Appraising growth, oxidative stress and copper phytoextraction potential of flax (Linum usitatissimum L.) grown in soil differentially spiked with copper

Elucidating the role of rice straw biochar in modulating Helianthus annuus L. antioxidants, secondary metabolites and soil post-harvest characteristics in different types of microplastics

The emergence of microplastics (MPs) as pollutants in agricultural soils is increasingly alarming, presenting significant threats to soil ecosystems. Given the widespread contamination of ecosystems by various types of MPs, including polystyrene (PS), polyvinyl chloride (PVC), and polyethylene (PE), it is crucial to understand their effects on agricultural productivity. The present study was conducted to investigate the effects of different types of MPs (PS, PVC, and PE) on various aspects of sunflower (Helianthus annuus L.) growth with the addition of rice straw biochar (RSB). This study aimed to examine plant growth and biomass, photosynthetic pigments and gas exchange characteristics, oxidative stress indicators, and the response of various antioxidants (enzymatic and non-enzymatic) and their specific gene expression, proline metabolism, the AsA-GSH cycle, cellular fractionation in the plants and post-harvest soil properties. The research outcomes indicated that elevated levels of different types of MPs in the soil notably reduced plant growth and biomass, photosynthetic pigments, and gas exchange attributes. Different types of MPs also induced oxidative stress, which caused an increase in various enzymatic and non-enzymatic antioxidant compounds, gene expression and sugar content; notably, a significant increase in proline metabolism, AsA-GSH cycle, and pigmentation of cellular components was also observed. Favorably, the addition of RSB significantly increased plant growth and biomass, gas exchange characteristics, enzymatic and non-enzymatic compounds, and relevant gene expression while decreasing oxidative stress. In addition, RSB amendment decreased proline metabolism and AsA-GSH cycle in H. annuus plants, thereby enhancing cellular fractionation and improving post-harvest soil properties. These results open new avenues for sustainable agriculture practices and show great potential for resolving the urgent issues caused by microplastic contamination in agricultural soils.

CoSn(OH)6 nanocubes as a solid sorbent for the effective preconcentration of copper ions in cinnamon (Cinnamomum zeylanicum) extract

This study was aimed at developing a simple and efficient CoSn(OH)6 nanocubes-based preconcentration method for the preconcentration of copper ions from cinnamon extracts for determination by flame atomic absorption spectrometry. The cube-shaped sorbent was synthesized using the simple stoichiometric co-precipitation method under ambient conditions. Experimental factors of the method were evaluated with a comprehensive optimization approach to maximize the extraction efficiency for the analyte. Under the optimal conditions, the limit of detection (LOD), limit of quantitation (LOQ), and linear dynamic range were recorded as 0.98 µg/L, 3.28 µg/L, and 4.0-75 µg/L, respectively. The enhancement factor was calculated as 101.6-fold by comparing the LODs of the optimized and direct analysis systems. Percent recoveries were found to be within an acceptable range (77.6-115 %), with high repeatability using matrix matching calibration strategy. Results validated the proposed method as a highly efficient extraction approach for the monitoring of copper ions in herbal cinnamon extracts.

Exploring Bacillus mycoides PM35 efficacy in enhancing rice (Oryza sativa L.) response to different types of microplastics through gene regulation and cellular fractionation

Soil contamination with microplastics (MPs) is a persistent threat to crop production worldwide. With a wide range of MP types, including polystyrene (PS), polyvinyl chloride (PVC) and polyethylene (PE), contaminating our environment, it is important to understand their impact on agricultural productivity. The present study was conducted to investigate the effects of different types of MPs (PS, PVC and PE) on various aspects of plant growth. Specifically, we examined growth and biomass, photosynthetic pigments, gas exchange attributes, oxidative stress responses, antioxidant compound activity (both enzymatic and non-enzymatic), gene expression, proline metabolism, the AsA-GSH cycle and cellular fractionation and nutritional status, in different parts of rice (Oryza sativa L.) seedlings, which were also exposed to plant growth promoting rhizobacteria (PGPR), i.e. Bacillus mycoides PM35, i.e. 20 μL. The research outcomes indicated that the different types of MPs in the soil notably reduced plant growth and biomass, photosynthetic pigments and gas exchange attributes. However, MP stress also induced oxidative stress in the roots and shoots of the plants by increasing malondialdehyde (MDA), hydrogen peroxide (H2O2) and electrolyte leakage (EL) which also induced increased compounds of various enzymatic and non-enzymatic antioxidants and also the gene expression. Furthermore, a significant increase in proline metabolism, the AsA-GSH cycle, and the fractionations of cellular components was observed. Although the application of B. mycoides PM35 showed a significant increase in plant growth and biomass, gas exchange characteristics, enzymatic and non-enzymatic compounds and their gene expression and also decreased oxidative stress. In addition, the application of B. mycoides PM35 enhanced cellular fractionation and decreased the proline metabolism and AsA-GSH cycle in O. sativa plants. These results open new insights for sustainable agriculture practices and hold immense promise in addressing the pressing challenges of MP contamination in agricultural soils.

Unlocking the phytoremediation potential of organic acids: A study on alleviating lead toxicity in canola (Brassica napus L.)

Soil contamination with toxic heavy metals [such as lead (Pb)] is becoming a serious global problem due to the rapid development of the social economy. Organic chelating agents such as maleic acid (MA) and tartaric acid (TA) are more efficient, environmentally friendly, and biodegradable compared to inorganic chelating agents and they enhance the solubility, absorption, and stability of metals. To investigate this, we conducted a hydroponic experiment to assess the impact of MA (0.25 mM) and TA (1 mM) on enhancing the phytoremediation of Pb under its toxic concentration of 100 μM, using the oil seed crop canola (Brassica napus L.). Results from the present study showed that the Pb toxicity significantly (P < 0.05) decreased plant growth and biomass, photosynthetic pigments, gas exchange attributes and nutritional contents from the roots and shoots of the plants. In contrast, toxic concentration of Pb significantly (P < 0.05) increased oxidative stress indicators in term of malondialdehyde, hydrogen peroxide, and electrolyte leakage, increased enzymatic and non-enzymatic antixoidants and their specific gene expression and also increased organic acid exudation patter in the roots of B. napus. In addition, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that Pb toxicity significantly affected double membranous organelles while Fourier-transform infrared (FTIR) spectroscopy showed an nveiled distinct peak variations in Pb-treated plants, when compared to control. Additionally, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that Pb toxicity significantly affected double-membrane organelles, while Fourier-transform infrared (FTIR) spectroscopy unveiled distinct peak variations in Pb-treated plants compared to the control. The negative impact of Pb toxicity can overcome the application of MA and TA, which ultimately increased plant growth and biomass by capturing the reactive oxygen species, and decreased oxidative stress in B. napus. With the application of MA and TA, the values of the bioaccumulation factor (BAF) and translocation factor (TF) exceeded 1, indicating that the use of MA and TA enhances the phytoremediation potential of B. napus under Pb stress conditions. This finding could be beneficial for field environment studies, especially when explored through in-depth genetic and molecular analysis.

The impact of acid rain on cadmium phytoremediation in sunflower (Helianthus annuus L.)

Sunflower is an ideal crop for phytoremediation of cadmium-contaminated farmland, as it brings economic benefits while conducting soil remediation. Due to industrial emissions and car exhaust, Cd contaminated areas are often accompanied by acid rain. However, the impact of acid rain on the Cd remediation capacity of sunflowers and its potential influencing factors are unclear. An experiment was manipulated to elucidate the effects of Cd concentration (0,10,50,100 μmol/L) and acid rain (pH 4.0) on the phytoremediation ability of sunflowers, in which the properties of them were explored. The results indicated that Cd stress is the main factor affecting the growth of sunflowers. Without AR, Cd treatment decreased sunflower biomass by 67.5-85.6%. Under AR, Cd treatment decreased sunflower biomass 53.9-86.4%. Compared without AR, the relative chlorophyll content with AR increased by 22.3-23.1%, while the YII with AR decreased by 6.5-20.0%. There was an interaction between acid rain and Cd stress on antioxidant enzyme activity. With AR, CAT activity at 0 μmol/L Cd treatment increased by 25.6%, compared without AR. Whether there is acid rain or not, the POD and SOD activities were increased at 10, 50 μmol/L Cd treatment, but they were decreased at 100 μmol/L Cd treatment. Among them, acid rain exacerbated the impact of POD activity (decreased by 31.4%) at 100 μmol/L Cd treatment and SOD activity (decreased by 15.1%) at 50 μmol/L Cd treatment, compared without AR. In this experiment, the phytoremediation capacity of sunflowers mainly depended on the concentration of Ca in the leaves and their antioxidant capacity. Acid rain enhanced 77.5% the total Cd accumulation at 10 μmol/L Cd treatment, compared without AR. Acid rain exacerbated the damage of Cd to the chloroplast structure of sunflowers, and reduced the accumulation of starch particles. The study findings may be useful for improving the phytoremediation of Cd-contaminated soil.

Toxicity, physiological, and morphological alterations of Indian camphorweed (Pluchea indica) in response to excess copper

Indian camphorweed (Pluchea indica (L.) Less.) is used as herbal tea due to the presence of volatile aromatic oils and several phytochemical compounds. The aim of this study was to assess the impact of copper (Cu) contamination on the physiology and morphology of P. indica, and the health risks associated with its consumption as tea. The cuttings of P. indica were subjected to 0 mM (control), 5 mM (low Cu), and 20 mM (excess Cu) of CuSO4 treatments for 1, 2, and 4 weeks. Thereafter, Cu contamination as well as physiological and morphological parameters were assessed. Cu accumulation was higher in the root tissues of plants (25.8 folds higher as compared to the leaves) grown under 20 mM CuSO4 for 4 weeks. This increased Cu accumulation resulted in the inhibition of root length, root fresh weight, and root dry weight. Cu concentration was found maximum (1.36 μg g-1 DW) in the leaf tissues under 20 mM Cu exposure for 4 weeks, with the highest target hazard quotient (THQ = 1.85), whereas Cu was not detected in control. Under exposure to 20 mM Cu treatment for 4 weeks, leaf greenness, maximum quantum yield of photosystem II, and photon yield of photosystem II diminished by 21.4%, 16.1%, and 22.4%, respectively, as compared to the control. Leaf temperature was increased by 2.5 °C, and the crop stress index (CSI) exceeded 0.6 when exposed to 20 mM Cu treatment for 2 and 4 weeks; however, the control had a CSI below 0.5. This led to a reduced transpiration rate and stomatal conductance. In addition, the net photosynthetic rate was also found sensitive to Cu treatment, which resulted in decreased shoot and root growth. Based on the key results, it can be suggested that P. indica herbal tea derived from the foliage of plants grown under a 5 mM Cu level (0.75 μg g-1 DW) with a target hazard quotient below one aligns with the recommended dietary intake of Cu in leafy vegetables. The study recommends choosing cuttings from plants with a small canopy as plant material in the greenhouse microclimates to validate the growth performance in the Cu-contaminated soil and simulate the natural shrub architecture and life cycle.

