Changes in the phenylalanine ammonia lyase activity, total phenolic compounds, and flavonoids in Prosopis glandulosa treated with cadmium and copper

Enhancing the phytoextraction efficiency of heavy metals in acidic and alkaline soils by Sedum alfredii Hance: A study on the synergistic effect of plant growth regulator and plant growth-promoting bacteria

Plant growth regulators (PGR) and plant growth-promoting bacteria (PGPB) have the potential in phytoremediation of heavy metals (HMs) contaminated soils. However, their sole application may not yield the optimal results, thus necessitating the combined application. The present study aimed to enhance the phytoremediation efficiency of Sedum alfredii Hance (S. alfredii) in acidic and alkaline soils through the combination of PGR (Brassinolide, BR) and PGPB (Pseudomonas fluorescens, P. fluorescens). The combination of BR and P. fluorescens (BRB treatment) effectively increased the removal efficiency of S. alfredii for Cd, Pb, and Zn by 355.2 and 155.3 %, 470.1 and 128.9 %, and 408.4 and 209.6 %, in acidic and alkaline soils, respectively. Moreover, BRB treatment led to a substantial increase in photosynthetic pigments contents and antioxidant enzymes activities, resulting in a remarkable increase in biomass (86.71 and 47.22 %) and dry mass (101.49 and 42.29 %) of plants grown in acidic and alkaline soils, respectively. Similarly, BRB treatment significantly elevated the Cd (109.4 and 71.36 %), Pb (174.9 and 48.03 %), and Zn levels (142.8 and 104.3 %) in S. alfredii shoots, along with cumulative accumulation of Cd (122.7 and 79.47 %), Pb (183.8 and 60.49 %), and Zn (150.7 and 117.9 %), respectively. In addition, the BRB treatment lowered the soil pH and DTPA-HMs contents, while augmenting soil enzymatic activities, thereby contributing soil microecology and facilitating the HMs absorption and translocation by S. alfredii to over-ground tissues. Furthermore, the evaluation of microbial community structure in phyllosphere and rhizosphere after remediation revealed the shift in microbial abundance. The combined treatment altered the principal effects on S. alfredii HMs accumulation from bacterial diversity to the soil HMs availability. In summary, our findings demonstrated that synergistic application of BR and P. fluorescens represents a viable approach to strengthen the phytoextraction efficacy of S. alfredii in varying soils.

Leaf litter from Cynanchum auriculatum Royle ex Wight leads to root rot outbreaks by Fusarium solani, hindering continuous cropping

Cynanchum auriculatum Royle ex Wight (CA) is experiencing challenges with continuous cropping obstacle (CCO) due to soil-borne fungal pathogens. The leaf litter from CA is regularly incorporated into the soil after root harvesting, but the impact of this practice on pathogen outbreaks remains uncertain. In this study, a fungal strain D1, identified as Fusarium solani, was isolated and confirmed as a potential factor in CCO. Both leave extract (LE) and root extract (RE) were found to inhibit seed germination and the activities of plant defense-related enzymes. The combinations of extracts and D1 exacerbated these negative effects. Beyond promoting the proliferation of D1 in soil, the extracts also enhanced the hypha weight, spore number, and spore germination rate of D1. Compared to RE, LE exhibited a greater degree of promotion in the activities of pathogenesis-related enzymes in D1. Additionally, caffeic acid and ferulic acid were identified as potential active compounds. LE, particularly in combination with D1, induced a shift in the composition of fungal communities rather than bacterial communities. These findings indicate that the water extract of leaf litter stimulated the growth and proliferation of fungal strain D1, thereby augmenting its pathogenicity toward CA and ultimately contributing to the CCO process.

Plants from Arid and Semi-Arid Zones of Mexico Used to Treat Respiratory Diseases: A Review

Medicinal plants have been a traditional remedy for numerous ailments for centuries. However, their usage is limited due to a lack of evidence-based studies elucidating their mechanisms of action. In some countries, they are still considered the first treatment due to their low cost, accessibility, and minor adverse effects. Mexico is in second place, after China, in inventoried plants for medicinal use. It has around 4000 species of medicinal plants; however, pharmacological studies have only been carried out in 5% of its entirety. The species of the Mexican arid zones, particularly in semi-desert areas, exhibit outstanding characteristics, as their adverse growing conditions (e.g., low rainfall and high temperatures) prompt these plants to produce interesting metabolites with diverse biological activities. This review explores medicinal plants belonging to the arid and semi-arid zones of Mexico, focusing on those that have stood out for their bioactive potential, such as Jatropha dioica, Turnera diffusa, Larrea tridentata, Opuntia ficus-indica, Flourensia cernua, Fouquieria splendes, and Prosopis glandulosa. Their extraction conditions, bioactive compounds, mechanisms of action, and biological efficacy are presented, with emphasis on their role in the treatment of respiratory diseases. Additionally, current research, novel applications, and perspectives concerning medicinal plants from these zones are also discussed.

