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1.
Indian mustard (Brassica juncea L. cv. Vitasso) plants exposed to 10, 30, 50 and 100 μM of Cd for 5 d in hydroponic culture were analysed with reference
to the distribution of Cd2+, the accumulation of biomass and antioxidants and antioxidative enzymes in leaves. Cd induced a decrease in plant biomass.
The maximum accumulation of Cd occurred in roots followed by stems and leaves. Cd induced a decrease in catalase (CAT) and
guiacol peroxidase (GPX) activities but an increase in ascorbate peroxidase (APX) and monodehydroascorbate reductase (MDHAR)
activities. Enhancement in dehydroascorbate reductase (DHAR) activity was also at 10 μM Cd. Glutathione reductase (GR) activity
showed pronounced stimulation after all treatments, but glutathione S-transferase (GST) and glutathione peroxidase (GPOX)
activities decreased. The effectiveness of ascorbate-glutathione cycle (AGC) was determined by the ratio of ascorbate to H2O2. This ratio decreased in the Cd-treated leaves which indicated that the cycle was disordered. 相似文献
2.
Composition and Properties of Hydrogen Peroxide Decomposing Systems in Extracellular and Total Extracts from Needles of Norway Spruce (Picea abies L., Karst.) 总被引:18,自引:8,他引:10
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Hydrogen peroxide (H2O2) scavenging systems of spruce (Picea abies) needles were investigated in both extracts obtained from the extracellular space and extracts of total needles. As assessed by the lack of activity of symplastic marker enzymes, the extracellular washing fluid was free from intracellular contaminations. In the extracellular washing fluid ascorbate, glutathione, cysteine, and high specific activities of guaiacol peroxidases were observed. Guaiacol peroxidases in the extracellular washing fluid and needle homogenates had the same catalytic properties, i.e. temperature optimum at 50°C, pH optimum in the range of pH 5 to 6 and low affinity for guaiacol (apparent Km = 40 millimolar) and H2O2 (apparent Km = 1-3 millimolar). Needle homogenates contained ascorbate peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase, glutathione reductase, and catalase, but not glutathione peroxidase activity. None of these activities was detected in the extracellular washing fluid. Ascorbate and glutathione related enzymes were freeze sensitive; ascorbate peroxidase was labile in the absence of ascorbate. The significance of extracellular antioxidants for the detoxification of injurious oxygen species is discussed. 相似文献
3.
The involvement of enzymic antioxidant system, superoxide dismutase, guaiacol peroxidase, ascorbate peroxidase in defense
reaction to environmental stress evoked by air and soil pollution, was seasonally studied on three populations of Scots pine
(Pinus sylvestris L.) growing on experimental areas close two industrial objects in Poland. The first of them (Luboón) is localised near a
phosphate fertiliser factory, the second (Głogów) near a copper foundry, and control stand is placed in Kórnik. Głogów is
the most polluted site, where in 1998 monthly mean daily concentrations was: SO2 - 17 μg·m−3, NOx- 12 μg·m−3 and dust containing heavy metals (Cu, Pb, Cd) - 29 μg·m−3. Trees in Luboń were influenced for many years by high concentration of SO2 and fluor compounds. Few years ago emissions were markedly reduced, but changes in the soil (low pH and high concentration
of aluminium ions) still influence the growth of trees. In needles of two populations: 3 (Russia) and 8 (Poland), from the
polluted sites Głogów and Luboń, activities of superoxide dismutase (SOD) and guaiacol peroxidase (PO) were significantly
higher compared to Kórnik. However, in one population (16 - Slovakia), such dependance was not evident. Activity of ascorbate
peroxidase (AP) measured in winter was also higher in needles from polluted sites. The results indicated that the sensitivity
of free radical scavenging system in Scots pine needles differs among populations. 相似文献
4.