The adaptation of root cell wall pectin to copper toxicity in two citrus species differing in copper tolerance: remodeling and responding

Citrus species are prone to suffer from copper (Cu) toxicity because of improper application of Cu-based agrochemicals. Copper immobilization mediated by pectin methylesterase (PME) in the root cell wall (CW) is effective for Cu detoxification. However, the underlying mechanisms of the structural modification and stress responses of citrus root CW pectin to Cu toxicity have been less discussed. In the present study, seedlings of 'Shatian pummelo' (Citrus grandis L. Osbeck) and 'Xuegan' (Citrus sinensis L. Osbeck), which differ in Cu tolerance, were irrigated with nutrient solution containing 0.5 (as control), 100, 300 or 500 μM Cu for 18 weeks in sandy culture or 24 h in hydroponics. At the end of treatments in the 18-week sandy culture, Cu toxicity on CW pectin content, Cu distribution, degree of pectin methylesterification (DPM) and the PME enzyme activity were discussed. At the genome-wide level, PME gene family was identified from the two citrus species, and qRT-PCR array of citrus PMEs under control and 300 μM Cu stress for 18 weeks were performed to screen the Cu-responsive PME genes. Moreover, the candidate genes that responded to Cu toxicity were further examined within 24 h. The results showed that Cu toxicity increased the root CW pectin content. The root CW pectin under Cu toxicity was remodeled by upregulation of the expression of the Cu-responsive PME genes followed by increasing PME activity, which mainly promoted low methylesterased pectin level and the Cu content on root CW pectin. Compared with C. sinensis, C. grandis root CW had a lower DPM and higher Cu content on the Cu-stressed root CW pectin, contributing to its higher Cu tolerance. Our present study provided theoretical evidence for root CW pectin remodeling in response to Cu toxicity of citrus species.

The wound healing potential of Hedychium spicatum Sm. and Zinnia peruviana (L.) ethanolic extracts against excision wound model in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Medicinal plants used for wound healing, are key to unlock the doors for combating the resistance of pathogens by provision of new source of compounds.

AIM OF THE STUDY

This study is aimed to evaluate and compare the wound healing properties of ethanolic extract of Hedychium spicatum Sm. rhizome and of Zinnia peruviana's leaves and roots.

MATERIALS & METHODS

Albino rats were divided into 10 groups (n = 6), control, positive control, negative control, untreated, Hedychium spicatum Sm. (125 mg/kg), Hedychium spicatum Sm (250 mg/kg), Zinnia peruviana (L.)(Leaves) (125 mg/kg), Zinnia peruviana (L.) (Leaves) (250 mg/kg), Zinnia peruviana (L.)(Roots) (125 mg/kg), Zinnia peruviana (L.)(Roots) (250 mg/kg) respectively. Excision wound of 1.5 cm wound was inflicted on the dorsal side of each rat except control group. 5% CMC gel, fusidic acid and extract gels were applied topically once daily on the wound area which was measured at intervals of 3 days until epithelization and complete wound closure. Different biochemical markers were analyzed in both blood and skin to validate the wound healing potential of these plants.

RESULTS

Topical application of an ethanolic extract of Hedychium spicatum Sm. (250 mg/kg) had significant (p ˂ 0.001) rate of wound healing and reduced epithelization period. Marked amelioration of hydroxyproline content, remarkable results on histopathological changes, reduction in oxidative stress was observed with Hedychium spicatum Sm. ethanolic extract at dose level of 250 mg/kg in comparison with untreated group.

CONCLUSION

This study concluded that the Hedychium spicatum Sm. rhizome ethanolic extract gel is effective in wound repair and may possess potential for the development of dermatologic preparation for topical diseases.

Exogenous acetone O-(2-naphthylsulfonyl)oxime improves the adverse effects of excess copper by copper detoxification systems in maize

The current study is to elucidate the responses of maize seedlings to excess copper and acetone O-(2-naphthylsulfonyl)oxime (NS) pretreatment. The study was divided into the following experimental groups: 18 h distilled water (DW) control (C), 6 h 0.3 mM NS + then 12 h DW (NS), 6 h DW + then 12 h 1 mM CuSO4.5H2O (CuS), 0.3 mM NS for 6 h + then 1 mM CuSO4.5H2O (NS + CuS) for 12 h. When the NS + CuS group is compared with the CuS group; It accumulated 10% more copper, while the ABA, H2O2, MDA, and carotenoid contents decreased significantly, the total chlorophyll, proline, gallic acid, ascorbic acid, catechol, trans-P-qumaric acid, and cinnamic acid contents increased. While SOD activity, which is one of the antioxidant system enzymes, decreased with NS application, GPX, CAT, and APX activities increased despite copper stress. When all the findings are evaluated as a whole, exogenous NS, despite excessive copper, ameliorated the adverse effects of copper stress by increasing the effectiveness of the enzymatic and non-enzymatic components of the antioxidant system and the contents of phenolic substances. In addition, increasing the copper content by 10% reveals its importance in terms of NS phytoremediation.Abbreviation: Style-sheet: When full form and abbreviated form both are used as keywords, retain both as provided by the author.

New insights in to the ameliorative effects of zinc and iron oxide nanoparticles to arsenic stressed spinach (Spinacia oleracea L.)

Nanotechnology is capturing great interest worldwide due to their stirring applications in various fields and also individual application of iron oxide nanoparticle (FeO-NPs) and zinc oxide nanoparticle (ZnO-NPs) have been studied in many literatures. However, the combined application of FeO and ZnO-NPs is a novel approach and studied in only few studies. For this purpose, a pot experiment was conducted to examine the plant growth and biomass, photosynthetic pigments, gas exchange attributes, oxidative stress and response of antioxidant compounds (enzymatic and nonenzymatic), sugars, nutritional status of the plant, organic acid exudation pattern As accumulation from the different parts of the plants in spinach (Spinacia oleracea L.) under the different As concentrations i.e., 0 (no As), 60 and 120 μM] which were primed with combined application of two levels of FeO-NPs (10 and 20 mg L^-1) and ZnO-NPs (20 and 40 mg L^-1). Results from the present study showed that the increasing levels of As in the soil significantly (P < 0.05) decreased plant growth and biomass, photosynthetic pigments, gas exchange attributes, sugars, and nutritional contents from the roots and shoots of the plants. In contrast, increasing levels of As in the soil significantly (P < 0.05) increased oxidative stress indicators in term of malondialdehyde, hydrogen peroxide, and electrolyte leakage, and also increased organic acid exudation patter in the roots of S. oleracea. The negative impact of As toxicity can overcome the combined application of ZnO-NPs and FeO-NPs, which ultimately increased plant growth and biomass by capturing the reactive oxygen species, and decreased oxidative stress in S. oleracea by decreasing the As contents in the roots and shoots of the plants. Research findings, therefore, suggest that the combined application of ZnO-NPs and FeO-NPs can ameliorate As toxicity in S. oleracea, resulting in improved plant growth and composition under As stress, as depicted by balanced exudation of organic acids.

Exogenous hydrogen sulfide alleviates chromium toxicity by modulating chromium, nutrients and reactive oxygen species accumulation, and antioxidant defence system in mungbean (Vigna radiata L.) seedlings

Chromium (Cr), a highly toxic redox-active metal cation in soil, seriously threatens global agriculture by affecting nutrient uptake and disturbing various physio-biochemical processes in plants, thereby reducing yields. Here, we examined the effects of different concentrations of Cr alone and in combination with hydrogen sulfide (H₂S) application on the growth and physio-biochemical performance of two mungbeans (Vigna radiata L.) varieties, viz. Pusa Vishal (PV; Cr tolerant) and Pusa Ratna (PR; Cr sensitive), growing in a pot in hydroponics. Plants were grown in the pot experiment to examine their growth, enzymatic and non-enzymatic antioxidant levels, electrolyte balance, and plasma membrane (PM) H⁺-ATPase activity. Furthermore, root anatomy and cell death were analysed 15 days after sowing both varieties in hydroponic systems. The Cr-induced accumulation of reactive oxygen species caused cell death and affected the root anatomy and growth of both varieties. However, the extent of alteration in anatomical features was less in PV than in PR. Exogenous application of H₂S promoted plant growth, thereby improving plant antioxidant activities and reducing cell death by suppressing Cr accumulation and translocation. Seedlings of both cultivars treated with H₂S exhibited enhanced photosynthesis, ion uptake, glutathione, and proline levels and reduced oxidative stress. Interestingly, H₂S restricted the translocation of Cr to aerial parts of plants by improving the nutrient profile and viability of root cells, thereby relieving plants from oxidative bursts by activating the antioxidant machinery through triggering the ascorbate-glutathione cycle. Overall, H₂S application improved the nutrient profile and ionic homeostasis of Cr-stressed mungbean plants. These results highlight the importance of H₂S application in protecting crops against Cr toxicity. Our findings can be utilised to develop management strategies to improve heavy metal tolerance among crops.

Physiological and Biochemical Properties of Cotton Seedlings in Response to Cu2+ Stress

Copper(II) (Cu²⁺) is essential for plant growth and development. However, high concentrations are extremely toxic to plants. We investigated the tolerance mechanism of cotton under Cu²⁺ stress in a hybrid cotton variety (Zhongmian 63) and two parent lines with different Cu²⁺ concentrations (0, 0.2, 50, and 100 μM). The stem height, root length, and leaf area of cotton seedlings had decreased growth rates in response to increasing Cu²⁺ concentrations. Increasing Cu²⁺ concentration promoted Cu²⁺ accumulation in all three cotton genotypes' roots, stems, and leaves. However, compared with the parent lines, the roots of Zhongmian 63 were richer in Cu²⁺ and had the least amount of Cu²⁺ transported to the shoots. Moreover, excess Cu²⁺ also induced changes in cellular redox homeostasis, causing accumulation of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA). Conversely, antioxidant enzyme activity increased, while photosynthetic pigment content decreased. Our findings indicated that the hybrid cotton variety fared well under Cu²⁺ stress. This creates a theoretical foundation for the further analysis of the molecular mechanism of cotton resistance to copper and suggests the potential of the large-scale planting of Zhongmian 63 in copper-contaminated soils.

