Selenium-Priming mediated growth and yield improvement of turnip under saline conditions.

Salt toxicity is one of the foremost environmental stresses that declines nutrient uptake, photosynthetic activity and growth of plants resulting in a decrease in crop yield and quality. Seed priming has become an emergent strategy to alleviate abiotic stress and improve plant growth. During the current study, turnip seed priming with sodium selenite (Na2SeO3) was investigated for its ability to mitigate salt stress. Turnip (Brassica rapa L. var. Purple Top White Globe) seeds primed with 75, 100, and 125 µML-1 of Se were subjected to 200 mM salt stress under field conditions. Findings of the current field research demonstrated that salt toxicity declined seed germination, chlorophyll content, and gas exchange characteristics of B. rapa seedling. Whereas, Se-primed seeds showed higher germination rate and plant growth which may be attributed to the decreased level of hydrogen peroxide (H2O2) and malondialdehyde (MDA) decreased synthesis of proline (36%) and besides increased total chlorophyll (46%) in applied turnip plants. Higher expression levels of genes encoding antioxidative activities (CAT, POD, SO,D and APX) mitigated oxidative stress induced by the salt toxicity. Additionally, Se treatment decreased Na+ content and enhanced K+ content resulting in elevated K+/Na+ ratio in the treated plants. The in-silico assessment revealed the interactive superiority of Se with antioxidant enzymes including CAT, POD, SOD, and APX as compared to sodium chloride (NaCl). Computational study of enzymes-Se and enzymes-NaCl molecules also revealed the stress ameliorative potential of Se through the presence of more Ramachandran-favored regions (94%) and higher docking affinities of Se (-6.3). The in-silico studies through molecular docking of Na2SeO3, NaCl, and ROS synthesizing enzymes (receptors) including cytochrome P450 (CYP), lipoxygenase (LOX), and xanthine oxidase (XO), also confirmed the salt stress ameliorative potential of Se in B. rapa. The increased Ca, P, Mg, and Zn nutrients uptake nutrients uptake in 100 µML-1 Se primed seedlings helped to adjust the stomatal conductivity (35%) intercellular CO2 concentration (32%), and photosynthetic activity (41%) resulting in enhancement of the yield attributes. More number of seeds per plant (6%), increased turnip weight (115 gm) root length (17.24 cm), root diameter (12 cm) as well as turnip yield increased by (9%tons ha-1) were recorded for 100 µML-1 Se treatment under salinity stress. Findings of the current research judiciously advocate the potential of Se seed priming for salt stress alleviation and growth improvement in B. rapa.

According to our best of knowledge, it is the first time that seed primed with Selenium have been evaluated regarding NaCl stress mitigation in turnip. Salinity toxicity negatively affected physiochemical activities and growth of B.rapa.Seed priming with Selenium (Na₂SeO₃) mitigated salinity stress.Selenium (Se) enhanced nutrition, photosynthetic and antioxidant activity of applied plants.Selenium treated plants exhibited improved growth and reduced salinity content.

Exogenously applied nano-zinc oxide mitigates cadmium stress in Zea mays L. through modulation of physiochemical activities and nutrients homeostasis.

The increasing levels of cadmium (Cd) pollution in agricultural soil reduces plant growth and yield. This study aims to determine the impact of green synthesized zinc oxide nanoparticles (ZnO-NPs) on the physiochemical activities, nutrition, growth, and yield of Zea mays L. under Cd stress conditions. For this purpose, ZnO-NPs (450 ppm and 600 ppm) synthesized from Syzygium aromaticum were applied through foliar spray to Z. mays and also used as seed priming agents. A significant decline in plant height (35.24%), biomass production (43.86%), mineral content, gas exchange attributes, and yield (37.62%) was observed in Cd-spiked plants compared to the control. While, 450 ppm ZnO-NPs primed seed increased plant height (18.46%), total chlorophyll (80.07%), improved ascorbic acid (25.10%), DPPH activity (26.66%), and soil mineral uptake (Mg+2 (38.86%), K+ (27.83%), and Zn+2 (43.68%) as compared to plants only spiked with Cd. On the contrary, the foliar-applied 450 ppm ZnO-NPs increased plant height (8.22%), total chlorophyll content (73.59%), ascorbic acid (21.39%), and DPPH activity (17.61%) and yield parameters; cob diameter (19.45%), and kernels numbers 6.35% enhanced compared to plants that were spiked only with Cd. The findings of the current study pave the way for safer and more cost-effective crop production in Cd-stressed soils by using green synthesized NPs and provide deep insights into the underlying mechanisms of NPs treatment at the molecular level to provide compelling evidence for the use of NPs in improving plant growth and yield.