We investigated the net photosynthetic rates and antioxidative enzyme activity inPlatanus occidentalis trees growing on two separate streets in Seoul, and representing different degrees of air pollution. In general, concentrations
of SO2, NO2, and PM10 decreased from May to September. The photosynthetic rate was reduced significantly on the street with higher levels
of pollution. Moreover, activities of two antioxidative enzymes, ascorbate peroxidase and glutathione reductase, were greater
in May along the more polluted street. These data suggest thatP. occidentalis growing in highly polluted environments may increase their antioxidant enzyme activity to compensate for and to minimize
the damage from this stress. 相似文献
5.
The effect of stand density on the antioxidant system of Scots Pine (Pinus silvestris L.) and Siberian Pine (Pinus sibirica Du Tour) was studied. The dynamics of concentrations of chlorophyll, hydrogen peroxide, glutathione, ascorbic acid, and dehydroascorbic acid were investigated during the vegetation period. In addition, the activities of superoxide dismutase, catalase, peroxidase, glutathione reductase, and ascorbate peroxidase were observed in the 1-year needles of 26-year-old trees with an initial stand density of 0.5 and 128 thousand individuals ha?1. 相似文献
6.
Antioxidants and Manganese Deficiency in Needles of Norway Spruce (Picea abies L.) Trees 总被引:10,自引:1,他引:9
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Polle A Chakrabarti K Chakrabarti S Seifert F Schramel P Rennenberg H 《Plant physiology》1992,99(3):1084-1089
Chlorotic and green needles from Norway spruce (Picea abies L.) trees were sampled in the Calcareous Bavarian Alps in winter. The needles were used for analysis of the mineral and pigment contents, the levels of antioxidants (ascorbate, glutathione), and the activities of protective enzymes (superoxide dismutase, catalase, ascorbate peroxidase, monodehydroascorbate radical reductase, dehydroascorbate reductase, glutathione reductase). In addition, the activities of two respiratory enzymes (glucose-6-phosphate dehydrogenase, NAD-malate dehydrogenase), which might provide the NADPH necessary for functioning of the antioxidative system, were determined. We found that chlorotic needles were severely manganese deficient (3 to 6 micrograms Mn per gram dry weight as compared with up to 190 micrograms Mn per gram dry weight in green needles) but had a similar dry weight to fresh weight ratio, had a similar protein content, and showed no evidence for enhanced lipid peroxidation as compared with green needles. In chlorotic needles, the level of total ascorbate and the activities of superoxide dismutase, monodehydroascorbate radical reductase, NAD-malate dehydrogenase, and glucose-6-phosphate dehydrogenase were significantly increased, whereas the levels of ascorbate peroxidase, dehydroascorbate reductase, glutathione reductase, and glutathione were not affected. The ratio of ascorbate to dehydroascorbate was similar in both green and chlorotic needles. These results suggest that in spruce needles monodehydroascorbate radical reductase is the key enzyme involved in maintaining ascorbate in its reduced state. The reductant necessary for this process may have been supplied at the expense of photosynthate. 相似文献
7.
Changes in apoplastic antioxidants induced by powdery mildew attack in oat genotypes with race non-specific resistance 总被引:1,自引:0,他引:1
Three oat (Avena sativa L.) lines which show differential responses to attack by the biotrophic fungal pathogen Blumeria graminis DC f. sp. avenae Marchal, which causes powdery mildew, were studied: Maldwyn shows the strongest resistance in adult plants; Selma shows greater
susceptibility; while a Selma × Maldwyn hybrid, OM1387, has a similar degree of resistance to Maldwyn. Host responses to pathogen
attack were complete 48 h after inoculation but largely accomplished within the first 24 h, the point when material was taken
for enzyme and metabolic assays. In Maldwyn and OM1387 about 80% of attacked cells showed localized autofluorescent host-cell
responses but this fell to less than 20% in Selma. A cytoplasmic marker enzyme, glucose 6-phosphate dehydrogenase, was used
to determine contamination of the apoplastic extracts by cellular components. After correction for cytoplasmic contamination,
up to 4% of the total foliar activities of superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, dehydroascorbate
reductase and monodehydroascorbate reductase activities were detected in the apoplast. The apoplast contained about 2% of
the total foliar glutathione pool and dehydroascorbate, but not ascorbate, at values amounting to 10% of the total foliar
ascorbate plus dehydroascorbate pool. Twenty-four hours after inoculation the foliar or apoplastic ascorbate pools were similar
in inoculated and control leaves. Foliar catalase activity increased in both susceptible and resistant responses. Resistance
correlated with increased total foliar glutathione, an increase in the ratio of reduced to oxidized glutathione and with decreased
total activities of foliar ascorbate peroxidase, glutathione reductase, dehydroascorbate reductase and monodehydroascorbate
reductase.
