Genetic biofortification: advancing crop nutrition to tackle hidden hunger.

Malnutrition, often termed "hidden hunger," represents a pervasive global issue carrying significant implications for health, development, and socioeconomic conditions. Addressing the challenge of inadequate essential nutrients, despite sufficient caloric intake, is crucial. Biofortification emerges as a promising solution by enhance the presence of vital nutrients like iron, zinc, iodine, and vitamin A in edible parts of different crop plants. Crop biofortification can be attained through either agronomic methods or genetic breeding techniques. Agronomic strategies for biofortification encompass the application of mineral fertilizers through foliar or soil methods, as well as leveraging microbe-mediated mechanisms to enhance nutrient uptake. On the other hand, genetic biofortification involves the strategic crossing of plants to achieve a desired combination of genes, promoting balanced nutrient uptake and bioavailability. Additionally, genetic biofortification encompasses innovative methods such as speed breeding, transgenic approaches, genome editing techniques, and integrated omics approaches. These diverse strategies collectively contribute to enhancing the nutritional profile of crops. This review highlights the above-said genetic biofortification strategies and it also covers the aspect of reduction in antinutritional components in food through genetic biofortification.

Alleviating salinity stress in canola (Brassica napus L.) through exogenous application of salicylic acid.

Canola, a vital oilseed crop, is grown globally for food and biodiesel. With the enormous demand for growing various crops, the utilization of agriculturally marginal lands is emerging as an attractive alternative, including brackish-saline transitional lands. Salinity is a major abiotic stress limiting growth and productivity of most crops, and causing food insecurity. Salicylic acid (SA), a small-molecule phenolic compound, is an essential plant defense phytohormone that promotes immunity against pathogens. Recently, several studies have reported that SA was able to improve plant resilience to withstand high salinity. For this purpose, a pot experiment was carried out to ameliorate the negative effects of sodium chloride (NaCl) on canola plants through foliar application of SA. Two canola varieties Faisal (V1) and Super (V2) were assessed for their growth performance during exposure to high salinity i.e. 0 mM NaCl (control) and 200 mM NaCl. Three levels of SA (0, 10, and 20 mM) were applied through foliar spray. The experimental design used for this study was completely randomized design (CRD) with three replicates. The salt stress reduced the shoot and root fresh weights up to 50.3% and 47% respectively. In addition, foliar chlorophyll a and b contents decreased up to 61-65%. Meanwhile, SA treatment diminished the negative effects of salinity and enhanced the shoot fresh weight (49.5%), root dry weight (70%), chl. a (36%) and chl. b (67%). Plants treated with SA showed an increased levels of both enzymatic i.e. (superoxide dismutase (27%), peroxidase (16%) and catalase (34%)) and non-enzymatic antioxidants i.e. total soluble protein (20%), total soluble sugar (17%), total phenolic (22%) flavonoids (19%), anthocyanin (23%), and endogenous ascorbic acid (23%). Application of SA also increased the levels of osmolytes i.e. glycine betaine (31%) and total free proline (24%). Salinity increased the concentration of Na+ ions and concomitantly decreased the K+ and Ca2+ absorption in canola plants. Overall, the foliar treatments of SA were quite effective in reducing the negative effects of salinity. By comparing both varieties of canola, it was observed that variety V2 (Super) grew better than variety V1 (Faisal). Interestingly, 20 mM foliar application of SA proved to be effective in ameliorating the negative effects of high salinity in canola plants.

Exogenous ascorbic acid as a potent regulator of antioxidants, osmo-protectants, and lipid peroxidation in pea under salt stress.

