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Abstract Heavy metals (HMs) contamination, owing to their potential links to various chronic diseases, poses a global threat to agriculture, environment, and human health. Nickel (Ni) is an essential element however, at higher concentration, it is highly phytotoxic, and affects major plant functions. Beneficial roles of plant growth regulators (PGRs) and organic amendments in mitigating the adverse impacts of HM on plant growth has gained the attention of scientific community worldwide. Here, we performed a greenhouse study to investigate the effect of indole-3-acetic acid (IAA @ 10− 5 M) and compost (1% w/w) individually and in combination in sustaining cauliflower growth and yield under Ni stress. In our results, combined application proved significantly better than individual applications in alleviating the adverse effects of Ni on cauliflower as it increased various plant attributes such as plant height (49%), root length (76%), curd height and diameter (68 and 134%), leaf area (75%), transpiration rate (36%), stomatal conductance (104%), water use efficiency (143%), flavonoid and phenolic contents (212 and 133%), soluble sugars and protein contents (202 and 199%), SPAD value (78%), chlorophyll ‘a and b’ (219 and 208%), carotenoid (335%), and NPK uptake (191, 79 and 92%) as compared to the control. Co-application of IAA and compost reduced Ni-induced electrolyte leakage (64%) and improved the antioxidant activities, including APX (55%), CAT (30%), SOD (43%), POD (55%), while reducing MDA and H2O2 contents (77 and 52%) compared to the control. The combined application also reduced Ni uptake in roots, shoots, and curd by 51, 78 and 72% respectively along with an increased relative production index (78%) as compared to the control. Hence, synergistic application of IAA and compost can mitigate Ni induced adverse impacts on cauliflower growth by immobilizing it in the soil.

Abstract Micronutrient malnutrition is one of the major causes of human disorders in the developing world. Iron (Fe) is an important micronutrient due to its use in human metabolism such as immune system and energy production. Estimates indicate that above 30% of the global population is at risk of Fe deficiency, posing a particular threat to infants and pregnant women. Plants have adapted various strategies for uptake, transport, accumulation, and storage of Fe in tissues and organs which later can be consumed by humans. Biofortification refers to increase in micronutrient concentration in edible parts of plants and understanding the pathways for Fe accumulation in plants. Conventional plant breeding, transgenics, agronomic interventions, and microbe‐mediated biofortification are all potential methods to address Fe deficiency. This review article critically evaluates key aspects pertaining to Fe biofortification in cereal crops. It encompasses an in‐depth analysis of the holistic presence of Fe, its significance in both human and plant contexts, and the diverse strategies employed in Fe uptake, transport, accumulation, and storage in plant parts destined for human consumption. Additionally, the article explores the bioavailability of Fe and investigates strategies for biofortification, with a specific emphasis on both traditional methods and recent breakthroughs aimed at enhancing the Fe content in food crops. Keeping in view the significance of Fe for human life, appropriate biofortification strategies may serve better to eliminate hidden hunger rather than its artificial supplementation.

Abstract Worldwide, salinity severely affects agricultural production of crops such as mung bean in arid and semi-arid regions. In saline conditions, various species of Rhizobium can be used to enhance nodulation and induce salinity tolerance in maize. The present study conducted a pot experiment to determine the efficiency of three rhizobial isolates under different salinity conditions, such as 1.41, 4 and 6 dS m−1, on mung bean growth parameters, antioxidant status and yield. Results revealed that salt stress imparted adverse effects on the growth, antioxidants, yield and nodulation of mung bean. Under high salt stress conditions, fresh weights were reduced for roots (78.24%), shoots (64.52%), pods (58.26%) and height (32.33%) as compared to un-inoculated control plants. However, an increase in proline content (46.14%) was observed in high salt stressed plants. Three Rhizobium isolates (Mg1, Mg2, and Mg3), on the other hand, mitigated the negative effects of salt stress after inoculation. However, effects of Mg3 inoculation were prominent at 6 dS m−1 and it enhanced the plant height (45.10%), fresh weight of shoot (58.68%), root (63.64%), pods fresh weight (34.10%), pods number per plant (92.04%), and grain nitrogen concentration (21%) than un-inoculated control. Rhizobium strains Mg1, and Mg2 expressed splendid results at 1.41 and 4 dS m−1 salinity stress. The growth promotion effects might be due to improvement in mineral uptake and ionic balance that minimized the inhibitory effects caused by salinity stress. Thus, inoculating with these strains may boost mung bean growth and yield under salinity stress.