Extracellular Self- and Non-Self DNA Involved in Damage Recognition in the Mistletoe Parasitism of Mesquite Trees

Psittacanthus calyculatus parasitizes mesquite trees through a specialized structure called a haustorium, which, in the intrusive process, can cause cellular damage in the host tree and release DAMPs, such as ATP, sugars, RNA, and DNA. These are highly conserved molecules that primarily function as signals that trigger and activate the defense responses. In the present study, we generate extracellular DNA (exDNA) from mesquite (P. laevigata) tree leaves (self-exDNA) and P. calyculatus (non-self exDNA) mistletoe as DAMP sources to examine mesquite trees' capacity to identify specific self or non-self exDNA. We determined that mesquite trees perceive self- and non-self exDNA with the synthesis of O2•-, H2O2, flavonoids, ROS-enzymes system, MAPKs activation, spatial concentrations of JA, SA, ABA, and CKs, and auxins. Our data indicate that self and non-self exDNA application differs in oxidative burst, JA signaling, MAPK gene expression, and scavenger systems. This is the first study to examine the molecular biochemistry effects in a host tree using exDNA sources derived from a mistletoe.

Combined analysis of inorganic elements and flavonoid metabolites reveals the relationship between flower quality and maturity of Sophora japonica L

Flos Sophorae (FS), or the dried flower buds of Sophora japonica L., is widely used as a food and medicinal material in China. The quality of S. japonica flowers varies with the developmental stages (S1-S5) of the plant. However, the relationship between FS quality and maturity remains unclear. Inductively coupled plasma optical emission spectrometry (ICP-OES) and ultra-high performance liquid chromatography coupled with electrospray ionization-triple quadrupole-linear ion trap mass spectrometry (UPLC-ESI-Q TRAP-MS/MS) were used to analyze inorganic elements and flavonoid metabolites, respectively. A combined analysis of the inorganic elements and flavonoid metabolites in FS was conducted to determine the patterns of FS quality formation. Sixteen inorganic elements and 173 flavonoid metabolites that accumulated at different developmental stages were identified. Notably, 54 flavonoid metabolites associated with the amelioration of major human diseases were identified, and Ca, P, K, Fe, and Cu were postulated to influence flavonoid metabolism and synthesis. This study offers a novel perspective and foundation for the further exploration of the rules governing the quality of plant materials.

Physiological and biochemical mechanisms of grain yield loss in fumitory (Fumaria parviflora Lam.) exposed to copper and drought stress

Soil contamination with heavy metals adversely affects plants growth, development and metabolism in many parts of the world including arid and semi-arid regions. The aim of this study was to investigate the single and combined effects of drought and copper (Cu) stresses on seed yield, and biochemical traits of Fumaria parviflora in a split - factorial experiment at Research Field of Payam-E-Noor university of Kerman during 2019. The collected seeds from two Cu contaminated regions were evaluated under drought and Cu (0, 50, 150, 300, and 400 mg/kg) stresses. Drought stress levels were depletion of 50% (D1), 70% (D2) and 85% (D3) soil available water. The individual effects of drought and copper stresses were similar to each other as both reduced seed yield. The highest seed yield was observed at Cu concentration of 50 mg/kg under non-drought stress conditions. The maximum values of malondialdehyde (0.47 µmol/g), proline (2.45 µmol/g FW), total phenolics (188.99 mg GAE/g DW) and total flavonoids (22.1 mg QE/g DW) were observed at 400 mg/kg Cu treatment. However, the strongest antioxidant activity (83.95%) through DPPH assay, and the highest total soluble carbohydrate (115.23 mg/g DW) content were observed at 300 and 150 mg/kg Cu concentration under severe drought stress, respectively. The highest amount of anthocyanin (2.18 µmol/g FW) was observed at 300 mg/kg Cu and moderate drought stress. The findings of this study showed a high tolerance of F. parviflora plant to moderate drought stress and Cu exposure up to 150 mg/kg by modulating defense mechanisms, where grain yield was slightly lower than that of control. The results could also provide a criterion for the selection of tolerance species like F. parviflora for better acclimatization under Cu mines and/or agricultural contaminated soils subjected to drought stress.