Received: 17 April 1998 / Accepted: 28 August 1998 相似文献
8.
Interactive effects of ozone and drought stress on pigments and activities of antioxidative enzymes in Pinus halepensis 总被引:1,自引:0,他引:1
The aim of this study was to investigate the interactive effects of ozone (O3) and drought on pigments and antioxidant enzymes of Aleppo pine (Pinus halepensis). Two‐year‐old seedlings were exposed in open‐top chambers to charcoal‐filtered air or non‐filtered air plus an additional 40 nL L?1 of ozone. After 20 months of O3 exposure, a subset of plants was subjected to drought stress by withholding water supply for 11 d. Ozone induced higher guaiacol peroxidase, catalase and KCN‐resistant superoxide dismutase (SOD) activities in young needles, while drought stress increased glutathione reductase and CuZnSOD. One‐year‐old needles showed lower capacity to activate these enzymes in response to stress. Both ozone and drought activated the xanthophyll cycle pool and reduced chlorophyll contents in both current and 1‐year‐old needles. The combined effects of ozone and drought decreased antioxidant enzyme activities and the capacity of recovering after re‐watering. Similarly, interactive effects of O3 and drought reduced xanthophyll‐mediated photoprotection capacity in 1‐year‐old needles but induced a higher conversion of the cycle in current‐year needles. These results showed that ozone modified the Aleppo pine response to drought stress, suggesting that this pollutant might be reducing the ability of this species to withstand other environmental stresses. 相似文献
9.
Dahai Gao Qian Gao Hai-Yan Xu Fei Ma Chang-Ming Zhao Jian-Quan Liu 《Trees - Structure and Function》2009,23(4):717-728
Pinus densata is a homoploid hybrid species, originating from P. tabuliformis × P. yunnanensis. The physiological fitness of this natural hybrid compared to its two parental species remains unknown. In this study, we
investigated physiological responses of the three species by exposing artificially breed seedlings of each to drought stress
lasting 28 days. Our results suggest that, in all three species, drought affected the contents of the plants’ chlorophyll,
stomatal conductance, TBARS, hydrogen peroxide, and free proline and increased the activities of antioxidant enzymes, including
superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6), and peroxidase (POD; EC 1.11.1.7). The drought stress
also induced significant changes in the activity of ascorbate peroxidase (APX; EC 1.11.1.11), monodehydroascorbate reductase
(MDHAR; EC 1.6.5.4), dehydroascorbate reductase (DHAR; EC 1.8.5.1), glutathione reductase (GR; EC 1.6.4.2), and levels of
ascorbate and glutathione in the ascorbate–glutathione cycle. The hybrid species P. densata appeared to achieve greater drought tolerance and exhibit hybrid superiority in antioxidant processes and other related physiological
traits compared to the two parental species, although a few of the hybrid’s measured variables were similar to those of P. tabuliformis. However, P. yunnanensis was more sensitive to drought and appeared to have the lowest resistance to such stress. These physiological differences
are largely consistent with the species’ habitat preferences, which may reflect their early genetic divergences and niche
differentiation. These findings provide important information for management and forest restoration efforts of these species
in the future. 相似文献
10.
