POX Activity Research Articles

Physiological and biochemical responses of seedlings of six contrasting barley (Hordeum vulgare L.) cultivars grown under salt-stressed conditions

Salinity stress affects plant growth and development and underlying metabolisms. To mitigate the effects of the stress, plants responded by changing their physiological and biochemical activities and withstand the stress. The present study aimed to determine barley's (Hordeum vulgare L.) physiological and biochemical response to salinity stress conditions for 7 days and 14 days. Six barley cultivars (Alfa93, DWRB73, DL88, NB1, NB3, NDB1173) were grown under controlled conditions, and different level of salinity stress was applied. In addition, seedling growth, physiological and biochemical parameters, plant leaves RWC, and electrolyte leakage were analyzed. The overall seedling growth, RWC, and electrolyte leakage in salt susceptible lines Alfa93 and DWRB73 were low than the salt-tolerant barley lines (DL88, NB1, NB3, and NDB1173). Electrolyte leakage was 26.0 and 20.6% in Alfa93 and DWRB73, whereas it was 17.6, 14.6, 15.3, and 10.4% in DL88, NB1, NB3, and NDB1173, respectively at 300 mM salinity stress. The loss of photosynthetic pigments under salt stress was high in susceptible lines, salinity treated (300 mM NaCl) Alfa93 plants exhibit 49.5% and 59.5% of Chl-a than control plants after 7 and 14 days of treatment, respectively. However, at 300 mM stress level, NB1 (ST) showed less Chl-a loss after 7 days, whereas NDB1173 showed less reduction in Chl-a after 14 days. Antioxidant enzymes such as SOD, POX, CAT, and APX activities in susceptible line Alfa93 and DWRB73 were lower than tolerant lines. PCA analysis demonstrated a positive correlation between antioxidant enzyme activities and genotypes under salinity stress. PCA analysis described DL88 as the most tolerant, and DWRB73 was the most salt susceptible genotype among the studied barley genotypes. The present findings suggest that barley cultivars' physiological and biochemical activities under salinity stress conditions may be used to screen salt-tolerant crops.

The Effect of Plasma Activated Water on Maize (Zea mays L.) under Arsenic Stress.

Plasma activated water (PAW) is a source of various chemical species useful for plant growth, development, and stress response. In the present study, PAW was generated by a transient spark discharge (TS) operated in ambient air and used on maize corns and seedlings in the 3 day paper rolls cultivation followed by 10 day hydroponics cultivation. For 3 day cultivation, two pre-treatments were established, “priming PAW” and “rolls PAW”, with corns imbibed for 6 h in the PAW and then watered daily by fresh water and PAW, respectively. The roots and the shoot were then analyzed for guaiacol peroxidase (G-POX, POX) activity, root tissues for their lignification, and root cell walls for in situ POX activity. To evaluate the potential of PAW in the alleviation abiotic stress, ten randomly selected seedlings were hydroponically cultivated for the following 10 days in 0.5 Hoagland nutrient solutions with and without 150 μM As. The seedlings were then analyzed for POX and catalase (CAT) activities after As treatment, their leaves for photosynthetic pigments concentration, and leaves and roots for As concentration. The PAW improved the growth of the 3 day-old seedlings in terms of the root and the shoot length, while roots revealed accelerated endodermal development. After the following 10 day cultivation, roots from PAW pre-treatment were shorter and thinner but more branched than the control roots. The PAW also enhanced the POX activity immediately after the imbibition and in the 3 day old roots. After 10 day hydroponic cultivation, antioxidant response depended on the PAW pre-treatment. CAT activity was higher in As treatments compared to the corresponding PAW treatments, while POX activity was not obvious, and its elevated activity was found only in the priming PAW treatment. The PAW pre-treatment protected chlorophylls in the following treatments combined with As, while carotenoids increased in treatments despite PAW pre-treatment. Finally, the accumulation of As in the roots was not affected by PAW pre-treatment but increased in the leaves.