Lead (Pb) is one of the most dreadful non-essential elements whose toxicity has been well reported worldwide due to its interference with the major plant functions and its overall yield. Bioremediation techniques comprising the application of beneficial microorganisms have gained attention in recent times owing to their ecofriendly nature. Addition of organic matter to soil has been reported to stimulate microbial activities. Compost application improves soil structure and binds toxic contaminants due to its larger surface area and presence of functional groups. Furthermore, it stimulates soil microbial activities by acting as C-source. So, in current study, we investigated the individual and synergistic potential of two lead (Pb)-tolerant Pseudomonas strains alongwith compost (1% w/w) in sustaining sunflower growth under Pb contaminated soil conditions. Lead chloride (PbCl2) salt was used for raising desired Pb concentration (500 mg kg−1). Results revealed that Pb stress drastically affected all the measured attributes of sunflower plant, however joint application of rhizobacteria and compost counteracted these adverse effects. Among them, co-application of str-1 and compost proved to be significantly better than str-2, as its inoculation significantly improved shoot and root lengths (64 and 76%), leaf area and leaves plant−1 (95 and 166%), 100-achene weight (200%), no. of flowers plant−1 (138%), chl ‘a’, ‘b’ and carotenoid (86, 159 and 33%) contents in sunflower as compared to control treatments. Furthermore, inoculation of Pseudomonas fluorescens along with compost increased the NPK in achene (139, 200 and 165%), flavonoid and phenolic contents (258 and 185%) along with transpiration and photosynthetic rates (54 and 72%) in leaves as compared to control treatment under Pb contamination. In addition, Pb entry to roots, shoots and achene were significantly suppressed under by 87, 90 and 91% respectively due to integrated application of compost and str-1 as evident by maximum Pb-immobilization efficiency (97%) obtained in this treatment. Similarly, bioconcentration factors for roots, shoots and achene were found to be 0.58, 0.18 and 0.0055 with associated translocation factor (0.30), which also revealed phytostabilization of Pb under combined application of PGPR and compost. Since, phytoremediation of heavy metals under current scenario of increasing global population is inevitable, results of the current study concluded that tolerant PGPR species along with organic amendments such as compost can inhibit Pb uptake by sunflower and confer Pb tolerance via improved nutrient uptake, physiology, antioxidative defense and gas exchange.

Soil pollution due to heavy metal (HM) contamination has emerged as a global issue worldwide owing to their adverse impacts on plant growth. Bioremediation approaches employing living organisms for HM alleviation have gained considerable attention among scientific community. Biological agents such as plant growth-promoting rhizobacteria (PGPR) offer a sustainable way to restore soil health, and their combination with different organic amendments such as press mud (PM) can serve as potential approach for immobilizing HMs in soil. We performed a pot experiment to evaluate the role of individual and combined application of press mud and PGPR strain ‘FQ6’ (identified as Pseudomonas fluorescens) in the phytoremediation of different HMs (Pb, Ni and Cd) and growth promotion of aloe vera. Combined application of FQ6 strain and PM yielded more significant outcomes in terms of all the growth and yield attributes such as leaf length (123 %), plant height (57 %), number of leaves (115 %), fresh and dry weights of gel (246 and 280 %), gel contents (96 %), root length (164 %), root diameter (220 %), no. of root tips (138 %) and root area (315 %), as compared to control. Combined application of FQ6 and PM also led to a significant improvement in different antioxidant activities i.e., CAT (129 %), SOD (48 %), APX (17 %) and POD (83 %) as compared to control. Contrastingly, mobility of these HMs was reduced under combined application of Pseudomonas strain ‘FQ6’ and PM, as there existed a considerable difference between HMs concentrations in soil and plant body. We concluded that joint application of HM-tolerant Pseudomonas FQ6 strain and PM could be an ideal option to alleviate the HM induced adverse impacts on aloe vera by immobilizing them in soil, and subsequently, improving plant growth.

