Leaf nodule endosymbiotic Burkholderia confer targeted allelopathy to their Psychotria hosts.

After a century of investigations, the function of the obligate betaproteobacterial endosymbionts accommodated in leaf nodules of tropical Rubiaceae remained enigmatic. We report that the α-D-glucose analogue (+)-streptol, systemically supplied by mature Ca. Burkholderia kirkii nodules to their Psychotria hosts, exhibits potent and selective root growth inhibiting activity. We provide compelling evidence that (+)-streptol specifically affects meristematic root cells transitioning to anisotropic elongation by disrupting cell wall organization in a mechanism of action that is distinct from canonical cellulose biosynthesis inhibitors. We observed no inhibitory or cytotoxic effects on organisms other than seed plants, further suggesting (+)-streptol as a bona fide allelochemical. We propose that the suppression of growth of plant competitors is a major driver of the formation and maintenance of the Psychotria-Burkholderia association. In addition to potential agricultural applications as a herbicidal agent, (+)-streptol might also prove useful to dissect plant cell and organ growth processes.

Protocol for the Production of Doubled Haploid Plants of Brassica carinata.

Brassica carinata, also known as Ethiopian or Abyssinian mustard, is a drought- and heat-tolerant oilseed with great potential as a dedicated industrial feedstock crop for use in biofuel and other bio-based applications. Doubled haploid technology, a system that allows for the rapid development of doubled haploid, completely homozygous plants through microspore embryogenesis, has been applied routinely in both B. carinata breeding and basic research. Here, we present a comprehensive isolated microspore culture protocol detailing the various steps involved in doubled haploid plant production for this species, from growing donor plants over harvesting flower buds and isolating, culturing and inducing microspores to regenerating doubled haploid embryos and plantlets.

Role of Bacillus cereus in Improving the Growth and Phytoextractability of Brassica nigra (L.) K. Koch in Chromium Contaminated Soil.

Plant growth-promoting rhizobacteria (PGPR) mediate heavy metal tolerance and improve phytoextraction potential in plants. The present research was conducted to find the potential of bacterial strains in improving the growth and phytoextraction abilities of Brassica nigra (L.) K. Koch. in chromium contaminated soil. In this study, a total of 15 bacterial strains were isolated from heavy metal polluted soil and were screened for their heavy metal tolerance and plant growth promotion potential. The most efficient strain was identified by 16S rRNA gene sequencing and was identified as Bacillus cereus. The isolate also showed the potential to solubilize phosphate and synthesize siderophore, phytohormones (indole acetic acid, cytokinin, and abscisic acid), and osmolyte (proline and sugar) in chromium (Cr+3) supplemented medium. The results of the present study showed that chromium stress has negative effects on seed germination and plant growth in B. nigra while inoculation of B. cereus improved plant growth and reduced chromium toxicity. The increase in seed germination percentage, shoot length, and root length was 28.07%, 35.86%, 19.11% while the fresh and dry biomass of the plant increased by 48.00% and 62.16%, respectively, as compared to the uninoculated/control plants. The photosynthetic pigments were also improved by bacterial inoculation as compared to untreated stress-exposed plants, i.e., increase in chlorophyll a, chlorophyll b, chlorophyll a + b, and carotenoid was d 25.94%, 10.65%, 20.35%, and 44.30%, respectively. Bacterial inoculation also resulted in osmotic adjustment (proline 8.76% and sugar 28.71%) and maintained the membrane stability (51.39%) which was also indicated by reduced malondialdehyde content (59.53% decrease). The antioxidant enzyme activities were also improved to 35.90% (superoxide dismutase), 59.61% (peroxide), and 33.33% (catalase) in inoculated stress-exposed plants as compared to the control plants. B. cereus inoculation also improved the uptake, bioaccumulation, and translocation of Cr in the plant. Data showed that B. cereus also increased Cr content in the root (2.71-fold) and shoot (4.01-fold), its bioaccumulation (2.71-fold in root and 4.03-fold in the shoot) and translocation (40%) was also high in B. nigra. The data revealed that B. cereus is a multifarious PGPR that efficiently tolerates heavy metal ions (Cr+3) and it can be used to enhance the growth and phytoextraction potential of B. nigra in heavy metal contaminated soil.