Novelty statement: Phyto zinc nanoparticles improve stress tolerance and growth of Zea mays under cadmium stress.

Burkholderia cepacia CS8 improves phytoremediation potential of Calendula officinalis for tannery solid waste polluted soil.

Microbes have shown potential for the bioremediation of tannery waste polluted soil. During our previous study, it was observed that heavy metal resistant Burkholderia cepacia CS8 augmented growth and phytoremediation capability of an ornamental plant. Objective of the present research work was to evaluate the capability of B. cepacia CS8 assisted Calendula officinalis plants for the phytoremediation of tannery solid waste (TSW) polluted soil. The TSW treatment significantly reduced growth attributes and photosynthetic pigments in C. officinalis. However, supplementation of B. cepacia CS8 which exhibited substantial tolerance to the TSW amended soil, augmented growth traits, carotenoid, proline, and antioxidant enzymes level in C. officinalis under toxic and nontoxic regimes. Inoculation of B. cepacia CS8 augmented plant growth (shoot length 13%, root length 11%), physiological attributes (chlorophyll a 14%, chlorophyll b 17%), antioxidant enzyme activities (peroxidase 24%, superoxide dismutase 31% and catalase 19%), improved proline 36%, phenol 32%, flavonoids 14% and declined malondialdehyde (MDA) content 15% and hydrogen peroxide (H2O2) level 12% in C. officinalis at TSW10 stress compared with relevant un-inoculated plants of TSW10 treatment. Moreover, B. cepacia CS8 application enhanced labile metals in soil and subsequent metal uptake, such as Cr 19%, Cd 22%, Ni 35%, Fe 18%, Cu 21%, Pb 34%, and Zn 30%, respectively in C. officinalis plants subjected to TSW10 stress than that of analogous un-inoculated treatment. Higher plant stress tolerance and improved phytoremediation potential through microbial inoculation will assist in the retrieval of agricultural land in addition to the renewal of native vegetation.

During the current study, it was observed that combination of Calendula officinalis and metal tolerant Burkholderia cepacia CS8 not only improved plant growth but also helped phyto-extraction of pollutants present in the tannery solid waste polluted soil. According to our information, research work describing the phytoremediation potential of native metal tolerant microbes and ornamental plants has not been reported in Pakistan.

Exogenous application of glutathione enhanced growth, nutritional orchestration and physiochemical characteristics of Brassica oleracea L. under lead stress.

A major obstacle to agricultural production and yield quality is heavy metal contamination of the soil and water, which leads to lower productivity and quality of crops. The situation has significantly worsened as a result of the growing population and subsequent rise in food consumption. The growth of nutrient-rich plants is hampered by lead (Pb) toxicity in the soil. Brassica oleracea L. (broccoli) is a prominent vegetable crop in the Brassicaceae family subjected to a number of biotic and abiotic stresses that dramatically lower crop yields. Seed priming is a novel, practicable, and cost-effective method that can improve various abiotic stress tolerances. Many plant metabolic activities depend on the antioxidant enzyme glutathione (GSH), which also chelates heavy metals. Keeping in view the stress mitigation potential of GSH, current research work was designed to inspect the beneficial role of seed priming with GSH on the growth, morphological and gas exchange attributes of broccoli seedlings under Pb stress. For this purpose, broccoli seeds were primed with 25, 50, and 75 µM L-1 GSH. Plant growth and photosynthetic activity were adversely affected by Pb stress. Furthermore, Pb stress enhanced proline levels along with reduced protein and phenol content. The application of GSH improved growth traits, total soluble proteins, chlorophyll content, mineral content, and gas exchange parameters. The involvement of GSH in reducing Pb concentrations was demonstrated by an improved metal tolerance index and lower Pb levels in broccoli plants. The results of the current study suggest that GSH can be used as a strategy to increase broccoli tolerance to Pb by enhancing nutrient uptake, growth and proline.