Pea (Pisum sativum L.), a globally cultivated leguminous crop valued for its nutritional and economic significance, faces a critical challenge of soil salinity, which significantly hampers crop growth and production worldwide. A pot experiment was carried out in the Botanical Garden, The Islamia University of Bahawalpur to alleviate the negative impacts of sodium chloride (NaCl) on pea through foliar application of ascorbic acid (AsA). Two pea varieties Meteor (V1) and Sarsabz (V2) were tested against salinity, i.e. 0 mM NaCl (Control) and 100 mM NaCl. Three levels of ascorbic acid 0 (Control), 5 and 10 mM were applied through foliar spray. The experimental design was completely randomized (CRD) with three replicates. Salt stress resulted in the suppression of growth, photosynthetic activity, and yield attributes in pea plants. However, the application of AsA treatments effectively alleviated these inhibitory effects. Under stress conditions, the application of AsA treatment led to a substantial increase in chlorophyll a (41.1%), chl. b (56.1%), total chl. contents (44.6%) and carotenoids (58.4%). Under salt stress, there was an increase in Na+ accumulation, lipid peroxidation, and the generation of reactive oxygen species (ROS). However, the application of AsA increased the contents of proline (26.9%), endogenous AsA (23.1%), total soluble sugars (17.1%), total phenolics (29.7%), and enzymatic antioxidants i.e. SOD (22.3%), POD (34.1%) and CAT (39%) in both varieties under stress. Salinity reduced the yield attributes while foliarly applied AsA increased the pod length (38.7%), number of pods per plant (40%) and 100 seed weight (45.2%). To sum up, the application of AsA alleviated salt-induced damage in pea plants by enhancing photosynthetic pigments, both enzymatic and non-enzymatic activities, maintaining ion homeostasis, and reducing excessive ROS accumulation through the limitation of lipid peroxidation. Overall, V2 (Sarsabz) performed better as compared to the V1 (Meteor).

Exogenous application of sulfur-rich thiourea (STU) to alleviate the adverse effects of cobalt stress in wheat.

Heavy metal stress affects crop growth and yields as wheat (Triticum aestivum L.) growth and development are negatively affected under heavy metal stress. The study examined the effect of cobalt chloride (CoCl2) stress on wheat growth and development. To alleviate this problem, a pot experiment was done to analyze the role of sulfur-rich thiourea (STU) in accelerating the defense system of wheat plants against cobalt toxicity. The experimental treatments were, i) Heavy metal stress (a) control and (b) Cobalt stress (300 µM), ii) STU foliar applications; (a) control and (b) 500 µM single dose was applied after seven days of stress, and iii) Wheat varieties (a) FSD-2008 and (b) Zincol-2016. The results revealed that cobalt stress decreased chlorophyll a by 10%, chlorophyll b by 16%, and carotenoids by 5% while foliar application of STU increased these photosynthetic pigments by 16%, 15%, and 15% respectively under stress conditions as in contrast to control. In addition, cobalt stress enhances hydrogen peroxide production by 11% and malondialdehyde (MDA) by 10%. In comparison, STU applications at 500 µM reduced the production of these reactive oxygen species by 5% and by 20% by up-regulating the activities of antioxidants. Results have revealed that the activities of SOD improved by 29%, POD by 25%, and CAT by 28% under Cobalt stress. Furthermore, the foliar application of STU significantly increased the accumulation of osmoprotectants as TSS was increased by 23% and proline was increased by 24% under cobalt stress. Among wheat varieties, FSD-2008 showed better adaptation under Cobalt stress by showing enhanced photosynthetic pigments and antioxidant activities compared to Zincol-2016. In conclusion, the foliar-applied STU can alleviate the negative impacts of Cobalt stress by improving plant physiological attributes and upregulating the antioxidant defense system in wheat.

Harnessing plant extracts for eco-friendly synthesis of iron nanoparticle (Fe-NPs): Characterization and their potential applications for ameliorating environmental pollutants.