Comparative efficacy of Parthenium hysterophorus (L.) derived biochar and iron doped zinc oxide nanoparticle on heavy metals (HMs) mobility and its uptake by Triticum aestivum (L.) in chromite mining contaminated soils

In this study we investigated the efficacy of a novel material parthenium weed (Parthenium hysterophorus L.) biochar (PBC), iron doped zinc oxide nanoparticles (nFe-ZnO), and biochar modified with nFe-ZnO (Fe-ZnO@BC) to adsorb heavy metals (HMs) and reduce their uptake by wheat (Triticum aestivum L.) in a highly chromite mining contaminated soil. The co-application of the applied soil conditioners exhibited a positive effect on the immobilization and restricted the HMs uptake below their threshold levels in shoot content of wheat. The maximum adsorption capacity was because of large surface area, cation exchange capacity, surface precipitation, and complexation of the soil conditioners. The scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) showed porous smooth structure of parthenium weed derived biochar that helped in HMs adsorption, increase the efficiency of soil fertilizers and nutrients retention which help in the enhancement soil condition. Under different application rates the highest translocation factor (TFHMs) was obtained at 2 g nFe-ZnO rate followed the descending order: Mn > Cr > Cu > Ni > Pb. The overall TFHMs was found <1.0 indicating that low content of HMs accumulation in roots from soil slight transferred to shoot, thus satisfying the remediation requirements.

Effects of α-Fe2O3 nanoparticles and biochar on plant growth and fruit quality of muskmelon under cadmium stress

Cadmium pollution in farmland has become a global environmental problem, threatening ecological security and human health. Biochar is effective in remediation of soil pollution. However, high concentrations of biochar can inhibit plant growth, and low concentrations of biochar have limited mitigation effect on cadmium toxicity. Therefore, the combination of low-concentration biochar and other amendments is a promising approach to alleviate cadmium toxicity in plants and improve the safety of edible parts. In this study, muskmelon was selected as the research object, and different concentrations of α-Fe₂O₃ nanoparticles were used alone or combined with biochar to explore the effects of different treatments on muskmelon plants in cadmium-contaminated soil. The results showed that the combined application of 250 mg/kg α-Fe₂O₃ nanoparticles and biochar had a good effect on the repair of cadmium toxicity in muskmelon plants. Compared with cadmium treatment, its application increased plant height by 32.53%, cadmium transport factor from root to stem decreased by 32.95%, chlorophyll content of muskmelon plants increased by 14.27%, and cadmium content in muskmelon flesh decreased by 18.83%. Moreover, after plant harvest, soil available cadmium content in 250 mg/kg α-Fe₂O₃ nanoparticles and biochar combined treatment decreased by 31.18% compared with cadmium treatment. The results of this study provide an effective reference for the composite application of different exogenous amendments and a feasible idea for soil heavy metal remediation and mitigation of cadmium pollution in farmland.

Acinetobacter schindleri SR-5-1 decipher morpho-physio-biochemical and nutritional improvements to Pisum sativum L. and Linum usitatissimum L. maintained under wastewater/cadmium stress

Metal retention in wastewater fertigated crops poses a potential hazard to food chain. Current work demonstrates the bioremediation and growth-promoting potential of Acinetobacter schindleri SR-5-1 by using nitrogen-fixing (pea) and non-nitrogen fixing (linseed) plants under cadmium (Cd) and wastewater irrigation regimes. Both plants were grown at 250 or 500 CdCl2 and 75 or 100% wastewater, each separately with and without A. schindleri SR-5-1 inoculation. The results revealed that Cd and wastewater significantly decreased growth, biomass, antioxidants, and nutrient acquisition through increased malondialdehyde, H2O2, and Cd accumulation. However, application of A. schindleri SR-5-1 significantly promoted morpho-physio-biochemical attributes while diminishing MDA and H2O2 under applied Cd and wastewater stress levels in both pea and linseed. Further, PGPR inoculation positively influenced pea and linseed seedlings through a substantial decline in Cd accumulation in roots/shoots and retained the optimal level of essential nutrients. It was inferred that both pea and linseed, with A. schindleri SR-5-1 application, exhibited higher growth and metabolism under Cd and wastewater stress but substantial tolerance was acquired under wastewater stress. Studied plants exhibited tolerance in order of 75% WW ≥ 250 µM Cd ≥ 100%WW ≥ 500 µM Cd treatment under A. schindleri inoculation. Current findings revealed the potential of A. schindleri to be exploited both for bioremediation and bio-fertilization under Cd, and wastewater-polluted regimes to reduce metal contamination of edible plants. It was suggested that with inoculation of A. schindleri SR-5-1, 75% WW dilution can be applied for irrigation of both nitrogen-fixing and non-nitrogen-fixing crops.

Physiological and Ultrastructural Responses to Excessive-Copper-Induced Toxicity in Two Differentially Copper Tolerant Citrus Species

Over-applied copper (Cu)-based agrochemicals are toxic to citrus trees. However, less information is available discussing the ultrastructural alterations in Cu-stressed citrus species. In the present study, seedlings of Citrus sinensis and Citrus grandis that differed in Cu-tolerance were sandy-cultured with nutrient solution containing 0.5 µM Cu (as control) or 300 µM Cu (as Cu toxicity) for 18 weeks. At the end of the treatments, the physiological parameters and ultrastructural features of the citrus leaves and roots were analyzed. The results indicate that Cu toxicity significantly decreased the ratio of shoot biomass to dry weight, the Cu translocation factor and the total chlorophyll of two citrus species. The anatomical and ultrastructural alterations verified that excessive Cu resulted in starch granules accumulated in the leaves and roots of the two citrus species. Under Cu toxicity, increased root flocculent precipitate and thickened root cell wall might reduce the Cu translocation from citrus roots to the shoots. Compared with C. sinensis, C. grandis maintained a relatively integral root cellular structure under Cu toxicity, which provided a structural basis for a higher Cu tolerance than C. sinensis. The present results increase our understanding of the physiological and ultrastructural responses to Cu toxicity in citrus species.

Assessment of health risk, genotoxicity, and thiol compounds in Trigonella foenum-graecum (Fenugreek) under arsenic stress

Arsenic (As) traces have been reported worldwide in vegetables and crops cultivated in As-polluted soils. Being carcinogenic, the presence of As in edibles is of great concern as it ultimately reaches humans and animals through the food chain. Besides, As toxicity adversely affects the growth, physiology, metabolism, and productivity of crops. In the present study, Trigonella foenum-graecum (Fenugreek) was exposed to the As stress (0, 50, 100, and 150 μM sodium arsenate) for a week. Further, evaluation of As accumulation in roots and shoots, magnitude and visualization of oxyradicals, and thiol-based defence offered by Fenugreek was assessed. The root and leaf accumulated 258-453 μg g^-1 dry wt (DW) and 81.4-102.1 μg g^-1 DW of As, respectively. An arsenic-mediated decline in the growth index and increase in oxidative stress was noted. Arsenic stress modulated the content of thiol compounds; especially cysteine content increased from 0.36 to 0.43 µmole g^-1 FW protein was noted. Random Amplified Polymorphic DNA (RAPD)-based analysis showed DNA damage in As-treated plants. Health risk assessment parameters showed that As concentration in the consumable plant shoot was below the critical hazard level (hazard quotient < 1). Moreover, T. foenum-graecum showed varied responses to As-induced oxidative stress with applied concentrations (150 μM being more toxic than lower concentrations). In addition, the RAPD profile and level of thiol compounds were proved significant biomarkers to assess the As toxicity in plants. The conclusion of this study will help users of fenugreek to have a clue and create awareness regarding the consumption.

Investigation of drought induced biochemical and gene expression changes in carrot cultivars

BACKGROUND

Carrot is the most important vegetable in Apiaceae family, and it is consumed globally due to its high nutritional quality. Drought stress is major environmental constraint for vegetables especially carrot. Limited data is available regarding the mechanisms conferring drought tolerance in carrot. Methods and Results Eight commercial carrot cultivars were used in this study and subjected to drought stress under semi-controlled greenhouse conditions. Biochemical, antioxidant enzymatic activity and changes in transcript level of drought related genes was estimated, the gene expression analysis was done by using qRT-PCR in comparison with reference gene expression Actin (Act1). Results revealed that cultivars Coral Orange, Tendersweet and Solar Yellow were tolerant to drought stress, which was supported by their higher transcript levels of catalase gene (CAT), superoxide dismutase genes (Cu/ZN-SOD, Cu/Zn-SDC) in these cultivars. The downregulation of PDH1 gene (Proline dehydrogenase 1) was also observed that was associated with upregulation of proline accumulation in carrot plants. Moreover, results also suggested that PRT genes (Proline transporter genes) played a key role in drought tolerance in carrot cultivars. Conclusion Among the cultivars studied, Coral Orange showed overall tolerance to drought stress conditions, whereas cultivars Cosmic Purple and Eregli Black were sensitive based on their biochemical and gene expression levels. According to our knowledge, this is the first comparative study on drought tolerance in several carrot cultivars. It will provide a background for carrot breeding to understand biochemical and molecular responses of carrot plant to drought stress and mechanisms behind it.

Combined application of plant growth-promoting bacteria and iron oxide nanoparticles ameliorates the toxic effects of arsenic in Ajwain (Trachyspermum ammi L.)

Soil contamination with toxic heavy metals [such as arsenic (As)] is becoming a serious global problem because of the rapid development of the social economy. Although plant growth-promoting bacteria (PGPB) and nanoparticles (NPs) are the major protectants to alleviate metal toxicity, the study of these chemicals in combination to ameliorate the toxic effects of As is limited. Therefore, the present study was conducted to investigate the combined effects of different levels of Providencia vermicola (5 ppm and 10 ppm) and iron oxide nanoparticles (FeO-NPs) (50 mg/l^-1 and 100 mg/l^-1) on plant growth and biomass, photosynthetic pigments, gas exchange attributes, oxidative stress and response of antioxidant compounds (enzymatic and non-enzymatic), and their specific gene expression, sugars, nutritional status of the plant, organic acid exudation pattern As accumulation from the different parts of the plants, and electron microscopy under the soil, which was spiked with different levels of As [0 μM (i.e., no As), 50 μM, and 100 μM] in Ajwain (Trachyspermum ammi L.) seedlings. Results from the present study showed that the increasing levels of As in the soil significantly (p< 0.05) decreased plant growth and biomass, photosynthetic pigments, gas exchange attributes, sugars, and nutritional contents from the roots and shoots of the plants, and destroyed the ultra-structure of membrane-bound organelles. In contrast, increasing levels of As in the soil significantly (p< 0.05) increased oxidative stress indicators in term of malondialdehyde, hydrogen peroxide, and electrolyte leakage, and also increased organic acid exudation patter in the roots of T. ammi seedlings. The negative impact of As toxicity can overcome the application of PGPB (P. vermicola) and FeO-NPs, which ultimately increased plant growth and biomass by capturing the reactive oxygen species, and decreased oxidative stress in T. ammi seedlings by decreasing the As contents in the roots and shoots of the plants. Our results also showed that the FeO-NPs were more sever and showed better results when we compared with PGPB (P. vermicola) under the same treatment of As in the soil. Research findings, therefore, suggest that the combined application of P. vermicola and FeO-NPs can ameliorate As toxicity in T. ammi seedlings, resulting in improved plant growth and composition under metal stress, as depicted by balanced exudation of organic acids.