Role of exogenously applied putrescine in amelioration of cadmium stress in Coriandrum sativum by modulating antioxidant system.

Abiotic stress reduces the plant growth and biomass production. Putrescine (Put) may be applied to alleviate numerous types of abiotic stresses in plants. The present research was intended to evaluate the role of exogenously applied Put in extenuation of cadmium (Cd) stress in coriander plants. Coriander seeds primed with 0.25, 0.5, and1 mM Put were allowed to grow in 50 mg kg-1 Cd contaminated soil for one month. Put treatment improved seed germination, gas exchange attributes, root growth and shoot growth of coriander. The improved activity of stress-responsive enzymes such as superoxide dismutase, catalase and peroxidase, besides amplification of proline was observed in Put treated seedlings under Cd stress. In addition, a reduced amount of total soluble protein and sugars content were noticed in Cd stressed seedlings. Nevertheless, Put reduced MDA level in treated plants. Our results demonstrated that Put mitigated Cd induced stress by modulating antioxidants and photosynthetic activity of coriander plants.Novelty statement Most of the researchers have studied the role of endogenous putrescine in alleviation of plant stress. However, during current study, we primed coriander seeds with putrescine. Our results elucidated very promising role of exogenously applied putrescine in stress mitigation and growth improvement of coriander seedlings under Cd stress. The findings of current study advocate the application of putrescine for stress alleviation in crop plants.

Role of magnesium oxide nanoparticles in the mitigation of lead-induced stress in Daucus carota: modulation in polyamines and antioxidant enzymes.

During the current study, the effects of magnesium oxide nanoparticles (5 mmol/L) were observed on the growth and mineral nutrients of Daucus carota under lead (Pb) stress. The results demonstrated that Pb stress decreased the growth and photosynthetic rate of D. carota plants. Furthermore, Pb stressed plants showed decreased uptake of mineral nutrients including Zn, Na, Fe, K, Ca, Mg, K, and Cu. Similarly, Pb stressed plants showed enhanced electrolyte leakage (EL) and malondialdehyde (MDA) content. However, magnesium oxide nanoparticles detoxified ROS to mitigate Pb stress and improved the growth of plants. Magnesium oxide nanoparticles also escalated the activity of antioxidant enzymes including superoxide dismutase (SOD) and Catalase (CAT). A higher amount of Pb content was observed in the roots as compared to the shoot of plants. Lead toxicity reduced manganese accumulation in D. carota plants. The increased concentration of iron, manganese, copper, and zinc advocates stress the ameliorative role of Pb stress in plants. Novelty statementThe role of MgONPs in the alleviation of Pb-toxicity in Daucus carota has never been exploited. In addition, the potential of MgONPs to enhance nutritional content in D. carota via modulation in antioxidant system and polyamines have never been reported.

Karrikinolide alleviates BDE-28, heat and Cd stressors in Brassica alboglabra by correlating and modulating biochemical attributes, antioxidative machinery and osmoregulators.

In this study, we have evaluated the role of karrikin (KAR1) against the absorption and translocation of a persistent organic pollutant (POP), 2,4,4'-Tribromodiphenyl ether (BDE-28) in plants, in the presence of two other stressors, cadmium (Cd) and high temperature. Furthermore, it correlates the physiological damages of Brassica alboglabra with the three stresssors separately. The results revealed that the post-germination application of KAR1 successfully augmented the growth (200%) and pertinent physiochemical parameters of B. alboglabra. KAR1 hindered air absorption of BDE-28 in plant tissues, and reduced its translocation coefficient (TF). Moreover, BDE-28 was the most negatively correlated (-0.9) stressor with chlorophyll contents, while the maximum mitigation by KAR1 was also achieved agaist BDE-28. The effect of temperature was more severe on soluble sugars (0.51), antioxidative machinery (-0.43), and osmoregulators (0.24). Cd exhibited a stronger inverse interrelation with the enzymatic antioxidant cascade. Application of KAR1 mitigated the deleterious effects of Cd and temperature stress on plant physiological parameters along with reduced aero-concentration factor, TF, and metal tolerance index. The phytohormone reduced lipid peroxidation by decreasing synthesis of ROS and persuading its breakdown. The stability of cellular membranes was perhaps due to the commotion of KAR1 as a growth-promoting phytohormone. In the same way, KAR1 supplementation augmented the membrane stability index, antioxidant defense factors, and removal efficiency of the pollutants. Consequently, the exogenously applied KAR1 can efficiently alleviate Cd stress, heat stress, and POP toxicity.

