Divergent responses of ascorbate and glutathione pools in ozone-sensitive and ozone-tolerant wheat cultivars under elevated ozone and carbon dioxide interaction.

Crop plants face complex tropospheric ozone (O3) stress, emphasizing the need for a food security-focused management strategy. While research extensively explores O3's harmful effects, this study delves into the combined impacts of O3 and CO2. This study investigates the contrasting responses of O3-sensitive (PBW-550) and O3-resistant (HUW-55) wheat cultivars, towards elevated ozone (eO3) and elevated carbon dioxide (eCO2), both individually and in combination. The output of the present study confirms the positive effect of eCO2 on wheat cultivars exposed to eO3 stress, with more prominent effects on O3-sensitive cultivar PBW-550, as compared to the O3-resistant HUW-55. The differential response of the two wheat cultivars can be attributed to the mechanistic variations in the enzyme activities of the Halliwell-Asada pathway (AsA-GSH cycle) and the ascorbate and glutathione pool. The results indicate that eCO2 was unable to uplift the regeneration of the glutathione pool in HUW-55, however, PBW-550 responded well, under similar eO3 conditions. The study's findings, highlighting mechanistic variations in antioxidants, show a more positive yield response in PBW-550 compared to HUW-55 under ECO treatment. This insight can inform agricultural strategies, emphasizing the use of O3-sensitive cultivars for sustained productivity in future conditions with high O3 and CO2 concentrations.

Growth, ultrastructural and physiological characteristics of Abelmoschus cytotypes under elevated ozone stress: a study on ploidy-specific responses.

Tropospheric ozone (O3 ) is a significant abiotic stressor whose rising concentration negatively influences plant growth. Studies related to the differential response of Abelmoschus cytotypes to elevated O3 treatment are scarce and need further exploration to recognise the role of polyploidisation in stress tolerance. In this study, we analysed the changes in growth pattern, ultrastructure, physiology and foliar protein profile occurring under O3 stress in Abelmoschus moschatus (monoploid), Abelmoschus esculentus (diploid) and Abelmoschus caillei (triploid). Our findings showed that higher stomatal conductance in A. moschatus triggered higher O3 intake, causing damage to stomatal cells and photosynthetic pigments. Additionally, it caused a reduction in photosynthetic rates, leading to reduced plant growth, total biomass and economic yield. This O3 -induced toxicity was less in diploid and triploid cytotypes of Abelmoschus . Protein profiling by sodium dodecyl sulpate-polyacrylamide gel electrophoresis showed a significant decrease in the commonly found RuBisCO larger and smaller subunits. The decrease was more prominent in monoploid compared to diploid and triploid. This study provides crucial data for research that aim to enhance plant ability to withstand O3 induced oxidative stress. Our findings may help in developing a tolerant variety through plant breeding techniques, which will be economically more advantageous in reaching the objective of sustainable production at the high O3 levels projected under a climate change scenario.

Assessment of herbaceous community structure for identifying metal-tolerant species at different land uses in and around Varanasi city.

Plant community structure under different land uses provides an important understanding of vegetation dynamics to safeguard future restoration programmes and balance ecosystem services. Therefore, this study was carried out to estimate the alterations in soil properties and contamination by potentially toxic metals at different land uses (industrial, brick kiln, highway, and residential areas) compared to the reference (botanical garden area) site coupled with their subsequent influence on herbaceous community structure, bioconcentration, translocation, and extraction amount of metals in different plant species. Most of the total and phytoavailable metals (Co, Cr, Cd, Cu, Ni, Pb, Mn, and Zn) were higher at the contaminated sites compared to the reference site. The number of herbaceous species was highest at the reference site and minimum at the industrial site. Dominant and tolerant species were Cyanodon dactylon, Croton bonaplandianus, Achyranthus aspera, Malvestrum coromendelianum, Dicanthium annulatum, Nicotiana hindostana, Sporobolus virginicus, and Parthenium hysterophorus, found at the industrial, brick kiln, and highway sites. Based on transfer coefficients, C. bonaplandianus, D. annulatum, and Eleusine indica were recognized as potential accumulators, whereas C. dactylon, Commelina benghalensis, A. aspera, Amaranthus sessilis, and M. coromendelianum were found as excluder species for different metals. The identified tolerant herbaceous species could be used for future phytoremediation strategies and the prevention of hazardous risks to living components of contaminated sites.