Biochemical Responses to the Long-Term Impact of Copper Sulfate (CuSO4) in Tobacco Plants

Metabolic changes under stress are often studied in short-term experiments, revealing rapid responses in gene expression, enzyme activity, and the amount of antioxidants. In a long-term experiment, it is possible to identify adaptive changes in both primary and secondary metabolism. In this study, we characterized the physiological state of tobacco plants and assessed the amount and spectrum of phenolic compounds and the lignification of axial organs under excess copper stress in a long-term experiment (40 days). Plants were treated with 100 and 300 μM CuSO4, as well as a control (Knop solution). Copper accumulation, the size and anatomical structure of organs, stress markers, and the activity of antioxidant enzymes were studied. Lignin content was determined with the cysteine-assisted sulfuric method (CASA), and the metabolite profile and phenolic spectrum were determined with UHPLC-MS and thin-layer chromatography (TLC). Cu2+ mainly accumulated in the roots and, to a lesser extent, in the shoots. Copper sulfate (100 μM) slightly stimulated stem and leaf growth. A higher concentration (300 μM) caused oxidative stress; H2O2 content, superoxide dismutase (SOD), and guaiacol peroxidase (GPOX) activity increased in roots, and malondialdehyde (MDA) increased in all organs. The deposition of lignin increased in the roots and stems compared with the control. The content of free phenolics, which could be used as substrates for lignification, declined. The proportions of ferulic, cinnamic, and p-coumaric acids in the hydrolysate of bound phenolics were higher, and they tended toward additional lignification. The metabolic profile changed in both roots and stems at both concentrations, and changed in leaves only at a concentration of 300 μM. Thus, changes in the phenolic spectrum and the enhanced lignification of cell walls in the metaxylem of axial (root and stem) organs in tobacco can be considered important metabolic responses to stress caused by excess CuSO4.

Leaf proteomic profiles in cacao scion-rootstock combinations tolerant and intolerant to cadmium toxicity

Cd contamination in cacao beans is one of the major problems faced by cocoa producing countries in Latin America. Cacao scion-rootstock combinations influence the Cd accumulation in the shoot of the plant. The objective of this work was to carry out a comparative analysis between cacao scion rootstock combinations (CCN 51/BN 34, CCN 51/PS 13.19, CCN 51/PH 16 and CCN 51/CCN 51), contrasting for tolerance to cadmium (Cd) toxicity, by means of leaf proteomic profiles, in order to elucidate molecular mechanisms involved in tolerance to Cd toxicity. Cacao scion-rootstock combinations were grown in soil with 150 mg Cd kg-1 soil, together with the control treatment. Leaf samples were collected 96 h after treatments were applied. There were alterations in the leaf proteome of the cacao scion-rootstock combinations, whose molecular responses to Cd toxicity varied depending on the combination. Leaf proteomic analyzes provided important information regarding the molecular mechanisms involved in the tolerance and intolerance of cacao scion-rootstock combinations to Cd toxicity. Enzymatic and non-enzymatic antioxidant systems, efficient for eliminating ROS, especially the expressions of APX and SOD, in addition to the increase in the abundance of metalloproteins, such as ferredoxins, rubredoxin, ALMT, Trx-1 and ABC-transporter were key mechanisms used in the Cd detoxification in cacao scion-rootstock combinations tolerant to Cd toxicity. Carboxylic acid metabolism, glucose activation and signal transduction were also important processes in the responses of cacao scion-rootstock combinations to Cd toxicity. The results confirmed CCN 51/BN 34 as a cacao scion-rootstock combination efficient in tolerance to Cd toxicity.

Heavy Metals, Their Phytotoxicity, and the Role of Phenolic Antioxidants in Plant Stress Responses with Focus on Cadmium: Review

The current state of heavy metal (HM) environmental pollution problems was considered in the review: the effects of HMs on the vital activity of plants and the functioning of their antioxidant system, including phenolic antioxidants. The latter performs an important function in the distribution and binding of metals, as well as HM detoxification in the plant organism. Much attention was focused on cadmium (Cd) ions as one of the most toxic elements for plants. The data on the accumulation of HMs, including Cd in the soil, the entry into plants, and the effect on their various physiological and biochemical processes (photosynthesis, respiration, transpiration, and water regime) were analyzed. Some aspects of HMs, including Cd, inactivation in plant tissues, and cell compartments, are considered, as well as the functioning of various metabolic pathways at the stage of the stress reaction of plant cells under the action of pollutants. The data on the effect of HMs on the antioxidant system of plants, the accumulation of low molecular weight phenolic bioantioxidants, and their role as ligand inactivators were summarized. The issues of polyphenol biosynthesis regulation under cadmium stress were considered. Understanding the physiological and biochemical role of low molecular antioxidants of phenolic nature under metal-induced stress is important in assessing the effect/aftereffect of Cd on various plant objects-the producers of these secondary metabolites are widely used for the health saving of the world's population. This review reflects the latest achievements in the field of studying the influence of HMs, including Cd, on various physiological and biochemical processes of the plant organism and enriches our knowledge about the multifunctional role of polyphenols, as one of the most common secondary metabolites, in the formation of plant resistance and adaptation.

