Non-enzymatic Antioxidant Mechanisms Research Articles

Improving grapevine (Vitis vinifera L., cv. Superior Seedless) drought tolerance with cerium oxide nanoparticles: Agronomic and molecular insights

Drought stress poses a significant threat to global food security, impacting grapevine growth and development through physiological, biochemical, and molecular alterations. Cerium oxide nanoparticles (CeO2 NPs) have recently gained attention as a potential solution to environmental challenges, yet their application in grapevines remains understudied. This study examined the interaction between foliar-applied CeO2 NPs (at concentrations of 0, 5, 50, and 500 mg L−1) and drought stress (at 30% and 70% of field capacity humidity) in grapevine saplings. Among the different concentrations tested, 50 mg L−1 CeO2 NPs significantly improved the agronomic traits (e.g., shoot length, leaf area, shoot and root dry weights), photosynthetic parameters (stomatal conductance, chlorophyll a and chlorophyll b) and RWC of the grapevine saplings under drought stress. In parallel, CeO2 NPs significantly induced the activity of compatible solutes and SOD, CAT and APX under drought stress conditions. Moreover, the availability of CeO2 NPs alleviated drought stress-induced damage in grapevine saplings, as evidenced by decreased H2O2 (32.63%), EL (40.35%) and MDA (50.63%) levels. The molecular results revealed that CeO2 NPs caused significant changes in gene expression under drought stress by reducing the expression of the VvCLH1, VvCu/ZnSOD, VvRD29A and VvRBOHA genes by 4.54-fold, 27.73-fold, 14.6-fold and 46.12-fold, respectively. These findings suggest that CeO2 NPs applied via leaves enhance grapevine sapling resistance to drought-induced oxidative stress through cooperative enzymatic and nonenzymatic antioxidant mechanisms, influencing gene regulation. As a result, these findings revealed that CeO2 NPs could be promising elicitor candidates for alleviating drought stress in grapevines.

Functionality of Reactive Oxygen Species (ROS) in Plants: Toxicity and Control in Poaceae Crops Exposed to Abiotic Stress.

Agriculture and changing environmental conditions are closely related, as weather changes could adversely affect living organisms or regions of crop cultivation. Changing environmental conditions trigger different abiotic stresses, which ultimately cause the accumulation of reactive oxygen species (ROS) in plants. Common ROS production sites are the chloroplast, endoplasmic reticulum, plasma membrane, mitochondria, peroxisomes, etc. The imbalance in ROS production and ROS detoxification in plant cells leads to oxidative damage to biomolecules such as lipids, nucleic acids, and proteins. At low concentrations, ROS initiates signaling events related to development and adaptations to abiotic stress in plants by inducing signal transduction pathways. In plants, a stress signal is perceived by various receptors that induce a signal transduction pathway that activates numerous signaling networks, which disrupt gene expression, impair the diversity of kinase/phosphatase signaling cascades that manage the stress response in the plant, and result in changes in physiological responses under various stresses. ROS production also regulates ABA-dependent and ABA-independent pathways to mitigate drought stress. This review focuses on the common subcellular location of manufacturing, complex signaling mechanisms, and networks of ROS, with an emphasis on cellular effects and enzymatic and non-enzymatic antioxidant scavenging mechanisms of ROS in Poaceae crops against drought stress and how the manipulation of ROS regulates stress tolerance in plants. Understanding ROS systems in plants could help to create innovative strategies to evolve paths of cell protection against the negative effects of excessive ROS in attempts to improve crop productivity in adverse environments.

Unravelling the combined impacts of drought and Cu in barley plants – double trouble?

