Residual pollutants in treated pulp paper mill wastewater and their phytotoxicity and cytotoxicity in Allium cepa.

Discharged pulp and paper mill wastewater (PPMW) were collected near M/s K. R. pulp and papers Limited, Shahjahanpur, India. Chemical analysis of the wastewater showed high BOD (3653-4180 mg L-1) and COD (17,890-19100 mg L-1) values from two different sampling sites. The levels of total phenol were in the range of 389-432 mg L-1; nitrogen (125-234 mg L-1), sulfate (1926-2098 mg L-1), chloride (3.12-5.43 mg L-1) and lignin (38,950-39,000 mg L-1) along with various heavy metals (Fe, 87-79; Zn, 34-22; Cu, 3.28-2.57; Cd, 1.90-0.36; Ni, 6-5, and Pb, 41.23-36.54 mg L-1) were above the permissible limits recommended by the CPCB and the USEPA. The BOD/COD ratio was < 0.2 which indicated very low biodegradability of the organic matters present in the effluent. The organometallic complex generated from the pulp and paper industry persists in the environment and might be toxic to aquatic organisms. The organic polymers, lignin, metals and ions present in the PPMW were characterized using SEM, EDAX, FTIR, and UV-VIS spectroscopy. The major pollutants detected in the discharged PPMW included nonacosane, heptacosane, octadecanoic acid, hexadecane, and 6-benzamide- 3- [2- [1-(phenylmethyl)-4-piperidinyl] ethyl]-1, 2-benzisoxazole, as well as a group of plant fatty acids classified as EDCs, and mutagenic pollutants. The cytotoxic and androgenic properties of these complex organics were examined. The seed germination test with Phaseolus mungo and cytotoxicity test with Allium cepa showed that at > 20% concentration of PPMW, α-amylase production was inhibited and chromosomal segregation at metaphase and anaphase during cell division was disturbed, which resulted in c-mitosis, sticky chromosomes, and laggard chromosomes. In addition, SEM of the root of A. cepa showed fissures and fractured tissues of the root cap, probably due to the inhibition of auxins that were responsible for root cap formation. The findings indicated A. cepa as a good test model for examining the DNA damage and cytotoxicity by PPMW, and the discharged effluent should be treated at a tertiary stage for environmental protection.

Selenate and selenite affect photosynthetic pigments and ROS scavenging through distinct mechanisms in cowpea (Vigna unguiculata (L.) walp) plants.

Selenium (Se) is a beneficial element to higher plants. Application of Se at low concentrations enhances the antioxidant metabolism reducing the reactive oxygen species (ROS) generated by plant membrane cells. This study aimed to evaluate how the application of Se in the forms sodium selenate and sodium selenite regulates ROS scavenging in field-grown cowpea plants. Seven Se application rates (0; 2.5; 5; 10; 20; 40 and 60 g ha-1) of each of the two Se forms were applied to plants via the soil. Photosynthetic pigments concentration, gas exchange parameters, lipid peroxidation by malondialdehyde (MDA) concentration, hydrogen peroxide concentration, activity of catalase (CAT, EC:1.11.1.6), glutathione reductase (GR, EC:1.6.4.2), ascorbate peroxidase (APX, EC:1.11.1.11) and Se concentration in leaves and grains were evaluated. In general, Se application led to a decrease in chlorophyll a concentration whilst leading to an increase in chlorophyll b, indicating conservation of total chlorophyll concentration. Application of 2.5 g ha-1 of Se as selenate provided a notable increase in total chlorophyll and total carotenoids compared to the other application rates. Selenate and selenite application decreased lipid peroxidation. However, each Se source acted in a different pathway to combat ROS. While selenate showed more potential to increase activity of APX and GR, selenite showed a higher potential to increase CAT activity. The negative correlation between CAT and GR is indicative that both pathways might be activated under distinct circumstances. The more prominent activity of CAT under high rates of selenite resulted in a negative correlation of this enzyme with chlorophyll a and carotenoids. Both selenate and selenite application increased sucrose and total sugars concentration in leaves of cowpea plants. Overall, these results indicate that application of Se in cowpea under field conditions stimulates distinct pathways to scavenge ROS. This could prove beneficial to mitigate oxidative stress during plant development.