Copper stress-induced phytotoxicity associated with photosynthetic characteristics and lignin metabolism in wheat seedlings

Copper (Cu) pollution is one of environmental problems that adversely affects the growth and development of plants. However, knowledge of lignin metabolism associated with Cu-induced phytotoxicity mechanism is insufficient. The objective of this study was to reveal the mechanisms underlying Cu-induced phytotoxicity by evaluating changes in the photosynthetic characteristics and lignin metabolism in the seedlings of wheat cultivar 'Longchun 30'. Treatment with varying concentrations of Cu clearly retarded seedling growth, as demonstrated by a reduction in the growth parameters. Cu exposure reduced the photosynthetic pigment content, gas exchange parameters, and chlorophyll fluorescence parameters, including the maximum photosynthetic efficiency, potential efficiency of photosystem II (PS II), photochemical efficiency of PS II in light, photochemical quenching, actual photochemical efficiency, quantum yield of PS II electron transport, and electron transport rate, but notably increased the nonphotochemical quenching and quantum yield of regulatory energy dissipation. Additionally, a significant increase was observed in the amount of cell wall lignin in wheat leaves and roots under Cu exposure. This increase was positively associated with the up-regulation of enzymes related to lignin synthesis, such as phenylalanine ammonia-lyase, 4-coumarate:CoA ligase, cinnamyl alcohol dehydrogenase, laccase, cell wall bound (CW-bound) guaiacol peroxidase, and CW-bound conifer alcohol peroxidase, and TaPAL, Ta4CL, TaCAD, and TaLAC expression. Correlation analysis revealed that lignin levels in the cell wall were negatively correlated with the growth of wheat leaves and roots. Taken together, Cu exposure inhibited photosynthesis in wheat seedlings, resulting from a reduction in photosynthetic pigment content, light energy conversion, and photosynthetic electron transport in the leaves of Cu-stressed seedlings, and the Cu-inhibitory effect on seedling growth was related to the inhibition of photosynthesis and an increase in cell wall lignification.

Bioaccumulation of industrial heavy metals and interactive biochemical effects on two tropical medicinal plant species

Concentrations of heavy metals (Cr, Cu, Fe, Mn, Ni, Pb, and Zn) accumulation were studied in the leaves of two medicinal plant species, namely Holarrhena pubescens and Wrightia tinctoria, from two industrial areas and a control area. Our comparison study revealed that industrialization significantly increased the accumulation of heavy metals in both plant species. A comparison study in control and industrial areas exhibited that heavy metal accumulation was higher in the industrially affected area than in the control area. Heavy metal concentration exceeded the permissible limit recommended by the WHO in both species of two industrial areas. However, both species accumulated the least heavy metal concentration in the control area. Biochemical investigation specifies that in response to heavy metal accumulation, both species increased the activity of hydrogen peroxide (H₂O₂), malondialdehyde content, the activity of enzymatic (superoxide dismutase and peroxidase) and nonenzymatic (ascorbic acid) antioxidant, but decreased the primary (soluble carbohydrate and total protein), secondary metabolites (phenol and flavonoid) content and free radical scavenging (DPPH) activity. This study indicates that industrialization potentially harms medicinal plants by reducing the efficacy of their medicinal property.

Effect of Heavy Metal Stress on Phenolic Compounds Accumulation in Winter Wheat Plants

