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1.
P. Giampaoli F. Tresmondi G. P. P. Lima S. Kanashiro E. S. Alves M. Domingos A. R. Tavares 《Biologia Plantarum》2012,56(1):83-88
The aim of this study was to evaluate the growth and development of Aechmea blanchetiana Baker L.B. Sm. in vitro on medium with 0.0, 0.145, 1.45 and 14.5 μM Cu and 0.0, 2.75, 27.5 and 275 μM Zn. Significant accumulation of Cu and Zn occurred
at 14.5 μM Cu and 27.5 and 275 μM Zn, respectively, and there were no significant changes in contents of the other macro-
and micronutrients. Superoxide dismutase (SOD) activity significantly changed in the presence of both metals. Spermine content
increased as Zn concentration increased and decreased with increasing concentrations of Cu. There was an accumulation of H2O2 in the leaf tissue of plants grown in 1.45 and 14.5 μM Cu and 27.5 and 275 μM Zn. A. blanchetiana was found tolerant to the Cu and Zn in concentrations used in this study and displays the capacity to accumulate these metals. 相似文献
2.
Seaweeds growing in the intertidal zone are exposed to fluctuating nitrate and ultraviolet radiation (UVR) levels. While it
has been shown that elevated UVR levels and the decrease of nitrate concentration can reduce photosynthetic levels in seaweeds,
less is known about the combined effect of nitrate levels and UVR on metabolism and photoprotection mechanisms of intertidal
species. Consequently, the objective of this study was to evaluate the effect of nitrate concentration and UVR treatments
on photosynthesis, respiration, nitrate reductase activity and phenolic compound levels of Ulva rigida (Chlorophyta). There was a two- to threefold increase in maximal gross photosynthesis (GPmax) and respiration rates, as nitrate increased from 0 to 50 μM NO3−. Similarly, nitrate reductase activity increased linearly from low values in algae incubated at 0 μM NO3 to high values in tissue incubated at 50 μM NO3−. Phenolic compounds in the tissue of U. rigida increased approximately 60% under 50 μM NO3− relative to those incubated at 0 μM NO3−. Algae exposed to UVR (8 h) showed a significant decrease in the effective quantum yield and respiration, however, no effect
was observed in the phenolic compounds levels. Full recovery of effective quantum yield was observed after U. rigida was transferred for 48 h to low PAR. Nitrate reductase also decreased after an 8-h UVR exposure, but no differences were
observed among the nitrate treatments. This study shows that high nitrate levels reduced the negative effect of UVR on the
effective quantum yield and increased the recovery of key metabolic enzymes. It is possible that the increase of phenolic
compounds in the thallus of U. rigida under high nitrate levels provide a photoprotective mechanism when exposed to high UV levels during low tides. 相似文献
3.
Copper, Cd and Zn can be found at elevated concentrations in contaminated estuarine and coastal waters and have potential
toxic effects on phytoplankton species. In this study, the effects of these metals on the intracellular production of the
polypeptides phytochelatin and glutathione by the marine diatom Phaeodactylum tricornutum were examined in laboratory cultures. Single additions of Cu and Cd (0.4 μM Cu2 and 0.45 μM Cd2+) to the culture medium induced the production of short-chained phytochelatins ((γ-Glu-Cys)n-Gly where n = 2–5), whereas a single addition of Zn (2.2 μM Zn2+) did not stimulate phytochelatin production. Combination of Zn with Cu resulted in a similar phytochelatin production compared
with a single Cu addition. The simultaneous exposure to Zn and Cd led to an antagonistic effect on phytochelatin production,
which was probably caused by metal competition for cellular binding sites. Glutathione concentrations were affected only upon
exposure to Cd (85% increase) or the combination of Cd with Zn (65% decrease), relative to the control experiment. Ratios
of phytochelatins to glutathione indicated a pronounced metal stress in response to exposures to Cu or Cd combined with Zn.
This study indicates that variabilities in phytochelatin and glutathione production in the field can be explained in part
by metal competition for cellular binding sites. 相似文献
4.
The lelvels of seven heavy metals and their toxicity towardGanoderma lucidum under various cultivation conditions were assessed. The contents of Mn, Cu, Zn, Cd, Hg, Pb and U in the fruitbodies of cultivatedG. lucidum, and sawdust substrates were determined to be at trace levels for U, 0.01–0.1 μg/g for Cd and Hg, and 1–5 μg/g for Pb, 10–120
μg/g for Mn, Cu and Zn. The effects of heavy metals, on the growth of mycelia ofG. lucidium in pure cultures were examined over a wide range of concentrations (10–3,000 μg/ml), and their toxicities were found to decrease
in the order: Hg>Cd>Cu>U>Pb>Mn=Zn. The translocation and accumulation of Zn from contaminated substrates (at 10 μg/g) in fruitbodies
were investigated by using65Zn tracer, andG. lucidum was found to take up Zn with an efficiency of >60%, leading to accumulation of >100 μ/g, in fruitbodies and >80 μ/g Zn in
basidiospores. 相似文献
5.