The occurrence of drought in soils, particularly in those contaminated by metals, poses a current threat to crops, as these factors can interact and induce unique stress responses. Therefore, this study mainly focused on understanding the crosstalk between drought and copper (Cu) stress in the physiology of the barley (Hordeum vulgare L.) plant. Using a bifactorial experimental design, seedlings were grown in a natural soil under the following treatments: plants continuously irrigated in uncontaminated soil for 14 days (control); plants continuously irrigated in Cu-contaminated soil (115 mg Cu kg−1) for 14 days (Cu); plants only irrigated during the initials 7 days of growth in uncontaminated soil (drought); plants co-exposed to Cu and drought (combined). After 14 days of growth, the results revealed that drought prevented Cu bioaccumulation in barley roots, which were still severely affected by the metal, both individually and in combination with the water deficit. Furthermore, individual and combined exposure to these stressors resulted in impaired photosynthetic performance in barley plants. Despite the increased activation of enzymatic and non-enzymatic antioxidant defence mechanisms, particularly in the green organs, the plants co-exposed to both stress factors still showed higher oxidative damage, severely impacting biomass production.

The Role of Amino Acids in Non-Enzymatic Antioxidant Mechanisms in Cancer: A Review.

Currently, the antioxidant properties of amino acids and their role in the physicochemical processes accompanying oxidative stress in cancer remain unclear. Cancer cells are known to extensively uptake amino acids, which are used as an energy source, antioxidant precursors that reduce oxidative stress in cancer, and as regulators of inhibiting or inducing tumor cell-associated gene expression. This review examines nine amino acids (Cys, His, Phe, Met, Trp, Tyr, Pro, Arg, Lys), which play a key role in the non-enzymatic oxidative process in various cancers. Conventionally, these amino acids can be divided into two groups, in one of which the activity increases (Cys, Phe, Met, Pro, Arg, Lys) in cancer, and in the other, it decreases (His, Trp, Tyr). The review examines changes in the metabolism of nine amino acids in eleven types of oncology. We have identified the main nonspecific mechanisms of changes in the metabolic activity of amino acids, and described direct and indirect effects on the redox homeostasis of cells. In the future, this will help to understand better the nature of life of a cancer cell and identify therapeutic targets more effectively.

Application of Lavender and Rosemary Essential Oils (EOs), Their Mixture and Eucalyptol (EOs Main Compound) on Cucumber Fruit Quality Attributes and Microbial Load

Cucumber (Cucumis sativus L.), one of the most widely consumed vegetables, presents high perishability during storage and marketing if it is not handled and stored properly. Currently, there is an increased interest of the food industry to reduce waste (due to quality losses) and to utilize natural products for the preservation of fresh commodities. This study’s goal was to evaluate the effects of lavender (Lav) and rosemary (Ros) essential oils (EOs), their mixture (Lav + Ros, 1:1 v/v) and their main compound (eucalyptol) via vapor phase on cucumber’s postharvest quality. The outcomes of this study demonstrated that 200 μL/L of Lav and Ros EOs increased the respiration rate of cucumbers after 10 days of storage at 11 °C, while 100 μL/L of the EOs mixture and Eucalyptol (100 and 200 μL/L) had no effect on respiration, on the same day. The application of Eucalyptol (100 and 200 μL/L) resulted in less acceptable fruits (less pleasant aroma and unpleasant taste). A decrease in fruit firmness was found in cucumbers exposed to Lav 200 μL/L and Ros 100 μL/L. Interestingly, Eucalyptol was found to accelerate the fruit ripening index after five days of storage, and to decrease organoleptic properties of the fruit (i.e., aroma, taste) on the fifth day of storage. The fruit revealed increased oxidative stress (i.e., increased lipid peroxidation), especially at a high concentration (200 μL/L) of Eucalyptol after 10 days. This has resulted in the activation of other non-enzymatic antioxidant mechanisms such as the increase in fruit ascorbic acid content. Notably, no effects on fruit weight loss, total soluble solids and color were observed with the examined treatments. Overall, this study suggests that the investigated products (EOs and their main compound) have a putative role in postharvest storage for the preservation of cucumbers. However, further investigation is needed for the determination of the optimum application conditions (i.e., concentration, time and method of application) on cucumbers and other fresh produce.