Heavy metal stress can lead to many adverse effects that inhibit cellular processes at various levels of metabolism, causing a decrease in plant productivity. In response to environmental stressors, phenolic compounds fulfill significant molecular and biochemical functions in plants. Increasing the biosynthesis of phenolic compounds in plants subjected to heavy metal stress helps protect plants from oxidative stress. A pot experiment was carried out to determine the effect of the accumulation of copper (Cu) and lead (Pb) salts at concentrations of 200, 500, and 1000 ppm on seed germination, the activity of enzymes in the phenylalanine ammonia-lyase pathway (PAL) and tyrosine ammonia-lyase (TAL), along with the total phenol and flavonoid contents in seedlings of hybrid Triticum aestivum L. (winter wheat) cultivars. The accumulation of heavy metals, especially Cu, had a negative impact on the seed germination process. The cultivar "Hyacinth" reacted most strongly to heavy metal stress, which was confirmed by obtaining the lowest values of the germination parameters. Heavy metal stress caused an increase in the activity of PAL and TAL enzymes and an increase in the accumulation of phenolic compounds. Under the influence of Cu, the highest activity was shown in cv. "Hyvento" (especially at 200 ppm) and, due to the accumulation of Pb, in cv. "Hyacinth" (1000 ppm) and cv. "Hyking" (200 ppm). The cultivar "Hyking" had the highest content of phenolic compounds, which did not increase with the application of higher concentrations of metals. In other cultivars, the highest content of total phenols and flavonoids was usually observed at the lowest concentration (200 ppm) of the tested heavy metals, Cu and Pb.

Relationship between suppression of plant defence systems by Meloidogyne javanica with the distance of different parts of the plant from the nematode establishment site

Suppression of plant defence systems by plant-parasitic nematodes is an important aspect of research on resistance induction in plants. The present work aimed to address the question of whether this suppressive ability by nematodes can be spread systemically and equally to other parts of the plant. The root-knot nematode, Meloidogyne javanica, and the host plant, tomato, was used with salicylic acid (SA) as a potent inducer of the plant defence systems. SA was sprayed on the second and fifth leaves, as near and far from the nematode establishment site, respectively. The results of hydrogen peroxide and phenylalanine ammonia lyase enzyme evaluation in the root (site of nematode establishment), crown, second and fifth leaves showed that, firstly, the amount of defence compounds induced by SA in the leaves was not equal in all parts of the plant and gradually decreased from the aerial parts (treatment site) towards the roots. Furthermore, the synthesis and accumulation of the evaluated compounds in the younger parts of the plant (fifth leaf) was more than the older parts (second leaf), and the crown and root. Although the suppression of the plant defence systems by the nematode was transferred to other parts of the plant, the amount of this suppression gradually decreased in the parts farthest from the site of the nematode establishment. Based on the results, it is inferred that the success of a resistance induction strategy in plant disease management depends on the type of pathogen, type of inducer, place of application of the inducer on the plant and the induction area.

Identification of Key Genes during Ethylene-Induced Adventitious Root Development in Cucumber (Cucumis sativus L.)

Ethylene (ETH), as a key plant hormone, plays critical roles in various processes of plant growth and development. ETH has been reported to induce adventitious rooting. Moreover, our previous studies have shown that exogenous ETH may induce plant adventitious root development in cucumber (Cucumis sativus L.). However, the key genes involved in this process are still unclear. To explore the key genes in ETH-induced adventitious root development, we employed a transcriptome technique and revealed 1415 differentially expressed genes (DEGs), with 687 DEGs up-regulated and 728 DEGs down-regulated. Using Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, we further identified critical pathways that were involved in ETH-induced adventitious root development, including carbon metabolism (starch and sucrose metabolism, glycolysis/gluconeogenesis, citrate cycle (TCA cycle), oxidative phosphorylation, fatty acid biosynthesis, and fatty acid degradation), secondary metabolism (phenylalanine metabolism and flavonoid biosynthesis) and plant hormone signal transduction. In carbon metabolism, ETH reduced the content of sucrose, glucose, starch, the activity of sucrose synthase (SS), sucrose–phosphate synthase (SPS) and hexokinase (HK), and the expressions of CsHK2, pyruvate kinase2 (CsPK2), and CsCYP86A1, whereas it enhanced the expressions of β-amylase 1 (CsBAM1) and β-amylase 3 (CsBAM3). In secondary metabolism, the transcript levels of phenylalanine ammonia-lyase (CsPAL) and flavonoid 3′-monooxygenase (CsF3′M) were negatively regulated, and that of primary-amine oxidase (CsPAO) was positively regulated by ETH. Additionally, the indole-3-acetic acid (IAA) content and the expressions of auxin and ETH signaling transduction-related genes (auxin transporter-like protein 5 (CsLAX5), CsGH3.17, CsSUAR50, and CsERS) were suppressed, whereas the abscisic acid (ABA) content and the expressions of ABA and BR signaling transduction-related genes (CsPYL1, CsPYL5, CsPYL8, BRI1-associated kinase 1 (CsBAK1), and CsXTH3) were promoted by ETH. Furthermore, the mRNA levels of these genes were confirmed by real-time PCR (RT-qPCR). These results indicate that genes related to carbon metabolism, secondary metabolite biosynthesis, and plant hormone signaling transduction are involved in ETH-induced adventitious root development. This work identified the key pathways and genes in ETH-induced adventitious rooting in cucumber, which may provide new insights into ETH-induced adventitious root development and will be useful for investigating the molecular roles of key genes in this process in further studies.

