Jasmonic acid as modulator of lead toxicity in aquatic plant Wolffia arrhiza (Lemnaceae)

The present study was undertaken to test the influence of exogenously applied jasmonic acid (JA) upon the growth and metabolism of Wolffia arrhiza (Lemnaceae), the smallest vessel aquatic plant exposed to lead (Pb) stress. It was found, that JA acted in a concentration-dependent manner. Treatment with JA at the highest concentration 100 μM resulted in the enhancement of heavy metal toxicity leading to increase in metal biosorption and formation of lipid peroxides as well as decrease in fresh weight, chlorophyll a, carotenoid, monosaccharide and soluble protein content. In contrast, this phytohormone applied at 0.1 μM protected W. arrhiza fronds against Pb stress inhibiting heavy metal accumulation, restoring plant growth and primary metabolite level. Moreover, JA at 0.1 μM activated enzymatic (catalase, ascorbate peroxidase, NADH peroxidase) and non-enzymatic antioxidant (ascorbate, glutathione) system in W. arrhiza, and therefore, suppressed oxidative destruction of cellular components induced by heavy metal. The data suggest that JA plays an important role in the growth and metabolism of W. arrhiza exposed to abiotic stressor and its high adaptation ability to metal contamination of aquatic environment.     

Jasmonic acid as modulator of lead toxicity in aquatic plant Wolffia arrhiza (Lemnaceae)

The present study was undertaken to test the influence of exogenously applied jasmonic acid (JA) upon the growth and metabolism of Wolffia arrhiza (Lemnaceae), the smallest vessel aquatic plant exposed to lead (Pb) stress. It was found, that JA acted in a concentration-dependent manner. Treatment with JA at the highest concentration 100 μM resulted in the enhancement of heavy metal toxicity leading to increase in metal biosorption and formation of lipid peroxides as well as decrease in fresh weight, chlorophyll a, carotenoid, monosaccharide and soluble protein content. In contrast, this phytohormone applied at 0.1 μM protected W. arrhiza fronds against Pb stress inhibiting heavy metal accumulation, restoring plant growth and primary metabolite level. Moreover, JA at 0.1 μM activated enzymatic (catalase, ascorbate peroxidase, NADH peroxidase) and non-enzymatic antioxidant (ascorbate, glutathione) system in W. arrhiza, and therefore, suppressed oxidative destruction of cellular components induced by heavy metal. The data suggest that JA plays an important role in the growth and metabolism of W. arrhiza exposed to abiotic stressor and its high adaptation ability to metal contamination of aquatic environment.     

Modification of chromium (VI) phytotoxicity by exogenous gibberellic acid application in <Emphasis Type="Italic">Pisum sativum</Emphasis> (L.) seedlings

Effects of exogenous gibberellic acid (GA; 10 and 100 μM) application on growth, protein and nitrogen contents, ammonium (NH₄ ⁺) content, enzymes of nitrogen assimilation and antioxidant system in pea seedlings were investigated under chromium (VI) phytotoxicity (Cr VI; 50, 100 and 250 μM). Exposure of pea seedlings to Cr and 100 μM GA resulted in decreased seed germination, fresh and dry weight and length of root and shoot, and protein and nitrogen contents compared to control. Compared to control, Cr and 100 μM GA led to the significant alteration in nitrogen assimilation in pea. These treatments decreased root and shoot nitrate reductase (NR), glutamine synthetase (GS) and glutamine 2-oxoglutarate aminotransferase (GOGAT) activities (except 50 μM Cr alone for GOGAT) while glutamate dehydrogenase (GDH) activity and NH₄ ⁺ content increased. Compared to control, the root and shoot activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX) increased (except APX activity at 250 μM Cr + 100 μM GA) while catalase (CAT), glutathione reductase (GR) and dehydroascorbate reductase (DHAR) activities were decreased (except GR at 100 μM GA alone) following exposure of Cr and 100 μM GA. Total ascorbate and total glutathione in root and shoot decreased by the treatments of Cr and 100 μM GA while their levels were increased by the application of 10 μM GA compared to Cr treatments alone. It has been reported that application of 10 μM GA together with Cr alleviated inhibited levels of growth, nitrogen assimilation and antioxidant system compared to Cr treatments alone. This study showed that application of 10 μM GA counteracts some of the adverse effects of Cr phytotoxicity with the increased levels of antioxidants and sustained activities of enzymes of nitrogen assimilation; however, 100 μM GA showed apparently reverse effect under Cr phytotoxicity.     