The effects of methyl jasmonate (MJ) and salicylic acid (SA) on changes of the activities of major antioxidant enzymes, superoxide anion accumulation (O2
−), ascorbate, total glutathione (TG), malondialdehyde (MDA) content and ginsenoside accumulation were investigated in ginseng roots (Panax ginseng L.) in 4 l (working volume) air lift bioreactors. Single treatment of 200 μM MJ and SA to P. ginseng roots enhanced ginsenoside accumulation compared to the control and harvested 3, 5, 7 and 9 days after treatment. MJ and SA treatment induced an oxidative stress in P. ginseng roots, as shown by an increase in lipid peroxidation due to rise in O2
− accumulation. Activity of superoxide dismutase (SOD) was inhibited in MJ-treated roots, while the activities of monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), SOD, guaiacol peroxidase (G-POD), glutathione peroxidase (GPx) and glutathione reductase (GR) were induced in SA-treated roots. A strong decrease in the activity of catalase (CAT) was obtained in both MJ- and SA-treated roots. Activities of ascorbate peroxidase (APX) and glutathione S transferase (GST) were higher in MJ than SA while the contents of reduced ascorbate (ASC), redox state (ASC/(ASC+DHA)) and TG were higher in SA- than MJ-treated roots while oxidized ascorbate (DHA) decreased in both cases. The result of these analyses suggests that roots are better protected against the O2
− stress, thus mitigating MJ and SA stress. The information obtained in this work is useful for efficient large-scale production of ginsenoside by plant-root cultures. 相似文献
11.
The goal of this study was the characterization of the antioxidative protection system of current and 1-year-old needles of a cembran pine (Pinus cembra L.) and its possible responses to elevated concentrations of atmospheric O3. Twigs of a mature cembran pine at the alpine timberline (1950 m a.s.l.) were exposed in climate-controlled twig chambers for 91 d to charcoal-filtered air (CF), ambient air O3 concentration (A), and two-fold ambient air O3 concentration (2A). Additionally, a chamberless control group (AA) was used to examine chamber effects. At the end of the fumigation period the contents of free radical scavengers and photosynthetic pigments were measured in the needles. Independent from O3 exposure, total ascorbate and -tocopherol contents were higher in 1-year-old needles compared to the current flush while the opposite was found for glutathione. The amounts of pigments and antioxidants in P. cembra needles were comparable to those in other conifers growing at high-elevation sites. The only hint toward O3 induced changes in the composition of antioxidants was an increase in the glutathione redox state toward more oxidation in 1-year-old needles upon exposure to A or AA conditions, but not upon 2A exposure. Chlorophyll and carotenoid contents were not affected by O3 neither in current- nor in previous-year needles. The de-epoxidation state of the xanthophyll cycle pigments, however, was significantly increased in 1-year-old needles under A and AA compared to the CF control, but not under 2A. Hence, Pinus cembra, which is well adapted to the extreme environment of the timberline ecotone, exhibited only marginal biochemical changes in response to elevated O3. 相似文献
12.
Effects of exogenous salicylic acid (SA) on plant growth, contents of Na, K, Ca and Mg, activities of superoxide dismutase
(SOD), guaiacol peroxidase (GPX), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), glutathione reductase (GR)
and catalase (CAT), and contents of ascorbate and glutathione were investigated in tomato (Lycopersicon esculentum L.) plants treated with 100 mM NaCl. NaCl treatment significantly increased H2O2 content and lipid peroxidation indicated by accumulation of thiobarbituric acid reactive substances (TBARS). A foliar spray
of 1 mM SA significantly decreased lipid peroxidation caused by NaCl and improved the plant growth. This alleviation of NaCl
toxicity by SA was related to decreases in Na contents, increases in K and Mg contents in shoots and roots, and increases
in the activities of SOD, CAT, GPX and DHAR and the contents of ascorbate and glutathione. 相似文献
13.