Ameliorative role of foliar Zn-lysine application on wheat (Triticum aestivum L.) stressed by Tannery Wastewater

Tannery industries discharge a high concentration of chromium (Cr) along with other heavy metals, which are hazardous for all life forms. With increasing shortage of freshwater, tannery effluent is frequently used for crop an irrigation, causing damage to plants' health. In order to address this challenge, amino acid chelate fertilizer was used to investigate the impact on wheat crops against tannery waste water. Tannery wastewater (TW) was used at different levels such as 0%, 25%, 50%, and 100% with an amendment of foliar Zn-lysine (Zn-lys) at30 mg/L. This research highlighted the positive correlation of Zn-lysine on the morpho-physiological, biochemical, and gas exchange traits under different levels of tannery wastewater. The findings of this study showed that the application of Cr-rich tannery wastewater at different treatment levels resulted in a significant reduction in plant height (23%, 31%, and 36%), the number of tillers (21%, 30%, and 43%), spike (19%, 36%, and 55%) and dry weight (DW) of grains (10%, 25%, and 49%) roots DW (17%, 41%, 56%), and shoots DW (22%, 32%, and 47%) as compared to control. Foliar-applied Zn-lys positively enhanced photosynthetic attributes, antioxidant enzymes activities and gas exchange traits by reducing the oxidative stress alone and under Cr stress. The concentration of Cr in roots (21%, 37%, 38%) and shoots (11%, 36%, 37%) was reduced by the foliar application of Zn-lys at different treatment levels. These findings conclude that Zn-lys served as a protector for the growth and development of wheat and has an incredible potential to inhibit the phytotoxicity induced by excess Cr.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-022-01265-6.

Potential phytoremediation of Pampa biome native and invasive grass species cohabiting vineyards contaminated with Cu in Southern Brazil

The objectives were (a) to evaluate whether grasses native to the Pampa biome, Axonopus affinis Chase, Paspalum notatum Flüggé and Paspalum plicatulum Michx, and the invasive grass Cynodon dactylon (L.). Pers have the potential to phytoremediate soil contaminated with Cu (0, 35 and 70 mg Cu kg^-1); (b) assess whether the growth of these species is compromised by the excess of Cu available in the soil; and (c) determine the impact of excess Cu on the physiological responses of the studied species. C. dactylon presented the best performance in soil contaminated with 35 mg of Cu kg^-1. In C. dactylon, the concentrations of chlorophyll b and carotenoids increased, as did the photosynthetic rate and plant growth. Phytotoxic effects of Cu in soil contaminated with 70 mg of Cu kg^-1 were more severe on A. affinis and led to plant death. The other species presented reduced photosynthetic and growth rates, as well as increased activity of antioxidant enzymes such as superoxide dismutase and guaiacol peroxidase. This very same Cu level has decreased photosynthetic pigment concentrations in P. notatum and P. plicatulum. On the other hand, it did not change chlorophyll a and b concentrations in C. dactylon and increased carotenoid concentrations in it. High values recorded for Cu bioaccumulation-in-grass-root factor, mainly in P. plicatulum, have indicated that the investigated plants are potential phytostabilizers. High C. dactylon biomass production-in comparison to other species-compensates for the relatively low metal concentration in its tissues by increasing metal extraction from the soil. This makes C. dactylon more efficient in the phytoremediation process than other species.

Physiological and Molecular Mechanisms of Plant Responses to Copper Stress

Copper (Cu) is an essential micronutrient for humans, animals, and plants, and it participates in various morphological, physiological, and biochemical processes. Cu is a cofactor for a variety of enzymes, and it plays an important role in photosynthesis, respiration, the antioxidant system, and signal transduction. Many studies have demonstrated the adverse effects of excess Cu on crop germination, growth, photosynthesis, and antioxidant activity. This review summarizes the biological functions of Cu, the toxicity of excess Cu to plant growth and development, the roles of Cu transport proteins and chaperone proteins, and the transport process of Cu in plants, as well as the mechanisms of detoxification and tolerance of Cu in plants. Future research directions are proposed, which provide guidelines for related research.

Investigating the role of different maize (Zea mays L.) cultivars by studying morpho-physiological attributes in chromium-stressed environment

Because of global land surface warming, heavy metal toxicity is expected to occur more often and more intensely, affecting the growth and development of the major cereal crops such as maize (Zea mays L.) in several ways, thus affecting the production component of food security. Hence, it is important to know the best cultivars of Z. mays in abiotic stress environment to fulfill the market demand of this staple food. For this purpose, we investigate the present study to find the best Z. mays cultivar to be grown in chromium (Cr)-contaminated sand (200 µM). In this experiment, we have studied 10 cultivars (Malka, Sadaf, Pearl, CZP, YY, YH, MMRI-yellow, Sahiwal, EV-20, and EV-77) of Z. mays grown in plastic pots for 4 weeks (in addition with seed germination) under Cr - (0 µM) and Cr + (200 µM) in sand medium. Based on the findings of the current experiment, we illustrated that Cr toxicity induced a significant (P < 0.05) reduction in shoot length, root length, shoot fresh weight, root fresh weight, shoot dry weight and root dry weight, chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid content and induced oxidative damage to membrane-bounded organelles by increasing the malondialdehyde and hydrogen peroxide which were manifested by flavonoid and phenolic contents. Moreover, Cr uptake was also higher in the plants grown in the Cr-contaminated sand compared to the plants grown without the Cr-contaminated sand. We also noticed that Pearl, CZP, and Sahiwal cultivars are suggested to be Cr-tolerant cultivars as showed better growth and development in Cr-contaminated sand while Sadaf, MMRI, and EV-77 showed lower growth and composition in Cr-contaminated sand. The overall pattern of Z. mays cultivars grown in Cr-contaminated sand is as follows: Pearl > CZP > Sahiwal > YY > YH > EV-20 > Malka > EV-77 > MMRI-yellow > Sadaf. Conclusively, it can be identified that when grown in Cr-contaminated sand, Pearl, CZP, and Sahiwal have greater ability to grow in polluted soils. Overall, Z. mays cultivars showed better growth in Cr-stressed environment due to defense mechanism but further experiments needed to be conducted on molecular level.

Lead-induced modification of growth and yield of Linum usitatissimum L. and its soil remediation potential

This study was designed to evaluate the pre-reproductive and reproductive responses of Linum usitatissimum L. (flax, linseed plant) to different levels of Pb in the soil. Flax seeds were sown in garden soil-filled earthen pots and treated with three different levels of lead as lead chloride (150, 450, and 750 mg Pb kg^-1 soil) except control, and each treatment was replicated three times. Growth and reproductive parameters and photosynthetic pigments were significantly reduced (p ≤ 0.05) for all treatments. Quantitatively, Chlorophyll b content decreased more than chlorophyll a and the amount of proline content in the leaves increased in lockstep with the increase of Pb levels in the soil. Pb was found in substantial amounts in the roots, shoots, and seeds. The pattern of Pb accumulation in different organs was root > shoot > seeds. Pb levels in seeds obtained from 750 mg Pb kg^-1 soil-treated plants exceeded the permissible limits. Biological concentration factor (BCF), biological accumulation coefficient (BAC) and translocation factor (TF) values showed that roots of L. usitatissimum absorbed and accumulated a substantial quantity of Pb but translocated only a fraction of that to the shoots. Therefore, L. usitatissimum L. can be used in phytostabilization rather than phytoextraction of Pb.

Short-term responses of Spinach (Spinacia oleracea L.) to the individual and combinatorial effects of Nitrogen, Phosphorus and Potassium and silicon in the soil contaminated by boron

While of lesser prevalence than boron (B) deficient soils, B-rich soils are important to study as they can cause B toxicity in the field and subsequently decrease crop yields in different regions of the world. We have conducted the present study to examine the role of the individual or combined application of silicon (Si) and NPK fertilizer in B-stressed spinach plants (Spinacia oleracea L.). S. oleracea seedlings were subjected to different NPK fertilizers, namely, low NPK (30 kg ha-2) and normal NPK (60 kg ha-2)], which were also supplemented by Si (3 mmol L-1), for varying levels of B in the soil i.e., 0, 250, and 500 mg kg-1. Our results illustrated that the increasing levels of B in the soil caused a substantial decrease in the plant height, number of leaves, number of stems, leaf area, plant fresh weight, plant dry weight, chlorophyll a, chlorophyll b, total chlorophyll, carotenoid content, net photosynthesis, stomatal conductance, transpiration rate, magnesium content in the roots, magnesium contents in the shoots, phosphorus content in the roots, phosphorus content in the leaves in the shoots, iron content in the roots, iron content in the shoots, calcium content in the roots, and calcium content in the shoots. However, B toxicity in the soil increased the concentration of malondialdehyde, hydrogen peroxide, and electrolyte leakage which were also manifested by the increasing activities of enzymatic [superoxidase dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX)], and non-enzymatic antioxidants (phenolic, flavonoid, ascorbic acid, and anthocyanin content). B toxicity in the soil further increased the concentration of organic acids in the roots such as oxalic acid, malic acid, formic acid, citric acid, acetic acid, and fumaric acid. The addition of Si and fertilizer levels in the soil significantly alleviated B toxicity effects on S. oleracea by improving photosynthetic capacity and ultimately plant growth. The increased activity of antioxidant enzymes in Si and NPK-treated plants seems to play a role in capturing stress-induced reactive oxygen species, as was evident from the lower levels of oxidative stress indicators, organic acid exudation, and B concentration in the roots and shoots of Si and NPK-treated plants. Research findings, therefore, suggested that the Si and NPK application can ameliorate B toxicity in S. oleracea seedlings and result in improved plant growth and composition under metal stress as depicted by the balanced exudation of organic acids.

