Metal absorption properties of Mentha spicata grown under tannery sludge amended soil-its effect on antioxidant system and oil quality

Salicylic acid foliar application meliorates Portulaca oleraceae L. growth responses under Pb and Ni over-availability while keeping reliable phytoremediation potential

The efficacy of SA foliar use on Pb and Ni-induced stress tolerance and phytoremediation potential by Portulaca oleraceae L. were assayed as a factorial trial based on a completely randomized design with four repetitions. The factors included; SA foliar application (0 and 100 µM) and HMs application of Pb [0, 150, and 225 mg kg-1 soil Lead (II) nitrate] and Ni [0, 220, and 330 mg kg-1 soil Nickel (II) nitrate]. Plant height, stem diameter, shoot and root fresh and dry weight, photosynthetic pigments, total soluble proteins, palmitic acid, stearic acid, arachidic acid, and some macro- and micro-elements contents were reduced facing the HMs stress, but SA foliar application ameliorated these traits. HMs stress increased malondialdehyde content, total antioxidant activity, total flavonoids, phenolics, and linolenic acid content, while SA foliar application declined the mentioned parameters. Moreover, shoot and root Pb and Ni content enhanced in the purslane plants supplemented by SA under the HMs stress. The results propose SA foliar application as a reliable methodology to recover purslane growth characters and fatty acid profiles in the soil contaminated with the HMs. The idea is that SA would be potentially effective in alleviating HMs contamination while keeping reasonable phytoremediation potential.

Medicinal Plant Growth in Heavy Metals Contaminated Soils: Responses to Metal Stress and Induced Risks to Human Health

Accelerating heavy metal pollution is a hot issue due to a continuous growth in consumerism and increased activities in various global industries. Soil contamination with heavy metals has resulted in their incorporation into the human food web via plant components. Accumulation and amplification of heavy metals in human tissues through the consumption of medicinal plants can have hazardous health outcomes. Therefore, in this critical review we aim to bring together published information on this subject, with a special highlight on the knowledge gaps related to heavy metal stress in medicinal plants, their responses, and human health related risks. In this respect, this review outlines the key contamination sources of heavy metals in plants, as well as the absorption, mobilization and translocation of metal ions in plant compartments, while considering their respective mechanisms of detoxification. In addition, this literature review attempts to highlight how stress and defensive strategies operate in plants, pointing out the main stressors, either biotic or abiotic (e.g., heavy metals), and the role of reactive oxygen species (ROS) in stress answers. Finally, in our research, we further aim to capture the risks caused by heavy metals in medicinal plants to human health through the assessment of both a hazard quotient (HQ) and hazard index (HI).

Toxic Metals (As, Cd, Ni, Pb) Impact in the Most Common Medicinal Plant (Mentha piperita)

This study aimed to evaluate the behavior of Mentha piperita under Cd, Pb, Ni, and As soil contamination and their transfer from soil in plants as well as translocation in the roots/stems/leaves system compared with a control without metal addition. The mint seedlings were exposed for a three-month period using two metal mixtures in the same concentrations such as AsCd and AsCdNiPb (23.7 mg/kg As, 5 mg/kg Cd, 136 mg/kg Ni, and 95 mg/kg Pb). The results of metal concentration in plants showed that Cd, Ni, and Pb were accumulated in different parts of the plant, except for As. In plants organs, the order of metal accumulation was roots > stems > leaves. No significant impact on the growth, development, and chlorophyll content compared to the control was observed in the first month of exposure. After three months of exposure, phytotoxic effects occurred. Generally, the transfer coefficients and translocation factors values were less than 1, indicating that Mentha piperita immobilized the metals in root. The laboratory experiments highlighted that for a short period of time, Mentha piperita has the capacity to stabilize the metals at the root level and was a metal-tolerant plant when using a garden rich-substrate.

Glycine Betaine Accumulation, Significance and Interests for Heavy Metal Tolerance in Plants

Unexpected biomagnifications and bioaccumulation of heavy metals (HMs) in the surrounding environment has become a predicament for all living organisms together with plants. Excessive release of HMs from industrial discharge and other anthropogenic activities has threatened sustainable agricultural practices and limited the overall profitable yield of different plants species. Heavy metals at toxic levels interact with cellular molecules, leading towards the unnecessary generation of reactive oxygen species (ROS), restricting productivity and growth of the plants. The application of various osmoprotectants is a renowned approach to mitigate the harmful effects of HMs on plants. In this review, the effective role of glycine betaine (GB) in alleviation of HM stress is summarized. Glycine betaine is very important osmoregulator, and its level varies considerably among different plants. Application of GB on plants under HMs stress successfully improves growth, photosynthesis, antioxidant enzymes activities, nutrients uptake, and minimizes excessive heavy metal uptake and oxidative stress. Moreover, GB activates the adjustment of glutathione reductase (GR), ascorbic acid (AsA) and glutathione (GSH) contents in plants under HM stress. Excessive accumulation of GB through the utilization of a genetic engineering approach can successfully enhance tolerance against stress, which is considered an important feature that needs to be investigated in depth.

