity indices. TT had the highest total oxalate content at stage 1 as compared to TR while the soluble oxalate content increased in TR in all maturity stages. The highest percentage of soluble oxalate content was observed in TR at stage 4 with 95.5%. Conclusion: Phytochemical findings from these eggplant varieties showed their potentials to improve livelihood and public health. More comprehensive studies on the bioactive compounds, structural elucidation and pharmacological evaluation are to be conducted to understand the possible effects of these phytochemical results.

Variation in oxalate content among corm parts, harvest time, and cultivars of taro (Colocasia esculenta (L.) Schott)

Taro (Colocasia esculenta L. Schott) is considered a dietary staple food crop for millions of people throughout tropical and subtropical regions. Depending on the cultivar, taro may contain oxalic acid deposited in plant tissues as calcium oxalate crystals, causing a very unpleasant burning sensation in the mouth. In the present study, oxalate content was quantified in four different parts of the taro corm, as well as variation in dry matter, Ca, and the oxalate content of corms harvested at different developmental stages, from 5 months after planting (MAP) to 13 MAP. The results revealed that the level of oxalates varies according to corm part and cultivar. The cultivars with the lowest and highest water-soluble and total oxalate content in the central part, which is critical for human nutrition, were VU268 (87 and 134 mg 100 g−1 DW) and VU384 (182 and 230 mg 100 g−1 DW, respectively). Water-soluble oxalates accumulate mainly in the central and lower parts, while insoluble oxalates are concentrated in the marginal part of the corm. Their content can be almost halved by removing a 1 cm thick marginal layer (peeling). The oxalate/Ca molar ratio ranged from 0.78 in the upper to 1.31 in the central part, suggesting that the bioavailability of Ca in corms could be low. The dry matter content and Ca, insoluble and total oxalate levels vary according to the harvest time. The lowest total oxalate content was determined at 8 MAP (the usual time for taro harvest), while water-soluble oxalates increased with growing period. The proper assessment of corm maturity before harvest is, therefore, a critical step in controlling corm quality. Taro breeding programs aimed at reducing corm acridity need to take into consideration these results when designing protocols for optimum nutritional quality improvement of new cultivars.

The photocatalytic reduction of NO3− to N2 with ilmenite (FeTiO3): Effects of groundwater matrix

This work analyzes the role of natural groundwater, as well as the effect of HCO3−, Ca2+, Mg2+, K+, SO42- and Cl− concentrations, upon the photocatalytic nitrate reduction using ilmenite as catalyst and oxalic acid as hole scavenger. The nitrate removal and the selectivity towards N2 are significantly limited compared to previous experiments using ultrapure water matrix. Calcium (Ca2+), bicarbonate (HCO3−) as well as pH are claimed as the major controlling factors related to the process yield. Thus, Ca2+ promotes the formation of insoluble oxalate microcrystals, reducing the amount of hole scavenger available. The presence of HCO3− leads to a steeply increase in the pH value, favoring the adsorption onto the ilmenite surface of ions OH−instead of NO3−, NO2− and C2O42. The aforementioned issues are overcome by working with C2O42−/NO3− ratio well above the stoichiometric one, that also maintains the pH value in an acid range. A completed depletion of the starting NO3−, the no detection of either NO2− or NH4+ in the aqueous phase, and a selectivity towards N2 above 95% were achieved using two times the stoichiometric dose.

Accumulation and sub cellular distribution of lead (Pb) in industrial hemp grown in Pb contaminated soil

Industrial hemp has an excellent lead (Pb) tolerance and accumulation capacity. Further enhancing the Pb tolerance and its accumulation in industrial hemp is of great significance for its future application in phytoremediation. In present study, a pot experiment using Pb-contaminated soil was conducted to investigate the accumulation of Pb contents in various organs of industrial hemp and its subcellular distribution and extractable form in the leaves. It was found that under Pb stress, the Pb content in plants increased significantly with an increase in the soil Pb concentration. Lead was mainly concentrated in the roots, followed by stems and leaves, while the lowest Pb contents were found in seeds (<12 mg/kg). The Pb content in roots was 2–7 times higher than in stems, leaves, and fibers, and 6–25 times higher than in seeds. At the subcellular level, Pb in industrial hemp leaves was mainly distributed in the cell wall and chloroplasts, with the Pb content first increasing and then decreasingas the soil Pb concentration increased, reaching a maximum at 4000 and 3000 mg/kg, respectively. Lead was less accumulated in the vacuoles and soluble parts of cells, with the least accumulation occurring in the organelles. There was no nsignificant increase in Pb content in these subcellular locations with the increase in soil Pbconcentration. Treatments with different Pb concentrations affected the extractable form of Pb in hemp leaves. The HCl extractable form of Pb, with low activity, was predominant in the leaves. The proportional content of Pb in each form was different in the various parts of the plant. The Pb content of each form in the leaf was Pb HCl(hydrochloric acid)＞Pb E (ethanol)>Pb W (deionized water)>Pb HAc (acetic acid) >Pb NaCl (sodium chloride), indicating that Pb in industrial hemp mainly exists in the form of insoluble oxalate precipitates, thereby alleviating the toxicity of Pb. The results of this study provide a scientific reference for the use of industrial hemp to remediate Pb polluted soils.