A NAC-type transcription factor confers aluminium resistance by regulating cell wall-associated receptor kinase 1 and cell wall pectin.

Transcriptional regulation is important for plants to respond to toxic effects of aluminium (Al). However, our current knowledge to these events is confined to a few transcription factors. Here, we functionally characterized a rice bean (Vigna umbellata) NAC-type transcription factor, VuNAR1, in terms of Al stress response. We demonstrated that rice bean VuNAR1 is a nuclear-localized transcriptional activator, whose expression was specifically upregulated by Al in roots but not in shoot. VuNAR1 overexpressing Arabidopsis plants exhibit improved Al resistance via Al exclusion. However, VuNAR1-mediated Al exclusion is independent of the function of known Al-resistant genes. Comparative transcriptomic analysis revealed that VuNAR1 specifically regulates the expression of genes associated with protein phosphorylation and cell wall modification in Arabidopsis. Transient expression assay demonstrated the direct transcriptional activation of cell wall-associated receptor kinase 1 (WAK1) by VuNAR1. Moreover, yeast one-hybrid assays and MEME motif searches identified a new VuNAR1-specific binding motif in the promoter of WAK1. Compared with wild-type Arabidopsis plants, VuNAR1 overexpressing plants have higher WAK1 expression and less pectin content. Taken together, our results suggest that VuNAR1 regulates Al resistance by regulating cell wall pectin metabolism via directly binding to the promoter of WAK1 and induce its expression.

Effects of multiple N, P, and K fertilizer combinations on adzuki bean (Vigna angularis) yield in a semi-arid region of northeastern China.

Nitrogen (N), phosphorus (P), and potassium (K) exert various effects on adzuki bean yields. Our research was conducted in a semi-arid area, and four test sites were established in environments that have chernozem or sandy loam soils. During a five-year period, the effects of N, P, and K fertilizers on yield were comprehensively investigated in field trials (2014-2016) and for model-implementation trials (2017-2018), with models established prior to the latter. In the field trials, 23 treatments comprising different N, P, and K combinations significantly affected both yield and yield components, and regression analysis indicated that the experimental results were suitable for model establishment. The model subsequently demonstrated that the yield and the yield components were more sensitive to N and K fertilizer than to P fertilizer. Moreover, the yield and yield components increased. These yield increases were intense in response to the 0.5 to 1.34 levels in terms of the single effects; interaction effects; and the effects of combinations of N, P, and K fertilizers. Moreover, the effects of combinations of N, P, and K fertilizers were more significant on yield than were the single or interaction effects of N, P, and K fertilizers. The optimal fertilizer combination that resulted in high yields (≥1941.53 kg ha-1) comprised 57.23-68.43 kg ha-1 N, 36.04-47.32 kg ha-1 P2O5 and 50.29-61.27 kg ha-1 K2O. The fertilizer combination that resulted in the maximum yield was 62.98 kg ha-1 N, 47.04 kg ha-1 P2O5 and 59.95 kg ha-1 K2O (N:P2O5:K2O = 1:0.75:0.95), which produced the model-expected yield in trials at multiple sites. An economical fertilizer combination was determined on the basis of the best fertilizer measures in consideration of the cost of fertilizer and seed; this combination achieved yields of 2236.17 kg ha-1, the profit was 15,653.16 Yuan ha-1, and the corresponding rates were 57.60 kg ha-1 N, 47.03 kg ha-1 P2O5, and 31.64 kg ha-1 K2O (N:P2O5:K2O = 1:0.82:0.55).

Acetic acid: a cost-effective agent for mitigation of seawater-induced salt toxicity in mung bean.