Impact of Plantago ovata Forsk leaf extract on morpho-physio-biochemical attributes, ions uptake and drought resistance of wheat (Triticum aestivum L.) seedlings

The present study was conducted to examine the potential role of Plantago ovata Forsk leaf extract (POLE) which was applied at various concentration levels (control, hydropriming, 10, 20, 30, and 40% POLE) to the wheat (Triticum aestivum L.) seedlings. Drought stressed was applied at 60% osmotic potential (OM) to the T. aestivum seedlings to study various parameters such as growth and biomass, photosynthetic pigments and gas exchange characteristics, oxidative stress and response of various antioxidants and nutritional status of the plants. Various growth parameters such as gaseous exchange attributes, antioxidants and nutritional status of T. aestivum were investigated in this study. It was evident that drought-stressed condition had induced a negative impact on plant growth, photosynthetic pigment, gaseous exchange attributes, stomatal properties, and ion uptake by different organs (roots and shoots) of T. aestivum. The decrease in plant growth resulted from oxidative stress and overcome by the antioxidant (enzymatic and non-enzymatic) compounds, since their concentration increased in response to dehydration. Seed priming with POLE positively increased plant growth and photosynthesis, by decreasing oxidative stress indicators and increasing activities of antioxidant (enzymatic and non-enzymatic) compounds, compared to the plants which were grown without the application of POLE. Our results also depicted that optimum concentration of POLE for T. aestivum seedlings under drought condition was 20%, while further increase in POLE (30 and 40%) induced a non-significant (P < 0.05) effect on growth (shoot and root length) and biomass (fresh and dry weight) of T. aestivum seedling. Here we concluded that the understanding of the role of seed priming with POLE in the increment of growth profile, photosynthetic measurements and nutritional status introduces new possibilities for their effective use in drought-stressed condition and provides a promising strategy for T. aestivum tolerance against drought-stressed condition.

Functional Characterization of MaZIP4, a Gene Regulating Copper Stress Tolerance in Mulberry (Morus atropurpurea R.)

ZIP4 (zinc transporter 4) plays important roles in transporting Cu²⁺ ions in plants, which may contribute to the maintenance of plant metal homeostasis in growth, plant development and normal physiological metabolism. However, ZIP4 transporters have not been described in mulberry and the exact function of ZIP4 transporters in regulating the homeostasis of Cu in mulberry remains unclear. In this study, a new ZIP4 gene (MaZIP4) was isolated and cloned from Morus atropurpurea R. Phylogenetic analysis of amino sequences suggested that the amino-acid sequence of the MaZIP4 protein shows high homology with other ZIP4 proteins of Morus notabilis, Trema orientale, Ziziphus jujube and Cannabis sativa. In addition, a MaZIP4 silenced line was successfully constructed using virus-induced gene silencing (VIGS). The analysis of MaZIP4 expression by quantitative real-time PCR in mulberry showed that the level of MaZIP4 expression increased with increasing Cu concentration until the Cu concentration reached 800 ppm. Relative to the blank (WT) and the negative controls, malondialdehyde (MDA) levels increased significantly and rose with increasing Cu concentration in the MaZIP4 silenced line, whereas the soluble protein and proline content, superoxide dismutase (SOD) and peroxidase (POD) activities of these transgenic plants were lower. These results indicated that MaZIP4 may play an important role in the resistance of mulberry to Cu stress.

Hydrogen sulphide and nitric oxide mitigate the negative impacts of waterlogging stress on wheat (Triticum aestivum L.)

Nitric oxide (NO) and hydrogen sulphide (H₂ S) are important gaseous signalling molecules that regulate key physiochemical mechanisms of plants under environmental stresses. A number of attempts have been made to improve waterlogging tolerance in plants, but with limited success. Having said that, NO and H₂ S are vital signalling molecules, but their role in mitigating waterlogging effects on crop plants is not well established. We investigated the efficacy of exogenous NO and H₂ S to alleviate waterlogging effects in two wheat cultivars (Galaxy-2013 and FSD-2008). Waterlogging produced a noticeable reduction in plant growth, yield, chlorophyll, soluble sugars and free amino acids. Besides, waterlogging induced severe oxidative damage seen as higher cellular TBARS and H₂ O₂ content. Antioxidant enzyme activity increased together with a notable rise in Fe²⁺ and Mn²⁺ content. Proline content was higher in waterlogged plants compared with non-waterlogged plants. In contrast, waterlogging caused a substantial decline in endogenous levels of essential nutrients (K⁺ , Ca²⁺ and Mg²⁺ ). Waterlogged conditions led to Fe²⁺ and Mn²⁺ toxicity due to rapid reduction of Fe³⁺ and Mn³⁺ in the soil. Exogenous NO and H₂ S significantly protected plants from waterlogging effects by enhancing the oxidative defence and regulating nutritional status. Besides, the protective effects of exogenous NO were more prominent as compared with effects of H₂ S. Further, we did not study the effect of H₂ S and NO on photosynthetic attributes and expression of stress-related genes. Therefore, future studies should examine the effects of H₂ S and NO on wheat physiology and gene expression under waterlogging.

Salt stress mitigation in Lathyrus cicera by combining different microbial inocula

Arid and semi-arid areas are considered vulnerable to various environmental constraints which are further fortified by climate change. Salinity is one of the most serious abiotic factors affecting crop yield and soil fertility. Till now, no information is available on the effect of salinity on development and symbiotic nitrogen (N₂) fixation in the legume species Lathyrus cicera. Here, we evaluated the effect of different microbial inocula including nitrogen-fixing Rhizobium laguerreae, arbuscular mycorrhizal fungus (AMF) Rhizophagus irregularis, a complex mixed inoculum of AMF isolated from rhizospheric soil in "Al Aitha", and various plant growth-promoting bacteria (PGPB) including Bacillus subtilus, Bacillus simplex and Bacillus megaterium combined with Rhizobium, the AMF consortium, or R. irregularis on alleviating salt stress in this legume. A pot trial was conducted to evaluate the ability of different microbial inocula to mitigate adverse effects of salinity on L. cicera plants. The results showed that salinity (100 mM NaCl) significantly reduced L. cicera plant growth. However, inoculation with different inocula enhanced plant growth and markedly promoted various biochemical traits. Moreover, the combined use of PGPB and AMF was found to be the most effective treatment in mitigating deleterious effects of salinity stress on L. cicera. In addition, this co-inoculation upregulated the expression of two marker genes (LcHKT1 and LcNHX7) related to salinity tolerance. Our findings suggest that the AMF/PGPB formulation has a great potential to be used as a biofertilizer to improve L. cicera plant growth and productivity under saline conditions.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12298-022-01205-4.

Exogenous melatonin mitigates chromium toxicity in maize seedlings by modulating antioxidant system and suppresses chromium uptake and oxidative stress

Melatonin, being an endogenous signaling molecule plays important role in plant growth and stress alleviation. The present study was conducted to evaluate the ameliorative role of melatonin against Cr toxicity in maize seedlings. The Cr toxicity (50, 100 and 200 µM) severely affected hydroponically grown seedlings growth in a dose-dependent manner; however, the melatonin (0.5 and 1.0 µM) application markedly restored toxicity-induced growth retardation. Higher dose of melatonin (1.0 µM) was more effective in case of lower Cr toxicity (50 and 100 µM). Exposure of 200 µM Cr caused 45% and 43% reduction in shoot and root lengths and more than 80% reduction in biomass. In case of 200 µM Cr toxicity, application of 1.0 µM MT effectively restored shoot and root lengths reduction (from 45 to 30%) and biomass decline (from 80 to around 60%). Biomass restoration by 1.0 µM melatonin under 50 and 100 µM Cr was even more pronounced bringing it near to control plants having no Cr exposure. Further, both melatonin levels also improved root tips, root diameter, root volume and root surface area that had been damaged by Cr exposure. The melatonin also alleviated Cr-induced chlorophyll and carotenoids inhibition, improved relative water content, and markedly lowered proline and MDA content in shoots. Lower accumulation of MDA and proline, and greater membrane stability indices indicate that the melatonin conferred better plant growth by playing the role of antioxidant and detoxifying oxidative stress creating substances. Although antioxidant enzymes viz. SOD, POD, CAT and APX activities were also elevated by MT, this increase was not significantly different in the most of cases. No significant difference in NPK contents of shoot was observed by Cr and melatonin application indicating the growth retardation being caused directly by Cr intrinsic toxicity and not by nutrients deficiency. The melatonin-based amelioration of Cr toxicity in maize seedlings seems as the result of its nature as antioxidant, and not by activation/elevation of antioxidative enzymatic system.

Zinc Oxide Nanoparticles and Their Biosynthesis: Overview

Zinc (Zn) is plant micronutrient, which is involved in many physiological functions, and an inadequate supply will reduce crop yields. Its deficiency is the widest spread micronutrient deficiency problem; almost all crops and calcareous, sandy soils, as well as peat soils and soils with high phosphorus and silicon content are expected to be deficient. In addition, Zn is essential for growth in animals, human beings, and plants; it is vital to crop nutrition as it is required in various enzymatic reactions, metabolic processes, and oxidation reduction reactions. Finally, there is a lot of attention on the Zn nanoparticles (NPs) due to our understanding of different forms of Zn, as well as its uptake and integration in the plants, which could be the primary step toward the larger use of NPs of Zn in agriculture. Nanotechnology application in agriculture has been increasing over recent years and constitutes a valuable tool in reaching the goal of sustainable food production worldwide. A wide array of nanomaterials has been used to develop strategies of delivery of bioactive compounds aimed at boosting the production and protection of crops. ZnO-NPs, a multifunctional material with distinct properties and their doped counterparts, were widely being studied in different fields of science. However, its application in environmental waste treatment and many other managements, such as remediation, is starting to gain attention due to its low cost and high productivity. Nano-agrochemicals are a combination of nanotechnology with agrochemicals that have resulted in nano-fertilizers, nano-herbicides, nano-fungicides, nano-pesticides, and nano-insecticides being developed. They have anti-bacterial, anti-fungal, anti-inflammatory, antioxidant, and optical capabilities. Green approaches using plants, fungi, bacteria, and algae have been implemented due to the high rate of harmful chemicals and severe situations used in the manufacturing of the NPs. This review summarizes the data on Zn interaction with plants and contributes towards the knowledge of Zn NPs and its impact on plants.