Iron-nanoparticles (Fe-NPs) are increasingly been utilized in environmental applications due to their efficacy and strong catalytic activities. The novelty of nanoparticle science had attracted many researchers and especially for their green synthesis, which can effectively reuse biological resources during the polymerization reactions. Thus, the synthesis of Fe-NPs utilizing plant extracts could be considered as the eco-friendly, simple, rapid, energy-efficient, sustainable, and cost-effective. The green synthesis route can be recognized as a practical, valuable, and economically effective alternative for large-scale production. During the production process, some biomolecules present in the extracts undergo metal salts reduction, which can serve as both a capping and reducing mechanism, enhancing the reactivity and stability of green-synthesized Fe-NPs. The diversity of species provided a wide range of potential sources for green synthesis of Fe-NPs. With improved understanding of the specific biomolecules involved in the bioreduction and stabilization processes, it will become easier to identify and utilize new, potential plant materials for Fe-NPs synthesis. Newly synthesized Fe-NPs require different characterization techniques such as transmission electron microscope, ultraviolet-visible spectrophotometry, and X-ray absorption fine structure, etc, for the determination of size, composition, and structure. This review described and assessed the recent advancements in understanding green-synthesized Fe-NPs derived from plant-based material. Detailed information on various plant materials suitable of yielding valuable biomolecules with potential diverse applications in environmental safety. Additionally, this review examined the characterization techniques employed to analyze Fe-NPs, their stability, accumulation, mobility, and fate in the environment. Holistically, the review assessed the applications of Fe-NPs in remediating wastewaters, organic residues, and inorganic contaminants. The toxicity of Fe-NPs was also addressed; emphasizing the need to refine the synthesis of green Fe-NPs to ensure safety and environmental friendliness. Moving forward, the future challenges and opportunities associated with the green synthesis of Fe-NPs would motivate novel research about nanoparticles in new directions.

Genetic modification strategies for enhancing plant resilience to abiotic stresses in the context of climate change.

Enhancing the resilience of plants to abiotic stresses, such as drought, salinity, heat, and cold, is crucial for ensuring global food security challenge in the context of climate change. The adverse effects of climate change, characterized by rising temperatures, shifting rainfall patterns, and increased frequency of extreme weather events, pose significant threats to agricultural systems worldwide. Genetic modification strategies offer promising approaches to develop crops with improved abiotic stress tolerance. This review article provides a comprehensive overview of various genetic modification techniques employed to enhance plant resilience. These strategies include the introduction of stress-responsive genes, transcription factors, and regulatory elements to enhance stress signaling pathways. Additionally, the manipulation of hormone signaling pathways, osmoprotectant accumulation, and antioxidant defense mechanisms is discussed. The use of genome editing tools, such as CRISPR-Cas9, for precise modification of target genes related to stress tolerance is also explored. Furthermore, the challenges and future prospects of genetic modification for abiotic stress tolerance are highlighted. Understanding and harnessing the potential of genetic modification strategies can contribute to the development of resilient crop varieties capable of withstanding adverse environmental conditions caused by climate change, thereby ensuring sustainable agricultural productivity and food security.

Relative biochemical and physiological docking of cucumber varieties for supporting innate immunity against Podosphaera xanthii.

Powdery mildew in cucumber is caused by the Podosphaera xanthii. No strategy for improving disease resistance can be successful in the absence of thorough insights into the physiological and biochemical responses of cucumber plants to powdery mildew. Therefore, a field experiment was executed to evaluate five commercial cucumber varieties (V1: Dynasty, V2: Long green, V3:Desi Kheera, V4:Thamin II, V5:Cucumber 363) for their inherent immunity to powdery mildew. Upon inoculating cucumber plants with Podosphaera xanthii, we noted differential responses among the varieties. Compared to other varieties, V1 and V2 showed higher values (P ≤ 0.05) for chlorophyll-a under control and pathogen-attacked plants respectively. The minimum value of anthocyanin content (-53.73%) was recorded in V3 as compared to other varieties post pathogen infection. All pathogen-infected cucumber varieties showed a considerable (P ≤ 0.05) loss in flavonoid content except V2. The maximum destruction for Phenolics under powdery mildew (179%) were recorded in V4, whereas V1 exhibited maximum phenolic content under control conditions. In pathogen-infected plants, the minimum AsA was recorded in V5 as compared to all other varieties. Pathogen invasion impacted significantly (P ≤ 0.05) the activity of superoxide dismutase (SOD). Besides, cucumber plants after pathogen inoculation resulted in a considerable (P ≤ 0.05) increase of peroxidase (POD) activity in V1 (5.02%), V2 (7.5%), and V3 (11%) in contrast to V4. Our results confirmed that cucumber varieties perform differently, which was brought on by distinct metabolic and physiological modifications that have an impact on growth and development. The changes in different attributes were correlated with cucumber resistance against powdery mildew. The results would help us fully harness the potential of these varieties to trigger disease management initiatives and defense responses.