Enhanced performance of Bacillus megaterium OSR-3 in combination with putrescine ammeliorated hydrocarbon stress in Nicotiana tabacum.

Hydrocarbon stress (HS) has been causing decreased plant growth and productivity. Putrescine (Put) and growth promoting microbes are vital for plant growth and development under hydrocarbon stress. Current research work was carried out to evaluate the potential of Bacillus megaterium OSR-3 alone and in combination with Put to alleviate HS in Nicotiana tabacum (L.). The crude petroleum contaminated soil significantly reduced growth attributes of N. tabacum. B. megaterium OSR-3 inoculated plants subjected to HS exhibited improved photosynthetic rate, gas exchange characteristics, poline contents and protein level. Furthermore, bacterial inoculation enhanced the antioxidative activity of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) in tobacco plants subjected to HS. The HS alleviation in B. megaterium OSR-3 inoculated N. tabacum can be credited to the heightened activity of antioxidative enzymes, reduction in hydrogen peroxide (H2O2) and abridged synthesis of malondialdehyde (MDA). The increased synthesis of indole acetic acid (IAA) in HS stressed N. tabacum plants treated with co-application of B. megaterium OSR-3 and Put attenuated toxicity and amplified growth of plants. Additionally, the co-application of B. megaterium OSR-3 and Put also upregulated the activity of antioxidative enzymes and induced augmented level of proline and IAA in plants under HS regimes. Current research provides novel insight into the potential and mechanism of B. megaterium OSR-3 and Put in mitigation of HS in N. tabacum plants.

Synergistic ameliorative effect of iron oxide nanoparticles and Bacillus subtilis S4 against arsenic toxicity in Cucurbita moschata: polyamines, antioxidants, and physiochemical studies.

The present study was intended to assess the potential of iron oxide nanoparticles (IONPs) and Bacillus subtilis S4 in mitigation of arsenic (As) stress in Cucurbita moschata. Cucurbita moschata seedlings were subjected to As stress for 60 days. Reduced level of growth parameters including photosynthetic pigments, rate of photosynthesis and gas exchange characteristics was observed in seedlings subjected to As stress. However, IONPs and B. subtilis S4 improved growth attributes and proline contents in supplemented C. moschata seedlings. Bacillus subtilis S4 inoculated seedlings showed higher activity of peroxidase (POD) and superoxide dismutase (SOD) under As toxicity. Similarly, the co-application of IONPs and B. subtilis S4 further increased the activity of these antioxidative enzymes. The As stress alleviation in inoculated C. moschata seedlings is credited to reduced levels of hydrogen peroxide (H2O2), malondialdehyde (MDA) and electrolyte leakage (EL) in IONPs and B. subtilis S4-treated plants. Furthermore, synergism between plant growth promoting bacteria (PGPB) and IONPs enhanced the biosynthesis of stress mitigating polyamines including spermidine and putrescine in As-stressed seedlings. Current research reveals that synergistic application of IONPs and B. subtilis S4 is an effective sustainable and ecofriendly approach for alleviation of As stress in C. moschata seedlings.

2-Hydroxymelatonin induced nutritional orchestration in Cucumis sativus under cadmium toxicity: modulation of non-enzymatic antioxidants and gene expression.