Inhibition of monoterpene biosynthesis accelerates oxidative stress and leads to enhancement of antioxidant defenses in leaves of rubber tree (Hevea brasiliensis)

This paper mainly studies the possible antioxidant of monoterpene and effects of its absence on other antioxidant defense. The leaves of rubber tree (Hevea brasiliensis) were fed with fosmidomycin through transpiration stream, in the dark, at room temperature for 2 h, and were then exposed to bright illumination (1,500 μmol m⁻² s⁻¹) and moderately high temperature (30°C) for 1 h. The results showed that monoterpene biosynthesis in leaves was considerably inhibited by fosmidomycin, and the elevated levels of both hydrogen peroxide and malondialdehyde were observed in the leaves fed with fosmidomycin (LFF). Compared to the control leaves (CK), ∆F/F _m′ in the LFF was markedly lower during the first 20 min; however, there were no significant differences in non-photochemical quenching and photosynthetic pigments (chlorophylls and carotenoids). In contrast, the activities of antioxidant enzymes (superoxide dismutase, catalase, guaiacol peroxidase, ascorbate peroxidase, and glutathione reductase) were enhanced in the LFF. Meanwhile, the contents of antioxidant metabolites (ascorbate and glutathione) were also elevated in the LFF, when compared with the CK. The results obtained here suggest that monoterpene may be very effective molecule in protecting plants against oxidative stress, the absence of monoterpene leads to the increased responses of the enzymatic and non-enzymatic antioxidant defenses to oxidative stress, and the enhancement of the enzymatic and non-enzymatic antioxidant defenses may, in part, compensate for the loss of antioxidant conferred by monoterpene.     

Nitric Oxide Elicitation Induces the Accumulation of Secondary Metabolites and Antioxidant Defense in Adventitious Roots of<Emphasis Type="Italic">Echinacea purpurea</Emphasis>

Nitric oxide and reactive oxygen species are important signal molecules that play key roles in plant defense responses. We investigated the involvement of nitric oxide elicitation in the synthesis of secondary metabolites within the adventitious roots ofEchinacea purpurea. When roots were treated with 100 μM sodium nitroprusside (SNP), an exogenous nitric oxide producer, the accumulation of phenolics, flavonoids, and caffeic acid derivatives was enhanced. This level of SNP also induced an antioxidant defense, as indicated by increases in Superoxide dismutase, ascorbate peroxidase, and ascorbic acid, along with decreases in hydrogen peroxide, lipid peroxidation, and dehydroascorbate/ascorbic acid. However, a higher concentration (250 μM SNP) acted as a pro-oxidant, thereby raising the levels of hydrogen peroxide, lipid peroxidation, and dehydroascorbate/ascorbic acid while diminishing ascorbic acid, ascorbate peroxidase, and the accumulation of secondary metabolites compared with our observations at 100 μM SNP. Therefore, we conclude that elicitingE. purpurea adventitious roots with a concentration of 100 μM SNP is beneficial to their accumulation of secondary metabolites.     

Effect of salicylic acid and methyl jasmonate on antioxidant systems of <Emphasis Type="Italic">Haematococcus pluvialis</Emphasis>

The influence of phytohormones, salicylic acid (SA) and methyl jasmonate (MJ) on the antioxidant systems in Haematococcus pluvialis was investigated. Both SA and MJ at 500 μM concentration reduced the growth of alga with salicylic acid, having more pronounced effect. Carotenoid and chlorophyll contents were decreased by SA and increased by MJ. Salicylic acid (100 μM) increased astaxanthin content to 6.8-fold under low light (30 μmol m⁻² s⁻¹), while MJ (10 μM) showed marginal increase in astaxanthin. Salicylic acid (500 μM) increased superoxide dismutase activity to 4.5- and 3.3-fold and ascorbate peroxidase (APX) activity to 15.5- and 7.1-fold under low and high light, respectively. Methyl jasmonate increased catalase activity (1.4-fold) under high light and APX activity (5.4-fold) under low light. Different mechanism of oxidative stress induced antioxidant production may be the plausible reason for this varied response for salicylic acid and methyl jasmonate. Higher concentrations of SA and MJ inhibited astaxanthin accumulation by different mechanisms either by scavenging the free radicals or by increasing primary carotenoids production. At lower concentrations, these phytohormones could be used for elicitation of secondary carotenoid production.     