Exploring water-absorbing capacity: a digital image analysis of seeds from 120 wheat varieties.

Wheat is a staple food crop that provides a significant portion of the world's daily caloric intake, serving as a vital source of carbohydrates and dietary fiber for billions of people. Seed shape studies of wheat typically involve the use of digital image analysis software to quantify various seed shape parameters such as length, width, area, aspect ratio, roundness, and symmetry. This study presents a comprehensive investigation into the water-absorbing capacity of seeds from 120 distinct wheat lines, leveraging digital image analysis techniques facilitated by SmartGrain software. Water absorption is a pivotal process in the early stages of seed germination, directly influencing plant growth and crop yield. SmartGrain, a powerful image analysis tool, was employed to extract precise quantitative data from digital images of wheat seeds, enabling the assessment of various seed traits in relation to their water-absorbing capacity. The analysis revealed significant transformations in seed characteristics as they absorbed water, including changes in size, weight, shape, and more. Through statistical analysis and correlation assessments, we identified robust relationships between these seed traits, both before and after water treatment. Principal Component Analysis (PCA) and Agglomerative Hierarchical Clustering (AHC) were employed to categorize genotypes with similar trait patterns, providing insights valuable for crop breeding and genetic research. Multiple linear regression analysis further elucidated the influence of specific seed traits, such as weight, width, and distance, on water-absorbing capacity. Our study contributes to a deeper understanding of seed development, imbibition, and the crucial role of water absorption in wheat. These insights have practical implications in agriculture, offering opportunities to optimize breeding programs for improved water absorption in wheat genotypes. The integration of SmartGrain software with advanced statistical methods enhances the reliability and significance of our findings, paving the way for more efficient and resilient wheat crop production. Significant changes in wheat seed shape parameters were observed after imbibition, with notable increases in area, perimeter, length, width, and weight. The length-to-width ratio (LWR) and circularity displayed opposite trends, with higher values before imbibition and lower values after imbibition.

Application of thiourea ameliorates drought induced oxidative injury in Linum usitatissimum L. by regulating antioxidant defense machinery and nutrients absorption.

Thiourea (TU) is considered an essential and emerging biostimulant against the negative impacts of severe environmental stresses, including drought stress in plants. However, the knowledge about the foliar application of TU to mitigate drought stress in Linum usitatissimum L., has yet to be discovered. The present study was designed to assess the impact of foliar application of TU for its effects against drought stress in two flax cultivars. The study comprised two irrigation regimes [60% field capacity (FC) and the control (100% FC)], along with TU (0, 500, 1000 mg L-1) application at the vegetative stage. The findings indicated that drought stress reduced the shoot fresh weight (44.2%), shoot dry weight (67.5%), shoot length (41.5%), total chlorophyll (51.6%), and carotenoids (58.8%). Drought stress increased both cultivars' hydrogen peroxide (H2O2) and malondialdehyde (MDA). Foliar application of TU (1000 mg L-1) enhanced the growth and chlorophyll contents with or without drought stress. Under drought stress (60% FC), TU decreased MDA and H2O2 contents up to twofold. Moreover, TU application increased catalase (40%), peroxidase (13%), superoxide dismutase (30%), and total soluble protein contents (32.4%) differentially in both cultivars. Nevertheless, TU increased calcium (Ca2+) (42.8%), potassium (K+) (33.4%), and phosphorus (P) (72%) in shoots and decreased the elevated sodium (Na+) (28.2%) ions under drought stress. It is suggested that TU application (1000 mg L-1) enhances the growth potential of flax by enhancing photosynthetic pigment, nutrient uptake, and antioxidant enzymes under drought stress. Research outcomes, therefore, recommend that TU application can ameliorate drought-induced negative effects in L. usitatissimum L. seedlings, resulting in improved plant growth and mineral composition, as depicted by balanced primary and secondary metabolite accumulation.