The current study sought the effective mitigation measure of seawater-induced damage to mung bean plants by exploring the potential roles of acetic acid (AA). Principal component analysis (PCA) revealed that foliar application of AA under control conditions improved mung bean growth, which was interlinked to enhanced levels of photosynthetic rate and pigments, improved water status and increased uptake of K+, in comparison with water-sprayed control. Mung bean plants exposed to salinity exhibited reduced growth and biomass production, which was emphatically correlated with increased accumulations of Na+, reactive oxygen species and malondialdehyde, and impaired photosynthesis, as evidenced by PCA and heatmap clustering. AA supplementation ameliorated the toxic effects of seawater, and improved the growth performance of salinity-exposed mung bean. AA potentiated several physio-biochemical mechanisms that were connected to increased uptake of Ca2+ and Mg2+, reduced accumulation of toxic Na+, improved water use efficiency, enhanced accumulations of proline, total free amino acids and soluble sugars, increased catalase activity, and heightened levels of phenolics and flavonoids. Collectively, our results provided new insights into AA-mediated protective mechanisms against salinity in mung bean, thereby proposing AA as a potential and cost-effective chemical for the management of salt-induced toxicity in mung bean, and perhaps in other cash crops.

Insecticidal activity of Vanillosmopsis arborea essential oil and of its major constituent α-bisabolol against Callosobruchus maculatus (Coleoptera: Chrysomelidae).

Vigna unguiculata, one of the most important legumes, mainly in underdeveloped countries, is susceptible to post-harvest losses in storage by Callosobruchus maculatus (Fabricius, 1775) (Coleoptera: Chrysomelidae). The work evaluated the toxicity, inhibition of oviposition, instantaneous rate of population growth (ri) and the development of fumigated C. maculatus with the essential oil of Vanillosmopsis arborea and its major constituent, α-bisabolol. The experimental units consisted of 0.8 L flasks treated with concentrations of 1.2-11.2 µL L-1of air of the essential oil of V. arborea or its major constituent applied to disks of filter paper. α-Bisabolol was quantified as 409.33 mL L-1 of the essential oil. The development rate of C. maculatus was evaluated by daily adult counts. Oviposition was evaluated at lethal concentrations (LC50, LC25, LC10 and LC1). The LC50 and LC95 of the essential oil of V. arborea and α-bisabolol were 5.23 and 12.97 µL L-1 of air and 2.47 and 8.82 µL L-1 of air, respectively. At some concentrations, the α-bisabolol was more toxic to males than to females of the insect. Increased concentrations of the essential oil reduced the ri, rate of development, oviposition, and number of eggs of C. maculatus and therefore have potential for pest control.

Phytotoxicity, cytotoxicity and genotoxicity evaluation of organic and inorganic pollutants rich tannery wastewater from a Common Effluent Treatment Plant (CETP) in Unnao district, India using Vigna radiata and Allium cepa.

The leather industry is a major source of environmental pollution in India. The wastewater generated by leather industries contains very high pollution parameters due to the presence of a complex mixture of organic and inorganic pollutants even after the treatment at a Common Effluent Treatment Plant (CETP) and disturbs the ecological flora and fauna. The nature, characteristics and toxicity of CETP treated wastewater is yet to be fully elucidated. Thus, this study aims to characterize and evaluate the toxicity of CETP treated tannery wastewater collected from the Unnao district of Uttar Pradesh, India. In addition to measuring the physico-chemical parameters, the residual organic pollutants was identified by GC-MS analysis and phytotoxicity, cytotoxicity and genotoxicity of the treated wastewater was evaluated using Vigna radiata L. and Allium cepa L. Results showed that the treated wastewater contained very high pollution parameters (TDS 3850 mg/L, BOD 680 mg/L, COD-1300 mg/L). GC-MS analysis revealed the presence of various types of residual organic pollutants including benzoic acid, 3-[4,-(T-butyl) Phenyl] furan-2-5-dione, benzeneacetamide, resorcinol, dibutyl phthalate, and benzene-1,2,4-triol. Further, toxicological studies showed the phytotoxic nature of the wastewater as it inhibited seed germination in V. radiata L. and root growth of A. cepa. Genotoxicity was evidenced in the root tip cell of A. cepa where chromosomal aberrations (stickiness, chromosome loss, C-mitosis, and vagrant chromosome) and nuclear abnormalities like micronucleated and binucleated cells were observed. Thus, results suggested that it is not safe to discharge these wastewater into the environment.