2-Hydroxymelatonin (2-OHMT) is an important metabolite produced through melatonin interaction with oxygenated compounds. 2-OHMT pretreated seeds (50 µM, 100 µM, and 150 µM) were grown in soil contaminated with 50 mg kg-1 cadmium. Cadmium imposed stress reduced seed germination, growth, biomass production, and chlorophyll (Chl) content in Cucumis sativus seedlings. 2-OHMT application emphatically revamped germination, shoot length, root length, and plant biomass production. The 2-OHMT pretreatment modulated expression levels of plasma membrane H+-ATPase genes of C. sativus including CsHA2, CsHA3, CsHA4, CsHA8, and CsHA9. This biomolecule amplified the accumulation of antioxidants such as glutathione, proline, phenolics, and flavonoids. The reduced Cd-uptake in 2-OHMT treated C. sativus seedlings encouraged uptake of essential plant nutrients. Furthermore, conjugated increase of indole acetic acid contents and ethylene production rate were observed in 2-OHMT treated seedlings in a dose-dependent manner. The improved nutritional content in 2-OHMT applied seedlings was ascribed to enhanced expression of H+-ATPase regulating genes besides increased amount of non-enzymatic antioxidants in Cd-stressed plants. The present novel study elucidates the potential of 2-OHMT in improving nutritional content in cucumber plants by modulation of non-enzymatic antioxidants and gene expression.

Ameliorative effect of co-application of Bradyrhizobium japonicum EI09 and Se to mitigate chromium stress in Capsicum annum L.

The present study was conducted to explore the potential of Bradyrhizobium japonicum EI09 (EI09) and selenium (Se) alone or in combination to mitigate hexavalent chromium (Cr6+) stress in Capsicum annum L. Chromium stressed plants exhibited significant reduction in biomass, chlorophyll content and gas exchange characteristics. The inoculated seedlings subjected to Cr6+stress showed improvement in growth, proline content, gas exchange attributes and total soluble proteins. Likewise, inoculated C. annum seedlings exhibited augmented activity of ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) under Cr6+ stress. The Cr6+ stress mitigation in inoculated seedlings was ascribed to reduction in malondialdehyde (MDA) content, hydrogen peroxide (H2O2) besides increase activity of flavonoids, proline, phenolic content along with modulation of antioxidative enzymes. The growth-enhancing attributes of bacteria such as indole acetic acid (IAA) content and 1-aminocyclopropane-1-carboxylate deaminase (ACCD) activity enhanced growth in Cr6+-stressed plants. Moreover, co-treatment of EI09 and 5 µM Se effectively mitigated Cr (VI) stress in C. annum plants. Current studies provide a novel insight into potential of B. japonicum EI09 and Se in reduction of Cr6+ toxicity in C. annum plants.

Genome-wide association studies of seven agronomic traits under two sowing conditions in bread wheat.

BACKGROUND: Wheat is a cool seasoned crop requiring low temperature during grain filling duration and therefore increased temperature causes significant yield reduction. A set of 125 spring wheat genotypes from International Maize and Wheat Improvement Centre (CIMMYT-Mexico) was evaluated for phenological and yield related traits at three locations in Pakistan under normal sowing time and late sowing time for expose to prolonged high temperature. With the help of genome-wide association study using genotyping-by-sequencing, marker trait associations (MTAs) were observed separately for the traits under normal and late sown conditions. RESULTS: Significant reduction ranging from 9 to 74% was observed in all traits under high temperature. Especially 30, 25, 41 and 66% reduction was observed for days to heading (DH), plant height (PH), spikes per plant (SPP) and yield respectively. We identified 55,954 single nucleotide polymorphisms (SNPs) using genotyping by sequencing of these 125 hexaploid spring wheat genotypes and conducted genome-wide association studies (GWAS) for days to heading (DH), grain filled duration (GFD), plant height (PH), spikes per plant (SPP), grain number per spike (GNS), thousand kernel weight (TKW) and grain yield per plot (GY). Genomic regions identified through GWAS explained up to 13% of the phenotypic variance, on average. A total of 139 marker-trait associations (MTAs) across three wheat genomes (56 on genome A, 55 on B and 28 on D) were identified for all the seven traits studied. For days to heading, 20; grain filled duration, 21; plant height, 23; spikes per plant, 13; grain numbers per spike, 8; thousand kernel weight, 21 and for grain yield, 33 MTAs were detected under normal and late sown conditions. CONCLUSIONS: This study identifies the essential resource of genetics research and underpins the chromosomal regions of seven agronomic traits under normal and high temperature. Significant relationship was observed between the number of favored alleles and trait observations. Fourteen protein coding genes with their respective annotations have been searched with the sequence of seven MTAs which were identified in this study. These findings will be helpful in the development of a breeder friendly platform for the selection of high yielding wheat lines at high temperature areas.