Chromium (Cr) is a toxic heavy metal and severely reduces plant growth. It commonly exists in two forms, i.e., Cr+3 and Cr+6. Due to the high solubility and oxidizing potential, Cr+6 is more dangerous and can be converted into a less toxic form of Cr+3 by different physicochemical and biological techniques. Nitrogen-fixing rhizobia promote the growth of leguminous plants through various direct and indirect mechanisms, and their efficiency can be enhanced by integrating them with various organic amendments. Biogas slurry (BGS) improves the physical properties of soil and serves as an organic source of nutrients for plants and microbes. Rhizobia can convert the metal into a less toxic state, whereas BGS can bind it and make it unavailable for plants. Therefore, the current experiment evaluated the effect of rhizobia and BGS on the growth and yield of mung bean in Cr-contaminated soil. It was observed that individual and combined application of rhizobia and BGS ameliorated the Cr-induced adverse effects on crop growth and yield attributes. Combined application yielded more significant results than their sole application and control under Cr stress. Moreover, a significant decline in Cr uptake by the plant was observed due to the integrated application of rhizobia and BGS compared to the control. The collaborative effect of plant growth-promoting rhizobacteria (PGPR) and BGS can be suitable for improving mung bean growth under Cr-contaminated sites.

Chromium (Cr) is classified as an ecological toxin, and irrigation of soil with raw industrial effluents causes its concentration in soil and plants to reach fatal levels. Due to reduced metal mobility caused by organic amendment and availability of food for microbial activity, use of Cr-tolerant rhizobacteria in conjunction with compost has proven to be useful in supporting growth and survival of plants. We checked the simultaneous effects of rhizobacteria and compost on spinach (Spinacia oleracea) growth, physiology, biochemistry as well as uptake of Cr. Plants were treated with compost (1 % w/w) and subsequently inoculated with two different PGPR strains under Cr contamination. Among tested inoculants , inoculation of 'JS2′ strain along with compost significantly ameliorated the adverse effects of Cr on spinach, and improved root and shoot lengths (84 and 197 %), as well as their dry (104 and 89 %) and fresh (89 and 167 %) weights , along with chlorophyll content (84 %) as compared to relative control. In addition, combined application led to a significant increase in antioxidant activities, such as SOD (128 %), CAT (40 %), POD (73 %) and APX (57 %) concomitant with decreased MDA contents (68 %). Data regarding Cr movement from soil to roots and aboveground plant parts, as well as the results of translocation and bioconcentration factors, revealed that combined application of PGPR and compost reduced Cr entry to aboveground plant parts and led to its phytostabilization. Hence, compost and Cr-tolerant PGPR can efficiently immobilize Cr in soil, and reduce its harmful effects on spinach growth, physiology and other important attributes.

Pollution is a significant problem in both industrialized and developing countries, as well as in some developed countries. Heavy metal pollution poses a crucial concern for communities due to its detrimental impact on human health and the long-term well-being of the planet. Heavy metals, such as cadmium, chromium, arsenic, lead, and mercury, do not degrade and can enter the food chain, leading to significant health risks. Therefore, it is essential to monitor and take necessary steps to eliminate heavy metal residues that may be present in food, beverages, and the environment. Although the exact role of nanomaterials in pollution cleanup is still unclear, nanotechnology holds promise as a future solution. In the first part of this comprehensive review, a brief overview of nanoremediation is provided. The subsequent sections delve into various nanomaterials and their potential applications in different pollution cleanup scenarios. Following that, critical analysis is conducted on different nano-remediation methods, including oxidation, adsorption, chemical precipitation, filtration, ion exchange, coagulation-flocculation, and photo-catalysis. Lastly, further suggestions are put forward regarding the future utilization of nanotechnology for more effective and enduring pollution cleanup, particularly in eliminating heavy metals.