Secondary metabolites responses of plants exposed to ozone: an update.

Tropospheric ozone (O3) is a secondary pollutant that causes oxidative stress in plants due to the generation of excess reactive oxygen species (ROS). Phenylpropanoid metabolism is induced as a usual response to stress in plants, and induction of key enzyme activities and accumulation of secondary metabolites occur, upon O3 exposure to provide resistance or tolerance. The phenylpropanoid, isoprenoid, and alkaloid pathways are the major secondary metabolic pathways from which plant defense metabolites emerge. Chronic exposure to O3 significantly accelerates the direction of carbon flows toward secondary metabolic pathways, resulting in a resource shift in favor of the synthesis of secondary products. Furthermore, since different cellular compartments have different levels of ROS sensitivity and metabolite sets, intracellular compartmentation of secondary antioxidative metabolites may play a role in O3-induced ROS detoxification. Plants' responses to resource partitioning often result in a trade-off between growth and defense under O3 stress. These metabolic adjustments help the plants to cope with the stress as well as for achieving new homeostasis. In this review, we discuss secondary metabolic pathways in response to O3 in plant species including crops, trees, and medicinal plants; and how the presence of this stressor affects their role as ROS scavengers and structural defense. Furthermore, we discussed how O3 affects key physiological traits in plants, foliar chemistry, and volatile emission, which affects plant-plant competition (allelopathy), and plant-insect interactions, along with an emphasis on soil dynamics, which affect the composition of soil communities via changing root exudation, litter decomposition, and other related processes.

Assessment of the differential trade-off between growth, subsistence, and productivity of two popular Indian hybrid mango varieties under elevated ozone exposure.

The multifunctionality of plants is well known to be compromised in the areas experiencing higher concentrations of tropospheric ozone (O3). Mango (Mangifera indica L.) cultivation is essential to the economy of tropical regions, including India. Mango, widely grown in suburban and rural areas, experiences production loss due to air pollutants. Ozone, the most important phytotoxic gas in mango growing areas, warrants an investigation of its effects. Therefore, we assessed the differential sensitivity of mango saplings (two-year-old hybrid and regular-bearing mango varieties, Amrapali and Mallika) at two levels of O3: ambient and elevated (ambient + 20 ppb) using open-top chambers from September 2020 to July 2022. Under elevated O3, both varieties showed similar seasonal responses (winter and summer) for all the growth parameters but differed in their height-diameter allocation pattern. A decrease in stem diameter and an increase in plant height were observed in Amrapali, whereas Mallika showed a reverse response. Early emergence of phenophases was noticed during the reproductive growth of both varieties under elevated O3 exposure. However, these changes were more pronounced in Amrapali. Stomatal conductance was more negatively affected in Amrapali than in Mallika under elevated O3 during both seasons. Furthermore, leaf morpho-physiological traits (leaf nitrogen concentration, leaf area, leaf mass per area, and photosynthetic nitrogen use efficiency) and inflorescence parameters responded variably in both varieties under elevated O3 stress. A decrease in photosynthetic nitrogen use efficiency, further enhanced yield loss which was more pronounced in Mallika than in Amrapali under elevated O3 exposure. The results of this study could be useful in selecting a better-performing variety based on its productivity, which will be economically more beneficial in achieving the goal of sustainable production at the anticipated high O3 levels under a climate change scenario.

Effect of elevated ozone on the antioxidant response, genomic stability, DNA methylation pattern and yield in three species of Abelmoschus having different ploidy levels.