Oxalate contents in green juice prepared using either a high-speed blender or a masticating juicer

Green vegetables are very beneficial for health, but sometimes it is not understood that some vegetables also contain anti-nutrients. For example, oxalic acid can be found in some green vegetables, such as spinach. Oxalic acid can be absorbed from food and as it is a toxin it has to be removed from the body via the kidneys. Under certain conditions, oxalate can combine with calcium in the kidneys forming stones which can lead to impaired kidney function. This study aims to compare two techniques for making vegetable juice, using a high-speed blender or a masticating juicer. The content of oxalic acid, calcium, pH and titratable acidity (TA) was measured in both juices. Total oxalic acid was measured using HPLC, calcium content was analyzed using a Coupled Plasma Optical Emission Spectrophotometer. Dry matter, pH and TA were measured based on AOAC methods. The highest total oxalate (OA) was found in juice made using a masticating juicer of 7638.27 mg OA/100 g dry weight. The highest calcium content was found in the fiber fraction or in the remaining juice using the masticating juicer technique, which was 10.04 mg/100 g juice. Meanwhile, the TA value of the thick juice produced by the high speed blender was not significantly different from the runny juice produced by the masticating juicer. The smoothie-like green juice prepared using a high-speed blender was healthier as the soluble and insoluble oxalate extracted in the juice was lower than in the clear juice prepared using a masticating juicer.

Late onset primary hyperoxaluria after kidney transplantation in a 36-year-old woman

Primary hyperoxaluria is a rare congenital autosomal recessive disorder disrupting the glyoxylate metabolism pathway in the liver. Type1 primary hyperoxaluria is caused by a deficiency in a specific liver enzyme namely, alanine glyoxylate-aminotransferase which catalyzes the conversion of glyoxylate to glycine. By the absence of this enzyme, glyoxylate is converted to oxalate and high oxalate level causes deposition of insoluble calcium oxalate crystals in different organs specifically kidneys. The disease usually manifested by recurrent nephrolithiasis and/or nephrocalcinosis leads to renal failure. This report describes an end-stage renal disease case of a 36-year-old Iranian woman without any history of nephrolithiasis who underwent kidney transplantation. She developed an early onset transplant kidney failure. The patient underwent kidney biopsy, which revealed oxalate nephropathy, accordingly the genetic study confirmed diagnosis of primary hyperoxaluria. This rare case shows how type 1 primary hyperoxaluria can develop after kidney transplantation without having any manifestation prior to transplantation

Simple and ultrasensitive electrochemical sensor for oxalic acid detection in real samples by one step co-electrodeposition strategy

Oxalic acid (OA), naturally available in vegetables and foodstuffs derived from them, easily combines with calcium and iron to form insoluble oxalates. Their chelation will result in various renal diseases; thus, the accurate determination of OA is quite significant in the evaluation of food quality and healthcare settings. Here, we developed an electrochemically induced alcohol-free sol-gel method to obtain platinum nanoparticles (PtNPs) adhered with porous silica on glassy carbon electrode (PSiO2-PtNPs/GCE) by a one-step process, which can be potentially used as an excellent catalyst towards electrochemical oxidation of OA for the first time. Without any redox mediator, PSiO2-PtNPs/GCE exhibited a low oxidation overpotential and a significantly high current signal, achieving a wide linear range of concentration from 0 to 45μM and a detection limit as low as to 25nM for OA detection. Moreover, this present alcohol-free sol-gel approach towards OA determination was verified in real samples, which is promising for foodstuff analysis and clinical diagnosis. Graphical abstract.