Interplay of Calcium and Nitric Oxide in improvement of Growth and Arsenic-induced Toxicity in Mustard Seedlings.

In this study, Ca2+ mediated NO signalling was studied in response to metalloid (As) stress in Brassica seedlings. Arsenic toxicity strongly suppressed the growth (fresh weight, root and shoot length), photosynthetic pigments, Chl a fluorescence indices (Kinetic traits: Fv, Fm, Fv/Fo, Fm/Fo, ФPo or Fv/Fm, Ψo, ФEo, PIABS, Area and N and redox status (AsA/DHA and GSH/GSSG ratios) of the cell; whereas energy flux traits: ABS/RC, TRo/RC, ETo/RC and DIo/RC along with Fo, Fo/Fv, Fo/Fm, ФDo and Sm) were enhanced. Further, addition of EGTA (Ca2+ scavenger) and LaCl3 (plasma membrane Ca2+ channel blocker) to As + Ca; while c‒PTIO (NO scavenger) and L‒NAME (NO synthase inhibitor) to As + SNP treated seedlings, siezed recovery on above parameters caused due to Ca2+ and NO supplementation, respectively to As stressed seedlings thereby indicating their signalling behaviour. Further, to investigate the link between Ca2+ and NO, when c‒PTIO and L‒NAME individually as well as in combination were supplemented to As + Ca treated seedlings; a sharp inhibition in above mentioned traits was observed even in presence of Ca2+, thereby signifying that NO plays crucial role in Ca2+ mediated signalling. In addition, As accumulation, ROS and their indices, antioxidant system, NO accumulation and thiol compounds were also studied that showed varied results.

Pectin/Chitosan/Tripolyphosphate Nanoparticles: Efficient Carriers for Reducing Soil Sorption, Cytotoxicity, and Mutagenicity of Paraquat and Enhancing Its Herbicide Activity.

As a potent herbicide capable of contaminating water and soil environments, paraquat, which is still widely used worldwide, is toxic to mammals, algae, aquatic animals, etc. Paraquat was loaded on novel nanoparticles composed of pectin, chitosan, and sodium tripolyphosphate (PEC/CS/TPP). The size, polydispersity index, and ζ potential of nanoparticles were characterized. Further assessments were carried out by SEM, AFM, FT-IR, and DSC. The encapsulation was highly efficient, and there was a delayed release pattern of paraquat. The encapsulated herbicide was less toxic to alveolar and mouth cell lines. Moreover, the mutagenicity of the formulation was significantly lower than those of pure or commercial forms of paraquat in a Salmonella typhimurium strain model. The soil sorption of paraquat and the deep soil penetration of the nanoparticle-associated herbicide were also decreased. The herbicidal activity of paraquat for maize or mustard was not only preserved but also enhanced after encapsulation. It was concluded that paraquat encapsulation with PEC/CS/TPP nanoparticles is highly efficient and the formulation has significant herbicide activity. It is less toxic to human environment and cells, as was evidenced by less soil sorption, cytotoxicity, and mutagenicity. Hence, paraquat-loaded PEC/CS/TPP nanoparticles have potential advantages for future use in agriculture.

Targeted expression of a cysteine protease (AdCP) in tapetum induces male sterility in Indian mustard, Brassica juncea.

The development of male sterile plants is a prerequisite to developing hybrid varieties to harness the benefits of hybrid vigor in crops and enhancing crop productivity for sustainable agriculture. In plants, cysteine proteases have been known for their multifaceted roles during programmed cell death, and in ubiquitin- and proteasome-mediated proteolysis. Here, we showed that Arachis diogoi cysteine protease (AdCP) expressed under the TA-29 promoter induced complete male sterility in Indian mustard, Brassica juncea. The herbicide resistance gene bar was used for the selection of transgenic plants. Mustard transgenic plants exhibited male sterile phenotype and failed to produce functional pollen grains. Irregularly shaped aborted pollen grains with groove-like structures were observed in male sterile plants during scanning electron microscopy analysis. The T1 progeny plants obtained from the seed of primary transgenic male sterile plants crossed with the wild-type plants exhibited segregation of the progeny into male sterile and fertile plants with normal seed development. Further, male sterile plants exhibited higher transcript levels of AdCP in anther tissues, which is consistent with its expression under the tapetum-specific promoter. Our results clearly suggest that the targeted expression of AdCP provides a potential tool for developing male sterile lines in crop plants by the malfunction of tapetal cells leading to male sterility as shown earlier in tobacco transgenic plants (Shukla et al. 2014, Funct Integr Genomics 14:307-317).