Silicon and nitric oxide synergistically modulate the production of essential oil and rosmarinic acid in Salvia officinalis under Cu stress

The individual impact of silicon (Si) and nitric oxide (NO) on secondary metabolism in several plant species has been reported, but their combined effect has never been evaluated yet. Therefore, in this study, single and combined impacts of NO and Si on the biosynthesis of rosmarinic acid (RA) and essential oil (EO) content in leaves of Salvia officinalis were investigated under both non-stress and Cu stress conditions. The results indicated that high Cu concentration decreased biomass and the content of polyphenols, but elevated electrolyte leakage, while lower Cu concentrations, especially 200 μM Cu, increased the content of polyphenols, EO, and antioxidant capacity in leaves of S. officinalis. The foliar application of sodium silicate (1 mM Si) and sodium nitroprusside (200 μM SNP as a NO donor) alone and particularly in combination improved shoot dry biomass, restored chlorophyll and carotenoids, increased EO content, the amounts of flavonoids, and phenolic compounds especially RA, and enhanced antioxidant capacity in the leaves of S. officinalis under both non-stress and Cu stress conditions. Copper treatment increased NO content, upregulated expression of PAL, TAT, and RAS genes, and enhanced phenylalanine ammonia-lyase activity in the leaves, which were responsible for improving the production of phenolic compounds, particularly rosmarinic acid. Foliar spraying with Si and SNP intensified these attributes. All responses were more pronounced when NO and Si were simultaneously applied under Cu stress. These findings suggest that NO and Si synergistically modulate secondary metabolism through upregulation of related gene expression and enzyme activities under both non-stress and Cu stress conditions.

The ability of Meloidogyne javanica to suppress salicylic acid-induced plant defence responses

Suppression of the defence system of plants by some plant pathogens is an important mechanism of their parasitism, and plant-parasitic nematodes use several mechanisms to affect different parts of the plant defence system. This study was designed to investigate the ability of a root-knot nematode, Meloidogyne javanica, to reduce or suppress the plant (tomato) immune system, before or after activation by a strong inducer, salicylic acid (SA). The experimental treatments were tomato plants inoculated with nematodes alone, plants pre-treated with SA and then nematodes (‘SA then nematode’), plants treated with SA after nematode inoculation (‘nematode then SA’), plants treated with SA alone, and plants treated with sterile distilled water. The results showed that treatment of the plants with SA before or after nematode infection reduced nematode disease indices compared to the control (nematode alone). The number of eggs per individual egg mass, in ‘nematode then SA’ treatment was significantly greater than the control, which shows the effect of nematodes on reducing the plant defence mechanism in this treatment. Evaluation of the activity of some defence enzymes such as chitinase, protease, phenylalanine ammonia lyase, catalase and density of hydrogen peroxide also showed that M. javanica is able to suppress these compounds in the ‘SA then nematode’ treatment, and to a greater extent in the ‘nematode then SA’ treatment. Suppression of plant defence responses by phytonematodes is of great importance in their synergistic relationship with secondary pathogens and plants.

RESPUESTAS TEMPRANAS EN SIMPLASTO DE TALLO ASOCIADAS A LA RUTA DEL ÁCIDO SALICÍLICO EN LA INTERACCIÓN CLAVEL (Dianthus caryophyllus, caryophyllaceae)- FOD (Fusarium oxysporum f. sp. dianthi)

El marchitamiento vascular causado por Fusarium oxysporum f. sp. dianthi (Fod) es la enfermedad que más afecta el cultivo de clavel. Comprender la naturaleza de la interacción entre la planta y el patógeno permitirá el futuro desarrollo de nuevas alternativas de control de la enfermedad. Es por ello que se busca tener evidencia experimental que permita entender el papel de la ruta de señalización del ácido salicílico (SA) y enzimas asociadas con la resistencia de la planta como son fenilalanina amonio liasa (PAL), polifenoloxidasa (PFO), guayacol peroxidasa (GPX) y fosfolipasa D (PLD), a nivel del simplasto del tallo durante la interacción con él patógeno. Se estableció un ensayo in vivo utilizando dos variedades de clavel con diferentes niveles de resistencia a la enfermedad y se determinaron en simplasto de tallo los niveles de SA, MeSA (salicilato de metilo) y las enzimas objeto de estudio. Se presentó inducción de las enzimas estudiadas, evidenciando en el caso de la enzima GPX un aumento a nivel transcripcional. Así mismo, se presentó un incremento de MeSA en los 1 y 14 dpi, mientras que SA se acumuló en tiempos tardíos. La correlación de Pearson determinó que a este nivel existe una acumulación de la hormona MeSA al 1 dpi con los niveles de las enzimas GPX y PLD. Se propone que la respuesta en este órgano de clavel puede estar activada por la ruta de señalización que involucra SA, afectando el metabolismo secundario y la regulación de especies reactivas de oxígeno.