Non-toxicity of nano alumina: A case on mung bean seedlings.

Wide use of Al2O3 nanoparticles (NPs) leading to their possible escape into environment and their interaction with living organisms demands immediate attention. We evaluated impact of nanoparticulate (Al2O3-NPs) and ionic (Al3+) forms of aluminium on early seedling growth of Vigna radiata. While Al3+ inhibited growth of seedlings, Al2O3-NPs did not affect it negatively. Unlike enhancement in proline, malondialdehyde and H2O2 levels in roots and shoots induced by Al3+, these stress markers remained unaltered by Al2O3-NPs. No signs of membrane damage were recorded in roots of seedlings raised in presence of Al2O3-NPs; this was witnessed from insignificant electrolyte leakage and Evans blue uptake. Activities of antioxidant enzymes, i.e., superoxide dismustase, catalase, guaiacol peroxidase in root and shoot were enhanced by Al3+. However, they were unaffected by Al2O3-NPs. Al3+ enhanced levels of non-protein thiols, phenolics and ascorbate, with no alterations induced by Al2O3-NPs. These findings revealed that, Al2O3-NPs did not induce oxidative stress in seedlings. Seedlings raised in Al3+ showed higher uptake of Al than those grown in Al2O3-NPs; Al content was higher in roots. Al was not detected in shoots of seedlings grown in Al2O3-NPs. Lower translocation of Al in seedlings raised in Al2O3-NPs was due to adsorption/restriction of Al2O3-NPs on root surface. Al3+ caused ruptures on root epidermis of seedlings and inhibited root-hair formation, whereas no structural damage was caused by Al2O3-NPs. Our findings revealed that while ionic Al is highly toxic, nanoparticulate form of Al is non-toxic to growth of V. radiata.

Identification of phytotoxins in different plant parts of Brassica napus and their influence on mung bean.

Plants in Brassica genus have been found to possess strong allelopathic potential. They may inhibit seed germination and emergence of subsequent crops following them in a rotation system. Series of laboratory and greenhouse experiments were conducted to determine the allelopathic impacts of Brassica napus L. against mung bean. We studied (1) the effects of aqueous extract (5%) of different plant parts (root, stem, leaf, flower, and whole plant) of B. napus, (2) the effects of leaf and flower extracts of B. napus at 0, 1, 2, 3, and 4% concentrations, and (3) the effect of residues of different B. napus plant parts and decomposition periods (0, 7, 14, and 21 days) on germination and seedling growth of mung bean. Various types of phenolics including quercitin, chlorogenic acid, p-coumeric acid, m-coumaric acid, benzoic acid, caffeic acid, syringic acid, vanillic acid, ferulic acid, cinamic acid, and gallic acid were identified in plant parts of B. napus. Among aqueous extracts of various plant parts, leaf and flower were found to have stronger inhibitory effects on germination and seedling growth traits of mung bean, higher concentrations were more toxic. The decomposition period changed the phtotoxic effect of residues, more inhibitory effect was shown at 14 days decomposition while decomposition for 21 days reduced inhibitory effect. The more total water-soluble phenolic was found in 5% (w/v) aqueous extract and 5% (w/w) residues of B. napus flowers at 14 days of decomposition (89.80 and 10.47 mg L-1), respectively. The strong inhibitory effects of B. napus should be managed when followed in rotation.

Effects of different vermicompost extracts of palm oil mill effluent and palm-pressed fiber mixture on seed germination of mung bean and its relative toxicity.

Several treatment technologies are available for the treatment of palm oil mill wastes. Vermicomposting is widely recognized as efficient, eco-friendly methods for converting organic waste materials to valuable products. This study evaluates the effect of different vermicompost extracts obtained from palm oil mill effluent (POME) and palm-pressed fiber (PPF) mixtures on the germination, growth, relative toxicity, and photosynthetic pigments of mung beans (Vigna radiata) plant. POME contains valuable nutrients and can be used as a liquid fertilizer for fertigation. Mung bean seeds were sown in petri dishes irrigated with different dilutions of vermicomposted POME-PPF extracts, namely 50, 60, and 70% at varying dilutions. Results showed that at lower dilutions, the vermicompost extracts showed favorable effects on seed germination, seedling growth, and total chlorophyll content in mung bean seedlings, but at higher dilutions, they showed inhibitory effects. The carotenoid contents also decreased with increased dilutions of POME-PPF. This study recommends that the extracts could serve as a good source of fertilizer for the germination and growth enhancement of mung bean seedlings at the recommended dilutions.