Physiological and biochemical responses of Kinnow mandarin (Citrus nobilis × Citrus deliciosa) to EMS induced mutagenesis

The present study was carried out to enhance the genetic variability in Kinnow mandarin (Citrus nobilis Loureiro Physiological and biochemical responses of Kinnow mandarin (Citrus nobilis × Citrus deliciosa) to EMS induced mutagenesis Citrus deliciosa Tenora) using ethyl methanesulfonate (EMS) during 2016-17 and 2017-18. Plants created with different doses of EMS concentration, viz. 0.05%, 0.1%, 0.2% and 0.5% were examined for the various physiological and biochemical alterations in putative mutants aged six years and compared with the wild type (WT). A dose-dependent decrease in leaf area was recorded in the mutants with increasing doses of EMS concentration and as compared to WT, maximum reduction of 135.52 and 104.92% was witnessed in the mutants E-19 and E-17 developed from 0.5% EMS, whereas the leaves were more succulent in E-16. Chlorophyll a content was higher than chlorophyll b in the mutated population. As compared to WT, maximum decrease in chlorophyll a, total chlorophyll was noticed in the mutants E-19 generated from 0.5% EMS. Contrary to the physiological alterations, the total phenol, proline and total protein content in the mutants were upregulated by nearly two fold in the mutants developed beyond 0.1% EMS. Significant increase was also noticed in the antioxidant enzymes SOD, CAT, POX and GR activity in the mutants E-16 to E-20 induced from 0.5% EMS. The variation in traits of interest observed in the present study such as better leaf succulency and upregulated antioxidant enzyme activity in the mutant E-16 (0.5% EMS) suggests that the developed mutant could be utilised in Kinnow improvement for abiotic stress tolerance.

Comparative study of peripheral blood cells in two marine fishes (Synechogobius hasta and Sebastes schlegelii): Morphological and cytochemical characterization

The morphology, cell size and relative number of peripheral blood cells in two teleosts, Synechogobius hasta and Sebastes schlegelii, were compared using different staining methods. The results showed significant differences in cell size. The percentage of monocytes in S. hasta was greater than that in S. schlegelii (P < 0.01); however, the opposite results were obtained in the percentage of lymphocytes and thrombocytes. The two fishes shared common cytochemical-staining results, which showed that both erythrocytes were negative for all cytochemical staining; monocytes were strongly positive for PAS and positive for SBB and NAE; lymphocytes were negative for SBB, POX and NAE; neutrophils were positive for SBB and NAE; and thrombocytes were negative for SBB, ALP, POX and NAE. However, species specificity existed in the cytochemical properties. For S. hasta, monocytes were strongly positive for ALP and ACP; lymphocytes were strongly positive for ALP and weakly positive for ACP; neutrophils were strongly positive for ACP and POX; and thrombocytes were weakly positive for PAS and positive for ACP. Unlike S. hasta, monocytes were strongly positive for ACP and positive for ALP in S. schlegelii; lymphocytes were positive for ALP and partially positive for PAS; neutrophils were positive for ACP and POX; and thrombocytes were negative for PAS and ACP. The POX activity of monocytes in S. hasta was greater than that in S. schlegelii (P < 0.05), while the POX activity of neutrophils and the NAE activity of monocytes in S. hasta were significantly greater than those in S. schlegelii (P < 0.01). The results of this study can be used as a reference for the construction of haematological parameters in S. hasta and S. schlegelii for the assessment of fish health and can provide a research basis for fish diseases and immunity.

Response of physiological traits, antioxidant enzymes and nutrient uptake of soybean to Azotobacter Chroococcum and zinc sulfate under salinity