The effect of selected aminoglycoside antibiotics on human serum albumin antioxidant activity: a spectroscopic and calorimetric comparative study

BackgroundHuman serum albumin (HSA) is a valuable component of non-enzymatic and endogenous antioxidant mechanisms. The antioxidant activity of HSA can be modulated by ligands, including drugs. Although this is a central topic in the field of oxidation, there is still a lack of information about the protection against the effects of elevated free radical levels.MethodsThe aim of this study was to investigate the antioxidant activity of kanamycin (KAN) and neomycin (NEO) and their effect on the antioxidant potential of HSA using spectroscopic and microcalorimetric techniques.ResultsDespite the fact that kanamycin and neomycin interact with HSA, no changes in the secondary structure of the protein have been observed. The analysis of the aminoglycoside antibiotics showed their low antioxidant activity and a synergistic effect of the interaction, probably due to the influence of ligands (KAN, NEO) on the availability of HSA amino acid residues functional groups, such as the free thiol group (Cys-34).ConclusionsBased on the spectroscopic and microcalorimetric data, both KAN and NEO can be considered modulators of the HSA antioxidant activity.

Achieving abiotic stress tolerance in plants through antioxidative defense mechanisms.

Climate change has increased the overall impact of abiotic stress conditions such as drought, salinity, and extreme temperatures on plants. Abiotic stress adversely affects the growth, development, crop yield, and productivity of plants. When plants are subjected to various environmental stress conditions, the balance between the production of reactive oxygen species and its detoxification through antioxidant mechanisms is disturbed. The extent of disturbance depends on the severity, intensity, and duration of abiotic stress. The equilibrium between the production and elimination of reactive oxygen species is maintained due to both enzymatic and non-enzymatic antioxidative defense mechanisms. Non-enzymatic antioxidants include both lipid-soluble (α-tocopherol and β-carotene) and water-soluble (glutathione, ascorbate, etc.) antioxidants. Ascorbate peroxidase (APX), superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR) are major enzymatic antioxidants that are essential for ROS homeostasis. In this review, we intend to discuss various antioxidative defense approaches used to improve abiotic stress tolerance in plants and the mechanism of action of the genes or enzymes involved.

Cadmium exposure induces testicular oxidative damage and histopathological changes in the freshwater leech Limnatis nilotica (Savigny, 1822): the protective role of salicylic acid

The present study examined the histopathological changes and some parameters of oxidative stress in the testes of the freshwater leech Limnatis nilotica, following their exposure to 50 µg l−1 of cadmium (Cd). The protective effects of salicylic acid (SA) in mitigating Cd-induced oxidative and histopathological injury were also investigated. We found that Cd exposure caused several histopathological changes in leech testes, such as vacuolisation of spermatogenic cysts which were strongly destroyed and disorganised. Biochemical study showed oxidative stress damage marked by a substantial increase in malondialdehyde and hydrogen peroxidase levels as well as disturbance in the activity of the leech antioxidant system. Interestingly, the testes from the Cd and SA leech-exposed group exhibited increased enzymatic and nonenzymatic antioxidant mechanism defenses, including superoxide dismutase, catalase, glutathione peroxidase, glutathione, oxidized glutathione, thiols, and ascorbic acid, in comparison with the testes of leeches exposed to Cd alone. Thus, SA supplementation considerably attenuated the histopathological lesions induced by Cd exposure, thereby restoring the normal appearance of the testes. In summary, the findings of this study indicate that SA treatment ameliorated the testicular histopathological and oxidative stress-induced damages caused by exposure to Cd through enhancing the antioxidant defense system.

Antioxidant response of Impatiens walleriana L. to drought

Stress caused by drought induces plant morphology, biochemistry, and physiology changes, leading to considerable reductions in plant growth and productivity. This study aimed to evaluate the antioxidant defence system of impatiens seedlings (Impatiens walleriana L.) under drought. The antioxidant response of impatiens to drought was evaluated using following parameters: the activity of catalase, guaiacol peroxidase, pyrogallol peroxidase and ascorbate peroxidase, total phenolic and flavonoids contents and total antioxidant capacity. The experiment was conducted during 2020 in a greenhouse under controlled conditions. Half of the impatiens seedlings (20 plants), after the acclimation period in the greenhouse, were exposed to drought for a period of five days, while the second half was not (20 plants were regularly watered). The results of the study showed that the exposure of impatiens seedlings to drought increased the activity of enzymatic components, total phenolics and flavonoids contents and total antioxidant capacity of leaves. Greater exposure of impatiens to drought (in the observed period) implied a higher plant enzymatic and non-enzymatic antioxidant defence system activity. These results confirm that impatiens has evolved both enzymatic and non-enzymatic antioxidant defence mechanisms to adapt and survive the short-term drought exposure.