The majority of polyploids can withstand many stresses better than their monoploid counterparts; however, there is no proven mechanism that can fully explain the level of tolerance at the biochemical and molecular levels. Here, we make an effort to provide an explanation for this intriguing but perplexing issue using the antioxidant responses, genomic stability, DNA methylation pattern and yield in relation to ploidy level under the elevated level of ozone in Abelmoschus cytotypes. The outcome of this study inferred that the elevated ozone causes an increase in reactive oxygen species leading to enhanced lipid peroxidation, DNA damage and DNA de-methylation in all the Abelmoschus cytotypes. The monoploid cytotype of Abelmoschus, that is Abelmoschus moschatus L., experienced the highest oxidative stress under elevated O3, resulting in maximum DNA damage and DNA de-methylation leading to the maximum reduction in yield. While the diploid (Abelmoschus esculentus L.) and triploid (Abelmoschus caillei A. Chev.) cytotypes of Abelmoschus with lower oxidative stress result in lesser DNA damage and DNA de-methylation which ultimately leads to lower yield reduction. The result of this experiment explicitly revealed that polyploidy confers better adaptability in the case of Abelmoschus cytotypes under ozone stress. This study can further be used as a base to understand the mechanism behind the ploidy-induced stress tolerance in other plants mediated by gene dosage effect.

Ultraviolet-B and Heavy Metal-Induced Regulation of Secondary Metabolites in Medicinal Plants: A Review.

Despite a rich history and economic importance, the potential of medicinal plants has not been fully explored under different abiotic stress conditions. Penetration of UV-B radiation and contamination of heavy metals are two important environmental stress for plants with remarkable influence on the defense-related and pharmaceutically important secondary metabolites of medicinal plants. UV-B and heavy metal contamination may become a critical issue that either positively or negatively affects the quality and quantity of secondary metabolites. Such effects may result from changes in the expression level of genes that encode the corresponding enzymes or the inactivation and/or stimulation of specific enzymes involved in the different biosynthetic pathways of the secondary metabolites. Therefore, a comprehensive study of the impact of UV-B and heavy metals individually and in combination on the biosynthesis and accumulation of secondary metabolites in medicinal plants is discussed in the present review.

Effect of carbon quantum dots derived from extracts of UV-B-exposed Eclipta alba on alcohol-induced liver cirrhosis in Golden Hamster.

The Eclipta alba plant is considered hepatoprotective, owing to its phytoconstituents wedelolactone. In the current study, effect of elevated ultraviolet-B (eUV-B) radiation was investigated on biochemical, phytochemical, and antioxidative enzymatic activities of E. alba (Bhringraj) plant. The UV-B exposure resulted in an increase in oxidative stress, which has caused an imbalance in phytochemical, biochemical constituents, and induced antioxidative enzymatic activities. It was observed that the UV-B exposure promoted wedelolactone yield by 23.64%. Further, the leaf extract of UV-B-exposed plants was used for the synthesis of carbon quantum dots (CQDs) using low cost, one-step hydrothermal technique and its biocompatibility was studied using in vitro MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay on HepG2 liver cell line. It revealed no toxicity in any treatment groups in comparison to the control. Both CQDs and leaf extract were orally administered to the golden hamster suffering from alcohol-induced liver cirrhosis. In the morphometric study, it was clearly observed that a combination of UV-B-exposed leaf extract and synthesized CQDs delivered the best result with maximum recovery of liver tissues. The present study reveals the positive impact of UV-B exposure on the medicinally important plant, increased yield of wedelolactone, and its enhanced hepatoprotective efficacy for the treatment of damaged liver tissues.

Individual and combined effects of chromium and ultraviolet-B radiation on defense system, ultrastructural changes, and production of secondary metabolite psoralen in a medicinal plant Psoralea corylifolia L.

The present study focuses on the effects of individual and combined stress of chromium (Cr) and ultraviolet-B (UV-B) radiation on Psoralea corylifolia L. The experiment comprised four sets: (i) control, (ii) eUV-B (elevated UV-B i.e., ambient + 7.2 kJ m-2 day-1 UV-B), (iii) Cr (chromium; 30 mg kg-1 soil), and (iv) Cr + eUV-B (chromium and elevated UV-B; Cr 30 mg kg-1 and ambient + 7.2 kJ m-2 day-1 UV-B). The eUV-B and Cr individually and in combination showed the variable responses on ultrastructure, physiology and biomass however, the impact was more prominent under individual Cr treatment followed by Cr + eUV-B and eUV-B. Higher bioconcentration factor and the lowered translocation factor consequently led to a higher reduction in the below ground biomass and the lesser reduction in above ground biomass under Cr + eUV-B treatment as compared to individual Cr treatment. In addition, higher induction in the enzymatic (glutathione reductase, ascorbate peroxidase, superoxide dismutase, and glutathione-S-transferase) and non-enzymatic antioxidants (glutathione reduced) were found to be responsible for efficient scavenging of hydrogen peroxide and superoxide radical leading to lowered MDA content under combined treatment as compared to Cr treatment. Deposition of Cr as electron dense granules in the cytoplasm, vacuoles, and cell wall under Cr and Cr + eUV-B is contemplated as one of the cellular mechanisms of P. corylifolia against the toxicity of Cr. Psoralen increased under all treatments with a maximum increase under Cr + eUV-B treatment. Taken together our results accentuated that P. corylifolia can be grown in an area contaminated with Cr and has a higher influx of UV-B for the attainment of psoralen considering its pharmaceutical perspectives.