Nitric oxide alters nitrogen metabolism and PIN gene expressions by playing protective role in arsenic challenged Brassica juncea L.

Plants have ability to adapt themselves through altering their growth process. In the present study, we examined exogenous application of nitric oxide (NO) on nitrogen metabolism and auxin (PIN) gene expression, and its possible role in alleviation of arsenic (As) toxicity in Brassica juncea seedlings. Seven days old hydroponically grown B. juncea seedlings were exposed to AsIII (150 µM), Sodium nitroprusside (NO donor, 100 µM), AsIII + SNP and control (without metal)for 48 h. Experimental results revealed that AsIII stress: enhanced the level of nitrite, NiR activity, NO3- and NH4+content as well as NADH-GOGAT activity; but GDH level decreased; enhanced content of amino acids; upregulated gene expression level of N metabolism and downregulated polar auxin transporter genes (PIN); inhibited plant growth and morphological parameters; increased MDA, H2O2, cysteine, proline content, enzymatic antioxidants (SOD, CAT, APX; GSH, TT, NPT); and decreased nutrient content. AsIII + SNP combination reduced the accumulation of As; improved growth; chlorophyll, protein and mineral nutrient content by scavenging ROS generation; maintained amino acids content; downregulated expression of N metabolism genes and upregulated expression of auxin transporter (PIN) genes . Additional biochemical data depicts reduction in the level of nitrogen related enzymatic activities, and other stress related parameters. Overall, this study provides an integrated view that exogenous SNP (NO donor) supplementation alleviated the inhibitory role of AsIII in B. juncea seedlings by altering nutrients, amino acids and auxin redistribution via expression of nitrogen and PIN gene profiling.

In-situ localization and biochemical analysis of bio-molecules reveals Pb-stress amelioration in Brassica juncea L. by co-application of 24-Epibrassinolide and Salicylic Acid.

Lead (Pb) toxicity is a major environmental concern affirming the need of proper mitigation strategies. In the present work, potential of combined treatment of 24-Epibrassinolide (24-EBL) and Salicylic acid (SA) against Pb toxicity to Brassica juncea L. seedlings were evaluated. Seedlings pre-imbibed in EBL (0.1 mM) and SA (1 mM) individually and in combination, were sown in Pb supplemented petri-plates (0.25, 0.50 and 0.75 mM). Various microscopic observations and biochemical analysis were made on 10 days old seedlings of B. juncea. The toxic effects of Pb were evident with enhancement in in-situ accumulation of Pb, hydrogen peroxide (H2O2), malondialdehyde (MDA), nuclear damage, membrane damage, cell death and polyamine. Furthermore, free amino acid were lowered in response to Pb toxicity. The levels of osmoprotectants including total carbohydrate, reducing sugars, trehalose, proline and glycine betaine were elevated in response to Pb treatment. Soaking treatment with combination of 24-EBL and SA led to effective amelioration of toxic effects of Pb. Reduction in Pb accumulation, reactive oxygen content (ROS), cellular damage and GSH levels were noticed in response to treatment with 24-EBL and SA individual and combined levels. The contents of free amino acid, amino acid profiling as well as in-situ localization of polyamine (spermidine) was recorded to be enhanced by co-application of 24-EBLand SA. Binary treatment of 24-EBL and SA, further elevated the content of osmoprotectants. The study revealed that co-application of combined treatment of 24-EBL and SA led to dimination of toxic effects of Pb in B. juncea seedlings.

Heterotic patterns of primary and secondary metabolites in the oilseed crop Brassica juncea.