Analysis of the Antioxidant Mechanism of Tamarix ramosissima Roots under NaCl Stress Based on Physiology, Transcriptomic and Metabolomic.

There is a serious problem with soil salinization that affects the growth and development of plants. Tamarix ramosissima Ledeb (T. ramosissima), as a halophyte, is widely used for afforestation in salinized soils. At present, there are few reports on the antioxidant mechanism of T. ramosissima under NaCl stress. In this study, we learned about the superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities, and hydrogen peroxide (H2O2) and malondialdehyde (MDA) content changes in T. ramosissima. We also mined the relevant metabolic pathways in the antioxidant mechanism, candidate key genes, and their related differential metabolites and verified them using quantitative real-time PCR (qRT-PCR). The results show that the SOD, POD, and CAT activities, and the H2O2 and MDA content reached the highest values in the roots of T. ramosissima. Simultaneously, 92 differentially expressed genes (DEGs) related to antioxidant enzyme activities changed during 48 and 168 h of NaCl stress, and these DEGs were mainly upregulated in 168 h. Based on the association analysis of transcriptomic and metabolomic data, we found Unigene0089358 and Unigene0007782 as genes related to key enzymes in the flavonoid biosynthesis pathway. They were located in the upstream positive regulation at 48 and 168 h under NaCl stress, and their respective related metabolites (phloretin and pinocembrin) were involved in resistance to NaCl stress, and they were significantly correlated with their respective metabolites. In conclusion, at 48 and 168 h under NaCl stress, the roots of T. ramosissima resist NaCl stress by enhancing enzymatic and nonenzymatic antioxidant mechanisms, scavenging ROS generated by high-salt stress, alleviating NaCl toxicity, and maintaining the growth of T. ramosissima. This study provides genetic resources and a scientific theoretical basis for further breeding of salt-tolerant Tamarix plants and the molecular mechanism of antioxidants to alleviate NaCl toxicity.

Halotolerant Streptomyces spp. induce salt tolerance in maize through systemic induction of the antioxidant system and accumulation of proline

Plant Growth Promoting Rhizobacteria (PGPR) can mitigate the detrimental effects of salinity in plants. We characterized Streptomyces spp. as halotolerant PGPR and evaluated their influence on salt stress-tolerance mechanisms in maize plants. Bacterial halotolerance was evaluated at concentrations up to 900 mM NaCl, analyzing cell growth, viability, and production of secondary metabolites. The mechanisms of systemic tolerance in plants, such as the enzymatic activity of the antioxidant system and the production of osmolytes, were analyzed in bacterized plants under salt stress (100 and 300 mM NaCl). Isolates proved viable and produced indolic compounds and siderophores under NaCl conditions. Synthesis of indolic compounds and phosphate solubilization were induced in CLV179 by salt stress. The activity of the antioxidant enzymes and the synthesis of proline increased in bacterized plants submitted to salt stress, mainly those treated with isolate CLV97 and CLV179. Response of Streptomyces-treated plant to salinity was observed in roots and leaves, suggesting a mechanism of systemic tolerance. Therefore, bacterization with Streptomyces spp. alleviated the deleterious effects of salinity in maize plants by modulating the enzymatic and non-enzymatic antioxidant mechanisms.

Biotic elicitor-induced changes in growth, antioxidative defense, and metabolites in an improved prickleless Solanum viarum.