Antifungal activity of Zinc nitrate derived nano Zno fungicide synthesized from Trachyspermum ammi to control fruit rot disease of grapefruit

Grapefruit (Citrus paradisi) is a widely grown citrus and its fruit is affected by a variety of biotic and abiotic stress. Keeping in view the hazardous effects of synthetic fungicides, the recent trend is shifting towards safer and eco-friendly control of fruit diseases. The present study was aimed to diagnose the fruit rot disease of grapefruit and its control by using zinc oxide green nanoparticles (ZnO NPs). Fruit rot symptoms were observed in various grapefruit growing sites of Pakistan. Diseased samples were collected, and the disease-causing pathogen was isolated. Following Koch's postulates, the isolated pathogen was identified as Rhizoctonia solani. For eco-friendly control of this disease, ZnO NPs were prepared in the seed extract of Trachyspermum ammi and characterized. Fourier transform infrared spectroscopy (FTIR) of these NPs described the presence of stabilizing and reducing compounds such as phenols, aldehyde and vinyl ether, especially thymol (phenol). X-ray diffraction (XRD) analysis revealed their crystalline nature and size (48.52 nm). Energy dispersive X-ray (EDX) analysis elaborated the presence of major elements in the samples, while scanning electron microscopy (SEM) confirmed the morphology of bio fabricated NPs. ZnO NPs exhibited very good anti-fungal activity and the most significant fungal growth inhibition was observed at 1.0 mg/ml concentration of green NPs, in vitro and in vivo. These findings described that the bioactive constituents of T. ammi seed extract can effectively reduce and stabilize ZnO NPs. It is a cost-effective method to successfully control the fruit rot disease of grapefruit.

Buffer Green Patches around Urban Road Network as a Tool for Sustainable Soil Management

Urban areas are facing a range of environmental challenges including air, water and soil pollution as a result of industrial, domestic and traffic emissions. In addition, global climate change is likely to aggravate certain urban problems and disturb the urban ecology by increasing the frequency and severity of extreme weather events. In the context of urbanization growth and the consequent impact on the environment, there is a growing interest in maintaining urban soil quality and functions as they are the medium for green infrastructure development. Furthermore, urban soils are becoming one of the key factors in the delivery of many ecosystem services such as carbon storage, climate regulation, water flow regulation, etc. On the other hand, urban soils are well-known to be a major sink of air pollutants due to the wet and dry atmospheric deposition and recirculation. Soil has the ability to degrade some chemical contaminants but when the levels are high, urban soils could hold on large amounts and pose a risk to human health. A cost-effective technological solution is to use the ability of some plant species to metabolize, accumulate and detoxify heavy metals or other harmful organic or inorganic compounds from the soil layer. The establishment of urban lawns (grass covered surfaces) is a helpful, environmentally friendly, economically sustainable and cost-effective approach to remove contaminants from polluted soils (terrains), which also has some aesthetic benefits. In this paper, an overview of the benefits and limitations of urban lawn construction is presented. The focus is on the perspectives for sustainable management of urban lawns, especially as buffer green patches in the road network surroundings, that can represent strategies to provide ecological and social multifunctionality of urban soils, and thus, increasing their ecosystem services capacity. Specifically, the paper highlights (i) the possibilities for phytoremediation of urban soils, (ii) potential of some perennial grasses and (iii) key issues that should be considered in the planning and design of urban lawns.

The Impact of Bio-Stimulants on Cd-Stressed Wheat (Triticum aestivum L.): Insights Into Growth, Chlorophyll Fluorescence, Cd Accumulation, and Osmolyte Regulation

It has been established that wheat (Triticum aestivum L.) has a higher Cd absorption capacity than other cereal crops causing an excess daily Cd intake and a huge threat for public health. Therefore, the reduction of Cd accumulation in wheat from the soil is a crucial food-security issue. A pot trial was performed on Cd-stressed wheat seedlings to evaluate the morphological and physio-biochemical responses via foliage spray of two different bio-stimulants, i.e., ascorbic acid (AsA) and moringa leaf extract (MLE). Two wheat cultivars (Fsd-08 and Glxy-13) were exposed to cadmium (CdCl₂.5H₂O) stress (0, 500, and 1,000 μM), along with foliar spray of AsA (0 and 50 mM) and MLE (0 and 3%). The most observable growth reduction was documented in plants that are exposed to a higher Cd concentration (1,000 μM), followed by the lower Cd level (500 μM). The wheat growth attributes, such as number of leaves per plant, number of tillers per plant, biomass yield, shoot/root length, and leaf area, were greatly depressed under the Cd stress, irrespective of the cultivar. Under the increasing Cd stress, a significant diminution was observed in maximum photochemical efficiency (Fv/Fm), photochemical quenching (qP), and electron transport rate (ETR) accompanied with reduced gas exchange attributes. However, Cd-induced phytotoxicity enhanced the non-photochemical quenching (NPQ) and internal carbon dioxide concentration (Ci), which was confirmed by their significant positive correlation with Cd contents in shoot and root tissues of both cultivars. The contents of proline, AsA, glycine betaine (GB), tocopherol, total free amino acid (TFAA), and total soluble sugar (TSS) were greatly decreased with Cd stress (1,000 μM), while MLE and AsA significantly enhanced the osmolytes accumulation under both Cd levels (especially 500 μM level). The Cd accumulation was predominantly found in the root as compared to shoots in both cultivars, which has declined after the application of MLE and AsA. Conclusively, MLE was found to be more effective to mitigate Cd-induced phytotoxicity up to 500 μM Cd concentration, compared with the AsA amendment.

Regulating Vapor Pressure Deficit and Soil Moisture Improves Tomato and Cucumber Plant Growth and Water Productivity in the Greenhouse

Atmospheric vapor pressure deficit (VPD) is the driving force that regulates the rate of water transport within plants. Under High VPD (HVPD), plants always reduce their photosynthesis rate and close their stomata. Experiments were performed under greenhouse conditions with cucumber and tomato plants to identify the regulatory effect of VPD on plant water capacity. Treatments included two levels of soil water (100% and 60% field capacity [FC]) combined with two levels of VPD (LVPD and HVPD). Results indicated that with 60%FC, the plant heights of tomato and cucumber were enhanced under LVPD compared with those under HVPD. With 60%FC, relative leaf water contents under LVPD increased by 11% compared with those under HVPD. Furthermore, LVPD significantly improved the photosynthetic capacity of the two crops and changed their stress responses. Our results indicated that LVPD at different soil moisture levels reduced irrigation demand under greenhouse conditions. This approach can be applied in water management in greenhouse vegetable production in China and other regions of the world with temperate continental climates.

Spatial variations in the biochemical potential of okra [Abelmoschus esculentus L. (Moench)] leaf and fruit under field conditions

Okra (Abelmoschus esculentus L. (Moench) plays a significant role in humans nutrition because its fresh leaves, stems, flowers, pods and seeds, are used for multiple purposes. The present study attempted to determine the spatial variations in biochemical attributes of osmoprotectants and the oxidative defense system of okra plants. Samples of soil and okra plants (leaves and fruits) were collected from three different locations: Faisalabad region-1 (7 JB-I), Faisalabad region-2 (7 JB-II) and Pindi Bhattian. Chlorophyll contents, glycine betaine (GB), ascorbic acid (AsA), total phenolics, hydrogen peroxide (H2O2), proline, and malondialdehyde (MDA) contents were analyzed in the leaves and fruits of okra plants. Soil analyses showed that pH, electrical conductivity (EC), phosphorus (P), potassium (K), iron (Fe), and saturation of soil were higher in Faisalabad region 2, while organic matter, sand, Zn, and Cu were higher in the Pindi Bhattian region. The results from okra leaves showed that Pindi Bhattian had higher chlorophyll a, GB and H2O2 contents, while Faisalabad region 1 had a higher ratio of chlorophyll a/b compared to the other regions. However, Faisalabad regions 2 and 1 had higher leaf phenolic contents, Faisalabad regions 1 and 2 showed higher leaf proline contents, and Faisalabad region 2 possessed higher AsA and MDA contents. Analyses of okra fruits showed that Faisalabad region 2 had higher chlorophyll a and total chlorophyll contents, while Faisalabad region 1 had higher chlorophyll b contents. Faisalabad region 2 and Pindi Bhattian had higher ratios of chlorophyll a/b, and Faisalabad region 1 showed higher phenolic, AsA, H2O2, and MDA contents of okra fruit, whereas the Faisalabad regions exhibited higher proline and GB contents than the Pindi Bhattian region. Overall, okra leaves and fruits showed better responses in the Faisalabad regions, and these results may be used to screen for okra cultivars with better tolerance under different environmental conditions.

S-Fertilizer (Elemental Sulfur) Improves the Phytoextraction of Cadmium through Solanum nigrum L

Soil contamination with toxic heavy metals [such as cadmium (Cd)] is becoming a serious global problem due to the rapid development of the social economy. This study was carried out to assess the beneficial role of two different kinds of (S)-fertilizer in the phytoremediation of Cd contaminated soil through Solanum nigrum L. Gypsum (Gyp) and Elemental sulfur (ES) was applied alone and in combination with different ratios (0, 100:0, 0:100, 50:50 mg kg^-1) accompanied by different Cd levels (0, 25, 50 mg kg^-1). After seventy days of sowing, plants were harvested for determination of growth, physiological characteristics, oxidants and antioxidants, along with Cd uptake from different parts of the plant. Cd toxicity significantly inhibited growth, physiology and plant defence systems, and also increased Cd uptake in the roots and shoots of Solanum nigrum L. The application of Gyp 100 mg kg^-1 boosted plant growth and physiology along with oxidants and antioxidants activity as compared to ES 100 mg kg^-1 alone, and combine application of GYP+ES 50 + 50 mg kg^-1. The application of ES 100 mg kg^-1 showed an effective approach to decreasing Cd uptake as compared to Gyp 100 mg kg^-1. Overall results showed that the combined application of GYP+ES 50 + 50 mg kg^-1 significantly enhanced the phytoremediation potential of S. nigrum in Cd contaminated soil. Thus, it is highly recommended to apply the combined application of GYP+ES for phytoremediation of Cd contaminated soil.

Silicon Fertigation Regimes Attenuates Cadmium Toxicity and Phytoremediation Potential in Two Maize (Zea mays L.) Cultivars by Minimizing Its Uptake and Oxidative Stress

Silicon (Si) is an important plant-derived metabolite that is significantly involved in maintaining the stability of a plant’s metabiological, structural and physiological characteristics under the abiotic stressed environment. We conducted the present study using maize (Zea mays L.) cultivars (Sadaf and EV-20) grown in sand artificially contaminated with cadmium (500 µM) in Hoagland’s nutrient solution to investigate its efficiency. Results from the present study evidenced that the toxic concentration of Cd in sand significantly reduced shoot length, root length, shoot fresh weight, root fresh weight, shoot dry weight and root dry weight by 88, 94, 89, 86 99 and 99%, respectively, in Sadaf while decreasing by 98, 97, 93, 99, 84 and 91%, respectively, in EV-20. Similarly, Cd toxicity decreased total chlorophyll and carotenoid content in both varieties of Z. mays. Moreover, the activities of various antioxidants (superoxidase dismutase, peroxidase and catalase) increased under the toxic concentration of Cd in sand which was manifested by the presence of membrane permeability, malondialdehyde (MDA), and hydrogen peroxide (H2O2). Results additionally showed that the toxic effect of Cd was more severe in EV-20 compared with Sadaf under the same conditions of environmental stresses. In addition, the increased concentration of Cd in sand induced a significantly increased Cd accumulation in the roots (141 and 169 mg kg−1 in Sadaf and EV-20, respectively), and shoots (101 and 141 mg kg−1 in Sadaf and EV-20, respectively), while; EV-20 accumulated higher amounts of Cd than Sadaf, with the values for both bioaccumulation factor (BAF) and translocation factor (TF) among all treatments being less than 1. The subsequent negative results of Cd injury can be overcome by the foliar application of Si which not only increased plant growth and biomass, but also decreased oxidative damage induced by the higher concentrations of MDA and H2O2 under a Cd-stressed environment. Moreover, external application of Si decreased the concentration of Cd in the roots and shoots of plants, therefore suggesting that the application of Si can ameliorate Cd toxicity in Z. mays cultivars and results in improved plant growth and composition under Cd stress by minimizing oxidative damage to membrane-bound organelles.