Photosynthetic, Biochemical and Secondary Metabolite Changes in a Medicinal Plant Chlorophytum borivillianum (Safed musli) against Low and High Doses of UV-B Radiation.

Plants are inevitably grown in presence of sunlight, therefore bound to be exposed to natural UV-B radiation. Several studies have already been conducted with UV-B and medicinal plants and only few studies showed dose dependent variation. The present study aims to find out the variations and adaptation in Chlorophytum borivillianum under two different doses of UV-B radiation; ambient + low (3.2 kJm-2 d-1 ) and high (7.2 kJm-2 d-1 ) UV-B dose, denoted as LD and HD, respectively. Reduction in photosynthetic rate was higher at HD, while plants receiving LD displayed nonsignificant variation. During vegetative and reproductive stage, significant reduction (P ≤ 0.001) in stomatal conductance was obtained when exposed to HD-eUV-B. Fv /Fm showed more reductions in HD-eUV-B (12.6%) followed by LD-eUV-B (7.9%). Low and high doses of UV-B enhanced the anthocyanin content but the increase was significant in HD, indicates epidermal protection strategy by the plants. Under LD-eUV-B, the content of saponin, a major phytochemical constituent was enhanced by 26%. Phytochemical analysis of roots revealed reduction mostly in fatty acid components whereas the steroidal components (stigmasterol and sarsasapogenin) showed enhancement in response to LD. The study suggests the importance of LD-eUV-B in the stimulation of medicinal compounds in C. borivillianum.

Global Trends of Acidity in Rainfall and Its Impact on Plants and Soil.

Due to its deleterious and large-scale effects on the ecosystem and long-range transboundary nature, acid rain has attracted the attention of scientists and policymakers. Acid rain (AR) is a prominent environmental issue that has emerged in the last hundred years. AR refers to any form of precipitation leading to a reduction in pH to less than 5.6. The prime reasons for AR formation encompass the occurrence of sulfur dioxide (SO2), nitrogen oxides (NOx), ozone (O3), and organic acids in air produced by natural as well as anthropogenic activities. India, the top SO2 emitter, also shows a continuous increase in NO2 level responsible for AR formation. The plants being immobile unavoidably get exposed to AR which impacts the natural surrounding negatively. Plants get affected directly by AR due to reductions in growth, productivity, and yield by damaging photosynthetic mechanisms and reproductive organs or indirectly by affecting underground components such as soil and root system. Genes that play important role in plant defense under abiotic stress gets also modulated in response to acid rain. AR induces soil acidification, and disturbs the balance of carbon and nitrogen metabolism, litter properties, and microbial and enzymatic activities. This article overviews the factors contributing to AR, and outlines the past and present trends of rainwater pH across the world, and its effects on plants and soil systems.

Sensitivity of agricultural crops to tropospheric ozone: a review of Indian researches.

Tropospheric ozone (O3) is a long-range transboundary secondary air pollutant, causing significant damage to agricultural crops worldwide. There are substantial spatial variations in O3 concentration in different areas of India due to seasonal and geographical variations. The Indo-Gangetic Plain (IGP) region is one of the most crop productive and air-polluted regions in India. The concentration of tropospheric O3 over the IGP is increasing by 6-7.2% per decade. The annual trend of increase is 0.4 ± 0.25% year-1 over the Northeastern IGP. High O3 concentrations were reported during the summer, while they were at their minimum during the monsoon months. To explore future potential impacts of O3 on major crop plants, the responses of different crops grown under ambient and elevated O3 concentrations were compared. The studies clearly showed that O3 is an important stress factor, negatively affecting the yield of crops. In this review, we have discussed yield losses in agricultural crops due to rising O3 pollution and variations in O3 sensitivity among cultivars and species. The use of ethylene diurea (EDU) as a research tool in assessing the losses in yield under ambient and elevated O3 levels also discussed. Besides, an overview of interactive effects of O3 and nitrogen on crop productivity has been included. Several recommendations are made for future research and policy development on rising concentration of O3 in India.