Globally, one of the key restrictions on agricultural production is salinity and its impact is expected to increase. As a result, it is necessary to improve crop salinity tolerance. One promising approach is the use of plant nutrition technologies such as the application of zinc sulfate (Zn) and Azotobacter chroococcum (Az) which may improve plant survival under environmental stresses. A greenhouse experiment was conducted with three replications and included four levels of salinity (0, 40, 60 and 80 mM NaCl) in combination with four treatments [control, 2 mM zinc sulfate foliar application (Zn), inoculation with Azotobacter chroococcum (Az) and co-application of Az and Zn (Az+Zn)]. The results indicate that exposure to salinity increased soybean contents of anthocyanin, malondialdehyde (MDA), osmolytes, sodium ion (Na+), and the activities of antioxidant enzymes However, the amount of chlorophyll and carotenoid, relative water content (RWC), maximum quantum yield of photosystem II (PSII; Fv/Fm), membrane stability index (MSI), and ion contents decreased. Application of Zn and inoculation with Az enhanced the chlorophyll (a, b and a+b), carotenoid, RWC, Fv/Fm, MSI, anthocyanin, osmolytes, N, K+, P contents, and K+/Na+; the activities of CAT, SOD, POX, and APX as well as MDA and Na+ contents were reduced. Overall our results reveal that combined Zn and Az application was the most effective treatment for alleviating the negative effects of salinity stress in soybean.

STUDY OF KINETIN TRAETMENT ON GROWTH AND ACTIVITY OF SOME ANTIOXIDANT ENZYMES OF SPINACH UNDER SALT STRESS

Soil salinity reduces water availability of plant roots via negative (low) osmosis potential, as well as decrease of germination dynamics of plant seeds by ionic toxicity of Na and Cl, Significant differences in fruit-set, yield, photosynthetic rates, stomatal conductance, total chlorophyll content, proline, In general, salinity affects almost every aspect of the physiology and biochemistry of plants. This experiment was conducted on a private farm in Babylon Governorate at the period from 1/10/ 2013 to 15/5/ 2014, to study the effect of Kinetin treatment with three concentrations (0, 20 &amp; 40 mg /liter ) and the quality of irrigation water in three levels ( 1.3 , 5 &amp; 10) dS.m-1 the water salinity increased the POX and CAT activity, sodium and proline contents in leaves, resulting in decreased growth and leaf contents of NPK, The Kinetin applications alleviated negative effects of saline water by increasing dry weights of roots and NPK contents in leaves with an increasing of POX and CAT activity, and reduction of sodium contents in leaves.

Evaluation of the Potential Role of Bacillus altitudinis MT422188 in Nickel Bioremediation from Contaminated Industrial Effluents

The incessant pervasiveness of heavy metals in the environment is one of the precursory factors of pollution. This research study was endeavored upon to investigate the bioremediation potential of a nickel (Ni)-resistant bacterial isolate, identified as Bacillus altitudinis MT422188, whose optimum growth parameters were demonstrated at pH 7, temperature 32 °C, and 1 mM phosphate. Minimal Inhibitory Concentration (MIC) and EC50 for Ni were observed to be 20 and 11.5 mM, respectively, whereas the cross heavy-metal resistance was discerned as Cu2+ (25 mM) &gt; Zn2+ (15 mM) &gt; Cr6+ (10 mM) &gt; Pb2+ (5 mM) &gt; Co2+ (8 mM) &gt; Cd2+ (3 mM) &gt; Hg2+ (0 mM). Ni biosorption studies by live and heat-killed bacterial cells were suggestive of Ni uptake being facilitated by an ATP-independent efflux system. A pilot-scale study displayed the effective removal of Ni (70 mg/L and 85 mg/L) at 4- and 8-day intervals, respectively. Moreover, chemotaxis and motility assays indicated the role of Ni as a chemoattractant for bacterial cells. The presence of Ni reduced the GR (0.001 ± 0.003 Ug−1FW), POX (0.001 ± 0.001 Ug−1FW), and SOD (0.091 ± 0.003 Ug−1FW) activity, whereas Sodium dodecyl sulphate—Polyacrylamide gel electrophoresis (SDS-PAGE) revealed the presence of metallothionein (60 kDa). Kinetic and isotherm studies suggested a pseudo second-order and Freundlich model to be better fitted for our study. The thermodynamic parameters (∆H° = 3.0436 kJ/mol, ∆S° = 0.0224 kJ/mol/K) suggested the process to be endothermic, spontaneous, and favorable in nature. FTIR analysis elucidated the interaction of hydroxyl and carboxyl groups with Ni. Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS) demonstrated changes in the morphological and elemental composition of the bacterial cells, which affirmed their interaction with Ni during biosorption. In summary, our study concludes the efficient role of Bacillus altitudinis MT422188 in removing Ni from polluted industrial effluents.