The imbalanced use of fertilizers and irrigation water, particularly supplied from groundwater, has adversely affected crop yield and harvest quality in sugarcane (Saccharum officinarum L.). In this experiment, we evaluated the impact of potassium (K) and micronutrients [viz. Zinc (Zn), Iron (Fe), and Boron (B)] application and irrigation water from two sources, viz. canal, and tube well water on sugarcane growth, yield, and cane quality under field trails. Water samples from Mardan (canal water) and Rahim Yar Khan (tube well water) were analyzed for chemical and nutritional attributes. The results revealed that tube well water’s electrical conductivity (EC) was three-fold that of canal water. Based on the EC and total dissolved salts (TDS), 83.33% of the samples were suitable for irrigation, while the sodium adsorption ratio (SAR) indicated only a 4.76% fit and a 35.71% marginal fit compared with canal water. Furthermore, the application of K along with B, Fe, and Zn had led to a significant increase in cane height (12.8%, 9.8%, and 10.6%), cane girth (15.8%, 15.6%, and 11.6%), cane yield (13.7%, 12.3%, and 11.5%), brix contents (14%, 12.2%, and 13%), polarity (15.4%, 1.4%, and 14%), and sugar recovery (7.3%, 5.9%, and 6%) in the tube well irrigation system. For the canal water system, B, Fe, and Zn increased cane height by 15.3%, 13.42%, and 11.6%, cane girth by 13.9%, 9.9%, and 6.5%, cane yield by 42.9%, 43.5%, and 42%, brix content by 10.9%, 7.7%, and 8%, polarity by 33.4%, 28%, and 30%, and sugar recovery by 4.0%, 3.9%, and 2.0%, respectively, compared with sole NPK application. In conclusion, the utilization of tube well water in combination with canal water has shown better results in terms of yield and quality compared with the sole application of canal water. In addition, the combined application of K and B significantly improved sugarcane yields compared with Zn and Fe, even with marginally suitable irrigation water.

Soil contamination with cadmium (Cd) is a severe concern for the developing world due to its non-biodegradability and significant potential to damage the ecosystem and associated services. Industries such as mining, manufacturing, building, etc., rapidly produce a substantial amount of Cd, posing environmental risks. Cd toxicity in crop plants decreases nutrient and water uptake and translocation, increases oxidative damage, interferes with plant metabolism and inhibits plant morphology and physiology. However, various conventional physicochemical approaches are available to remove Cd from the soil, including chemical reduction, immobilization, stabilization and electro-remediation. Nevertheless, these processes are costly and unfriendly to the environment because they require much energy, skilled labor and hazardous chemicals. In contrasting, contaminated soils can be restored by using bioremediation techniques, which use plants alone and in association with different beneficial microbes as cutting-edge approaches. This review covers the bioremediation of soils contaminated with Cd in various new ways. The bioremediation capability of bacteria and fungi alone and in combination with plants are studied and analyzed. Microbes, including bacteria, fungi and algae, are reported to have a high tolerance for metals, having a 98% bioremediation capability. The internal structure of microorganisms, their cell surface characteristics and the surrounding environmental circumstances are all discussed concerning how microbes detoxify metals. Moreover, issues affecting the effectiveness of bioremediation are explored, along with potential difficulties, solutions and prospects.

Maize (Zea mays L.) is a salt-sensitive plant that experiences stunted growth and development during early seedling stages under salt stress. Salicylic acid (SA) is a major growth hormone that has been observed to induce resistance in plants against different abiotic stresses. Furthermore, plant growth-promoting rhizobacteria (PGPR) have shown considerable potential in conferring salinity tolerance to crops via facilitating growth promotion, yield improvement, and regulation of various physiological processes. In this regard, combined application of PGPR and SA can have wide applicability in supporting plant growth under salt stress. We investigated the impact of salinity on the growth and yield attributes of maize and explored the combined role of PGPR and SA in mitigating the effect of salt stress. Three different levels of salinity were developed (original, 4 and 8 dS m−1) in pots using NaCl. Maize seeds were inoculated with salt-tolerant Pseudomonas aeruginosa strain, whereas foliar application of SA was given at the three-leaf stage. We observed that salinity stress adversely affected maize growth, yield, and physiological attributes compared to the control. However, both individual and combined applications of PGPR and SA alleviated the negative effects of salinity and improved all the measured plant attributes. The response of PGPR + SA was significant in enhancing the shoot and root dry weights (41 and 56%), relative water contents (32%), chlorophyll a and b contents (25 and 27%), and grain yield (41%) of maize under higher salinity level (i.e., 8 dS m−1) as compared to untreated unstressed control. Moreover, significant alterations in ascorbate peroxidase (53%), catalase (47%), superoxide dismutase (21%), MDA contents (40%), Na+ (25%), and K+ (30%) concentration of leaves were pragmatic under combined application of PGPR and SA. We concluded that integration of PGPR and SA can efficiently induce salinity tolerance and improve plant growth under stressed conditions.