Implications of Foliar Particulate Matter Deposition on the Physiology and Nutrient Allocation of Dominant Perennial Species of the Indo-Gangetic Plains.

The ramifications of different concentrations of foliar particulate matter on the physiology, nutrient stoichiometry, allocation pattern, and their corresponding re-translocation rates were investigated for evergreen (Mangifera indica and Psidium guajava), semi-evergreen (Ficus religiosa and Azadirachta indica), and deciduous (Dalbergia sissoo) tree species in a simulation experiment over an exposure period of 2 years. Physiological parameters (Pn, gs, Ci, E, and WUE), nutrient stoichiometry (C: N) in different plant parts, and their allocation pattern for five macro- (C, N, K, Mg, Ca) and five (Zn, Ni, Mn, Cu, Fe) micro-elements at two different concentrations of particulate matter (ambient and elevated) with respect to control (no particulate load) were assessed. Significant differences in nutrient concentrations and their re-translocation rates were observed between the treatments in evergreen species compared to deciduous species. The photosynthetic rate significantly declined with an increase in foliar deposition of particulate matter. Higher variations in C, N, K, Mg, and Zn levels were found compared to other elements under particulate matter stress and the ratio of C/N showed a slight decline in mature leaves except in deciduous tree species. The nutrient stoichiometry revealed that the deciduous species were more tolerant whereas the re-translocation efficiency was maximum for the semi-evergreen tree species. The nutrient allocation was found greater in foliage compared to branch in evergreen and was opposite in semi-evergreen and deciduous tree species. The element re-translocation rate indicated an inconsistent behavior in nutrient recycling under the particulate matter load depending upon the tree species. The study entrenched a critical change in nutrient re-translocation and allocation pattern under the particulate stress in different parts of the tree, suggesting a novel approach for screening the tree species for sustainable plantation and planning of urban areas.

Dose differentiation in elevated UV-B manifests variable response of carbon-nitrogen content with changes in secondary metabolites of Curcuma caesia Roxb.

Despite acting as environmental stress, UV-B also plays a regulatory role in the plant's growth and secondary metabolism. UV-B-induced changes show variations between and among the species. The present study mainly focuses on variations in carbon and nitrogen contents and their relation with the phytochemical constituents of Curcuma caesia exposed to two different doses of UV-B (ambient ± elevated UV-B for 1 h (2.4 kJ m-2 day-1) and 2 h (4.8 kJ m-2 day-1)) under natural field conditions. Results showed that increasing the dose of eUV-B leads to high tuber biomass and reduced rhizome biomass (the medicinally important part). Increased expression of compounds at the initial rhizome formation stage might be due to the increased carbon content, whereas no such trend was found at the final growth or rhizome maturation stage. After final harvesting, carbon content was reduced, with an increase of nitrogen content which might be responsible for enhanced production of major components of essential oil (D-camphor and 1,8-cineole) in 2 h of UV-B exposure followed by 1 h. The phytochemical analysis at the final stage showed induction of compounds (15 and 10 in 1 h and 2 h, respectively) after UV-B exposure which was not detected in controls. The present study suggests that the change in carbon-nitrogen played an important role in the fraction of compounds at different stages, and a lower dose of UV-B (1 h) favoured the increased production of essential oil; however, 2 h dose is important for the enhanced production of major active compounds of essential oil.

Improvements in Soil Physical, Chemical and Biological Properties at Natural Saline and Non-Saline Sites Under Different Management Practices.