Heat stress-mediated effects on the morphophysiological, biochemical, and ultrastructural parameters of germinating Melanoxylon brauna Schott. seeds.

The present study showed that the heat stress (40°C) caused changes in morphophysiological, biochemical, and ultrastructural parameters to the seeds Melanoxylon brauna, ultimately leading to loss of germination capacity. Temperature is an abiotic factor that influences seed germination. In the present study, we investigated morphophysiological, biochemical, and ultrastructural changes during the germination of Melanoxylon brauna seeds under heat stress. Seed germination was evaluated at constant temperatures of 25 and 40°C. The samples consisted of seeds soaked in distilled and ionized water for 48 and 96h at both temperatures. For the evaluation of internal morphology, the seeds were radiographed. Ultrastructural parameters were assessed using transmission electron microscopy (TEM). The production of reactive oxygen species (ROS), content of malondialdehyde (MDA) and glucose, carbonylated proteins, and activity of the enzymes (superoxide dismutase-SOD, ascorbate peroxidase-APX, catalase-CAT, peroxidase-POX, glucose-6-phosphate dehydrogenase-G6PDH, lipase, α- and β-amylase, and protease) were measured by spectrophotometric analysis. An 82% reduction in the germination of M. brauna seeds was observed at 25°C, and 0% at 40°C. TEM showed that seeds submitted to heat stress (40°C) had poorly developed mitochondria and significantly reduced respiration rates. The content of ROS and protein carbonylation in seeds subjected to 40°C increased compared to that at 25°C. The activity of antioxidant enzymes, namely SOD, APX, CAT, and POX, was significantly reduced in seeds subjected to heat stress. Glucose content, G6PDH, and lipase activity also decreased when the seeds were exposed to heat stress. Conversely, α- and β-amylase enzymes and the protease increased due to the increase in temperature. Our data showed that the increase in temperature caused an accumulation of ROS, increasing the oxidative damage to the seeds, which led to mitochondrial dysfunction, ultimately leading to loss of germination.

Effect of silicon on the young maize plants exposed to nickel stress

Nickel (Ni) is involved in several physiological processes in plants but its excess in environment has many phytotoxic effects. Silicon (Si), an element required for optimal plant performance, has been shown to have beneficial effects for plants coping with various types of stresses. Here we studied the alleviative potential of Si (2.5 mM) added to hydroponically grown maize (Zea mays L.) plants under Ni (100 μM) stress. Ni decreased most of the growth parameters, total chlorophyll (Chl) and leaf relative water content (RWC), and catalase (CAT; EC 1.11.1.6) activity, while leaf water loss (LWL), contents of proline (Pro), hydrogen peroxide (H2O2) and ascorbate (AsA), membrane lipid peroxidation and activities of peroxidase (POX; EC 1.11.1.7) and superoxide dismutase (SOD; EC 1.15.1.1) were increased. Supplementation of Si to Ni-treated plants enhanced the leaf area, Chl content, RWC, CAT and POX (only in younger leaf) activities and decreased LWL, the contents of Pro (in younger leaf), H2O2 (roots) and AsA, lipid peroxidation and POX and SOD activities. We may conclude that Si mitigated the Ni-induced stress in maize by amelioration of the leaf water deficient status (Pro, RWC, LWL), enhancing membrane stability (MDA) and influencing enzymatic (SOD, POX, CAT) and non-enzymatic (Pro, AsA) defence systems. The increased Chl content and leaf area improve overall plant performance.