Heterosis refers to the superior performance of F1 hybrids over their respective parental inbred lines. Although the genetic and expression basis of heterosis have been previously investigated, the metabolic basis for this phenomenon is poorly understood. In a preliminary morphological study in Brassica juncea, we observed significant heterosis at the 50% flowering stage, wherein both the growth and reproduction of F1 reciprocal hybrids were greater than that of their parents. To identify the possible metabolic causes or consequences of this heterosis, we carried out targeted LC-MS analysis of 48 primary (amino acids and sugars) and secondary metabolites (phytohormones, glucosinolates, flavonoids, and phenolic esters) in five developmental tissues at 50% flowering in hybrids and inbred parents. Principal component analysis (PCA) of metabolites clearly separated inbred lines from their hybrids, particularly in the bud tissues. In general, secondary metabolites displayed more negative heterosis values in comparison to primary metabolites. The tested primary and secondary metabolites displayed both additive and non-additive modes of inheritance in F1 hybrids, wherein the number of metabolites showing an additive mode of inheritance were higher in buds and siliques (52.77-97.14%) compared to leaf tissues (47.37-80%). Partial least regression (PLS) analysis further showed that primary metabolites, in general, displayed higher association with morphological parameters in F1 hybrids. Overall, our results are consistent with a resource-cost model for heterosis in B. juncea, where metabolite allocation in hybrids appears to favor growth, at the expense of secondary metabolism.

SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 influences flowering time, lateral branching, oil quality, and seed yield in Brassica juncea cv. Varuna.

SOC1, a MADS-box type II transcription factor, integrates environmental and endogenous cues to promote flowering in angiosperms. Recent reports implicating SOC1 in roles beyond floral transition prompted functional characterization of SOC1 in polyploid rapeseed mustard genomes. Gene characterization in Brassicas necessitates analysis of composite homeolog function. While insertional mutagenesis is untenable in Brassicas owing to gene redundancy, gain-of-function approach entails serial characterization of individual homeologs. Herein, we demonstrate modulated floral promotive effects in natural variants of Brassica SOC1 and provide lateral branching as a probable outcome of polyploidy-induced gene diversification. Ectopic expression of two B genome specific SOC1 variants in Arabidopsis thaliana resulted in differential floral acceleration and manifestation of multiple vegetative rosettes. Characterization of composite homeolog function in B. juncea via introgression of Brassica SOC1 specific artificial miRNA, designed to target homeologs, also exhibited modifications in floral transition and lateral branching. Comprehensive analysis of field performance of B. juncea transgenics displayed altered fitness across 11 agronomic traits. Crucially, reduced SOC1 levels directly impacted two developmental traits, namely, flowering time and number of lateral branches which in turn influenced several dependent agronomic traits. While delayed flowering and crop maturity resulted in altered fatty acid composition with higher SFA and lower PUFA in transgenics relative to controls, reduction in overall count of lateral branches caused a concomitant decrease in silique count which ultimately impacted total seed yield in transgenics. Statistical analysis revealed number of secondary branches as the most critical trait influencing seed yield. Based on our findings, we propose enhancing levels Brassica SOC1, a key target, for achieving earliness in flowering, improved seed yield and oil quality, and studying trait trade-offs.

Cd induced generation of free radical species in Brassica juncea is regulated by supplementation of earthworms in the drilosphere.