Combined application of zinc and iron-lysine and its effects on morpho-physiological traits, antioxidant capacity and chromium uptake in rapeseed (Brassica napus L.)

Environmental contamination of chromium (Cr) has gained substantial consideration worldwide because of its high levels in the water and soil. A pot experiment using oil seed crop (rapeseed (Brassica napus L.)) grown under different levels of tannery wastewater (0, 33, 66 and 100%) in the soil using the foliar application of zinc (Zn) and iron (Fe)-lysine (lys) has been conducted. Results revealed that a considerable decline in the plant growth and biomass elevates with the addition of concentrations of tannery wastewater. Maximum decline in plant height, number of leaves, root length, fresh and dry biomass of root and leaves were recorded at the maximum level of tannery wastewater application (100%) compared to the plants grown without the addition of tannery wastewater (0%) in the soil. Similarly, contents of carotenoid and chlorophyll, gas exchange parameters and activities of various antioxidants (superoxidase dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX)) were also reduced significantly (P < 0.05) with the increasing concentration of tannery wastewater (33, 66 and 100%) in the soil. In addition, a combined application of Zn and Fe-lys reduced the accumulation and uptake of toxic Cr, while boosting the uptake of essential micronutrients such as Zn and Fe in different tissues of the plants. Results concluded that exogenous application of micronutrients chelated with amino acid successfully mitigate Cr stress in B. napus. Under field conditions, supplementation with these micronutrient-chelated amino acids may be an effective method for alleviating metal stress in other essential seed crops.

Plant Growth-Promoting Bacteria (PGPB) integrated phytotechnology: A sustainable approach for remediation of marginal lands

Land that has little to no utility for agriculture or industry is considered marginal land. This kind of terrain is frequently found on the edge of deserts or other arid regions. The amount of land that can be used for agriculture continues to be constrained by increasing desertification, which is being caused by climate change and the deterioration of agriculturally marginal areas. Plants and associated microorganisms are used to remediate and enhance the soil quality of marginal land. They represent a low-cost and usually long-term solution for restoring soil fertility. Among various phytoremediation processes (viz., phytodegradation, phytoextraction, phytostabilization, phytovolatilization, phytofiltration, phytostimulation, and phytodesalination), the employment of a specific mechanism is determined by the state of the soil, the presence and concentration of contaminants, and the plant species involved. This review focuses on the key economically important plants used for phytoremediation, as well as the challenges to plant growth and phytoremediation capability with emphasis on the advantages and limits of plant growth in marginal land soil. Plant growth-promoting bacteria (PGPB) boost plant development and promote soil bioremediation by secreting a variety of metabolites and hormones, through nitrogen fixation, and by increasing other nutrients' bioavailability through mineral solubilization. This review also emphasizes the role of PGPB under different abiotic stresses, including heavy-metal-contaminated land, high salinity environments, and organic contaminants. In our opinion, the improved soil fertility of marginal lands using PGPB with economically significant plants (e.g., Miscanthus) in dual precession technology will result in the reclamation of general agriculture as well as the restoration of native vegetation.

Effect of nano-silicon on the regulation of ascorbate-glutathione contents, antioxidant defense system and growth of copper stressed wheat (Triticum aestivum L.) seedlings

Copper (Cu²⁺) toxicity can inhibit plant growth and development. It has been shown that silicon (Si) can relieve Cu²⁺ stress. However, it is unclear how Si-nanoparticles (SiNPs) relieve Cu²⁺ stress in wheat seedlings. Therefore, the current study was conducted by setting up four treatments: CK, SiNP: (2.5 mM), Cu²⁺: (500 µM), and SiNP+Cu²⁺: (2.5 mM SiNP+500 µM Cu²⁺) to explore whether SiNPs can alleviate Cu²⁺ toxicity in wheat seedlings. The results showed that Cu²⁺ stress hampered root and shoot growth and accumulated high Cu²⁺ concentrations in roots (45.35 mg/kg) and shoots (25.70 mg/kg) of wheat as compared to control treatment. Moreover, Cu²⁺ treatment inhibited photosynthetic traits and chlorophyll contents as well as disturbed the antioxidant defense system by accumulating malondialdehyde (MDA) and hydrogen peroxidase (H₂O₂) contents. However, SiNPs treatment increased root length and shoot height by 15.1% and 22%, respectively, under Cu²⁺ toxicity. Moreover, SiNPs application decreased MDA and H₂O₂ contents by 31.25% and 19.25%, respectively. SiNPs increased non-enzymatic compounds such as ascorbic acid-glutathione (AsA-GSH) and enhanced superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbic peroxidase (APX) activities by 77.5%, 141.7%, 68%, and 80%, respectively. Furthermore, SiNPs decreased Cu²⁺ concentrations in shoots by 26.2%, as compared to Cu²⁺ treatment alone. The results concluded that SiNPs could alleviate Cu²⁺ stress in wheat seedlings. The present investigation may help to increase wheat production in Cu²⁺ contaminated soils.

Impact of foliar application of syringic acid on tomato (Solanum lycopersicum L.) under heavy metal stress-insights into nutrient uptake, redox homeostasis, oxidative stress, and antioxidant defense

Soil contamination with toxic heavy metals [such as lead (Pb)] is becoming a serious global problem due to the rapid development of the social economy. However, accumulation of Pb in plant parts is very toxic for plant growth and decreases crop yield and productivity. In the present study, we have investigated the different concentrations of Pb in the soil i.e., [0 (no Pb), 50, and 100 mg kg^-1] to study plant growth and biomass, photosynthetic pigments and gas exchange characteristics, oxidative stress indicators and the response of various antioxidants (enzymatic and non-enzymatic), nutritional status of the plant, organic acid exudation pattern and also Pb accumulation in the roots and shoots of the plants of two varieties of tomato (Solanum lycopersicum L.) i.e., Roma and Cchuas, grown under different levels of synergic acid [no spray (NS), water spray (WS), 0.3-0.5°μM]. Results from the present study showed that the increasing levels of Pb in the soil decreased non-significantly (P < 0.05) shoot length, root length, shoot fresh weight, root fresh weight, shoot dry weight, root dry weight, chlorophyll-a, chlorophyll-b, total chlorophyll, carotenoid content, net photosynthesis, stomatal conductance, transpiration rate, soluble sugar, reducing sugar, non-reducing sugar contents, calcium (Ca²⁺), magnesium (Mg²⁺), iron (Fe²⁺), and phosphorus (P) contents in the roots and shoots of the plants. However, Pb toxicity also induced oxidative stress in the roots and shoots of the plants by increasing malondialdehyde (MDA), hydrogen peroxide (H₂O₂), and electrolyte leakage (EL) which also induced increased the compounds of various enzymatic and non-enzymatic antioxidants and also organic acids exudation pattern in the roots such as fumaric acid, acetic acid, citric acid, formic acid, malic acid, oxalic acid contents and increased the concentration of Pb in different parts of the plants. Results also show that the Cchuas showed better growth and development compared to Roma, under the same levels of Pb in the soil. The alleviation of Pb toxicity was induced by the application of synergic acid, and results showed that the application of synergic acid increased plant growth and biomass and also increased the gas exchange characteristics and antioxidant capacity in the roots and shoots of the plants. Research findings, therefore, suggested that synergic acid application can ameliorate Pb toxicity in S. lycopersicum varieties and result in improved plant growth and composition under metal stress as depicted by balanced exudation of organic acids.

Addressing the challenge of cold stress resilience with the synergistic effect of Rhizobium inoculation and exogenous melatonin application in Medicago truncatula

Cold stress is an adverse environmental condition that limits the growth and yield of leguminous plants. Thus, discovering an effective way of ameliorating cold-mediated damage is important for sustainable legume production. In this study, the combined use of Rhizobium inoculation (RI) and melatonin (MT) pretreatment was investigated in Medicago truncatula plants under cold stress. Eight-week-old seedlings were divided into eight groups: (i) CK (no stress, noninoculated, no MT), (ii) RI (Rhizobium inoculated), (iii) MT (75 μM melatonin), (iv) RI+MT, (v) CS (cold stress at 4 °C without Rhizobium inoculation and melatonin), (vi) CS+RI, (vii) CS+MT, and (viii) CS+RI+MT. Plants were exposed to cold stress for 24 hrs. Cold stress decreased photosynthetic pigments and increased oxidative stress. Pretreatment with RI and MT alone or combined significantly improved root activity and plant biomass production under cold stress. Interestingly, chlorophyll contents increased by 242.81% and MDA levels dramatically decreased by 34.22% in the CS+RI+MT treatment compared to the CS treatment. Moreover, RI+MT pretreatment improved the antioxidative ability by increasing the activities of peroxidase (POD; 8.45%), superoxide dismutase (SOD; 50.36%), catalase (CAT; 140.26%), and ascorbate peroxidase (APX; 42.63%) over CS treated plants. Additionally, increased osmolyte accumulation, nutrient uptake, and nitrate reductase activity due to the combined use of RI and MT helped the plants counteract cold-mediated damage by strengthening the nonenzymatic antioxidant system. These data indicate that pretreatment with a combined application of RI and MT can attenuate cold damage by enhancing the antioxidation ability of legumes.