Jasmonic acid induced changes in protein pattern, antioxidative enzyme activities and peroxidase isozymes in peanut seedlings

Protein pattern, ammonia content, glutamine synthetase activity, lipid peroxidation, superoxide dismutase, catalase, peroxidase and peroxidase isoforms were studied in the leaves and roots of 7-d-old peanut (Arachis hypogaea L. cv. JL-24) seedlings treated by 25, 100 and 250 μM jasmonic acid (JA). SDS-PAGE protein profile of leaves and roots after JA application showed a significant increase in 18, 21, 30, 45, 47 and 97.4 kDa proteins and significant decrease in 22 and 36 kDa proteins. Pathogenesis related PR-18 was specific in leaves at 250 μM JA and PR-21 have cross reacted differently with 21 and 30 kDa proteins in leaves and roots treated by all JA concentrations. Further, the immunoblot analysis with glutamine synthetase, GS-45 antibodies revealed a specific cross reaction with 45 and 47 kDa proteins of both control and JA treated leaves, however, higher at 100 and 250 μM JA treated leaves than control ones. Further, the malondialdehyde (MDA) content significantly increased in leaves and roots treated with JA, indicated membrane damage with JA treatments that led to the generation of peroxidation products. The peroxidase isozymic pattern showed two specific isoforms. Besides, the activities of SOD and catalase were significantly elevated in JA treated leaves.     

Jasmonic acid affects changes in the growth and some components content in alga Chlorella vulgaris

The present study was undertaken to test the influence of exogenous applied jasmonic acid upon the growth and changes in some metabolites levels in the cells of green alga Chlorella vulgaris Beijerinck (Chlorophyceae). It was found, that JA in algal cells acted in a concentration-dependent manner. Treatment with JA at high concentrations range of 10⁻⁵–10⁻⁴ M, resulted in the decrease in cell number and reduction of major photosynthetic pigments, monosaccharides, soluble cellular and extracellular proteins levels as well as decrease in pH of the medium. In contrast to 10⁻⁵ and 10⁻⁴ M JA, this phytohormone applied at 10⁻⁸–10⁻⁶ M induced the increase in cell number, photosynthetic pigments and monosaccharides contents, significant accumulation and extracellular secretion of soluble proteins over control and neutralization of the medium. Quantitative changes in polypeptide pattern of total cellular proteins after treatment with the optimal concentration of 10⁻⁷ M JA on the 7^th day of cultivation as analyzed by SDS-PAGE, was also observed. JA induced synthesis de novo of 15 specific polypeptides with molecular weight 334-16 kDa which were’t detected in the control. The data suggest that JA plays a important role in algal growth and development.     

Effects of cadmium stress on seed germination,seedling growth and antioxidative enzymes in <Emphasis Type="Italic">Achnatherum inebrians</Emphasis> plants infected with a <Emphasis Type="Italic">Neotyphodium</Emphasis> endophyte

The effects of cadmium (Cd) on germination, and antioxidative enzyme activity (AEA) involving superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase, and on amounts of malondialdehyde and proline present within Achnatherum inebrians, were determined for specimens infected (E+) vs. non-infected (E−) by Neotyphodium gansuense, and cultivated in the presence of various concentrations of CdCl₂ (0, 50, 100, 200 and 300 μmol/l). Under high Cd concentrations (100, 200 and 300 μM), E+ (vs. E−) specimens exhibited a higher germination rate and index, and higher values for shoot length, root length and dry biomass, but there was no significant difference (P > 0.05) under low Cd concentrations (0 and 50 μM). AEA and the proline content increased, but malondialdehyde content declined in the E+ (vs. E−) specimens under high Cd concentrations (100, 200 and 300 μM). There was no significant difference (P > 0.05) under low Cd concentrations (0 and 50 μM). Endophyte infection was concluded to be of benefit to the germination and anti-oxidative mechanisms within A. inebrians under plant exposures to high CdCl₂ concentrations.     