The antioxidant defense system of Brassica juncea under Cd stress was examined on supplementation of earthworms in the rhizosphere at different concentrations of Cd (0.50, 0.75, 1.00 and 1.25 mM i.e. 56, 84, 112 and 140 mg kg-1 respectively). Seedlings were raised in small pots containing soil spiked with Cd and earthworms under controlled conditions for 15 days. Improved Cd accumulation, as well as enhanced plant dry weight and metal tolerance were observed following the addition of earthworms. Earthworm supplementation reduced reactive oxygen species (ROS) generation by 7.3% for hydrogen peroxide (H2O2), 7.1% for superoxide anion (O2-), and 8.4% for malondialdehyde (MDA) in plants treated with 1.25 mM (140 mg kg-1) Cd. Confocal microscopy revealed improved cell viability and reduced H2O2 content due to enhanced antioxidative activity. Activity and expression levels of genes coding for antioxidative enzymes (superoxide dismutase; SOD, catalase; CAT, guaicol peroxidase; POD, glutathione reductase; GR, and glutathione-S-transferase; GST) were higher in plants raised in soils inoculated with earthworms, with expression of SOD increasing by 58.8%, CAT by 75%, POD by 183%, GR by 106.6%, and GST by 11.8%. Moreover, plant pigment (chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids) concentrations increased by 8%, 9.1%, 9.1%, and 7.7% respectively, in plants grown in soils supplemented with earthworms. The results of our study suggest that the addition of earthworms to soil increases antioxidative enzyme activities, gene expression in plants, and ROS inhibition, which enhances tolerance to Cd during the phytoextraction process.

A Reduced Phosphorus Application Rate Using a Mycorrhizal Plant as the Preceding Crop Maintains Soybean Seeds' Nutritional Quality.

We tested whether introducing an arbuscular mycorrhizal fungi (AMF)-host plant with a reduced P application rate could maintain soybean seeds' nutrient quality. The dynamic variation of 14 nutrients was analyzed in source and sink organs during the seed-filling stage. The AMF-host and non-AMF-host plants, sunflower and mustard, were grown as preceding crops (PCs). Soybeans, the succeeding crops, were planted with three different phosphorus levels, namely, 0, 50, and 150 kg P2O5 ha-1. The results showed that the AMF-host PC with a reduced P application rate maintained the seed's yield and nutrients quality. During the seed-filling stage, the AMF-host PC with a reduced P application rate increased the uptake of most nutrients compared to the non-AMF-host PC, and improved the remobilization efficiency of all nutrients except Mn, Fe, and Se, compared to the optimal P application rate. These results could help improve the utilization efficiency of P fertilizers and protect soybeans' nutritional value.

Bioaccessible selenium sourced from Se-rich mustard cake facilitates protection from TBHP induced cytotoxicity in melanoma cells.

Selenium (Se) is an essential dietary supplement that resolves inflammatory responses and offers antioxidant cytoprotection. In this study, we present the data on the cytoprotective effect of Se-rich mustard protein isolated from mustard cultivated in seleniferous soils in Punjab, India. The concentrations of total Se in mustard seed, oil-free mustard cake, and mustard protein were 110.0 ± 3.04, 143.0 ± 5.18, and 582.3 ± 6.23 µg g-1, respectively. The cytoprotective effect of Se-rich mustard protein was studied on tert-butyl hydroperoxide (TBHP)-induced cytotoxicity in a mouse melanoma cell line (B16-F10). When compared with TBHP treated cells (where no viable cells were found), Se-rich protein made bioaccessible through simulated gastrointestinal digestion protected melanoma cells from cytotoxicity with decreased levels of oxidative stress resulting in 73% cell viability. Such an effect was associated with a significant increase in glutathione peroxidase activity as a function of bioaccessible Se and its response towards cytoprotection.

How are arbuscular mycorrhizal associations related to maize growth performance during short-term cover crop rotation?

BACKGROUND: Better cover crop management options aiming to maximize the benefits of arbuscular mycorrhizal fungi (AMF) to subsequent crops are largely unknown. We investigated the impact of cover crop management methods on maize growth performance and assemblages of AMF colonizing maize roots in a field trial. The cover crop treatments comprised Italian ryegrass, wheat, brown mustard and fallow in rotation with maize. RESULTS: The diversity of AMF communities among cover crops used for maize management was significantly influenced by the cover crop and time course. Cover crops did not affect grain yield and aboveground biomass of subsequent maize but affected early growth. A structural equation model indicated that the root colonization, AMF diversity and maize phosphorus uptake had direct strong positive effects on yield performance. CONCLUSION: AMF variables and maize performance were related directly or indirectly to maize grain yield, whereas root colonization had a positive effect on maize performance. AMF may be an essential factor that determines the success of cover crop rotational systems. Encouraging AMF associations can potentially benefit cover cropping systems. Therefore, it is imperative to consider AMF associations and crop phenology when making management decisions. © 2017 Society of Chemical Industry.