Role of Burkholderia cepacia CS8 in Cd-stress alleviation and phytoremediation by Catharanthus roseus.

The current study was performed to assess the effect of Burkholderia cepacia CS8 on the phytoremediation of cadmium (Cd) by Catharanthus roseus grown in Cd-contaminated soil. The plants cultivated in Cd amended soil showed reduced growth, dry mass, gas-exchange capacity, and chlorophyll contents. Furthermore, the plants exhibited elevated levels of malondialdehyde (MDA) and hydrogen peroxide (H2O2) under Cd stress. The bacterized plants showed higher shoot length, root length; fresh and dry weight. The improved stress tolerance in inoculated plants was attributed to the reduced quantity of MDA and H2O2, enhanced synthesis of protein, proline, phenols, flavonoids, and improved activity of antioxidant enzymes including peroxidase, superoxide dismutase, ascorbate peroxidase, and catalase. Similarly, the 1-aminocyclopropane-1-carboxylate deaminase activity, phosphate solubilization, auxin, and siderophore production capability of B. cepacia CS8 improved growth and stress alleviation in treated plants. The bacterial inoculation enhanced the amount of water extractable Cd from soil. Furthermore, the inoculated plants showed higher bioconcentration factor and translocation factor. The current study exhibits that B. cepacia CS8 improves stress alleviation and phytoextraction potential of C. roseus plants growing under Cd stress.

The beneficial role of potassium in Cd-induced stress alleviation and growth improvement in Gladiolus grandiflora L.

Heavy metal contaminated agricultural soils are one of the most important constraints for successful cultivation of crops. The current research was conducted to evaluate the role of potassium (K) on plant growth and amelioration of cadmium (Cd) stress in Gladiolus grandiflora under greenhouse conditions. G. grandiflora corms were sown in media contaminated with 0 (C), 50 (Cd50) and 100 (Cd100) mg Cd kg-1 soil. The plants growing in Cd-contaminated media exhibited reduced gas exchange attributes, chlorophyll (Chl) contents, vegetative and reproductive growth as compared to control. The plants raised in Cd contaminated media showed reduced nutrition yet higher Cd contents. However, supplementation of 60 mg Kg-1 K in treated plants (C+K, Cd50+K and Cd100+K) improved quantity of total soluble protein and proline (Pro) along with activity of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) under Cd stress. Similarly, K supplementation reduced the level of malondialdehyde (MDA) and hydrogen peroxide (H2O2) in treated plants. Potassium supplemented plants exhibited better vegetative and reproductive growth. The improved stress tolerance in K supplemented plants was attributed to the reduced quantity of MDA and H2O2, enhanced synthesis of protein, proline, phenols, flavonides and improved activity of antioxidant enzymes. The present research supports the application of K for alleviation of Cd stress in G. grandiflora.

Effect of Pseudomonas fluorescens RB4 and Bacillus subtilis 189 on the phytoremediation potential of Catharanthus roseus (L.) in Cu and Pb-contaminated soils.