Solanum viarum serves as a raw material for the steroidal drug industry due to its alkaloid and glycoalkaloid content. Elicitation is well-known for measuring the increase in the yield of bioactive compounds in in vitro cultures. The current study was performed for the accumulation of metabolites viz. solasodine, solanidine, and α-solanine in S. viarum culture using microbial-based elicitors added in 1%, 3%, 5%, and 7% on 25th and 35th day of culture period and harvested on 45th and 50th days of culture cycle. The treatment of 3% Trichoderma reesei and Bacillus tequilensis culture filtrate (CF) significantly increased biomass, alkaloids/glycoalkaloid content, and yield in S. viarum. T. reesei was found to be the best treatment for enhanced growth (GI = 11.65) and glycoalkaloid yield (2.54mg DW plant-1) after the 50th day of the culture cycle when added on the 25th day. The abundance of gene transcripts involved in the biosynthesis of alkaloids/glycoalkaloids, revealed by quantitative real-time PCR expression analysis correlates with the accumulation of their respective metabolites in elicited plants. Biochemical analysis shows that elicited plants inhibited oxidative damage caused by reactive oxygen species by activating enzymes (superoxide dismutase and ascorbate peroxidase) as well as non-enzymatic antioxidant mechanisms (alkaloids, total phenols, total flavonoids, carotenoids, and proline). The findings of this study clearly demonstrate that the application of T. reesei and B. tequilensis CF at a specific dose and time significantly improve biomass as well as upregulates the metabolite biosynthetic pathway in an important medicinal plant- S. viarum. KEY POINTS: • Biotic elicitors stimulated the alkaloids/glycoalkaloid content in S. viarum plant cultures. • T. reesei was found to be most efficient for enhancing the growth and alkaloids content. • Elicited plants activate ROS based-defense mechanism to overcome oxidative damage.

Salicyclic acid against the disruptive effects of cadmium induces oxidative stress and ‎biochemical and histopathological changes in the ovary of the freshwater leech Limnatis ‎nilotica (Savigny, 1822)‎

ABSTRACT In this study, we investigated the effect of Cd on the ovaries of the freshwater leech Limnatis nilotica and the ability of salicylic acid (SA) treatment to alleviate the Cd harmful effects. Our results showed that Cd treatment increased the level of oxidative stress leading to severe alterations in histopathological and biochemical indexes. Cd exposure was found to induce a substantial increase in malondialdehyde (MDA) and hydrogen peroxidase (H2O2) contents as well as an impairment in catalase (CAT) and Glutathione peroxidase (GPx) activities. These findings are thoroughly supported by histopathological evidence which showed several modifications in the ovary cord organization. However, SA addition reduced the toxic effect of Cd-exposure through decreasing MDA and H2O2 levels, the regulation of enzymatic and nonenzymatic antioxidant mechanism pathways leading to the alleviation of the histopathological lesions. These results suggest that SA can prevent damage under Cd toxicity in the leech ovaries.

A Brief Review on Evaluation and Exploration of Antioxidant Activity of Mango Ginger

Many free radicals are generates in the human body due to metabolic processes and in order to counteract the harmful effects of these antioxidants, human body has a complex system of natural enzymatic and non-enzymatic antioxidant defenses or mechanisms. These free radicals are mainly responsible for generation of different types of diseases and disorders. Hence protection of body against free radical is important and which can also be done by taking diet with maximum antioxidants. Naturally occurring antioxidant are very important in preventing body from various free radicals. Many medicinal plants and their extracts have been reported for potential anti-oxidant activity. Curcuma amada Roxb (Mango Ginger) is the most important genera come under the Zingiberaceae family. Chemically it has reported for the presence of wide range of phytoconstituents which include the flavonoids, terpenoids, tannins steroids, alkaloids, glycosides and essential oils. Due to presence of wide variety of phytoconstituents plant has very well traditional value reported for pharmacological significance for a variety of ailments. It effectively treats skin allergies, stomach problems, and high blood cholesterol and has been reported for antioxidant properties. In the present review work various research articles published on antioxidant activity of Mango Ginger Have been collected from various journal site and databases and explored systematically

Reduction of ethylene biosynthesis in sugarcane induces growth and investment in the non-enzymatic antioxidant apparatus.