Plant mating systems: self-incompatibility and evolutionary transitions to self-fertility in the mustard family.

Flowering plants have evolved diverse mechanisms that promote outcrossing. The most widespread of these outbreeding devices are self-incompatibility systems, the highly selective prefertilization mating barriers that prevent self-fertilization by disrupting pollen-pistil interactions. Despite the advantages of outcrossing, loss of self-incompatibility has occurred repeatedly in many plant families. In the mustard family, the highly polymorphic receptors and ligands that mediate the recognition and inhibition of self-pollen in self-incompatibility have been characterized and the 3D structure of the receptor-ligand complex has been solved. Sequence analyses and empirical studies in self-incompatible and self-compatible species are elucidating the genetic basis of switches from the outcrossing to selfing modes of mating and beginning to provide clues to the diversification of the self recognition repertoire.

Maleic acid assisted improvement of metal chelation and antioxidant metabolism confers chromium tolerance in Brassica juncea L.

Chromium (Cr) is a highly toxic environmental pollutant that negatively affects plant growth and development. Thus, remediating Cr from soil or increasing plant tolerance against Cr stress is urgent. Organic acids are recognized as agents of phytoremediation and as exogenous protectants, but using maleic acid (MA) to attain these results has not yet been studied. Therefore, our study investigated the effects of MA on Cr uptake and mitigation of Cr toxicity. We treated 8-d-old Indian mustard (Brassica juncea L.) seedlings with Cr (0.15mM and 0.3mM K2CrO4, 5 days) alone and in combination with MA (0.25mM) in a semi-hydroponic medium. Under Cr stress, plants accumulated Cr in both the roots and shoots in a dose-dependent manner, where the roots showed higher accumulation. Chromium stress reduced the growth and biomass of the Indian mustard plants by reducing water status and photosynthetic pigments, and increased oxidative damage due to generation of toxic reactive oxygen species (ROS) and methylglyoxal (MG). Chromium stress also interfered with the function of the antioxidant defense and glyoxalase systems. However, using MA in the Cr-stressed plants further increased Cr uptake in the roots, but it slightly reduced the translocation of Cr from the roots to the shoots at a lower dose of Cr and significantly at a higher dose. Moreover, MA also increased the other non-protein thiols (NPTs) containing phytochelatin (PC) content of the seedlings, which reduced Cr toxicity. Supplementing the stressed plants with MA upregulated the non-enzymatic antioxidants (ascorbate, AsA; glutathione, GSH); the activities of the enzymatic antioxidants including ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), glutathione reductase (GR), glutathione peroxidase (GPX), superoxide dismutase (SOD), and catalase (CAT); and the enzymes of the glyoxalase system including glyoxalase I (Gly I) and glyoxalase II (Gly II); and finally reduced oxidative damage and increased the chlorophyll content and water status as well the growth and biomass of the plants. Our findings suggested two potential uses of MA: first, enhancing phytoremediation, principally phytostabilization and second, working as an exogenous protectant to enhance Cr tolerance.

Comparison of the metabolism of inorganic and organic selenium species between two selenium accumulator plants, garlic and Indian mustard.

The metabolism of selenomethionine (SeMet) in two major selenium (Se) accumulator plants, garlic and Indian mustard, was compared to that of stable isotope labeled selenate. Indian mustard more efficiently transported Se from roots to leaves than garlic. In addition, Indian mustard accumulated larger amounts of Se than garlic. γ-Glutamyl-Se-methylselenocysteine (γ-GluMeSeCys) and Se-methylselenocysteine (MeSeCys) were the common metabolites of selenate and SeMet in garlic and Indian mustard. Indian mustard had a specific metabolic pathway to selenohomolanthionine (SeHLan) from both inorganic and organic Se species. SeMet was a more effective fertilizer for cultivating Se-enriched plants than selenate in terms of the production of selenoamino acids.

Co-application of 6-ketone type brassinosteroid and metal chelator alleviates cadmium toxicity in B. juncea L.