Soil salinity is known to be a significant threat to food security for the increasing population, which is further aggravated under the climate change scenario. Indo-Gangetic plain (IGP) is one of the most productive in the world and is most affected by salinity. To understand the modifications in soil characteristics under different management practices followed to reclaim salinity affected land, the present study was conducted at variously reclaimed saline areas of three districts of Uttar Pradesh situated in IGP. Soil from six sites (electrical conductivity (EC) ranging from 0.89 to 10.28 mS) following different management practices, RJT (Rajatalab, rice-wheat +organic), BBN (Beerbhanpur, rice-wheat +inorganic), MZM (Mirzamurad, rice-mustard +organic), BRP (Baraipur, rice-wheat +organic), DHR (Dharahara, rice-fallow +organic) and SLM (Salempur, rice-wheat +inorganic) were assessed for physical, chemical and biological properties during the vegetative stage and after harvest of crops. Soil quality index (SQI) based on representative parameters obtained by principal component analysis and yield of crops were also calculated at saline and non-saline sites. The SLM site showed highest salinity followed by BRP, DHR, MZM, while BBN and RJT were non-saline. Total organic carbon, total nitrogen, microbial activity, and microbial biomass were low at saline compared to non-saline sites but were higher under organic matter amendment compared to inorganic. Activities of soil enzymes were negatively influenced while ß-glucosidase and alkaline phosphatase activities were enhanced under higher salinity. Organic amendments were more efficient in improving the soil properties along with SQI at saline soil resulting into a better yield in all crop combinations compared to inorganic amendments.

Assessment of physiological, biochemical and yield responses of wheat plants under natural saline and non-saline field conditions.

Soil salinity is a major threat to crop productivity all over the world including the Indo-Gangetic plain (IGP) region of India. Therefore, a field study was conducted for two consecutive years in wheat growing areas in IGP affected by salinity. Plants grown at a saline site (Salempur, SLM) and a non-saline site (Rajatalab, RJT), were analysed for selected biochemical, physiological and yield traits. Results showed that photosynthetic rate was not significantly affected, but transpiration rate and stomatal conductance declined at saline compared to non-saline site. Photosynthetic pigments increased during vegetative growth period, but decreased during reproductive stage at SLM site, while anthocyanin showed an opposite trend. Membrane damage, solute leakage, H2O2 and ·O2 - productions were intensified at saline site, SLM. Accumulation of osmolytes and antioxidants occurred in plants at saline compared to non-saline sites. K/Na and Ca/Na ratios in plants at SLM were reduced significantly compared to non-saline site, RJT. Biomass and yield also declined at SLM compared to RJT. Principle component and path analyses on the measured parameters clearly showed that defense strategies adopted by plants helped to maintain the photosynthetic rate but biomass and yield of wheat got compromised under high salinity.

An assessment of dose-dependent UV-B sensitivity in Eclipta alba: Biochemical traits, antioxidative properties, and wedelolactone yield.

The UV-B-induced signals play a crucial role in improving the analeptic values of medicinally important plants. Eclipta alba L. (Hassak), commonly known as False Daisy, holds supreme stature with its pharmaceutical association in treating various ailments, particularly in Ayurvedic medicine. The present study aimed to evaluate the response of E. alba plants exposed to ambient (AT) and two different supplemental UV-B doses (eUV-B, ambient ±7.2 kJ m-2 day-1), i.e., intermittent (IT) and continuous (CT) UV-B treatment for 130 and 240 h respectively. Antioxidative activities and medicinally important compounds (wedelolactone) were measured in different plants' parts at three growth stages. Under both the eUV-B treatments, the photosynthetic pigments were adversely affected (along with reductions in protein content) with a concomitant increase in secondary metabolites. Substantial variations in enzymatic antioxidants and non-enzymatic compounds showed the adaptive resilience strategies of plants against eUV-B. The wedelolactone content increased in leaves but compromised in stem and roots under IT. The results concluded that IT UV-B exposure led to the improvement of plant growth and the yield of wedelolactone compared to CT, suggesting its ameliorative role in improving the test plant's medicinal value.

Salinity alleviates the toxicity level of ozone in a halophyte Mesembryanthemum crystallinum L.