Effect of exogenous ATP on the postharvest properties and pectin degradation of mung bean sprouts (Vigna radiata).

The effects of exogenous ATP on the postharvest quality, browning and softening of mung bean (Vigna radiata) sprouts were evaluated. ATP treatment significantly alleviated the quality loss and browning events during the storage of 3 days. It also reduced the oxidant damage by inducing high activities of peroxidase (9.3-13.9%) and superoxide dismutase (8.8-10.3%) which scavenged the reactive oxygen species (ROS) effectively. Transcriptional results indicated that ATP treatment decreased VrPL1, VrPME and VrPG1 gene expression levels more than 2 folds at some time points. Furthermore, the atomic force microscope (AFM) images revealed that the pectin degradation was notably slowed by ATP treatment and the width and height of pectin backbone were better maintained (47.1% and 45.6% higher than control without ATP treatment). The cooperative effects of ROS scavenging and decreased expressions of pectin-related genes might contribute to the deferred pectin deterioration and firmness loss by ATP treatment.

Role of plant growth-promoting Ochrobactrum sp. MC22 on triclocarban degradation and toxicity mitigation to legume plants.

Triclocarban (TCC) is an emerging and persistent pollutant once released into environment. In this study, TCC-degrading Ochrobactrum sp. MC22, was isolated and characterized. This is the first report on plant-growth promoting bacterium with versatile capability of TCC degradation under aerobic and anaerobic conditions. The aerobic degradation of TCC occurred completely of which the kinetic analysis revealed a non-self-inhibitive substrate effect, and broad-concentration-range degradation efficiency (ranging from 0.16-30mgL-1). Anaerobic TCC degradation was feasible, but was significantly enhanced up to 40-50% when ferric, or acetate was provided as electron donor, or acceptor, respectively. TCC biodegradation under both conditions was proposed to initially occur through hydrolysis leading to transient accumulation of chloroanilines, which could be completely metabolized and detoxified. With concern on TCC adverse effect to plants, role of MC22 on toxicity mitigation was investigated using two legume plants: Vigna radiata and Glycine max (L.) Merr. Upon TCC exposure, damage of both plant structures, especially root system was observed, but was substantially mitigated by MC22 bioaugmentation. This study not only provides thorough TCC degradation characteristic and kinetics of MC22, but also suggests a potential role of this bacterial strain for a rhizoremediation in crop area with TCC contamination.

Phytotoxicity attenuation in Vigna radiata under heavy metal stress at the presence of biochar and N fixing bacteria.

This study assesses the effect of N-fixing bacteria and biochar synergism on plant growth and development of Vigna mungo under heavy metal stress (HM). Heavy metal stress is a worldwide problem, which causes critical effects on plant life due to oxidative stress. Application of biochar is a recent biological remediation technique, which often leads to an immobilization of heavy metals in soil. . Synergism of bacteria and biochar is a novel aspect to enhance plant growth under heavy metal stress. Woody biochar a byproduct of a dendro power industry was added as 1, 2.5 and 5% amounts combination with Bradyrhizobium japonicum, where mung seedlings were planted in serpentine soil rich in Ni, Mn, Cr and Co. Pot experiments were conducted for 12 weeks. The plant height, heavy metal uptake by plants, soil bioavailable heavy metal contents, soil N and P and microbial biomass carbon (MBC) were measured. The plant growth was enhanced with biochar amendment but a retardation was observed with high biochar application (5%). The soil N and P increased with the increase of biochar addition percentage while soil MBC showed reductions at 5% biochar amendment. Both soil bioavailable fractions of HM and up take of HMs by plants were gradually reduced with increase in biochar content. Based on the results, 2.5% biochar synergism with bacteria was the best for plant growth and soil nutrition status. Despite the synergism, available N was negatively correlated with the decrease of bioavailable metal percentage in soil whereas it was conversely for P.