Dopamine Alleviates Hydrocarbon Stress in Brassica oleracea through Modulation of Physio-Biochemical Attributes and Antioxidant Defense Systems

Hydrocarbon stress has become one of the most restrictive factors for crop choice and productivity in most parts of the world. Dopamine (DA) has positively influenced the metabolic, physiological and biochemical activities besides the growth of plants under numerous abiotic stress conditions. The current study was performed to analyze the potential of DA to alleviate hydrocarbon stress and improve growth of Brassica oleracea plants. Hydrocarbon stress in plants was induced by growing in 5% and 10% crude oil contaminated soil. Crude oil stressed plants exhibited reduced growth besides decreased level of photosynthetic pigments and gas exchange attributes. Moreover, oil stressed plants showed elevated level of hydrogen peroxide (H₂O₂), electrolyte leakage (EL), malondialdehyde (MDA) and superoxide radical (O^2-). However, exogenous application of 50, 100 and 200 μmol L^-1 DA improved photosynthesis, shoot and root dry weight of B. oleracea seedlings growing in hydrocarbon amended soil. Additionally, DA100 treatments improved non-enzymatic and enzymatic antioxidants of treated seedlings. Our results demonstrate that increased gas exchange attributes, modulation of osmoregulators and improved activity of the antioxidative enzymes alleviated hydrocarbon stress in DA supplemented B. oleracea plants. Consequently, the first time observed ameliorative role of DA in hydrocarbon stress opens a new arena for application of this dynamic biomolecule for sustainable crop production.

The effect of EDTA and citric acid on biochemical processes and changes in phenolic compounds profile of okra (Abelmoschus esculentus L.) under mercury stress

The present study aimed to explore the effect of synthetic and naturally occurring chelators, EDTA and citric acid (CA), respectively, on changes in physiological and biochemical factors including cell death, level of mercury ions accumulation, malondialdehyde (MDA) content, total phenol and total flavonoids, anthocyanins and DPPH free radical scavenging activity, in the leaves of okra (Abelmoschus esculentus L.) plants exposed to mercury stress. In addition, polyphenolic compounds profile was assessed by high-performance liquid chromatography. The okras were planted in completely controlled hydroponic conditions (Hoagland solution). After they reached the four-leaf stage, they were treated simultaneously with different concentrations of HgCl₂, EDTA and CA chelators, and their combination for one month. At the stage of maturity, the physiological and biochemical factors of the plant leaves were measured. The results showed that with the application of higher concentration of HgCl₂, cell death, level of shoot and root Hg²⁺ content and root MDA, total phenols and total flavonoids, anthocyanin content, and DPPH free radical scavenging activity were increased. Also, the results indicated that okra plants have high biomass and a high rate of Hg mobilization and accumulation in the shoot versus the roots (TF=2.152 for the plants treated with 60 mg L^-1 Hg²⁺), hence, can be considered as Hg hyperaccumulator plant for the phytoremediation of Hg-polluted soils and waters. In the Hg-treated plants changes in their phenolic profile were induced, and the increase of chlorogenic acid, rosmaric acid, apigenin, quercetin and rutin content was observed. The application of EDTA and CA improved the toxic effects of Hg²⁺, by modifying phenolic compounds, chelating Hg²⁺, and its proper compartmentation, while EDTA outperformed CA in this respect. Based on the results, it could be concluded that due to the high biomass and growth of okra in the presence of Hg²⁺, this plant is suitable for phytoremediation of soil and water contaminated with mercury. In addition, EDTA and CA can play a significant role in removing this toxic metal through transferring it from the culture medium to the plant.