Proline-mediated redox regulation in wheat for mitigating nickel-induced stress and soil decontamination.

Nickel (Ni) is known as a plant micronutrient and serves as a component of many significant enzymes, however, it can be extremely toxic to plants when present in excess concentration. Scientists are looking for natural compounds that can influence the development processes of plants. Therefore, it was decided to use proline as a protective agent against Ni toxicity. Proline (Pro) is a popularly known osmoprotectant to regulate the biomass and developmental processes of plants under a variety of environmental stresses, but its role in the modulation of Ni-induced toxicity in wheat is very little explored. This investigation indicated the role of exogenously applied proline (10 mM) on two wheat varieties (V1 = Punjab-11, V2 = Ghazi-11) exposed to Ni (100 mg/kg) stress. Proline mediated a positive rejoinder on morphological, photosynthetic indices, antioxidant enzymes, oxidative stress markers, ion uptake were analyzed with and without Ni stress. Proline alone and in combination with Ni improved the growth, photosynthetic performance, and antioxidant capacity of wheat plants. However, Ni application alone exhibited strong oxidative damage through increased H2O2 (V1 = 28.96, V2 = 55.20) accumulation, lipid peroxidation (V1 = 26.09, V2 = 38.26%), and reduced translocation of macronutrients from root to shoot. Application of Pro to Ni-stressed wheat plants enhanced actions of catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and total soluble protein (TSP) contents by 45.70, 44.06, 43.40, and 25.11% in V1, and 39.32, 46.46, 42.22, 55.29% in V2, compared to control plants. The upregulation of antioxidant enzymes, proline accumulation, and uptake of essential mineral ions has maintained the equilibrium of Ni in both wheat cultivars, indicating Ni detoxification. This trial insight into an awareness that foliar application of proline can be utilized as a potent biochemical method in mitigating Ni-induced stress and might serve as a strong remedial technique for the decontamination of polluted soil particularly with metals.

Recent Advances in Microbial-Assisted Remediation of Cadmium-Contaminated Soil.

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.

Effect of strigolactone on growth, photosynthetic efficiency, antioxidant activity, and osmolytes accumulation in different maize (Zea mays L.) hybrids grown under drought stress.

Drought alters plant physiology, morphology, and biochemical pathways, necessitating effective mitigation strategies. Strigolactones (SLs) are phytohormones known to enhance plant growth under abiotic stress. However, their specific impact on drought stress in maize remains unclear. This study aimed to determine the optimal SL concentration for mitigating drought stress in two maize hybrids (HY-1898, FH-1046). Maize plants were subjected to 60% field capacity drought stress in a pot experiment. After 40 d, different concentrations (0, 0.001, 0.01, and 0.1 mg L-1) of the synthetic SL analogue GR24 were applied to evaluate their effects on growth features, photosynthesis attributes, and osmolyte accumulation in the maize hybrids. Results showed that exogenous SL application significantly increased photosynthetic pigments in maize hybrids under drought stress. Chlorophyll content, gas exchange characteristics, net CO2 assimilation rate, stomatal conductance, water use efficiency, and antioxidant activities were enhanced by GR24. Leaf ascorbic acid and total phenolics also increased with SL application. Organic osmolytes, such as glycine betaine and free proline, were elevated in both maize hybrids under drought stress. Yield-related parameters, including cob diameter, cob weight, number of seeds per cob, and number of seeds per plant, were significantly increased by GR24 under drought stress. Our findings highlight the potential of GR24 foliar application to mitigate drought stress and promote maize growth and grain yield in a concentration-dependent manner. The minimum effective SL concentration against drought stress was determined to be 0.01 mg L-1. Overall, foliar application of GR24 could serve as a sustainable approach for drought tolerance in agriculture.

Phenylalanine supply alleviates the drought stress in mustard (Brassica campestris) by modulating plant growth, photosynthesis, and antioxidant defense system.