Copper-induced changes in the growth, oxidative metabolism, and saponin production in suspension culture roots of Panax ginseng in bioreactors

Roots of Panax ginseng exposed to various concentrations of Cu (0.0, 5, 10.0, 25.0, and 50.0 μM) accumulated high amounts of Cu in a concentration-dependent and duration-dependent manner. Roots treated with 50 μM Cu resulted in 52% and 89% growth inhibition after 20 and 40 days, respectively. Saponin synthesis was stimulated at a Cu concentration between 5 and 25 μM but decreased at 50 μM Cu. Malondialdehyde content (MDA), lipoxygenase activity (LOX), superoxide ion (O₂ ^•−) accumulation, and H₂O₂ content at 5 and 10 μM Cu-treated roots were not increased but strongly increased at 50 μM Cu resulting in the oxidation of ascorbate (ASC) and glutathione (GSH) to dehydroascorbate (DHA) and glutathione disulfide (GSSG), respectively indicating a clear oxidative stress. Seven well-resolved bands of superoxide dismutase (SOD) were detected in the gel and an increase in SOD activity seemed to be mainly due to the induction of Fe-SOD 3. Five to 10 μM Cu slightly induced activity of ascorbate peroxidase (APX) and dehydroascorbate reductase (DHAR), guaiacol peroxidase (G-POD) but inhibited monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR) enzyme activities. No changes in catalase (CAT) activity and in activity gel were found up to 25 μM Cu, but both G-POD and CAT activities were inhibited at 50 μM Cu. Glutathione metabolism enzymes such as γ-glutamylcysteine synthetase (γ-GCS), glutathione-S-transferase (GST), and glutathione peroxidase activities (GPx) were activated at 5 and 10 μM Cu but were strongly inhibited at 50 μM Cu due to the Cu accumulation in root tissues. The strong depletion of GSH at 50 μM Cu was associated to the strong induction of γ-glutamyltranspeptidase (γ-GGT) activity. These results indicate that plant could grow under Cu stress (5–25 μM) by modulating the antioxidant defense mechanism for combating Cu induced oxidative stress.     

Induction of metal binding compounds and antioxidative defence in callus cultures of two black poplar (<Emphasis Type="Italic">P. nigra</Emphasis>) clones with different tolerance to cadmium

Callus cultures of two parental clones of Populus nigra L., Poli and 58-861, originating from contrasting environments, were exposed to different cadmium concentrations (0, 150 and 250 μM CdSO₄). Clones showed different growth responses to cadmium, evaluated by the tolerance index (Ti), with Poli being more tolerant to the metal at both concentrations. The cadmium concentration at the end of the treatment was very similar between clones at 150 μM CdSO₄, while a higher value in 58-861 compared to Poli was detected at 250 μM CdSO₄. The bioconcentration factor evidenced the lowest value in Poli at 250 μM CdSO₄. Unlike 58-861, cadmium provoked a strong induction of thiols and phytochelatins in clone Poli. In both clones, organic acid concentration differed notably in untreated calli and cadmium treatment induced a general lowering of these compounds. A notably higher antioxidant enzyme activity (ascorbate peroxidase, APX; catalase, CAT; guaiacol peroxidase, GPX) was measured in control calli of clone Poli compared to 58-861. Cadmium induced a remarkable enhancement of APX and CAT, but not GPX, activity at 150 μM CdSO₄ in Poli. Conversely, in 58-861 at 150 μM CdSO₄, and in both clones at 250 μM CdSO₄, a decrease in the antioxidant activity occurred. This investigation provided evidence that these two contrasting genotypes of P. nigra are characterised by a different response to cadmium in callus cultures. In particular, in Poli, the higher tolerance to cadmium is associated with a higher activity of antioxidative enzymes and the ability to strongly increase thiol and PC concentration in response to metal exposure.     