Transcriptome divergence between developmental senescence and premature senescence in Nicotiana tabacum L

Senescence is a degenerative process triggered by intricate and coordinated regulatory networks, and the mechanisms of age-dependent senescence and stress-induced premature senescence still remain largely elusive. Thus we selected leaf samples of developmental senescence (DS) and premature senescence (PS) to reveal the regulatory divergence. Senescent leaves were confirmed by yellowing symptom and physiological measurement. A total of 1171 and 309 genes (DEGs) were significantly expressed respectively in the whole process of DS and PS. Up-regulated DEGs in PS were mostly related to ion transport, while the down-regulated DEGs were mainly associated with oxidoreductase activity and sesquiterpenoid and triterpenoid biosynthesis. In DS, photosynthesis, precursor metabolites and energy, protein processing in endoplasmic reticulum, flavonoid biosynthesis were notable. Moreover, we found the vital pathways shared by DS and PS, of which the DEGs were analyzed further via protein-protein interaction (PPI) network analysis to explore the alteration responding to two types of senescence. In addition, plant hormone transduction pathway was mapped by related DEGs, suggesting that ABA and ethylene signaling played pivotal roles in formulating the distinction of DS and PS. Finally, we conducted a model containing oxidative stress and ABA signaling as two hub points, which highlighted the major difference and predicted the possible mechanism under DS and PS. This work gained new insight into molecular divergence of developmental senescence and premature senescence and would provide reference on potential mechanism initiating and motivating senescence for further study.

Characterization of physiochemical and anatomical features associated with enhanced phytostabilization of copper in Bruguiera cylindrica (L.) Blume

Copper is an essential micronutrient for normal plant metabolism and it is involved in number of physiological processes in plants but at the same time, at concentrations above threshold level, it acts as a potential stress factor. In this study, the phytoremediation potential of Bruguiera cylindrica (L.) Blume with respect to Cu was evaluated for the first time. Various physiochemical and anatomical parameters were analyzed in three-month-old healthy plantlets of B. cylindrica on exposure to different concentrations of CuSO₄ (0, 0.05, 0.15, and 0.25 mM)for 20 d. Higher uptake and accumulation of Cu in the roots indicates that the roots are the primary site of Cu accumulation and thus the plant perform as an excluder. Tolerance index values (TI > 60) reveals the phytoremediation potential of this plant. Metabolites are accumulated in plants to cope up with the oxidative damage due to Cu stress. Increased rate of proline and free amino acids content and soluble sugar content especially in leaves of B. cylindrica subjected to CuSO₄ contributes toward higher osmolality so as to counter the reduced water transport from roots. Nonenzymatic antioxidants like ascorbic acid, glutathione, and phenolics are the ROS scavenging compounds in the Defense system of B. cylindrica toward higher concentrations of CuSO₄, and of these, phenolics accumulation plays greater role in the antioxidative function in B. cylindrica in response to Cu stress. The histochemistry of B. cylindrica revealed the prominent occurrence of star-shaped calcium oxalate crystals when exposed to 0.25 mM CuSO₄, and it seems to be a prominent defense mechanism under Cu stress. Also a remarkable finding was the accumulation of Cu in the xylem vessels of plants on exposure of 0.25 mM CuSO₄ as compared to control. The infrared spectra were analyzed to compare the functional groups in the phenolics and carbohydrate constituents of control and CuSO₄-treated B. cylindrica plantlets and it indicated that carboxyl and hydroxyl groups are involved in the Cu binding so as to achieve tolerance to Cu. Thus this study revealed the potential role of B. cylindrica as a promising candidate for phytostabilization of copper.

Influence of Monometallic and Bimetallic Phytonanoparticles on Physiological Status of Mezquite

The present study was conducted to evaluate the impact of monometallic and bimetallic nanoparticles (NPs) of copper (Cu) and silver (Ag) from Justicia spicigera on the photochemical efficiency and phenol pattern of Prosopis glandulosa. In this study, the existence of localized surface plasmon resonance absorption associated with the nano-sized nature of Ag, Cu and Cu/Ag particles was confirmed by the presence of a single peak around 487, 585, and 487/580 nm respectively. Zeta potential and electrophoretic mobility were found to be 0.2 mV and 0.02 μmcm/(Vs) for synthesized NPs indicating less stability and thus tendency to agglomerate, and broad distribution of particles. Cu-NPs and Cu/Ag-NPs demonstrate that the dispersed phase is stable and has a minimum particle size at zeta potentials above -30 mV. Changes in phenolic compounds, total chlorophyll, and photochemical efficiency in leaves exposed to Ag, Cu and Cu/Ag phyto-nanoparticles were evaluated up to 72 hours. The results revealed that Ag-NP and Cu-NP from J. spicigera at 100 mg/L showed significant reduction in chlorophyll, epidermal polyphenol content and photochemical efficiency of P. glandulosa. In contrast, the application of bimetallic Cu/Ag-NP from J. spicigera showed a positive impact on physiological parameters of P. glandulosa after 72 h of exposure.