Mustard (Brassica campestris L.) is a major oilseed crop that plays a crucial role in agriculture. Nevertheless, a number of abiotic factors, drought in particular, significantly reduce its production. Phenylalanine (PA) is a significant and efficacious amino acid in alleviating the adverse impacts of abiotic stressors, such as drought. Thus, the current experiment aimed to evaluate the effects of PA application (0 and 100 mg/L) on brassica varieties i.e., Faisal (V1) and Rachna (V2) under drought stress (50% field capacity). Drought stress reduced the shoot length (18 and 17%), root length (12.1 and 12.3%), total chlorophyll contents (47 and 45%), and biological yield (21 and 26%) of both varieties (V1 and V2), respectively. Foliar application of PA helped overcome drought-induced losses and enhanced shoot length (20 and 21%), total chlorophyll contents (46 and 58%), and biological yield (19 and 22%), whereas reducing the oxidative activities of H2O2 (18 and 19%), MDA concentration (21 and 24%), and electrolyte leakage (19 and 21%) in both varieties (V1 and V2). Antioxidant activities, i.e., CAT, SOD, and POD, were further enhanced under PA treatment by 25, 11, and 14% in V1 and 31, 17, and 24% in V2. Overall findings suggest that exogenous PA treatment reduced the drought-induced oxidative damage and improved the yield, and ionic contents of mustard plants grown in pots. It should be emphasized, however, that studies examining the impacts of PA on open-field-grown brassica crops are still in their early stages, thus more work is needed in this area.

Foliar Application of Ethylenediamine Tetraacetic Acid (EDTA) Improves the Growth and Yield of Brown Mustard (Brassica juncea) by Modulating Photosynthetic Pigments, Antioxidant Defense, and Osmolyte Production under Lead (Pb) Stress.

Lead (Pb) toxicity imposes several morphological and biochemical changes in plants grown in Pb-contaminated soils. Application of ethylenediamine tetraacetic acid (EDTA) in mitigating heavy metal stress has already been studied. However, the role of EDTA in mitigating heavy metal stress, especially in oilseed crops, is less known. Therefore, the study aimed to explore the potential effect of foliar application of 2.5 mM EDTA on two different varieties of Brassica juncea L., i.e., Faisal (V1) and Rohi (V2), with and without 0.5 mM Lead acetate [Pb(C2H3O2)2] treatment. Statistical analysis revealed that Pb stress was harmful to the plant. It caused a considerable decrease in the overall biomass (56.2%), shoot and root length (21%), yield attributes (20.16%), chlorophyll content (35.3%), total soluble proteins (12.9%), and calcium (61.7%) and potassium (40.9%) content of the plants as compared to the control plants. However, the foliar application of EDTA alleviated the adverse effects of Pb in both varieties. EDTA application improved the morphological attributes (67%), yield (29%), and photosynthetic pigments (80%). Positive variations in the antioxidant activity, ROS, and contents of total free amino acid, anthocyanin, flavonoids, and ascorbic acid, even under Pb stress, were prominent. EDTA application further improved their presence in the brown mustard verifying it as a more stress-resistant plant. It was deduced that the application of EDTA had significantly redeemed the adverse effects of Pb, leaving room for further experimentation to avoid Pb toxification in the mustard oil and the food chain.

Mitigation of lead toxicity in Vigna radiata genotypes by silver nanoparticles.