Effect of traumatic acid on antioxidant activity in <Emphasis Type="Italic">Chlorella vulgaris</Emphasis> (Chlorophyceae)

The present study was undertaken to test the influence of exogenously applied traumatic acid (TA) upon the activity of several antioxidant enzymes as well as lipid and protein peroxidation in green algae Chlorella vulgaris. Treatment with TA in concentration range of 10⁻⁶–10⁻⁵ M resulted in an increase of antioxidant enzyme (sodium dismutase, catalase, ascorbate peroxidase, NADH peroxidase, glutathione reductase) activity. Moreover, TA suppressed lipid peroxidation and oxidative destruction of proteins belonging to the SH groups. This data suggest that TA plays an important role in the metabolism of C. vulgaris and probably in its high ability to adapt to various environmental stress factors.     

Alterations in architecture and metabolism induced by ultraviolet radiation-B in the carragenophyte <Emphasis Type="Italic">Chondracanthus teedei</Emphasis> (Rhodophyta,Gigartinales)

The in vivo effect of ultraviolet radiation-B (UVBR) in apical segments of Chondracanthus teedei was examined. Over a period of 7 days, the segments were cultivated and exposed to photosynthetically active radiation (PAR) at 80 μmol photons m⁻² s⁻¹ and PAR + UVBR at 1.6 W m⁻² for 3 h per day. The samples were processed for electron microscopy and histochemistry; also was analyzed growth rates, mitochondrial activity, protein levels, content of photosynthetic pigments and photosynthetic performance. UVBR elicited increased cell wall thickness and accumulation of plastoglobuli, changes in mitochondrial organization and destruction of chloroplast internal organization. Compared to controls, algae exposed to PAR + UVBR showed a growth rate reduction of 55%. The content of photosynthetic pigments, including chlorophyll a and phycobiliproteins, decreased after exposure to PAR + UVBR. This result agrees with the decreased photosynthetic performance observed after exposing algae to PAR + UVBR. Irradiation also elicited increased activity of the antioxidant enzyme glutathione peroxidase and decreased mitochondrial NADH dehydrogenase activity, which correlated with the decreased protein content in plants exposed to PAR + UVBR. Taken together, these findings strongly indicate that UVBR negatively affects the architecture and metabolism of the carragenophyte C. teedei.     

Adventitious rooting is enhanced by methyl jasmonate in tobacco thin cell layers

Adventitious roots (ARs) are induced by auxins. Jasmonic acid (JA) and methyl jasmonate (MeJA) are also plant growth regulators with many effects on development, but their role on ARs needs investigation. To this aim, we analyzed AR formation in tobacco thin cell layers (TCLs) cultured with 0.01–10 μM MeJA, either under root-inductive conditions, i.e., on medium containing 10 μM indole-3-butyric acid (IBA) and 0.1 μM kinetin, or without hormones. The explants were excised from the cultivars Samsun, Xanthii and Petite Havana, and from genotypes with altered AR-forming ability in response to auxin, namely the non-rooting rac mutant and the over-rooting Agrobacterium rhizogenes rolB transgenic line. Results show that NtRNR1 (G1/S) and Ntcyc29 (G2/M) gene activity, cell proliferation and meristemoid formation were stimulated in hormone-cultured TCLs by submicromolar MeJA concentrations. The meristemoids developed either into ARs and xylogenic nodules, or into xylogenic nodules only (rac TCLs). MeJA-induced meristemoid over-production characterized rolB TCLs. No rooting or xylogenesis occurred under hormone-free conditions, independently of MeJA and genotype. Endogenous JA progressively (days 1–4) increased in hormone-cultured TCLs in the absence of MeJA. JA levels were enhanced by 0.1 μM MeJA, on both days 1 and 4. Endogenous IBA was the only auxin detected, both in the free form and as IBA-glucose. Free IBA increased up to day 2, remaining constant thereafter (day 4). Its level was enhanced by 0.1 μM MeJA only on day 1, while IBA conjugation was not affected by MeJA. Taken together, these results show that an interplay between jasmonates and auxins regulates AR formation and xylogenesis in tobacco TCLs.     