Aluminium-induced excessive ROS causes cellular damage and metabolic shifts in black gram Vigna mungo (L.) Hepper.

Aluminium-induced oxidative damage caused by excessive ROS production was evaluated in black gram pulse crop. Black gram plants were treated with different aluminium (Al3+) concentrations (10, 50 and 100 µM with pH 4.7) and further the effects of Al3+ were characterised by means of root growth inhibition, histochemical assay, ROS content analysis, protein carbonylation quantification and 1H-NMR analysis. The results showed that aluminium induces excessive ROS production which leads to cellular damage, root injury, stunt root growth and other metabolic shifts. In black gram, Al3+ induces cellular damage at the earliest stage of stress which was characterised from histochemical analysis. From this study, it was observed that prolonged stress can activate certain aluminium detoxification defence mechanism. Probably excessive ROS triggers such defence mechanism in black gram. Al3+ can induce excessive ROS initially in the root region then transported to other parts of the plant. As much as the Al3+ concentration increases, the rate of cellular injury and ROS production also increases. But after 72 h of stress, plants showed a lowered ROS level and cellular damage which indicates the upregulation of defensive mechanisms. Metabolic shift analysis also showed that the black gram plant under stress has less metabolic content after 24 h of treatment, but gradually, it was increased after 72 h of treatment. It was assumed that ROS played the most important role as a signalling molecule for aluminium stress in black gram.

In vitro screening of calli of mungbean to cercosporin, a photoactivated toxin.

Mungbean or Green gram [Vigna radiata (L.) R. Wilczek] is an arid/semiarid pulse crop, native to India, grown mostly as a rotational crop with cereals like wheat, rice, maize, sorghum, etc. It is an affordable source of protein, carbohydrate, vitamins and minerals preferred for its nutrient digestibility, food processing properties and bioavailability. India accounts for 65% of mungbean's world acreage and 54% of its world production. Various pests, diseases and environmental stresses have kept mungbean yield quite unstable over decades and researcher's worldover are looking for resistant varieties to overcome these challenges. Cercospora leaf spot (CLS) caused by Cercospora canescens is one of the most destructive diseases of mungbean and the key polyketide toxin cercosporin plays an important role in pathogenesis. Such toxins as selective agents in the tissue culture medium can help in selecting genotype with suitable levels of resistance to the toxin and/or to the pathogen among the available germplasm. Here, we standardized the dose of cercosporin for in vitro selection of resistant mungbean genotypes and variable expression of peroxidase, catalase and superoxide dismutase. Murashige and Skoog (MS) medium supplemented with 1.0 mg L-1 NAA and 1.0 mg L-1 BAP was standardized for the development of callus from mungbean using hypocotyls as an explant. The calli from six cultivars of mungbean were tested in medium amended with cercosporin (0-40 µg mL-1) and calli survived up to 20 µg mL-1 of cercosporin. The calli from resistant cultivars survived 83.33-93.00%, and showed lower reduction in fresh weight (25.97-28.83%). Calli from the susceptible cultivars survived 50-60% and showed higher reduction in fresh weight. Callus showed browning, exposure to cercosporin (5-20 µg mL-1). Enzymes assay from survived calli of different cultivars showed higher peroxidase activity (7.90-8.91 ∆OD min-1 mg­1 callus), superoxide dismutase (0.96-1.03 ∆OD min-1 mg-1 callus) and a lower catalase (0.35-0.43 µ moles of H2O2 utilized min-1 mg­1 callus) in resistant, followed by moderately resistance and susceptible cultivars. The necrosis in leaves was recorded with 200 µg mL-1 of cercosporin, and no visible necrosis was observed below this concentration. Enzyme assayed from the controlled and cercosporin-treated (100-200 µg mL-1) leaves of mungbean genotypes showed variable activity of peroxidase, catalase and superoxide dismutase.