Lower ethylene production in sugarcane results in plants with higher stature, expression of growth-promoting genes, higher photosynthetic rate, and increased antioxidant compounds. The hormone ethylene is involved in critical processes in sugarcane, such as the growth and accumulation of sucrose. The lack of mutants for ethylene biosynthesis or signaling genes makes it difficult to understand the role of this phytohormone throughout sugarcane development. This study aimed to evaluate the physiology and development of sugarcane plants with low ethylene production. To achieve this goal, we used RNA interference to silence three genes, ScACS1, ScACS2, and ScACS3, encoding 1-aminocyclopropane-1-carboxylic acid synthases (ACS), responsible for a limiting step of the ethylene biosynthesis pathway. Sugarcane plants with reduced ethylene levels presented increased growth, faster germination of lateral gems, and activation of non-enzymatic antioxidant mechanisms. We observed an augmentation in the expression of ScACO5, which encodes the final enzyme regulating ethylene biosynthesis, and ScERF1, encoding a transcription factor, linked to the ethylene response. The increase in plant height was correlated with higher expression of ScPIF3, ScPIF4, and ScPIF5, which encode for transcription factors related to growth induction. Interestingly, there was also an increase in the expression of the ScGAI gene, which encodes a DELLA protein, a growth repressor. The final content of sucrose in the stems was not affected by the low levels of ethylene, although the rate of CO2 assimilation was reduced. This study reports for the first time the impacts of low endogenous production of ethylene in sugarcane and provides helpful insights on the molecular mechanisms behind ethylene responses.

Changes in Antioxidant Defence System in Durum Wheat under Hyperosmotic Stress: A Concise Overview.

Durum wheat is one of the most commonly cultivated species in the world and represents a key commodity for many areas worldwide, as its grain is used for production of many foods, such as pasta, bread, couscous, and bourghul. Durum wheat grain has a relevant role in the human diet, providing carbohydrates, proteins, lipids, fibres, vitamins, and minerals, as well as highly valued bioactive compounds contributing to a healthy diet. Durum wheat is largely cultivated in the Mediterranean basin, where it is mainly grown under rain-fed conditions, thus currently undergoing drought stress, as well as soil salinity, which can hamper yield potential and influence the qualitative characteristics of grain. When plants suffer drought and/or salinity stress, a condition known as hyperosmotic stress is established at cellular level. This leads to the accumulation of ROS thus generating in turn an oxidative stress condition, which can ultimately result in the impairment of cellular integrity and functionality. To counteract oxidative damage due to excessive ROS production under stress, plants have evolved a complex array of both enzymatic and non-enzymatic antioxidant mechanisms, working jointly and synergically for maintenance of ROS homeostasis. Enhancement of antioxidant defence system has been demonstrated as an adaptive mechanism associated to an increased tolerance to hyperosmotic stress. In the light of these considerations, this review provides a concise overview on recent advancements regarding the role of the ascorbate-glutathione cycle and the main antioxidant enzymes (superoxide dismutase, catalase, and peroxidases) in durum wheat response to drought and salt stresses that are expected to become more and more frequent due to the ongoing climate changes.

Silicon Improves the Redox Homeostasis to Alleviate Glyphosate Toxicity in Tomato Plants-Are Nanomaterials Relevant?

Given the widespread use of glyphosate (GLY), this agrochemical is becoming a source of contamination in agricultural soils, affecting non-target plants. Therefore, sustainable strategies to increase crop tolerance to GLY are needed. From this perspective and recalling silicon (Si)’s role in alleviating different abiotic stresses, the main goal of this study was to assess if the foliar application of Si, either as bulk or nano forms, is capable of enhancing Solanum lycopersicum L. tolerance to GLY (10 mg kg−1). After 28 day(s), GLY-treated plants exhibited growth-related disorders in both shoots and roots, accompanied by an overproduction of superoxide anion (O2•−) and malondialdehyde (MDA) in shoots. Although plants solely exposed to GLY have activated non-enzymatic antioxidant mechanisms (proline, ascorbate and glutathione), a generalized inhibition of the antioxidant enzymes was found, suggesting the occurrence of great redox disturbances. In response to Si or nano-SiO2 co-application, most of GLY phytotoxic effects on growth were prevented, accompanied with a better ROS removal, especially by an upregulation of the main antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX). Overall, results pointed towards the potential of both sources of Si to reduce GLY-induced oxidative stress, without major differences between their efficacy.