Assessment of the response reactions of tomatoes depending on the phytosanitary status in condition of infection with viral agents

Relevance. Oxidative reactions (based on peroxidase activity, POX and polyphenol oxidase, PPO; hydrogen peroxide content) that occur in response to infection or reinfection of the off-spring of infected plants depend on the type of host-virus interaction (sensitive, tolerant, stable) and the nature of the interaction with viral infection (primary infection, reinfection of second and third generations).Results. Reinfection with tomato aspermy virus (TАV) or tobacco mosaic virus (TMV) of the off-spring of third infected tomato generation caused a significant decrease in POX activity compared to successive generations of infected plants (G2) for Craigella (Tm-22/Tm- 22) and S. pimpinellifolium genotypes or an increase for Rufina and Craigella (Tm-1/Tm-1) ones. In genotypes containing resistance genes, Rufina and Craigella, no differences were observed in PPO of TMV primary infection and control, while significant differences were found in case of TAV (susceptibility). As a result of TMV infection, the sensitive (Elvira) and tolerant (S. pimpinellifolium) genotypes showed an increase in PPO values compared to the control. At the same time, in most genotypes primarily / secondarily infected with TAV or TMV, statistically significant differences were revealed in the activity of POX or PPO, as well as the accumulation of hydrogen peroxide in plant leaves, which indicates specific protective reactions of the genotypes.

Modulations of the antioxidants defence system in two maize hybrids during flooding stress.

Flooding stress nowadays is one of the major stressors for plants under climate change. This kind of stress may cause severe depression of the plant's growth through inhibition of photosynthesis and oxidative cell damage as well as changes in cell respiration. The present work aimed to study the effect of flooding stress on oxidative and antioxidative parameters in leaves of two maize hybrids (ZP 555 and ZP 606). Leaves of maize plants at the stage of three fully developed leaves were harvested after 6, 24, 72, and 144h of applied flooding stress. Leaves were used for determination of physiological (the content of photosynthetic pigments and soluble proteins), oxidative stress parameters (the content of malondialdehyde (MDA) and H2O2) as well as antioxidants (the total polyphenols content, and activity of antioxidative enzymes [catalase (CAT, EC 1.11.1.6), superoxide dismutase (SOD, EC 1.15.1.1), and Class III peroxidases (POX, EC, 1.11.1.7)]). Results indicated that flooding stress-induced time-dependent changes of measured parameters and those hybrids differ in response to stress. The noticeable difference between hybrids was detected in the H2O2 and MDA content. An increase in the activity of SOD, POX and polyphenols content, with the most pronounced changes in POX activity and polyphenols concentration, could minimize the cellular damage caused by flooding. The results of the present study suggest that a more robust antioxidative metabolism is essential under flooding stress and could be a protective strategy against oxidative damage induced by flooding in ZP 606 maize plants compared to ZP 555 plants.

Pseudomonas putida P3-57 induces cucumber (Cucumis sativus L.) defense responses and improves fruit quality characteristics under commercial greenhouse conditions

The possibility of chemical fertilizer residues in cucumber has raised concerns about the consumption of this beneficial fruit. Although very good studies have been reported on the effect of growth-promoting bacteria on increasing the health of cucumber plants, their performance in commercial greenhouse conditions has been less studied. A two-year study was conducted to evaluate the effect of P. putida strain P3-57 with 100 % or 70 % of the recommended amount of NPK fertilizers on cucumber fruit yield and quality compared to Barvar NPK® commercial biofertilizer under commercial greenhouse conditions. The 30 % reduction in chemical fertilizers reduced yield and overall fruit acceptance score in the sensory evaluation test. Plant treatment with P3-57 or Barvar had no significant effect on yield but when 70 % of chemical fertilizers were used, they increased the quality of cucumber due to the increase in the score of some sensory traits. P3-57-100% had the highest overall acceptance score, which was associated with increased aroma, flavor and fruit juice, and the lowest levels of nitrate, Zn, Mg, Mo, Sr, Ba and Li. Also, the concentration of protein and CAT activity of fruits was higher compared to control-100 % and Barvar-100 %. Evaluation of CAT, APX and POX activity and expression of PR1-1a, GLU, APX, CHIT, LOX and PAL showed that P3-57-100 % and Barvar-100 % stimulate plant immune system through ISR/SAR and SAR pathways respectively. Based on the results of this study, strain P3-57, as a bio-stimulator that increases cucumber quality, has great potential to enter the market.