The remediation of heavy metal-contaminated soils has become a critical issue due to toxic effects of these metals on living organisms. The current research was conducted to study the effect of Pseudomonas fluorescens RB4 and Bacillus subtilis 189 on the growth and phytoremediation potential of Catharanthus roseus in Cu- and Pb-contaminated soils. The bacterial strains exhibited significantly higher level of water-extractable Pb and Cu in Pb, Cu, and Cu+Pb-contaminated. The P. fluorescens RB4 inoculated plants, produced 102%, 48%, and 45% higher fresh weight (FW) in soils contaminated with Cu, Pb, and both elements, respectively, as compared to un-inoculated control plants. Similarly, B. subtilis 189 inoculated plants produced 108%, 43%, and 114% more FW in the presence of Cu, Pb, and both elements. The plants co-cultivated with both bacteria exhibited 121%, 102%, and 177% higher FW, in Cu, Pb, and both elements contaminated soils, as compared to respective un-inoculated control. Co-cultivation of P. fluorescens RB4, B. subtilis 189, and P. fluorescens RB4 + B. subtilis 189 resulted in higher accumulation of Cu and Pb in shoots of the C. roseus grown in contaminated soils as compared to un-inoculated control. Bacterial treatments also improved the translocation and metal bioconcentration factors. The growth and phytoextraction capability of C. roseus was improved by inoculation of P. fluorescens RB4 and B. subtilis 189.

Role of Ni-tolerant Bacillus spp. and Althea rosea L. in the phytoremediation of Ni-contaminated soils.

In our current study, four nickel-tolerant (Ni-tolerant) bacterial species viz, Bacillus thuringiensis 002, Bacillus fortis 162, Bacillus subtilis 174, and Bacillus farraginis 354, were screened using Ni-contaminated media. The screened microbes exhibited positive results for synthesis of indole acetic acid (IAA), siderophore production, and phosphate solubilization. The effects of these screened microbes on Ni mobility in the soil, root elongation, plant biomass, and Ni uptake in Althea rosea plants grown in Ni-contaminated soil (200 mg Ni kg-1) were evaluated. Significantly higher value for water-extractable Ni (38 mg kg-1) was observed in case of Ni-amended soils inoculated with B. subtilis 174. Similarly, B. thuringiensis 002, B. fortis 162, and B. subtilis 174 significantly enhanced growth and Ni uptake in A. rosea. The Ni uptake in the shoots and roots of B. subtilis 174-inoculated plants enhanced up to 1.7 and 1.6-fold, respectively, as compared to that in the un-inoculated control. Bacterial inoculation also significantly improved the root and shoot biomass of treated plants. The current study presents a novel approach for bacteria-assisted phytoremediation of Ni-contaminated areas.

Application of Bacillus megaterium MCR-8 improved phytoextraction and stress alleviation of nickel in Vinca rosea.

The current research was performed to evaluate the effect of Bacillus megaterium MCR-8 on mitigation of nickel (Ni) stress in Vinca rosea grown on Ni-contaminated soil (50, 100, and 200 mg Ni kg-1 soil). The treated plants exhibited reduced growth, biomass, gas exchange capacity, and chlorophyll (Chl) content under Ni stress. The inoculated plants growing in Ni-contaminated media exhibited relatively higher growth, total soluble protein, and proline contents. Similarly, bacterial inoculation improved the activity of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) under Ni stress. The Ni stress alleviation in inoculated plants was attributed to the reduced level of malondialdehyde (MDA) and hydrogen peroxide (H2O2), enhanced synthesis of protein, proline, phenols, and flavonides in conjunction with improved activity of antioxidant enzymes. The growth-promoting characteristics of microbe such as 1-aminocyclopropane-1-carboxylate deaminase (ACCD) and phosphate solubilization activity, siderophore, and auxin production capability also improved the growth and stress mitigation in inoculated plants. Furthermore, the inoculated plants exhibited higher value for bioconcentration factor (BCF), translocation factor (TF), and resulted in higher loss of Ni content from soil. The current results exhibited the beneficial role of B. megaterium MCR-8 regarding stress alleviation and Ni phytoextraction by V. rosea.

Calcium oxide nanoparticles mitigate lead stress in Abelmoschus esculentus though improving the key antioxidative enzymes, nutritional content and modulation of stress markers.