Trace Metal Accumulation in Rice Variety Kainat Irrigated with Canal Water

Due to the rapid increase in industrial and urban areas, environmental pollution is increasing worldwide, causing unwanted changes in the air, water, and soil at biological, physical, and chemical levels, ultimately causing negative effects for living things. This work was performed in Jhang, Punjab, Pakistan, and examined and measured heavy metal levels in various plant parts of the rice (Oryza sativa) variety Kainat (roots, shoots, and grains) with results been set in relation to the soil around the root area. The samples were taken from five different sites. The mean level of trace metals (mg/kg) in grains was soil-dependent and varied from cadmium (Cd) (2.49–5.52), zinc (Zn) (5.8–10.78), copper (Cu) (4.82–7.85), cobalt (Co) (1.48–6.52), iron (Fe) (8.68–14.73), manganese (Mn) (6.87–13.93), and nickel (Ni) (2.3–8.34). Excluding Cd, the absorption of all metals under inspection was recorded within permissible limits, as recommended by the FAO and WHO. The pollution load index for Cd was highest at all sites. The enrichment coefficient of Co, Cd, and Cu were greater. The bioaccumulation factor at all studied sites was present, in order: Cu ˃ Zn ˃ Fe ˃ Mn ˃ Co ˃ Ni ˃ Cd. The translocation factor was present at five different sites: Mn ˃ Fe ˃ Cu ˃ Zn ˃ Co ˃ Cd ˃ Ni. The health risk index of all inspected metals was lower than 1 and was within safe limits. The higher pollution of Cd suggested maintenance of rice crop is recommended, decreasing health risks in humans.

Interactive effects of gibberellic acid and NPK on morpho-physio-biochemical traits and organic acid exudation pattern in coriander (Coriandrum sativum L.) grown in soil artificially spiked with boron

It was aimed to examine the role of gibberellic acid (GA₃) and NPK fertilizer in alleviating boron (B) toxicity in coriander (Coriandrum sativum L.) plants. Two weeks old C. sativum seedlings were subjected to different NPK fertilizers [low NPK (30 kg ha^-1) and normal NPK (60 kg ha^-1)], which were also supplied by GA₃ (50 mg L^-1), under varying levels of B i.e., 0, 200 and 400 mg kg^-1 in the soil. Results revealed that B toxicity led to a substantial decreased in the plant growth and biomass, photosynthetic pigments, gas exchange characteristics, sugars and essential nutrients in the roots and shoots of C. sativum seedlings. However, B toxicity boosted the production of reactive oxygen species (ROS) by increasing the contents of malondialdehyde (MDA), which is the indication of oxidative stress in C. sativum seedlings and was also manifested by hydrogen peroxide (H₂O₂) contents and electrolyte leakage (EL) to the membrane bounded organelles. Although, activities of various antioxidative enzymes like superoxidase dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX), non-enzymatic antioxidants like phenolic, flavonoid, ascorbic acid and anthocyanin contents and organic acids from the roots such as oxalic acid, malic acid, formic acid, citric acid, acetic acid and fumaric acid contents were increased with the increasing levels of B in the soil. The application if NPK and GA₃ mitigated B toxicity by stimulated plant growth and biomass, photosynthetic efficiency, nutritional status and antioxidant machinery of the plant by decreasing MDA contents, H₂O₂ initiation and EL (%) in the roots and leaves of C. sativum seedlings. In addition, the application of NPK and GA₃ further decreased the organic acids exudation contents in the roots C. sativum seedlings. Research findings, therefore, suggested that NPK and GA₃ application can ameliorate B toxicity in C. sativum seedlings and resulted in improved plant growth and composition under B stress as depicted by balanced contents of organic acids.

Performance of Zea mays L. cultivars in tannery polluted soils: Management of chromium phytotoxicity through the application of biochar and compost

Soil contamination with heavy metals caused by various industrial activities is a threatening global environmental issue of the current era. Chromium (Cr) is the most toxic heavy metal used in leather industry and disposal of untreated wastewater into natural water bodies leads to contamination of natural soil and water resources. We studied the combined effect of biochar and compost on improving the tolerance to Cr toxicity by enhancing the morpho-physiological and biochemical attributes of two maize cultivars (P-1543 and NK-8441) grown in tannery waste polluted soils. The results of this study reveal that Cr toxicity reduced the plant growth by affecting physiological and biochemical attributes. Here, compost and biochar application significantly increased the plant biomass (fresh and dry), height, photosynthesis, chlorophyll content, water relation, starch, and protein content over treatment set as control. However, significant decline in electrolyte leakage (EL), proline, lipid peroxidation, soluble sugars, and antioxidant enzymes (APX, GPX, GR, GST, GSH, SOD, and CAT) was observed by combined application of compost and biochar. Hexavalent chromium concentration was maximum decreased to 4.1 μg g^-1 in soil after post-harvesting of maize cultivar NK-8441, while in roots and shoots to 22.6 and 19.2 μg g^-1 of maize cultivar P-1543, respectively, by combined application of compost and biochar. Moreover, these both amendments in combination showed considerably better results than their sole application and cultivar P-1543 comparatively performed better than NK 8441, in both K and S soils. Correlation and principal component analysis (PCA) revealed mostly highly positive associations among all the studied morpho, physio, and biochemical attributes of maize plant with the few exceptions, particularly concentration of Cr(III) and Cr(VI) in soil. The present work concluded that combined use of biochar and compost has great potential to decrease Cr toxicity and improve plant growth in tannery polluted soils.

Processed animal manure improves morpho-physiological and biochemical characteristics of Brassica napus L. under nickel and salinity stress

Soil contamination with readily soluble salts and heavy metals is a major challenge concerning sustainable crop production. The use of organic wastes in agriculture not only helps in waste reduction but also acts as a soil conditioner and bio-stimulant for enhancing crop growth. In this regard, a pot experiment was conducted to investigate the effect of raw and processed animal manure (AM) on the growth, yield, and physicochemical parameters of Brassica napus L. developed under salinity and Ni stress. The experiment comprised two salinity levels (1.05 and 8 dS m^-1), two Ni levels (0 and 50 mg kg^-1), and two types of AMs (raw and processed at a rate of 2% w/w). A control treatment without AM incorporation was also included. In results, the application of AM markedly increased the growth and yield of B. napus under Ni and salinity stress; at the same time, it improved the physiological and chemical parameters of the said crop. Similarly, incorporation of processed AM significantly improved nutrient uptake and decreased Na/K ratios in the shoot and grain under the different stress conditions, as compared to the control. Likewise, Ni uptake in the grain, shoot, and root samples was also significantly reduced under the AM treatment. Also, the application of AM significantly reduced the daily intake of metal (DIM) index and the health risk index (HRI) values under the different stress conditions, as compared to the control. In conclusion, the application of processed AM constitutes an effective agricultural strategy to alleviate the adverse effects of Ni and salinity stress on growth, physiology, and yield of B. napus, thus resulting in enhanced productivity, as well as reduced risks associated with human health.

Could acetone O-(4-chlorophenylsulfonyl)oxime be a copper chelating and antioxidative molecule on maize seedlings?

The main purpose of study is to determine if Acetone O- (4-chlorophenylsulfonyl) oxime (AO) has a positive effect on maize seedlings under copper (Cu) stress or not. Seedlings were allocated to following experimental groups: 18-hour distilled water (DW) Control (C), ago 6-hour 0.66 mM AO + later 12-hour DW (AO), ago 6-hour DW + later 12-hour 1 mM Cu (Cu), ago 6-hour 0.66 mM AO + later 12-hour 1 mM Cu (AO + Cu). The results showed that AO + Cu caused approximately three times more copper accumulation compared to Cu treatment. AO and AO + Cu treatments significantly decreased membrane damage and H₂O₂ formation compared to its control. The proline content was significantly increased in AO and AO + Cu compared to its control. While the highest catalase, Guaiacol Peroxidase and superoxide dismutase activity was observed in Cu application, the highest ascorbate peroxidase activity was determined in AO application. It was observed that AO had a protective effect on chlorophyll content and RWC, but a positive effect on carotenoid content could not be determined. In addition, the effects of AO on the content of 17 phenolic substances in maize leaves were determined. In the light of the current findings, AO may prevent the formation of radical compounds.

Copper Tolerance and Accumulation on Pelargonium graveolens L'Hér. Grown in Hydroponic Culture

Heavy metal contamination is a major health issue concerning the commercial production of medicinal and aromatic plants (MAPs) that are used for the extraction of bioactive molecules. Copper (Cu) is an anthropogenic contaminant that, at toxic levels, can accumulate in plant tissues, affecting plant growth and development. On the other hand, plant response to metal-induced stress may involve the synthesis and accumulation of beneficial secondary metabolites. In this study, hydroponically grown Pelargonium graveolens plants were exposed to different Cu concentrations in a nutrient solution (4, 25, 50, 100 μM) to evaluate the effects Cu toxicity on plant growth, mineral uptake and distribution in plants, some stress indicators, and the accumulation of bioactive secondary metabolites in leaf tissues. P. graveolens resulted in moderately tolerant Cu toxicity. At Cu concentrations up to 100 μM, biomass production was preserved and was accompanied by an increase in phenolics and antioxidant capacity. The metal contaminant was accumulated mainly in the roots. The leaf tissues of Cu-treated P. graveolens may be safely used for the extraction of bioactive molecules.

Plant growth regulators and EDTA improve phytoremediation potential and antioxidant response of Dysphania ambrosioides (L.) Mosyakin & Clemants in a Cd-spiked soil

Soil pollution due to potentially toxic elements is a worldwide challenge for health and food security. Chelate-assisted phytoextraction along with the application of plant growth regulators (PGRs) could increase the phytoremediation efficiency of metal-contaminated soils. The present study was conducted to investigate the effect of different PGRs [Gibberellic acid (GA3) and indole acetic acid (IAA)] and synthetic chelator (EDTA) on growth parameters and Cd phytoextraction potential of Dysphania ambrosioides (L.) Mosyakin & Clemants grown under Cd-spiked soil. GA3 (10-7 M) and IAA (10-5 M) were applied four times with an interval of 10 days through a foliar spray, while EDTA (40 mg kg-1 soil) was once added to the soil. The results showed that Cd stress significantly decreased fresh biomass, dry biomass, total water contents, and photosynthetic pigments as compared to control. Application of PGRs significantly enhanced plant growth and Cd phytoextraction. The combined application of GA3 and IAA with EDTA significantly increased Cd accumulation (6.72 mg pot-1 dry biomass) and bioconcentration factor (15.21) as compared to C1 (Cd only). The same treatment significantly increased chlorophyll, proline, phenolic contents, and antioxidant activities (CAT, SOD, and POD) while MDA contents were reduced. In roots, Cd accumulation showed a statistically significant and positive correlation with proline, phenolics, fresh biomass, and dry biomass. Similarly, Cd accumulation showed a positive correlation with antioxidant enzyme activities in leaves. D. ambrosioides showed hyperaccumulation potential for Cd, based on bioconcentration factor (BCF) > 1. In conclusion, exogenous application of GA3 and IAA reduces Cd stress while EDTA application enhances Cd phytoextraction and ultimately the phytoremediation potential of D. ambrosioides.