Affinity of class I and class III peroxidases for H2O2 in pepper leaves of different maturity

Paper deals with activities of Class III peroxidases (POX, EC 1.11.1.7) and Class I peroxidases (ascorbate peroxidase, APX, EC 1.11.1.11) as well as the Km of these enzymes for hydrogen peroxide (H2O2) in the pepper leaves of different maturity. The obtained results suggest that the youngest pepper leaves compared to more mature ones have different strategies for H2O2 removal. There was an increase in APX activity with leaf maturity, while POX activity had the opposite trend, and its lowest activity was observed in the oldest leaves. The accumulation of reducing substrates i.e., ascorbate and total phenols was in positive correlation with corresponding enzymes following leaf maturity. The comparison of POX and APX affinity for H2O2 in pepper leaves of different maturity and their relationship between these enzymes' activities were showed.

Simultaneous Treatment of Different Gibberellic Acid Doses InducesIon Accumulation and Response Mechanisms to Salt Damage in MaizeRoots

The present study was aimed to find out the changes in plant responses to salinity with GA3 treatments. With this aim, combinations effects of salinity (350 mM NaCl) and three different doses of gibberellic acid (100, 300 and 500 ppm) on physiological and biochemical analysis of maize (Zea mays L.) roots were studied in soil experiment. The obtained results showed that treatment of GA3 (300-500 ppm) caused a reduction in salt-induced damage, improvement in biomass yield, regulation in water status, increasing proline level, reactive oxygen species (ROS) scavenging capacity, induction of SOD (36.6% at 500 ppm), CAT (28.5% at 500 ppm), APX (3.18 and 3.26 fold at 100 ppm and 500 ppm), GST (2.83 and 2.59 at 100 ppm and 500 ppm) enzyme activities, while POX activity was decreased only at GA3 (31.3% at 500 ppm), and thus alleviation of the oxidative damage. The results indicated that the salt application had a negative effect on the macro and micronutrient concentrations in roots. Otherwise, N, Ca and P concentration was increased by gibberellic acid under salinity, while, K, Cu, Mn, Fe and Zn were reduced compared to salt treatment alone. To sum up, these results showed that GA3 could be used as a signal molecule in antioxidant enzyme regulation related with ions for increasing salt tolerance in maize under salinity.

MITIGATING SALT STRESS EFFECTS BY EXOGENOUS APPLICATION OF PROLINE AND YEAST EXTRACT ON MORPHO-PHYSIOLOGICAL, BIOCHEMICAL AND ANATOMICAL CHARACTERS OF CALENDULA PLANTS

To avoid the hazard effect of salinity on calendula (Calendula officinalis L.), two field experiments were carried out at Sahl El-Husseinieh Research Station, Al-Sharqia Governorate, Egypt during two successive winter seasons of 2017/2018 and 2018/2019 in silty clay soil to evaluate the effects of foliar spraying with yeast at 0, 4, 8 and 12 g l-1, proline at 0, 50, 75 and 100 mg l-1 and the interaction between them. The obtained results showed that foliar application of proline, yeast and their interactions led to improve and increase plant growth, floral, physiological and biochemical characters of calendula plants significantly more than those obtained by control, such as plant height, number of branches plant-1, plant fresh and dry weights, number of flowers plant-1, flowers fresh and dry weight, relative water content, carotenoid, total chlorophyll, proline content in plant leaves, as well as the activity of PPO, POX and CAT. Also, the above treatments led to improve calendula plant growth by reducing the activity of both superoxide and hydrogen peroxide and decreasing EL. Application of proline, yeast and their interactions increased the elements content of calendula plant for N, P, K, Ca and Mg %. In the contrary, they decreased Na % in the plant. Results showed that vegetative growth, floral parameters as well as anatomical characters of leaves were significantly decreased under salt stress conditions. The physiological and biochemical characters such as photosynthetic pigments content, relative water content (RWC %) and mineral elements (N, P, K, Ca and Mg %) in the leaves also significantly decreased. Whereas, Na %, proline concentration, the activity of (O-2 and H2O2) and electrolyte leakage (EL %) were increased. Moreover, available N, P and K (mg kg-1) in the soil is negatively affected by salt stress. The combined treatments of proline at 100 mg l-1 + yeast at 12 g l-1 followed by proline at 100 mg l-1 + yeast at 8 g l-1 gave the higher values of plant growth, biochemical and elemental content in plant besides improved the anatomical characters, consequently, increased the tolerance of calendula plants to salt stress under field conditions.