Mesembryanthemum crystallinum (Ice plant) is an annual halophytic plant species spread in the coastal areas of the Mediterranean Sea, Egypt. Information about the behaviour of halophytes under the future concentration of ozone (O3) is scanty. Therefore, we have assessed the effects of elevated O3 (ambient + 20 ppb), moderate salinity (200 mM NaCl), and their combined treatment (salinity + elevated O3) on various morphological, growth, physiological, biochemical and anatomical parameters of Egyptian ice plant. Under salinity stress, plant growth, percentage of pigmented leaf and its thickness, ROS levels, antioxidative enzymes, and ROS scavenging activities were increased, while photosynthetic pigments and efficiency were decreased compared to the control. Elevated O3 exposure led to reductions in most of the growth parameters and pigments, while ROS levels, histochemical localization of H2O2 and ·O2-, antioxidative enzymes and non-enzymatic antioxidants (betacyanin, phenolics, thiols and ascorbic acid) showed increases. Surprisingly, salinity alleviated the oxidative stress of elevated O3 due to the rise of SOD activity, antioxidant compounds, and a decrease of ·O2- production rate with concomitant increases of most of the growth parameters. Thick lower collenchyma and enhancement of xylem parenchyma under O3 and combined treatment suggested that anatomical acclimation also operated under O3 stress and salinity played a vital role in the growth of this plant under combined stress. Results showed that salt is essential for the optimum development of this species and its role is extended to alleviate the oxidative damage caused by elevated O3. The results further recommend the use of Egyptian M. crystallinum as a O3 tolerant crop for saline areas along the Mediterranean Sea coast.

Ultraviolet-B mediated biochemical and metabolic responses of a medicinal plant Adhatoda vasica Nees. at different growth stages.

In the present study, the effects of elevated UV-B (eUVB; ambient ± 7.2 kJ m-2 day-1) were evaluated on the biochemical and metabolic profile of Adhatoda vasica Nees. (an indigenous medicinal plant) at different growth stages. The results showed reduction in superoxide radical production rate, whereas increase in the content of hydrogen peroxide which was also substantiated by the histochemical localization. Malondialdehyde content, which is a measure of oxidative stress, did not show significant changes at any of the growth stages however photosynthetic rate and chlorophyll content showed reduction at all growth stages under eUV-B exposure. Increased activities of the enzymatic and non-enzymatic antioxidants were noticed except ascorbic acid, which was reduced under eUV-B exposure. The metabolic profile of A. vasica revealed 43 major compounds (assigned under different classes) at different growth stages. Triterpenes, phytosterols, unsaturated fatty acids, diterpenes, tocopherols, and alkaloids showed increment, whereas reduction in saturated fatty acids and sesquiterpenes were observed under eUV-B treatment. Vasicinone and vasicoline, the two important alkaloids of A. vasica, showed significant induction under eUV-B exposure as compared to control. Treatment of eUV-B leads to the synthesis of some new compounds, such as oridonin oxide (diterpene) and α-Bisabolol oxide-B (sesquiterpene), which possess potent anti-inflammatory and anticancerous activities. The study displayed that differential crosstalk between antioxidants and secondary metabolites at different growth stages, were responsible for providing protection to A. vasica against eUV-B induced oxidative stress and enhancing its medicinal properties.

Examining the effectiveness of biomass-derived biochar for the amelioration of tropospheric ozone-induced phytotoxicity in the Indian wheat cultivar HD 2967.

A pot study was performed to evaluate the influence of O3 stress with different biochar treatments on a wheat cultivar (HD 2967). Plants were subjected to ambient and elevated (ambient+20 ppb) O3 along with three doses of biochar (0%, 2.5%, and 5%). Elevated ozone alone reduced most of the growth parameters, negatively affecting the test cultivar's physiology. Although enzymatic antioxidants were up-regulated by elevated O3, damage to the membrane integrity was evident by higher MDA content in the wheat leaves. Besides, the uptake of nutrients was observed to be reduced under elevated O3 due to the reduced phyto-availability of the soil's nutrients and cation exchange capacity. Such limitation of assimilates and nutrients marked a trade-off between growth and defence, translating to grain yield loss. However, applying biochar as a soil conditioner ameliorated the detrimental effects of O3 with respect to the economic yield of wheat. Biochar alone improved soil properties and nutrient phyto-availability, which translated to better plant growth, stronger physiological capacity, and higher crop productivity. Thus, the study inferred that altered nutrient phyto-availablity and its uptake, likely associated with biochar-induced improved soil properties, relayed stronger plant physiology and antioxidative defence system to combat O3 induced oxidative stress.