Lead (Pb) is thought to be one of most injurious metals on the earth. Lead stress in plants enhances synthesis of highly toxic reactive oxygen species (ROS). During present research, impact of calcium-oxide nanoparticles (CaO-NPs) was observed on antioxidative defense mechanism in Abelmoschus esculentus plants prone to Pb stress. A CRD experiment was employed with 5 replicates having four treatments (T0 = Control, T1 = Pb stress (200 ppm), T2 = CaO-NPs and T3 = Pb + CaO-NPs). Pb-stressed seedlings exhibited decreased root growth, shoot growth, chlorophyll concentration and biomass accumulation. Moreover, higher synthesis of hydrogen-peroxide (H2O2), malondialdehyde (MDA) and electrolyte leakage (EL) resulting in cellular injuries were noted in plants growing in Pb spiked conditions. Similarly, stressed plants showed higher accumulation of total soluble sugar and proline content besides elevated activity of antioxidative enzymes counting catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR) and ascorbate peroxidase (APX). On the contrary side, CaO-NPs alleviated the Pb induced phytotoxicity through improving activity of antioxidative enzymes. The elevated activity of antioxidant enzymes reduced biosynthesis of H2O2 and MDA which was revealed through the increased growth parameters. In addition, CaO-NPs persuaded enhancement in plant defence machinery by decreased chlorophyll deprivation and augmented the uptake of plant nutrients including K and Ca content. Hence, CaO-NPs can be potent regulators of the antioxidative enzymes and stress markers to ameliorate abiotic stresses.

28-Homobrassinolide Primed Seed Improved Lead Stress Tolerance in Brassica rapa L. through Modulation of Physio-Biochemical Attributes and Nutrient Uptake.

Brassinosteroids (BRs) influence a variety of physiological reactions and alleviate different biotic and abiotic stressors. Turnip seedlings were grown with the goal of further exploring and expanding their function in plants under abiotic stress, particularly under heavy metal toxicity (lead stress). This study's objective was to ascertain the role of applied 28-homobrassinolide (HBL) in reducing lead (Pb) stress in turnip plants. Turnip seeds treated with 1, 5, and 10 µM HBL and were grown-up in Pb-contaminated soil (300 mg kg-1). Lead accumulation reduces biomass, growth attributes, and various biochemical parameters, as well as increasing proline content. Seed germination, root and shoot growth, and gas exchange characteristics were enhanced via HBL treatment. Furthermore, Pb-stressed seedlings had decreased total soluble protein concentrations, photosynthetic pigments, nutrition, and phenol content. Nonetheless, HBL increased chlorophyll a and chlorophyll b levels in plant, resulting in increased photosynthesis. As a result, seeds treated with HBL2 (5 µM L-1) had higher nutritional contents (Mg+2, Zn+2, Na+2, and K+1). HBL2-treated seedlings had higher DPPH and metal tolerance indexes. This led to the conclusion that HBL2 effectively reduced Pb toxicity and improved resistance in lead-contaminated soil.

Potassium silicate and zinc oxide nanoparticles modulate antioxidant system, membranous H+-ATPase and nitric oxide content in faba bean (Vicia faba) seedlings exposed to arsenic toxicity.

Current research focused on the potential role of zinc oxide nanoparticles (ZnONPs) and potassium (K+ ) in mitigation of arsenic (As) toxicity in Vicia faba L. seedlings. Faba bean seedlings were grown for 30days in potted soil. As stress curtailed root and shoot length, chlorophyll (Chl) content and net photosynthetic rate in V. faba seedlings. However, ZnONPs and K+ curtailed As stress in faba bean seedling through enhanced activity of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and peroxidase (POD) enzyme. Furthermore, ZnONPs and K+ significantly enhanced cysteine (Cys) content and serine acetyletransferase (SAT) activity in faba bean seedling exposed to As-toxificated soil. Application of ZnONPs and K+ curtailed superoxide ionic content and hydrogen peroxide (H2 O2 ) accumulation in V. faba seedlings exposed to As-polluted soil. Nitric oxide (NO) content also increased in faba bean seedlings treated with ZnONPs and K+ in normal and As-polluted soil. As stress alleviation was credited to reduce As uptake in faba bean seedlings treated with synergistic application of ZnONPs and K+ . It is proposed that K+ interaction with nanoparticles can be exploited at molecular level to understand the mechanisms involved in abiotic stress tolerance.