Study of Bread Wheat Genotype Physiological and Biochemical Responses to Drought Stress

This study investigates the impacts of drought-induced stress on the responses of ten bread (common) wheat genotypes to the physiological parameters and activities of POX, catalase CAT, and SOD under irrigation and stress conditions. The results of variance and mean comparison analysis indicated that the drought stress increased the activity of CAT while significantly decreased POX and SOD levels. In comparison with the irrigated plants, the photochemical efficiency of photosystem II (Fv/Fm) didn't change significantly; however, the concentration of chlorophyll and the relative water content in the flag leaves decreased in response to harsh environmental conditions. The observations included a significant enzyme activity in cultivar's interactions with the environment, which indicates various biochemical reactions of bread wheat plants under stress and non-stress environmental conditions.

Impact of foliar application of some metal nanoparticles on antioxidant system in oakleaf lettuce seedlings

BackgroundNanoparticles (NPs) serve various industrial and household purposes, and their increasing use creates an environmental hazard because of their uncontrolled release into ecosystems. An important aspect of the risk assessment of NPs is to understand their interactions with plants. The aim of this study was to examine the effect of Au (10 and 20 ppm), Ag, and Pt (20 and 40 ppm) NPs on oakleaf lettuce, with particular emphasis on plant antioxidative mechanisms. Nanoparticles were applied once on the leaves of 2-week-old lettuce seedlings, after next week laboratory analyses were performed.ResultsThe antioxidant potential of oakleaf lettuce seedlings sprayed with metal NPs at different concentrations was investigated. Chlorophylls, fresh and dry weight were also determined. Foliar exposure of the seedlings to metal NPs did not affect ascorbate peroxidase activity, total peroxidase activity increased after Au-NPs treatment, but decreased after applying Ag-NPs and Pt-NPs. Both concentrations of Au-NPs and Pt-NPs tested caused an increase in glutathione (GSH) content, while no NPs affected L-ascorbic acid content in the plants. Ag-NPs and Pt-NPs applied as 40 ppm solution increased total phenolics content by 17 and 15%, respectively, compared to the control. Carotenoids content increased when Ag-NPs and Au-NPs (20 and 40 ppm) and Pt-NPs (20 ppm) were applied. Plants treated with 40 ppm of Ag-NPs and Pt-NPs showed significantly higher total antioxidant capacity and higher concentration of chlorophyll a (only for Ag-NPs) than control. Pt-NPs applied as 40 ppm increased fresh weight and total dry weight of lettuce shoot.ConclusionsResults showed that the concentrations of NPs applied and various types of metal NPs had varying impact on the antioxidant status of oakleaf lettuce. Alteration of POX activity and in biosynthesis of glutathione, total phenolics, and carotenoids due to metal NPs showed that tested nanoparticles can act as stress stimuli. However, judging by the slight changes in chlorophyll concentrations and in the fresh and dry weight of the plants, and even based on the some increases in these traits after M-NPs treatment, the stress intensity was relatively low, and the plants were able to cope with its negative effects.

Effect of antimony in soils of an Sb mine on the photosynthetic pigments and antioxidant system of Dittrichia viscosa leaves.