《Free radical research》2013,47(1-5):193-197
The response of ascorbate peroxidase and glutathione reductase activities in peas (Pisum sativum var. Waverex) was investigated after three weeks of exposure to mixed fumigations with S02, NO, and O, (0.050 parts per million each) and increasing concentrations of O, (0-0.150 parts per million). The results show that plants respond similarly to a high concentration (0.150 parts per million) of a single air pollutant (ozone) and to mixtures of air pollutants (S02, NO: and O,) when individual concentrations are low (0.050 parts per million each). In both cases, levels of ascorbate peroxidase and glutathione reductase activites were approximately twice those to be found in plants grown in charcoal-filtered air (p 0.01). 相似文献
14.
Vitrification of shoots of Prunus avium L. L. was induced and expressed in a four week in vitro multiplication cycle simply by replacing agar by gelrite. The first vitrification symptoms were visible from the 7th day on. Enzymatic antioxidants were compared weekly in crude extract of normal (on agar) and vitrifying (on gelrite) shoots. The activity of superoxide dismutase was higher in vitrifying shoots. The other enzymes (gaîacol-peroxidase, catalase, ascorbate peroxidase, mono- and dehydro-ascorbate reductases, glutathione reductase) had lower activities. Increased superoxide dismutase activity might mean hydrogen peroxide accumulation and decreased activities of the other enzymes, deficiency in its detoxification. The question therefore is raised whether the hyperhydric morphological abnormalities result from the accumulation of toxic oxygen forms. Vitrification is often considered as a morphological response to several stresses. Contrary to most plants which adapt themselves to stresses by increasing all the above defence enzymes, in vitro shoots under vitrifying conditions appear unable to react in a similar manner.Abbreviations Apx
ascorbate peroxidase
- Gpx
gaîacol peroxidase
- CAT
catalase
- H2O2
hydrogen peroxide
- SOD
superoxide dismutase
- MDHAR
monodehydroascorbate reductase
- DHAR
dehydroascorbate reductase
- GR
glutathione reductase
- MS
Murashige and Skoog (1962)
- IBA
indolebutyric acid
- BAP
benzyladenine
- GA3
gibberellic acid 相似文献
15.
Antioxidant defences of the apoplast 总被引:1,自引:0,他引:1
Summary The apoplast of barley and oat leaves contained superoxide dismutase (SOD), catalase, ascorbate peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase, and glutathione reductase activities. The activities of these enzymes in the apoplastic extracts were greatly modified 24 h after inoculation with the biotrophic fungal pathogenBlumeria graminis. The quantum efficiency of photosystem II, which is related to photosynthetic electron transport flux, was comparable in inoculated and healthy leaves during this period. Apoplastic soluble acid invertase activity was also modified in inoculated leaves. Inoculation-dependent increases in apoplastic SOD activity were observed in all lines. Major bands of SOD activity, observed in apoplastic protein extracts by activity staining of gels following isoelectric focusing, were similar to those observed in whole leaves but two additional minor bands were found in the apoplastic fraction. The apoplastic extracts contained substantial amounts of dehydroascorbate (DHA) but little or no glutathione (GSH). Biotic stress decreased apoplastic ascorbate and DHA but increased apoplastic GSH in resistant lines. The antioxidant cycle enzymes may function to remove apoplastic H2O2 with ascorbate and GSH derived from the cytoplasm. DHA and oxidized glutathione may be reduced in the apoplast or returned to the cytosol for rereduction.Abbreviations AA
reduced ascorbate
- APX
ascorbate peroxidase
- DHA
dehydroascorbate (oxidised ascorbate)
- DHAR
dehydroascorbate reductase
- G6PDH
glucose-6-phosphate dehydrogenase
- GSH
reduced glutathione
- GSSG
glutathione disulphide
- GR
glutathione reductase
- MDHA
monodehydroascorbate
- MDHAR
monodehydroascorbate reductase
- SOD
superoxide dismutase 相似文献
16.