Copper Precipitation as Insoluble Oxalates by Thermotolerant Aspergillus spp. from Burning Wastes of Coal Mining

Micromycetes can precipitate metals in the form of insoluble oxalates, thus participating in metal removal from geochemical cycling and in secondary mineral formation. Metal precipitation has a practical application for bioleaching and bioremediation. Micromycetes from the genus Aspergillus are used as model organisms to study metal precipitation. All known biomineralization processes carried out by micromycetes described so far involved mesophilic organisms. Thermophilic eukaryotes may be advantageous for biotechnologies. This study reports the isolation of thermophilic/thermotolerant Aspergillus spp. from burning wastes of coal mining in Kuzbass and their participation in formation of insoluble copper oxalate, moolooite. Copper-enriched extracellular vesicles formed in the process may act as nucleation sites for the moolooite crystals formation.

Oxalate contents of Thai rice paddy herbs (L. aromatica and L. geoffrayi) are affected by drying method and changes after cooking

Food processing, including drying and cooking, generally influences the physical and chemical qualities of food products. The present study assessed the changes in oxalate contents of two rice paddy herbs (phak-kha-yaeng in Thai), Limnophila aromatica (phak-kha-yaeng khao) and Limnophila geoffrayi (phak-kha-yaeng daeng), as affected by different drying methods, namely hot-air, freeze and vacuum drying. The entire, soluble and insoluble oxalate contents of the cooked samples were also evaluated. Dried samples showed a significant increase in soluble oxalate content compared to fresh samples except for hot-air dried phak-kha-yaeng daeng, while entire and insoluble oxalate contents in dried samples were significantly decreased. Levels of soluble oxalates which were 30% in fresh phak-kha-yaeng khao and 46% in fresh phak-kha-yaeng daeng can be significantly reduced after cooking by boiling. In addition, the cooking of both the hot-air dried phak-kha-yaeng samples also showed greater losses in oxalates than those of other samples studied. Hot-air drying should be considered as a suitable drying method for phak-kha-yaeng with respect to reducing its oxalates. The present study has provided useful information for the drying of vegetables or plant foods to reduce the risk of consuming plant foods which contain high levels of oxalates.

Determination of Oxalates in Corms of Selected Taro (Colocasia esculenta) Varieties in Malaysia Using Ultra High-Performance Liquid Chromatography

Aims: To determine the oxalate contents in different varieties of taro (Colocasia esculenta) collected in Peninsular Malaysia.&#x0D; Study Design: Ultra High-Performance Liquid Chromatography (UHPLC) with UV detector (Diode Array Detection, (DAD)) was used to determine the total and soluble oxalate contents in different varieties of taro corms. Meanwhile, the insoluble oxalate content (calcium oxalate) was estimated from the subtraction of soluble oxalate content from total oxalate content.&#x0D; Place and Duration of Study: Malaysian Agriculture Research and Development Institute (MARDI Headquarters), Persiaran MARDI-UPM, 43400 Serdang, Selangor, Malaysia between December 2018 to December 2019.&#x0D; Methodology: 9 different varieties of taro were collected from different locations in Peninsular Malaysia. All the samples were analysed for their oxalate contents. Extractions were carried out to determine the total oxalate and soluble oxalate contents. All the samples were analysed using UHPLC. The generated data of oxalate contents were analysed using Analysis of Variance (ANOVA).&#x0D; Results: There is a significant difference (P &lt;.05) between the oxalate content in the examined varieties with respect to the amount of total, soluble and insoluble oxalate contents. The putih variety has significantly the highest amount of total oxalate content with 218.8 ± 28.2 mg/100 g DW (dry weight) followed by the udang variety with 184.2 ± 24.7 mg/100 g DW and the wangi variety with 178.3 ± 5.1 mg/100 g DW. Tapak badak variety has the lowest total oxalate content with 70.5 ± 20.1 mg/100 g DW. Result showed that wangi variety has significantly the highest soluble oxalate content with 135.1 ± 4.8 mg/100 g DW followed by udang with 100.9 ± 49.8 mg/100 g DW. The lowest soluble oxalate content was found in tapak badak with 17.7 ± 2.9 mg/100 g DW.&#x0D; Conclusion: Despite many factors contributing to the difference in oxalate content between varieties, this study would help researchers or policy makers to suggest potential taros for commercial cultivation.

Elderberry (Sambucus spp.) interspecific hybridization and its impact on fruit oxalates

AbstractElderberry fruits are a good source of minerals and antioxidants; however, the presence of anti‐nutrients like oxalates may limit their utilization. The presented study which involves chemical evaluation of numerous interspecific hybrids is based on a hypothesis that interspecific genetic recombination may significantly improve the production and the nutritional quality of elderberry fruits. The aim of the first part of this study was to determine the oxalates (total, water‐soluble and insoluble) in fruits of 73 elderberry genotypes. In the second part, the dynamics of oxalate contents during fruit maturation was analysed. The average content of total oxalates in analysed genotypes was 721 ± 33 mg/100 g DW. The majority (91%, on average) were health harmless insoluble oxalates. The average content of total oxalates was increasing at the beginning of maturation and then it began to decrease significantly and reached its minimum value at full maturity, while the average of water‐soluble oxalates was gradually decreasing throughout maturation. Due to relatively high oxalate contents, some of the analysed hybrids should not be used for further breeding process.