Effects of paraquat on lipid peroxidation and antioxidant enzymes in aquatic fern <Emphasis Type="Italic">Azolla microphylla</Emphasis>

Paraquat is most extensively used methyl viologen herbicide to control weeds in the rice-Azolla ecosystem. The effects of different paraquat (PQ) dosages on growth, lipid peroxidation, and activity of antioxidant enzymes of Azolla microphylla Kaul. were investigated. The results indicated that Azolla fronds survived only at the concentrations of 2–6 μM PQ. Frond fragmentation and browning occurred after 24 h at 8 μM PQ. At 24 h, the amount of proteins decreased by 48.7 % in Azolla fronds exposed to 10 μM PQ than that in control fronds. The supplementation of 10 μM PQ increased the activities of superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX), and ascorbate peroxidase (APX) by 2,4-, 1,8-, 3,0-, and 2,2-fold, respectively, as compared with control. The content of PQ and activities of SOD, CAT, GPX, and APX were found to be positively correlated. Our study showed that PQ (2–6 μM) caused ROS overproduction in Azolla fronds, which were scavenged by induced activities of antioxidant enzymes.     

Role of Jasmonic and Salicylic Acid on Enzymatic Changes in the Root of Two Alyssum inflatum Náyr. Populations Exposed to Nickel Toxicity

Phytohormones, including salicylic acid (SA) and jasmonic acid (JA) have the potential to ameliorate plant development and tolerance to deleterious effects of toxic metals like nickel (Ni). Therefore, the current study was carried out to evaluate SA and JA's interactive effect on the root antioxidative response of two Alyssum inflatum Nyár. populations against Ni-toxicity. Two A. inflatum species under different Ni concentrations (0, 100, 200, and 400 μM) were exposed to alone or combined levels of SA (0, 50, and 200 μM) and JA (0, 5, and 10 μM) treatments. Results showed that high Ni concentration (400 μM) reduced roots fresh weight in both populations than in control. However, external application of individual SA and JA or combined SA?+?JA in higher doses had ameliorated roots biomass by mitigating Ni-toxicity, especially in the NM population, in comparison to 400 μM Ni. Under Ni toxicity, SA and JA, especially their combination, induced high Ni accumulation in plants' roots. Moreover, the application of SA and JA alone, as well as combined SA?+?JA, was found to be effective in the scavenging of hydrogen peroxide by improving the activity of superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase in both populations under Ni-toxicity. Overall, our results manifest that SA and JA's external use, especially combined SA?+?JA treatments, ameliorate root biomass and plant tolerance by restricting Ni translocation to the shoot, accumulating in roots, and enhancing antioxidant defense systems.

     

Induction of oxidative stress and antioxidant responses in <Emphasis Type="Italic">Vigna mungo</Emphasis> by zinc stress

Significant changes were observed in the antioxidant systems in the leaves of black gram (Vigna mungo L., var. DPU-88-31) grown under deficient and excess supply of Zn. Plant grown with Zn supply ranging from 0.01 to 10.0 μM under glasshouse conditions showed optimal growth and biomass yield at 1.0 μM Zn supply. Deficient (0.001 and 0.01 μM) as well as excess (2.0 and 10.0 μM) supply of Zn decreased the concentrations of chlorophyll, carotenoids, and nonprotein thiols and increased that of ascorbate. The activity of superoxide dismutase and carbonic anhydrase was decreased at deficient levels and increased with increase in Zn supply up to 10 μM. At both stages of growth, the activities of antioxidant enzymes, such as catalase and ascorbate peroxidase, were decreased, whereas the activities of glutathione reductase and peroxidase were increased at both deficient and excess supply of Zn. An accumulation of hydrogen peroxide and thiobarbituric acid-reactive substances was observed in Zn-stressed leaves, indicating oxidative damage. Different responses to deficient and excess supply of Zn were observed in the production of oxidative damage.     

The effect of natural and synthetic auxins on the growth,metabolite content and antioxidant response of green alga Chlorella vulgaris (Trebouxiophyceae)