Seasonal changes of ascorbate peroxidase and monodehydroascorbateradical reductase activities were studied in foliar tissuesof Norway spruce (Picea abies L.). In mature needles, APX activitiesdid not show seasonal fluctuations and were similar to thosefound in resting buds. Monodehydroascorbate radical reductaseactivity was higher in needles than in buds and higher in winterthan in summer. Maximum activities of both enzymes were foundbefore bud break and minimum activities in newly formed needles.When spruce seedlings were exposed to an artifical frost eventof 5°C for one night in spring, ascorbate peroxidaseactivity declined in young needles before the onset of visibleinjury but corresponding to a sudden upsurge in lipid peroxidation.After one week, some shoots showed severe symptoms of injury,some were slightly injured and others did not show any visibleinjury. In lethally injured needles, antioxidative protection(ascorbate peroxidase, monodehydroascorbate radical reductase,glutathione reductase, glutathione, ascorbate, superoxide dismutase)had collapsed. Surviving needles showed a coordinated increasein all components of the antioxidative system suggesting anefficient induction of defense systems. However, enhanced protectionwas observed only transiently. In fall, needles that had beenexposed to frost in spring contained significantly less antioxidantsthan unstressed needles indicating that unseasonal frost causedmemory effects. (Received September 16, 1995; Accepted May 28, 1996) 相似文献
17.
Oxidative stress responses were tested in the unicellular cyanobacterium Synechococcus PCC 7942 (R2). Cells were exposed to hydrogen peroxide, cumene hydroperoxide and high light intensities. Activities of ascorbate peroxidase and catalase were correlated with the extent and time-course of oxidative stresses. Ascorbate peroxidase was found to be the major enzyme involved in the removal of hydrogen peroxide under the tested oxidative stresses. Catalase activity was inhibited in cells treated with high H2O2 concentrations, and was not induced under photo-oxidative stress. Regeneration of ascorbate in peroxide-treated cells was found to involve mainly monodehydroascorbate reductase and to a lesser extent dehydroascorbate reductase. The induction of the antioxidative enzymes was dependent on light and was inhibited by chloramphenicol. Peroxide treatment was found to induce the synthesis of eight proteins, four of which were also induced by heat shock.Abbreviations ASC
ascorbate
- DHA
dehydroascorbate
- MDA
monodehydroascorbate
- GSH
reduced glutathione
- GSSG
oxidized glutathione
- ASC Per
ascorbate peroxidase
- DHA red.
dehydroascorbate reductase
- MDA red.
monodehydroascorbate reductase
- GSSG red.
glutathione reductase
- HSP
heat shock proteins
- PSP
peroxide shock proteins
- Cm
chloramphenicol 相似文献
18.
Imen Tarchoune Cristina Sgherri Riccardo Izzo Mokhtar Lachaal Flavia Navari-Izzo Zeineb Ouerghi 《Acta Physiologiae Plantarum》2012,34(5):1873-1881
The effects of different sodium salts on some physiological parameters and antioxidant responses were investigated in a medicinal and aromatic plant, Ocimum basilicum L. (cultivar Fine). Plants were subjected to an equimolar concentration of Na2SO4 (25?mM) and NaCl (50?mM) for 15 and 30?days. Growth, oxidative stress parameters [electrolyte leakage, peroxidation, and hydrogen peroxide (H2O2) concentration], antioxidant enzyme activities [ascorbate peroxidase (APX, EC 1.11.1.11), glutathione reductase (GR, EC 1.6.4.2), and peroxidases (POD, EC 1.11.1.7)], as well as antioxidant molecules [ascorbate and glutathione] were determined. The two salts affected leaf growth rates to the same extent, after 15 or 30?days of treatment, indicating a similar effect of Na2SO4 and NaCl salinity on growth, even if different (enzymatic and non-enzymatic) antioxidant mechanisms were involved in H2O2 detoxification. However, under both salts, the efficiency of the antioxidant metabolism seemed to be sufficient to avoid the deleterious effects of reactive oxygen species (ROS). Indeed, both ion leakage and peroxidation did not change under either Na2SO4 or NaCl salinity. As a whole, these data suggest that a cooperative process between the antioxidant systems is important for the tolerance of Ocimum basilicum L., cv. Fine to Na2SO4 and NaCl salinity. 相似文献
19.