Plant growth regulator-assisted phytoremediation has been assessed as a novel strategy to improve phytoremediation potential of plants. In the present work, potential of castasterone, a plant growth regulator, combined with citric acid was explored for phytoremediation of cadmium in Brassica juncea seedlings. The seedlings were raised under controlled laboratory conditions for 7 days. Results revealed that 0.6 mM cadmium exposure induced toxicity in the seedlings, which was reflected through root growth inhibition, accumulation of hydrogen peroxide and malondialdehyde, and loss of cell viability. Pre-sowing treatment of castasterone supplemented with citric acid enhanced cadmium accumulation in the roots (from 752 µg/g DW to 1192 µg/g DW) and shoots (from 88 µg/g DW to 311 µg/g DW) and also improved root length, shoot length, fresh weight, and dry weight of seedlings by 81, 17, 39, and 35 %, respectively. The co-application reduced malondialdehyde accumulation by 39 % and reduced oxidative stress by enhancing the activities of antioxidant enzymes (superoxide dismutase, guaiacol peroxidase, catalase, ascorbate peroxidase, dehydroascorbate, glutathione reductase, glutathione peroxidase, glutathione-S-transferase, polyphenol oxidase), maximum enhancement (82 %) being in polyphenol oxidase. Similarly, the contents of water- and lipid-soluble antioxidants were found to increase by 31 and 4 %, respectively. Confocal microscopy revealed enhanced content of NO. Results suggested that binary combination of castasterone and citric acid is helpful in improving cadmium accumulation and ameliorating metal toxicity in B. juncea seedlings.

Growth response modulation by putrescine in Indian mustard Brassica juncea L. under multiple stress.

Plants, in general, are put to various kinds of stress, biotic and abiotic, both natural and manmade. Infestation by insect pests and diseases, and extreme conditions such as salinity, temperature, etc., as well as heavy metal contamination affect their growth performance. Here, we studied the impact of salinity and heavy metal pollution on the growth performance of Indian Mustard Brassica juncea L. and its amelioration by the diamine, putrescine, a known media supplement. We evaluated the putrescine (Put) modulation potential on multiple stress effect in 7-day old Indian mustard. The germination, seedlings length and photosynthetic pigments decline under salinity and metal (Cd/Pb) stress condition, alone or in combination, were checked by putrescine. The stress induced increase in root-shoot ratio, RNA and total amino acids content, as well as Na⁺/K⁺ ratio in leaf tissues were also comparatively less. The increased endogenous Cd/Pb accumulation in plants exposed to either metal further elevated under salinity was also found decelerated. However, the multiple stressed seedlings showed increase in glutathione content, which was further elevated with putrescine application. The increase in protein contents in leaf under single or combined stresses in the presence of putrescine could be a qualitative change. The differential changes in parameters examined here resulted in improved growth (> 10%) suggests stress mitigation by the putrescine up to an extent.

Co-composting solid biowastes with alkaline materials to enhance carbon stabilization and revegetation potential.

Co-composting biowastes such as manures and biosolids can be used to stabilize carbon (C) without impacting the quality of these biowastes. This study investigated the effect of co-composting biowastes with alkaline materials on C stabilization and monitored the fertilization and revegetation values of these co-composts. The stabilization of C in biowastes (poultry manure and biosolids) was examined by their composting in the presence of various alkaline amendments (lime, fluidized bed boiler ash, flue gas desulphurization gypsum, and red mud) for 6 months in a controlled environment. The effects of co-composting on the biowastes' properties were assessed for different physical C fractions, microbial biomass C, priming effect, potentially mineralizable nitrogen, bioavailable phosphorus, and revegetation of an urban landfill soil. Co-composting biowastes with alkaline materials increased C stabilization, attributed to interaction with alkaline materials, thereby protecting it from microbial decomposition. The co-composted biowastes also increased the fertility of the landfill soil, thereby enhancing its revegetation potential. Stabilization of biowastes using alkaline materials through co-composting maintains their fertilization value in terms of improving plant growth. The co-composted biowastes also contribute to long-term soil C sequestration and reduction of bioavailability of heavy metals.