Suitability of aromatic plants for phytoremediation of heavy metal contaminated areas: a review

This review briefly elucidates the research undertaken and benefits of using aromatic plants for remediation of heavy metal polluted sites. A sustainable approach to mitigate heavy metal contamination of environment is need of the hour. Phytoremediation has emerged to be one of the most preferable choices for combating the metal pollution problem. Aromatic plants can be used for remediation of contaminated sites as they are non-food crops thus minimizing the risk of food chain contamination. Most promising aromatic plants for phytoremediation of heavy metal contaminated sites have been identified from families - Poaceae, Lamiaceae, Asteraceae, and Geraniaceae. They act as potential phytostabilisers, hyper accumulators, bio-monitors, and facultative metallophytes. Being high value economic crops, monetary benefits can be obtained by growing them in tainted areas instead of food crops. It has been observed that heavy metal stress enhances the essential oil percentage of certain aromatic crops. Research conducted on some major aromatic plants in this context has been highlighted in the present review which suggests that aromatic plants hold a great potential for phytoremediation. It has been reported that essential oil from aromatic crops is not contaminated by heavy metals significantly. Thus, aromatic plants are emerging as an ideal candidate for phytoremediation. Highlights • Aromatic plants hold a great potential for phytoremediation of heavy metal contaminated sites. • Being high value economic crops, monetary benefits can be obtained by growing them in contaminated areas instead of food crops. • Research done on some major aromatic plants in this context has been highlighted in the present review.

Influence of metals on essential oil content and composition of lemongrass (Cymbopogon citratus (D.C.) Stapf.) grown under different levels of red mud in sewage sludge amended soil

Lemongrass is a commercially important perennial herb with medicinal value and ability to tolerate high alkaline and saline conditions. Essential oil bearing plants can grow safely in soil contaminated with heavy metals without severe effects on morphology and oil yield. The present study was aimed to assess the essential oil content and composition in lemongrass in response to elevated metals in above-ground plant parts. Pot experiment was conducted for six months using sewage sludge as soil amendment (soil: sludge: 2:1 w/w) followed by red mud treatments (0, 5, 10 and 15% w/w). Garden soil without sludge and red mud was control and there were ten replicates of each treatment. Oil content in leaves was differently affected due to presence of metals in soil under different treatments. Oil content under S_RM5 (5% red mud) treatment was raised by 42.9 and 11.5% compared to the control and S_RM0 treatment, respectively. Among identified compounds in oil under red mud treatments, 17 compounds contributed more than 90% of total volatiles (citral contributing approximately 70%). Under S_RM10 treatment, essential oil showed maximum citral content (75.3%). Contents of Fe, Zn, Cu, Cd, Ni and Pb in above-ground plant parts exceeded, whereas Mn was detected within WHO permissible limits for medicinal plants. However, metal contents in essential oil were well within FSSAI limits for food. The study suggests utilization of 5 and 10% red mud in sludge amended soil for lemongrass cultivation to have better oil yield and quality, without metal contamination.

Inoculating chlamydospores of Trichoderma asperellum SM-12F1 changes arsenic availability and enzyme activity in soils and improves water spinach growth

Arsenic (As)-contaminated agricultural soils threaten crop yields and pose a human health risk. Augmentation of exogenous microorganisms exhibiting plant-growth promoting and As speciation changing shows potential to improve crop growth and change soil As availability. Trichoderma asperellum SM-12F1 exhibiting both traits was developed into chlamydospores to improve its persistence in contaminated soils. After inoculation, As availability and enzyme activity in two types of soils and the growth as well as As uptake of water spinach (Ipomoea aquatic Forsk.) were investigated. The results indicated that inoculation significantly improved water spinach growth in both soils. Inoculating chlamydospores at 5% significantly increased As concentration (139%), bioconcentration factor (150%), and translocation factor (150%) in water spinach grown in Chenzhou (CZ) soils, while no significant change for these in Shimen (SM) soils. Inoculating chlamydospores at 5% caused a significant increase (16%) of available As content in CZ soils, while a significant decrease (13%) in SM soils. Inoculation significantly caused As methylation in both soils, while significant As reduction merely observed in CZ soils. The differential changes in available As contents in both soils were attributed to the soil pH, As fractionations and speciation characteristics. Furthermore, Inoculating chlamydospores at 5% significantly improved the activities of β-glucosidase (155%), chitinase (211%), and phosphatase (108%) in SM soils, while significant decreases in β-glucosidase (81%), phosphatase (54%), aminopeptidase (60%), and catalase (67%) in CZ soils. Bioaugmentation and As availability change were responsible for this result. These observations will be helpful for the application of fungal chlamydospores in the future bioremediation.

Identification of Aroma Compounds of Lamiaceae Species in Turkey Using the Purge and Trap Technique

The present research was planned to characterize the aroma composition of important members of the Lamiaceae family such as Salvia officinalis, Lavandula angustifolia and Mentha asiatica. Aroma components of the S. officinalis, L. angustifolia and M. asiatica were extracted with the purge and trap technique with dichloromethane and analyzed with the gas chromatography–mass spectrometry (GC–MS) technique. A total of 23, 33 and 33 aroma compounds were detected in Salvia officinalis, Lavandula angustifolia and Mentha asiatica, respectively including, acids, alcohols, aldehydes, esters, hydrocarbons and terpenes. Terpene compounds were both qualitatively and quantitatively the major chemical group among the identified aroma compounds, followed by esters. The main terpene compounds were 1,8-cineole, sabinene and linalool in Salvia officinalis, Lavandula angustifolia and Mentha asiatica, respectively. Among esters, linalyl acetate was the only and most important ester compound which was detected in all samples.