Heavy metal (HM) contamination of the soil through anthropogenic activities influences the living systems and drastically impacts food chain. This study examined the application of silver nanoparticles (AgNPs) in two genotypes (G1 and G2) of Mung bean (Vigna radiata) for ameliorating the Pb toxicity. Different doses of Pb (0, 25, 50 µM) were differentially tackled by AgNPs with the aim of ameliorating the plant attributes. Both genotypes displayed statistically significant quantitative and qualitative modulations for Pb tolerance. In G2, the most prominent increase in plant height (43.79%), fresh biomass (49.56%) and total chlorophyll (20%) was observed at L2 (AgNPs 10 mg/L) in comparison with the control. Overall, photosynthetic rate was increased by 26% in G2 at L6 (AgNPs 25 mg/L + Pb 25 µM). In addition, the results presented 78.5% increase in water use efficiency of G2 while G1 experienced a maximum internal CO2 concentration (209.8%) at L8 (Pb 50 µM). AgNPs triggered balanced uptake of minerals and improved growth of Vigna genotypes. 50 µM Pb was most hazardous and caused maximum reduction in growth of Vigna plants along with a significant suppression in photosynthetic activity, increase in MDA (199.7%) in G1 and H2O2 (292.8%) in G2. In comparison to control, maximum superoxide dismutase (376%), peroxidase (659.8%) and catalase (9.3%) activity was observed in G2 at L11. The application of AgNPs substantially enhanced plant growth and helped them in surviving well in absence as well as presence of Pb. G2 genotype exhibited substantial tolerance capability and revealed less impairment in the studied attributes than G1 and treatment of AgNPs i.e. 25 mg/L was the best level that yielded best results in both genotypes. The results demonstrate that AgNPs mediate response(s) of plants under Pb stress and particularly contributed to HM tolerance of plants and thus showing great promise for use in phytoremediation.

Alleviation of cadmium toxicity in Zea mays L. through up-regulation of growth, antioxidant defense system and organic osmolytes under calcium supplementation.

Calcium (Ca) is a macronutrient and works as a modulator to mitigate oxidative stress induced by heavy metals. In this study, we investigated the role of Ca to ameliorate the Cd toxicity in Zea mays L. by modulating the growth, physio-biochemical traits, and cellular antioxidant defense system. Maize genotype Sahiwal-2002 was grown under a controlled glasshouse environment with a day/night temperature of 24 ± 4°C/14 ± 2°C in a complete randomized design with three replications and two Cd levels as (0 and 150 µM) and six regimes of Ca (0, 0.5, 1, 2.5, 5, and 10 mM). Maize seedlings exposed to Cd at 150 µM concentration showed a notable decrease in growth, biomass, anthocyanins, chlorophylls, and antioxidant enzymes activities. A higher level of Cd (150 µM) also caused an upsurge in oxidative damage observed as higher electrolyte leakage (increased membrane permeability), H2O2 production, and MDA accumulation. Supplementation of Ca notably improved growth traits, photosynthetic pigments, cellular antioxidants (APX, POD, and ascorbic acid), anthocyanins, and levels of osmolytes. The significant improvement in the osmolytes (proteins and amino acids), and enzymatic antioxidative defense system enhanced the membrane stability and mitigated the damaging effects of Cd. The present results concluded that exogenously applied Ca potentially improve growth by regulating antioxidants and enabling maize plants to withstand the Cd toxicity.

Cadmium Phytotoxicity, Tolerance, and Advanced Remediation Approaches in Agricultural Soils; A Comprehensive Review.

Cadmium (Cd) is a major environmental contaminant due to its widespread industrial use. Cd contamination of soil and water is rather classical but has emerged as a recent problem. Cd toxicity causes a range of damages to plants ranging from germination to yield suppression. Plant physiological functions, i.e., water interactions, essential mineral uptake, and photosynthesis, are also harmed by Cd. Plants have also shown metabolic changes because of Cd exposure either as direct impact on enzymes or other metabolites, or because of its propensity to produce reactive oxygen species, which can induce oxidative stress. In recent years, there has been increased interest in the potential of plants with ability to accumulate or stabilize Cd compounds for bioremediation of Cd pollution. Here, we critically review the chemistry of Cd and its dynamics in soil and the rhizosphere, toxic effects on plant growth, and yield formation. To conserve the environment and resources, chemical/biological remediation processes for Cd and their efficacy have been summarized in this review. Modulation of plant growth regulators such as cytokinins, ethylene, gibberellins, auxins, abscisic acid, polyamines, jasmonic acid, brassinosteroids, and nitric oxide has been highlighted. Development of plant genotypes with restricted Cd uptake and reduced accumulation in edible portions by conventional and marker-assisted breeding are also presented. In this regard, use of molecular techniques including identification of QTLs, CRISPR/Cas9, and functional genomics to enhance the adverse impacts of Cd in plants may be quite helpful. The review's results should aid in the development of novel and suitable solutions for limiting Cd bioavailability and toxicity, as well as the long-term management of Cd-polluted soils, therefore reducing environmental and human health hazards.