The effect of exogenously applied natural [indole-3-acetic acid (IAA), phenylacetic acid (PAA), indole-3-butyric acid (IBA)] and synthetic [1-naphthaleneacetic acid (NAA)] auxins on the growth and metabolism of green microalga Chlorella vulgaris was examined. Exogenous auxins acted in a concentration-dependent manner on algal growth. Phytohormones at concentration of 100 μM inhibited algal growth expressed as the number of cells. IAA and IBA displayed the highest biological activity at 0.1 μM, whereas PAA and NAA were characterized by the greatest stimulatory effect on the number of cells at 1 μM. Treatment with IAA and IBA at 0.1 μM or NAA and PAA at 1 μM increased the concentration of photosynthetic pigments, monosaccharides and soluble proteins in C. vulgaris. Moreover, all auxins stimulated enzymatic (ascorbate peroxidase, catalase, superoxide dismutase) and non-enzymatic antioxidant (ascorbate, glutathione) systems in C. vulgaris, and therefore, suppressed lipid peroxidation and hydrogen peroxide accumulation. The data supports the hypothesis that auxins play a central role in the regulation of C. vulgaris growth and metabolism and the components of cellular redox systems that are thought to have a prominent role in the regulation of auxin-dependent processes.     

Modulation of copper toxicity-induced oxidative damage by excess supply of iron in maize plants

In this study, we examined the modulation of Cu toxicity-induced oxidative stress by excess supply of iron in Zea mays L. plants. Plants receiving excess of Cu (100 μM) showed decreased water potential and simultaneously showed wilting in the leaves. Later, the young leaves exhibited chlorosis and necrotic scorching of lamina. Excess of Cu suppressed growth, decreased concentration of chloroplastic pigments and fresh and dry weight of plants. The activities of peroxidase (EC 1.11.1.7; POD), ascorbate peroxidase (EC 1.11.1.11; APX) and superoxide dismutase (EC 1.15.1.1; SOD) were increased in plants supplied excess of Cu. However, activity of catalase (EC 1.11.1.6; CAT), was depressed in these plants. In gel activities of isoforms of POD, APX and SOD also revealed upregulation of these enzymes. Excess (500 μM)-Fe-supplemented Cu-stressed plants, however, looked better in their phenotypic appearance, had increased concentration of chloroplastic pigments, dry weight, and improved leaf tissue water status in comparison to the plants supplied excess of Cu. Moreover, activities of antioxidant enzymes including CAT were further enhanced and thiobarbituric acid reactive substance (TBARS) and H₂O₂ concentrations decreased in excess-Fe-supplemented Cu-stressed plants. In situ accumulation of H₂O₂, contrary to that of O₂ ^·− radical, increased in both leaf and roots of excess-Cu-stressed plants, but Cu-excess plants supplied with excess-Fe showed reduced accumulation H₂O₂ and little higher of O₂ ^·− in comparison to excess-Cu plants. It is, therefore, concluded that excess-Cu (100 μM) induces oxidative stress by increasing production of H₂O₂ despite of increased antioxidant protection and that the excess-Cu-induced oxidative damage is minimized by excess supply of Fe.     

Salicylic Acid-induced Nitric Oxide and ROS Generation Stimulate Ginsenoside Accumulation in Panax ginseng Roots

We evaluated the involvement of nitric oxide (NO) in salicylic acid (SA)-induced accumulation of ginsenoside in adventitious roots of Panax ginseng and its mediation by reactive oxygen species (ROS). Related effects of SA on components of the antioxidant system were also sought. Adventitious roots of P. ginseng were grown in suspension culture for 3 weeks in MS medium and treated over 5 days with SA (100 μM) alone, SA in combination with the NO scavenger 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO), or PTIO alone. Nitric oxide, the superoxide anion (O₂^·−), H₂O₂, nitrite, nonprotein thiol, and ascorbate were monitored together with ginsenoside, NADPH oxidase activity, and several antioxidant enzymes. Salicylic acid did not inhibit root growth but induced accumulation of ginsenoside, lipid peroxidation, and generation of NO and O₂^·−. It also enhanced activities of NADPH oxidase, superoxide dismutase, catalase, and peroxidase, including ascorbate peroxidase. These effects were suppressed by PTIO. Salicylic acid also decreased glutathione reductase activity. Inclusion of PTIO with SA decreased the activity of glutathione reductase further. Treatment with SA plus PTIO also decreased nonprotein thiol and ascorbate contents but caused nitrite to overaccumulate. Salicylic acid applied to adventitious roots in culture induced accumulation of ginsenoside in an NO-dependent manner that was mediated by the associated increases in O₂^·−, which gave other antioxidant responses that were dependent on NO.