Changes in oxalate composition and other nutritive traits in root tubers and shoots of sweet potato (Ipomoea batatas L. [Lam.]) under water stress.

The presence of insoluble calcium oxalate druse crystals (CaOx) in sweet potato (Ipomoea batatas) can negatively affect its nutritional quality. Photosynthesis, starch, and protein composition are linked with oxalate synthesis and tuber quality under water scarcity. Our main objective was the oxalate quantitation of sweet potato tubers and shoots and also to assess how drought changes their nutritional value. Eight sweet potato accessions from Madeira, the Canaries and Guinea-Bissau were analyzed for their response to drought stress. Tubers and shoots were analyzed for total (T-Ox), soluble (S-Ox) and insoluble (CaOx) oxalates, protein, chlorophyll content index (CCI), soluble starch, starch swelling power, and starch solubility in water. The S-Ox and CaOx content was higher in shoots. Six accessions were above maximum CaOx levels for raw consumption. Accessions with more favorable responses to drought had decreased CaOx with S-Ox increase content for osmoregulation. They also presented slightly decreased CCI and protein contents. These accessions also had an increased shoot starch content, for further tuber storage starch hydrolysis, and maintained the quality and functional properties of the tuber starch grain. Those with a less favorable response to drought had a higher T-Ox and CaOx content in both organs, hindering water absorption. They also had decreased protein and CCI, with a slight increase in tuber starch hydrolysis. Oxalate content was significantly related to carbohydrate metabolism, CCI, and protein synthesis. This study significantly contributed to the screening of the sweet potato stress response to drought, to adapt this crop to climatic change through breeding programs. © 2019 Society of Chemical Industry.

Gadolinium accumulation, distribution, chemical forms, and influence on the growth of rice seedlings

The content of gadolinium (Gd) is continuously increased in environment, which potentially threatens human health and ecological equilibrium. However, the phytotoxicity of Gd on plants remains unknown until now. In this study, the accumulation, distribution, and chemical forms of Gd as well as its influence on growth and nutrient balance were systematically studied in rice seedlings after the treatments of different concentrations of Gd (0, 1, 10, 100, and 1000 μM) for 10 days. The results showed that most Gd was accumulated in the roots and only a little percentage of Gd was transported to shoots. The accumulation of Gd was increased in a dose-dependent manner in various chemical forms and subcellular fractions. More than 80% of Gd was in the forms of insoluble oxalates and phosphates. Gd was mainly compartmentalized in the cell wall, and the content of Gd was increased with increasing concentrations of Gd. In addition, hormetic effects of Gd were found on rice growth. The growth of rice was induced by the lower concentration of Gd, but inhibited by the higher concentration of Gd. The results indicated that rice seedlings could cope with Gd toxicity through cell wall compartmentalization as well as forming of precipitates with oxalate and phosphate.

The Role of Different Nitrogen Sources Combined with Foliar Applications of Molybdenum, Selenium or Sucrose in Improving Growth and Quality of Edible Parts of Spinach (Spinacia oleracea L.)

Two pots experiments, at two successive winter seasons, were carried out to investigate the effects of two nitrogen (N) sources (ammonium nitrate and urea) and foliar applications of molybdenum (Mo), sucrose (Suc) or selenium (Se) on the growth and quality of the edible parts of spinach (Spinacia oleracea L. cv. Balady). The results indicated that the growth and quality of spinach plants can be greatly determined by the applied N source. The edible parts of spinach plants that received urea as N source showed lower content of NO3-, soluble oxalate, insoluble oxalate and total oxalate plus higher level of P content, however, higher moisture content as well as lower accumulation of dry mass, vitamin C and Fe were also observed in both seasons. Among the tested foliar applications at different concentrations, the treatment with 10% sucrose showed superior effects for increasing spinach growth (increase fresh weight, dry weight and leaves area) and quality (increase the contents of N, P, K, Ca, Fe, total protein and chlorophyll, as well as decreasing the contents of soluble oxalate and total oxalate) relative to the control (distilled water) in both seasons. The interaction treatment of urea fertilizer with foliar application of 10% sucrose was the most efficient one in decreasing NO3- and soluble oxalate contents without reductions in growth (fresh and dry weights), the contents of vitamin C and minerals against the corresponding control in both seasons.