Drought stress not only effect the population and activities of microorganisms inhabiting the rhizosphere but also various physiological and biochemical process in plants that is, photosynthesis, ...respiration, translocation, uptake of ions, carbohydrates, and nutrient metabolism. Plant growth promoting rhizobacteria (PGPR) and their exopolysaccharides (EPS) showed profound effects on plant growth and drought tolerance. Reactions of bacteria to drought stress at various organizational levels are different which depends on intensity of stress, duration, species, and growth stage. PGPR could be effectively utilized in developing strategies to facilitate water conservation strategies of plants. They have the ability to improve plant growth directly by enhancing level of phytohormones, siderophore, biofilm, and exopolysaccharides production and by increasing the nutrient availability in the rhizosphere or indirectly by protecting plants from pathogen attack. EPS producing bacteria are capable to maintain higher soil moisture content and growth of plants even under severe dried sandy soils. The evidence of survival of rhizobacteria under low moisture content obtained from the fact of rhizobacterial occurrence in the soil of desert and effective nodule formation in desert soil. Beside this, EPS produced by PGPR form rhizosheath around the roots and thus protect the plant roots from desiccation for a longer period of time. Important role exhibited by exopolysaccharides includes, protection from desiccation, microbial aggregation, plant‐microbe interaction, surface attachment, bioremediation and its use by many industries for stabilizing, thickening, coagulating, gelling, suspending and for film forming. Plants inoculated with EPS‐producing bacteria showed higher accumulation of proline, sugars, and free amino acids under water deficit stress. Biofilms formed by the PGPR around the roots are made up of bacterial populations or bacterial communities that encased inside the polymeric extracellular matrix formed by bacteria itself, they adhered to the external surfaces that contain sufficient moisture. It is concluded that the application of PGPR in combination with their EPS is a promising measure to combat drought stress thus, increasing global food security.
Chitosan is a naturally occurring biodegradable as well as a non-toxic polymer generated from chitin through alkaline deacetylation reaction, and it is insoluble in organic/inorganic solvents and ...water. Furthermore, chitosan is one of the most plentiful cationic polymers in natural surroundings. Due to its non-toxicity and biocompatibility, chitosan is extensively employed in industrial, biomedical, food, pharmaceutical, environmental, and agricultural industry. Chitosan-based biomaterials exhibit great potential in various biotechnological applications, such as anti-hypertensive therapy, anti-oxidant, anti-microbial, anti-allergic, immunostimulant, cancer therapy, delivery of genetic materials, delivery of bone morphogenetic type-2, wound healing, treatment of wastewater, hypocholesterolemic, and bio-imaging. Therefore, this review mainly focuses on the biotechnological potential of chitosan and its derivatives as well as presents the potential of chitosan-based biomaterial/pharmaceutical for the prevention of various life-threating chronic disorders.
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•This manuscript reviews foliar uptake of heavy metals by plants.•Modern development has enhanced atmospheric heavy metal pollution worldwide.•Atmospheric heavy metals can deposit and ...enter plants via foliar transfer.•Atmospheric heavy metals can induce severe health risk by vegetable contamination.•Unlike root transfer, foliar metal transfer is not well known.
Anthropologic activities have transformed global biogeochemical cycling of heavy metals by emitting considerable quantities of these metals into the atmosphere from diverse sources. In spite of substantial and progressive developments in industrial processes and techniques to reduce environmental emissions, atmospheric contamination by toxic heavy metals and associated ecological and health risks are still newsworthy. Atmospheric heavy metals may be absorbed via foliar organs of plants after wet or dry deposition of atmospheric fallouts on plant canopy. Unlike root metal transfer, which has been largely studied, little is known about heavy metal uptake by plant leaves from the atmosphere. To the best of our understanding, significant research gaps exist regarding foliar heavy metal uptake. This is the first review regarding biogeochemical behaviour of heavy metals in atmosphere-plant system. The review summarizes the mechanisms involved in foliar heavy metal uptake, transfer, compartmentation, toxicity and in plant detoxification. We have described the biological and environmental factors that affect foliar uptake of heavy metals and compared the biogeochemical behaviour (uptake, translocation, compartmentation, toxicity and detoxification) of heavy metals for root and foliar uptake. The possible health risks associated with the consumption of heavy metal-laced food are also discussed.