Abstract A number of resources, every year, being spent to tackle early detection of cardiac abnormalities which is one of the leading causes of deaths all over the Globe. The challenges for healthcare systems includes early detection, portability and mobility of patients. This paper presents a categorical review of smartphone-based systems that can detect cardiac abnormalities by the analysis of Electrocardiogram (ECG) and Photoplethysmography (PPG) and the limitation and challenges of these system. The ECG based systems can monitor, record and forward signals for analysis and an alarm can be triggered in case of abnormality, however the limitation of smart phone’s processing capabilities, lack of storage and speed of network are major challenges. The systems based on PPG signals are non-invasive and provides mobility and portability. This study aims to critically review the existing systems, their limitation, challenges and possible improvements to serve as a reference for researchers and developers.

Salt-tolerant plant growth-promoting rhizobacteria (PGPR) can improve soil enzyme activities, which are indicators of the biological health of the soil, and can overcome the nutritional imbalance in plants. A pot trial was executed to evaluate the effect of inoculation of different salt-tolerant PGPR strains in improving soil enzyme activities. Three different salinity levels (original, 5, and 10 dS m–1) were used and maize seeds were coated with the freshly prepared inocula of ten different PGPR strains. Among different strains, inoculation of SUA-14 (Acinetobacter johnsonii) caused a maximum increment in urease (1.58-fold), acid (1.38-fold), and alkaline phosphatase (3.04-fold) and dehydrogenase (72%) activities as compared to their respective uninoculated control. Acid phosphatase activities were found to be positively correlated with P contents in maize straw (r = 0.96) and grains (r = 0.94). Similarly, a positive correlation was found between alkaline phosphatase activities and P contents in straw (r = 0.77) and grains (r = 0.75). In addition, urease activities also exhibited positive correlation with N contents in maize straw (r = 0.92) and grains (r = 0.91). Moreover, inoculation of Acinetobacter johnsonii caused a significant decline in catalase (39%), superoxide dismutase (26%) activities, and malondialdehyde contents (27%). The PGPR inoculation improved the soil’s biological health and increased the uptake of essential nutrients and conferred salinity tolerance in maize. We conclude that the inoculation of salt-tolerant PGPR improves soil enzyme activities and soil biological health, overcomes nutritional imbalance, and thereby improves nutrient acquisition by the plant under salt stress.

The contamination of crude oil in soil matrices is a persistent problem with negative repercussions because of the recalcitrant, hazardous, and mutagenic properties of its constituents. To mitigate the effect of crude oil contamination in soil, the use of microorganisms is a cheap and feasible option. In the current study, bacterial species from numerous polluted oil field surfaces were isolated and examined for their ability to degrade crude oil. Random soil samples polluted with hydrocarbons were collected and various bacterial isolates were isolated. Results revealed that 40% of total isolates had potential use for hydrocarbon biodegradation, the synthesis of exopolysaccharides and the solubilization of phosphorous. Following isolation and characterization to degrade crude oil, a pot trial was conducted using maize inoculated with the four best strains—i.e., S1 (PMEL-63), S2 (PMEL-67), S3 (PMEL-80), and S4 (PMEL-79)—in artificially hydrocarbon-polluted soil with concentrations of crude oil of 0, 1000, and 2000 ppm. Results revealed that S4 (PMEL-79) had significant potential to degrade hydrocarbon in polluted soils. The root length, shoot length, and fresh biomass of maize were increased by 65%, 45%, and 98%, respectively, in pots inoculated with S4 (PMEL-79) Enterobacter cloacae subsp., whereas the lowest root length was observed where no strain was added and the concentration of crude oil was at maximum. Moreover, S4 (PMEL-79) Enterobacter cloacae subsp. was found to be the most effective strain in degrading crude oil and increasing maize growth under polluted soil conditions. It was concluded that the isolation of microorganisms from oil-contaminated sites should be considered in order to identify the most effective microbial consortium for the biodegradation of naturally hydrocarbon-contaminated soils.

An amendment to this paper has been published and can be accessed via the original article.