Analysis of antioxidant response in pomelo fruitlets subjected to external injury stress: Significance of naringin biosynthesis

We simulated 2 types of external injuries in fruitlets—throwing and cutting with knife, and evaluated the degree of putrefaction. The external injury-induced toxicity was determined by observing changes in the spatial structure of the cells. Next, we determined the contents of lignin and total flavonoids, and the expression of phenylpropanoid pathway-related genes encoding enzymes that alleviate peroxidation toxicity. By measuring the content of naringin, we uncovered a non-enzymatic antioxidant mechanism that eliminates excessive reactive oxygen species (ROS) in fruitlets. We also determined that external injury triggers an increased activity of antioxidant enzymes. Overall, in fruitlets, external injuries activate naringin biosynthesis in response to stress.

Nanoparticles as elicitors and harvesters of economically important secondary metabolites in higher plants: A review.

Nanoparticles possess some unique properties which improve their biochemical reactivity. Plants, due to their stationary nature, are constantly exposed to nanoparticles present in the environment, which act as abiotic stress agents at sub‐toxic concentrations and phytotoxic agents at higher concentrations. In general, nanoparticles exert their toxicological effect by the generation of reactive oxygen species to which plants respond by activating both enzymatic and non‐enzymatic anti‐oxidant defence mechanisms. One important manifestation of the defence response is the increased or de novo biosynthesis of secondary metabolites, many of which have commercial application. The present review extensively summarizes current knowledge about the application of different metallic, non‐metallic and carbon‐based nanoparticles as elicitors of economically important secondary metabolites in different plants, both in vivo and in vitro. Elicitation of secondary metabolites with nanoparticles in plant cultures, including hairy root cultures, is discussed. Another emergent technology is the ligand‐harvesting of secondary metabolites using surface‐functionalized nanoparticles, which is also mentioned. A brief explanation of the mechanism of action of nanoparticles on plant secondary metabolism is included. Optimum conditions and parameters to be evaluated and standardized for the successful commercial exploitation of this technology are also mentioned.

Physiological responses and phytoremediation capability of Avicennia marina to oil contamination

The impact of oil pollution on coastal vulnerable ecosystems has been a major concern especially, in the Persian Gulf area. The current study was carried out to assess to what extent Avicennia marina can tolerate oil contamination and degrade crude oil polycyclic aromatic hydrocarbons (PAHs) from rhizosphere soil. Seeds of A. marina were grown in control and crude oil-contaminated (2.5, 5.0, 7.5, and 10% w/w) soil under ambient greenhouse conditions. Four-month-old plants were collected, measured for their biometry, and assayed for physiological characteristics in relation to degradation of PAHs. A. marina exposed to petroleum responded by allocating proportionally more biomass to root than shoot, activating enzymatic and non-enzymatic antioxidative mechanisms and removing of PAHs, particularly in lower concentrations of crude oil in the soil. The content of total PAHs in A. marina rhizosphere soil, grown on 2.5, 5.0, 7.5 and 10% oil-treated soils were, respectively, 37 ± 0.4, 21.84 ± 0.27, 12.78 ± 0.11 and 14.74 ± 0.03% lower than non-rhizosphere soil. Comparison of PAHs content of rhizospheric and non-rhizospheric soil also indicated that the highest rate of PAH removal was for acenaphthene (74.63 ± 0.78) in control, fluoranthene (71.18 ± 0.56) in 2.5%, and anthracene (69.45 ± 6.33, 55.66 ± 4.38 and 35.97 ± 0.22) in 5.0, 7.5 and 10% oil-contaminated soil and acenaphthene (74.63 ± 0.78) in control. Activities of peroxidase, ascorbate peroxidase, and polyphenol oxidase were more prominent in the roots of plants exposed to increasing concentrations of oil in soil than control plants. Conversely, the activity of superoxide dismutase decreased. These findings render A. marina as a phytoremediation candidate for small scale oil spills and residual oil pollution in coastal marine environments.