Antimony is a toxic element whose concentration in soil and water has been rising due to anthropogenic activities. This study focuses on its accumulation in leaves of Dittrichia viscosa growing in soils of an abandoned Sb mine, and the effect on oxidant/antioxidant systems and photosynthetic efficiency. The results showed leaves to have a high Sb accumulation capacity. The amount of total chlorophyll decreased depending on Sb concentration and of carotenoids increased slightly, with a consequent increase in carotenoid/chlorophyll ratio. Photosynthetic efficiency was unaffected. The amount of O 2 .- rose, although there was no increase in cell membrane damage, with lipid peroxidation levels being similar to normal. This response may be due to considerable increases that were observed in total phenolics, PPO activity, and enzymatic antioxidant system. SOD, POX, and DHAR activities increased in response to increased Sb amounts in leaves. The ascorbate/glutathione cycle was also affected, with strong increases observed in all of its components, and consequent increases in total contents of the ascorbate and glutathione pools. However, the ratio between reduced and oxidized forms declined, reflecting an imbalance between the two, especially that between GSH and GSSG. Efficient detoxification of Sb may take place either through increases in phenolics, carotenoids, and components of the glutathione-ascorbate cycle or through the enzymatic antioxidant system. Since Dittrichia viscosa accumulates large amounts of Sb without suffering oxidative damage, it could be used for phytoremediation.

Nitric Oxide-Mediated Enhancement in Photosynthetic Efficiency, Ion Uptake and Carbohydrate Metabolism that Boosts Overall Photosynthetic Machinery in Mustard Plants

Nitric oxide (NO) acts as a gaseous diffusible plant growth regulator. It plays an important role in growth and development of plants. Therefore, in present study mustard plants were sprayed with different concentrations of sodium nitroprusside (0, 10–4 M, 10–5 M and 10–6 M), a donor of NO, at 25 days after sowing to assess different physiological parameters. The results indicate that foliar spray of SNP upregulate chlorophyll content, chlorophyll fluorescence along with gaseous exchange parameters which further boost overall photosynthetic efficiency. A gradual increase in carbon metabolism (total reducing sugars, total carbohydrate content, glucose, fructose, sucrose and starch content) was also observed in SNP-treated plants as compared to control. Nutrient status (carbon, nitrogen, phosphorus, sulfur, potassium and magnesium) of leaves also shows a significant increase. The activity of various enzymes associated with nitrogen metabolism, CO2/HCO3− homeostasis, glycolysis, Calvin cycle and Krebs cycle (nitrate reductase, carbonic anhydrase, hexokinase, rubisco, fumarase and succinate dehydrogenase) were also increased in the presence of SNP. It was also reported that O2−, H2O2 and MDA were decreased in SNP-treated samples. SNP application also upregulate antioxidative defense system by increasing the activity of antioxidant enzymes, i.e., CAT, POX and SOD. Thus, it can be concluded from the present observation that SNP proved beneficial and alter most of the parameters which ultimately improve photosynthetic efficiency in mustard plants.

Interactive effects and competitive shift between Triticum aestivum L. (wheat) and Chenopodium album L. (fat-hen) under ambient and elevated ozone

The aim of this study was to evaluate the impact of ambient and elevated O3 (ambient+20 ppb) under the competition between a crop plant Triticum aestivum L.cv. HD 2967 and a weed, Chenopodium album L. (fat-hen) grown singly and in mix-culture (1:1) using open-top chambers. The competition posed a relatively lesser effect on the growth of fat-hen as compared to the wheat under ambient O3 at both the sampling time, however, the effects of stress factors (competition and O3) were more pronounced at the reproductive stage on both the plants. Fat-hen possess a stronger antioxidative potential against elevated O3 (eO3), irrespective of competition, making it more resistant against the existing stress factors. Significant stimulation in the activities of CAT, POX, GR and SOD in fat-hen and non-enzyme antioxidants (AsA, thiols, and total phenolics) might have helped the plants to pose a superior ROS scavenging potential under competition + O3. Strong stimulation of flavonols (kaempferol and quercetin) and phenolic acid (p-coumaric acid and ferulic acid) in fat-hen not only helped the plants to withstand the oxidative damage under eO3 but also might have influenced the allelopathic interaction (competition + O3). Yield loss in wheat was observed to be larger under competition + O3 (33.1%) followed by O3 (20.5%) than only under competition (16.3%). The study suggests stringent weed management strategies to be established recognizing the existing threat from O3 to the productivity of a staple crop-wheat.