Chromium (Cr) is a potentially toxic heavy metal which does not have any essential metabolic function in plants. Various past and recent studies highlight the biogeochemistry of Cr in the soil-plant ...system. This review traces a plausible link among Cr speciation, bioavailability, phytouptake, phytotoxicity and detoxification based on available data, especially published from 2010 to 2016. Chromium occurs in different chemical forms (primarily as chromite (Cr(III)) and chromate (Cr(VI)) in soil which vary markedly in term of their biogeochemical behavior. Chromium behavior in soil, its soil-plant transfer and accumulation in different plant parts vary with its chemical form, plant type and soil physico-chemical properties. Soil microbial community plays a key role in governing Cr speciation and behavior in soil. Chromium does not have any specific transporter for its uptake by plants and it primarily enters the plants through specific and non-specific channels of essential ions. Chromium accumulates predominantly in plant root tissues with very limited translocation to shoots. Inside plants, Cr provokes numerous deleterious effects to several physiological, morphological, and biochemical processes. Chromium induces phytotoxicity by interfering plant growth, nutrient uptake and photosynthesis, inducing enhanced generation of reactive oxygen species, causing lipid peroxidation and altering the antioxidant activities. Plants tolerate Cr toxicity via various defense mechanisms such as complexation by organic ligands, compartmentation into the vacuole, and scavenging ROS via antioxidative enzymes. Consumption of Cr-contaminated-food can cause human health risks by inducing severe clinical conditions. Therefore, there is a dire need to monitor biogeochemical behavior of Cr in soil-plant system.
•This review summarizes biogeochemical behavior of Cr in soil-plant system.•Cr speciation governs its biogeochemical behavior in soil-plant system.•Soil microbes governs biogeochemical behavior of Cr in soil-plant system.•Cr provokes numerous deleterious effects to biochemical processes.•Plants tolerate Cr via numerous detoxification mechanisms.
Soil contamination with persistent and potentially (eco)toxic heavy metal(loid)s is ubiquitous around the globe. Concentration of these heavy metal(loid)s in soil has increased drastically over the ...last three decades, thus posing risk to the environment and human health. Some technologies have long been in use to remediate the hazardous heavy metal(loid)s. Conventional remediation methods for heavy metal(loid)s are generally based on physical, chemical and biological approaches, which may be used in combination with one another to clean-up heavy metal(loid) contaminated soils to an acceptable and safe level. This review summarizes the soil contamination by heavy metal(loid)s at a global scale, accumulation of heavy metal(loid)s in vegetables to toxic levels and their regulatory guidelines in soil. In this review, we also elucidate and compare the pool of available technologies that are currently being applied for remediation of heavy metal(loid) contaminated soils, as well as the economic aspect of soil remediation for different techniques. This review article includes an assessment of the contemporary status of technology deployment and recommendations for future remediation research. Finally, the molecular and genetic basis of heavy metal(loid) (hyper)accumulation and tolerance in microbes and plants is also discussed. It is proposed that for effective and economic remediation of soil, a better understanding of remediation procedures and the various options available at the different stages of remediation is highly necessary.
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•Soil heavy metal contamination is ubiquitous around the globe.•Bioremediation is more economical & eco-friendly than physical & chemical methods.•Combined remediation is the most effective and economical at large scale.•Microbial assisted genetically modified plants have high future perspectives.