Chromium toxicity, speciation, and remediation strategies in soil-plant interface: A critical review.

In recent decades, environmental pollution with chromium (Cr) has gained significant attention. Although chromium (Cr) can exist in a variety of different oxidation states and is a polyvalent element, only trivalent chromium [Cr(III)] and hexavalent chromium [Cr(VI)] are found frequently in the natural environment. In the current review, we summarize the biogeochemical procedures that regulate Cr(VI) mobilization, accumulation, bioavailability, toxicity in soils, and probable risks to ecosystem are also highlighted. Plants growing in Cr(VI)-contaminated soils show reduced growth and development with lower agricultural production and quality. Furthermore, Cr(VI) exposure causes oxidative stress due to the production of free radicals which modifies plant morpho-physiological and biochemical processes at tissue and cellular levels. However, plants may develop extensive cellular and physiological defensive mechanisms in response to Cr(VI) toxicity to ensure their survival. To cope with Cr(VI) toxicity, plants either avoid absorbing Cr(VI) from the soil or turn on the detoxifying mechanism, which involves producing antioxidants (both enzymatic and non-enzymatic) for scavenging of reactive oxygen species (ROS). Moreover, this review also highlights recent knowledge of remediation approaches i.e., bioremediation/phytoremediation, or remediation by using microbes exogenous use of organic amendments (biochar, manure, and compost), and nano-remediation supplements, which significantly remediate Cr(VI)-contaminated soil/water and lessen possible health and environmental challenges. Future research needs and knowledge gaps are also covered. The review's observations should aid in the development of creative and useful methods for limiting Cr(VI) bioavailability, toxicity and sustainably managing Cr(VI)-polluted soils/water, by clear understanding of mechanistic basis of Cr(VI) toxicity, signaling pathways, and tolerance mechanisms; hence reducing its hazards to the environment.

Methionine Promotes the Growth and Yield of Wheat under Water Deficit Conditions by Regulating the Antioxidant Enzymes, Reactive Oxygen Species, and Ions.

The individual application of pure and active compounds such as methionine may help to address water scarcity issues without compromising the yield of wheat. As organic plant growth stimulants, amino acids are popularly used to promote the productivity of crops. However, the influence of the exogenous application of methionine in wheat remains elusive. The present investigation was planned in order to understand the impact of methionine in wheat under drought stress. Two wheat genotypes were allowed to grow with 100% field capacity (FC) up to the three-leaf stage. Twenty-five-day-old seedlings of two wheat genotypes, Galaxy-13 and Johar-16, were subjected to 40% FC, denoted as water deficit-stress (D), along with 100% FC, called control (C), with and without L-methionine (Met; 4 mM) foliar treatment. Water deficit significantly reduced shoot length, shoot fresh and dry weights, seed yield, photosynthetic, gas exchange attributes except for transpiration rate (E), and shoot mineral ions (potassium, calcium, and phosphorus) in both genotypes. A significant increase was recorded in superoxide dismutase (SOD), catalase (CAT), hydrogen peroxide (H2O2), malondialdehyde (MDA), and sodium ions (Na+) due to water deficiency. However, foliar application of Met substantially improved the studied growth, photosynthetic, and gas exchange attributes with water deficit conditions in both genotypes. The activities of SOD, POD, and CAT were further enhanced under stress with Met application. Met improved potassium (K), calcium (Ca2+), and phosphorus (P) content. In a nutshell, the foliar application of Met effectively amended water deficit stress tolerance by reducing MDA and H2O2 content under water deficit conditions in wheat plants. Thus, we are able to deduce a positive association between Met-induced improved growth attributes and drought tolerance.