Elena Toll Pierre Crespi Hubert Greppin F. J. Castillo 《Trees - Structure and Function》1998,13(1):13-18
One- and 2-year-old Pinus sylvestris saplings were exposed to chronic doses of ozone (O3) and sulphur dioxide (SO2) in short-term (3 months) and long-term (18 months) experiments. Microsomal and plasma membrane fractions were purified by
phase partitioning from current-year needles. The following membrane enzyme activities were determined in the microsomal and/or
purified plasma membrane fractions: K+, Mg2+-ATPase (EC 3.6.1.3), NADH ferricyanide oxidoreductase (EC 1.6.99.3), NADH-duroquinone reductase (EC 1.6.5.1), NADH oxidase
type I (EC 1.6.99.2), NADH oxidase type II or peroxidase-like enzyme (EC 1.11.1.7) and pyrophosphatase (EC 3.6.1.1). NADH
oxidase type I was slightly stimulated in the microsomal fraction after a short-term exposure to O3 whereas NADH-dependent duroquinone reductase was not affected by this pollutant. However, in the long term experiment, NADH
oxidase type II measured in the plasma membrane fraction was more than 2-fold stimulated in the SO2 treated pines and more than 4-fold when O3 was added to SO2. However, pyrophosphatase was decreased by 50% in trees treated with SO2+O3 and remained unchanged in the SO2 treatment, indicating that this enzyme is probably sensitive to oxidation. K+, Mg2+-ATPase showed a trend towards an enhancement of activity when exposed to chronic concentrations of air pollutants, this enhancement
was more important in the long-term experiment after the combined effect of SO2 and O3. However, the K+-stimulated component was inhibited by the combination of both pollutants. Finally, NADH ferricyanide reductase was significantly
enhanced after O3 and SO2+O3 exposures appearing as the most sensitive oxidoreductase to these air pollutants. The stimulation of ATPase and membrane
oxidoreductases could facilitate the adaptation and defense of trees by maintaining an adequate redox potential in the plasma
membrane region and perhaps stimulating the reduction of extracellular electron acceptors generated by the exposure to air
pollutants.
Received: 15 September 1997 / Accepted: 4 May 1998 相似文献
20.
The effect of magnesium (Mg2+)‐deficiency on the antioxidant responses of Capsicum annuum was investigated over a 60‐day period under controlled conditions. This Mg2+‐deficiency aimed to mimic the physiological conditions that plants may experience in the field. At each harvest time, five different leaf‐levels (L2 to L6) were distinguished. L2 and L6 correspond to the second and sixth youngest leaves, respectively. The following parameters were determined: Mg2+, chlorophyll and protein contents, total and redox pools of ascorbate and glutathione, and the activities of superoxide dismutase, ascorbate peroxidase, dehydroascorbate reductase, and glutathione reductase. Under Mg2+‐deficiency, leaf Mg2+ contents decreased over time in all leaf‐levels except in the second youngest leaves (L2), where they remained constant at about 0.25% (dry weight basis). Mg2+‐deficiency led to an increase in the antioxidant enzyme activities concomitant with an increase in the ascorbate and glutathione pools, whereas total chlorophyll and soluble protein contents decreased. The L2 leaves showed an increase in glutathione reductase activity and in the ascorbate redox state whereas no difference was observed for the other parameters. Superoxide dismutase activities increased in L5 leaves from day 15 and, afterwards, in L3 to L5 leaves, irrespective of Mg2+ content. At day 30, glutathione reductase activities increased in L2 to L4 leaves and dehydroascorbate reductase activities in L4 leaves. At day 45, we observed an increase in the ascorbate peroxidase activities in L3 to L5 leaves. At the same time, ascorbate and glutathione pools increased in intermediate leaves, whereas chlorophyll content decreased in L3 and L4 leaves, and protein content decreased in L4 leaves. Results suggest that pepper leaves enhance their defence capacities against oxidative stress by increasing ascorbate more than glutathione synthesis. However, cells showed higher regeneration rates for the glutathione redox state than for the ascorbate redox state. 相似文献