Present study was conducted to evaluate the effect of lead tolerant plant growth promoting rhizobacteria (LTPGPR) on growth, physiology, yield, antioxidant activities and lead uptake in sunflower in ...soil contaminated with lead under pot conditions. Three pre-characterized LTPGP strains (S2 (Pseudomonas gessardii strain BLP141), S5 (Pseudomonas fluorescens A506) and S10 (Pseudomonas fluorescens strain LMG 2189)) were used to inoculate sunflower growing in soil contaminated with different levels (300, 600 and 900 mg kg−1) of lead by using lead nitrate salt as source of lead. Treatments were arranged according to completely randomized design with factorial arrangements. At harvesting, data regarding growth attributes (root shoot length, root shoot fresh and dry weights), yield per plant, physiological attributes (Chlorophyll ‘a’, ‘b’ and carotenoids content), antioxidant activities (Ascorbate peroxidase, catalase, superoxide dismutase and glutathione reductase), proline and malanodialdehyde content, and lead content in root, shoot and achenes of sunflower were recorded. Data were analysed by standard statistical procedures. Results showed that lead contamination reduced the plants growth, physiology and yield at all levels of lead stress. But application of LTPGPR in soil contaminated with lead improved plant growth, physiology, yield, and antioxidant activities, proline, and reduced the malanodialdehyde content (that is reduced by the application of different strains in lead contamination) of sunflower as compared to plants grown in soil without inoculation. Inoculation also promoted the uptake of lead in root, shoots and reduced the uptake of lead in achenes of plants as compared to plants in lead contamination without inoculation.
•Lead tolerant PGPR promoted the growth of sunflower plants under lead stress.•Lead tolerant PGPR induce stress tolerance in plants.•Physiology and antioxidant activities are improved by PGPR.•Lead tolerant PGPR improved lead uptake in sunflower plants.•By using this strategy plant and soil health is improved.
The popularity and widespread use of social media are constantly generating unmonitored data, spreading unwanted content such as hate speech and expressions that incite violence. Automatic detection ...of violence incitation is a challenging task and to the best of our knowledge, Urdu language has been completely neglected. Therefore, a robust framework is proposed for identifying expressions exhibiting violence incitation in Urdu tweets. The potentials of the semantic, word embeddings, and language models are explored to learn contextualized representations of the violence incitation in Urdu tweets. In addition, the strength of the 1-Dimensional Convolutional Neural Network (1D-CNN) is exploited by tunning its parameters on the newly proposed annotated Urdu corpus. The annotated dataset consists of 4808 tweets manually collected from Pakistani Twitter accounts. The performance of 1D-CNN with word uni-gram, Urdu Bidirectional Encoder Representations from Transformer (Urdu-BERT), and Urdu- Robustly Optimized BERT Approach (Urdu-RoBERTa) models is compared to fine-tuned Urdu-RoBERTa, Bidirectional Long short-term memory (BiLSTM), Convolutional BiLSTM (CBi-LSTM), and six state-of-the-art Machine Learning (ML) models. The results reveal that the 1D-CNN with word uni-gram model shows benchmark performance by demonstrating 89.84% accuracy and 89.80% macro f1-score. Furthermore, it outperforms all comparable models and achieves 89.76% f1-score for the violence class, and 89.84% f1-score for not-violence class identification. The uniqueness of the proposed model is evaluated using MARS shine-through and MARS occlusion metrics and the CNN model outperformed the others. The MARS metrics facilitate evaluation and visualization of the classifier performance in terms of capturing unique true positive samples that are not predicted by other models. The findings of the proposed framework are very supportive for further investigation in this domain.
Modern research has revealed that dietary consumption of flavonoids and flavonoids-rich foods significantly improve cognitive capabilities, inhibit or delay the senescence process and related ...neurodegenerative disorders including Alzheimer's disease (AD). The flavonoids rich foods such as green tea, cocoa, blue berry and other foods improve the various states of cognitive dysfunction, AD and dementia-like pathological alterations in different animal models. The mechanisms of flavonoids have been shown to be mediated through the inhibition of cholinesterases including acetylcholinesterase (AChE), and butyrylcholinesterase (BChE), β-secretase (BACE1), free radicals and modulation of signaling pathways, that are implicated in cognitive and neuroprotective functions. Flavonoids interact with various signaling protein pathways like ERK and PI3-kinase/Akt and modulate their actions, thereby leading to beneficial neuroprotective effects. Moreover, they enhance vascular blood flow and instigate neurogenesis particularly in the hippocampus. Flavonoids also hamper the progression of pathological symptoms of neurodegenerative diseases by inhibiting neuronal apoptosis induced by neurotoxic substances including free radicals and β-amyloid proteins (Aβ). All these protective mechanisms contribute to the maintenance of number, quality of neurons and their synaptic connectivity in the brain. Thus flavonoids can thwart the progression of age-related disorders and can be a potential source for the design and development of new drugs effective in cognitive disorders.
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