The effects of heavy metals on the growth, mineral composition (P, K, Fe and Mn) and metal accumulation of five populations of Cistus ladanifer subsp. ladanifer from NE Portugal were investigated in hydroponic experiments. Plants were exposed to increasing concentrations (0–2000 M) of one of eight heavy metals: Cd, Co, Cr, Cu, Mn, Ni, Pb or Zn. Populations of C. ladanifer, whose origin was ultramafic soils (S and UB) or soils developed on basic rocks (B), showed a higher tolerance to the metals Cd, Co, Cr, and Mn, and a considerable degree of tolerance to Ni. In contrast, populations originating on acid-rock soils (M and SC) showed higher tolerance to the metals Cu and Zn. Populations showed different patterns of metal accumulation and distribution in the plant parts, suggesting different mechanisms of metal tolerance are used. The more Cd-, Co- and Mn-tolerant populations (S, UB, B and SC (Cd)) showed accumulation of these three metals in the shoots (shoot:root metal concentration ratios (S:R) > 1). Shoot concentrations of up to 309 g Cd g–1, 2667 g Co g–1 and 6214 g Mn g–1 were found in these populations. The populations, UB and M, showed considerable tolerance to Ni and Zn, respectively. These populations accumulated up to 4164 g Ni g–1 and 7695 g Zn g–1 in their shoot tissues, and these metals were efficiently transported from the roots to aerial parts (S:R > 3 (Ni), S:R > 1 (Zn)). In contrast, the S and SC populations maintained higher growth rates in the presence of Ni and Zn, respectively, but showed exclusion mechanisms of metal tolerance: reduced Ni and Zn transport to shoots (S:R < 1). Cistus ladanifer was not able to efficiently transport Cr, Cu or Pb from its roots to its aerial parts (S:R ranged from 0–0.4). The more Cu-tolerant populations, M and SC, showed a greater restriction of Cu transport to the shoots than the ultramafic- or basic-rock populations. Significant changes in the plant mineral composition were found, however, concentrations were generally above mineral deficiency levels. Based on these preliminary results the possible usefulness of this plant for phytoremediation technologies is discussed. However, further investigations are necessary to evaluate its growth and metal accumulation under soil and field conditions. 相似文献
6.
Nzengue Y Steiman R Rachidi W Favier A Guiraud P 《Biological trace element research》2012,146(3):410-419
In this report, we have investigated the role of copper (Cu) and zinc (Zn) in oxidative stress induced by cadmium (Cd) in
C6 cells. Cells were exposed to 20 μM Cd, 500 μM Cu, and 450 μM Zn for 24 h. Then, toxic effects, cellular metals levels,
oxidative stress parameters, cell death, as well as DNA damage were evaluated. Cd induced an increase in cellular Cd, Cu,
and Zn levels. This results not only in the inhibition of GSH-Px, GRase, CAT, and SOD activities but also in ROS overproduction,
oxidative damage, and apoptotic cell death not related to Cu and Zn mechanisms. The thiol groups and GSH levels decreased,
whereas the lipid peroxidation and DNA damage increased. The toxicity of Zn results from the imbalance between the inhibition
of antioxidant activities and the induction of MT synthesis. The increase in Cu and Zn levels could be explained by the disruption
of specific transporter activities, Cd interference with signaling pathways, and metal displacement. Our results suggest that
the alteration of Cu and Zn homeostasis is involved in the oxidative stress induced by Cd. 相似文献
7.
Isabelle Lefèvre Geoffrey Marchal Enrique Corréal Andréa Zanuzzi Stanley Lutts 《Plant Growth Regulation》2009,59(1):1-11
Seeds, young plants and adult plants of the perennial Mediterranean leguminous shrub Dorycnium pentaphyllum Scop. were exposed to Cd (1–100 μM) or Zn (10–10,000 μM) on nutrient solution. This species is resistant to Cd and Zn at
different phenological stages. The lowest doses of Zn and Cd improved seed germination and young seedling growth, while only
the highest doses of both heavy metals inhibited germination and decreased growth. High doses of Cd reduced seed imbibition
and young seedling water content, while Zn did not. Osmotic adjustment was more efficient in Zn-treated young plants than
in Cd-treated ones, while chlorophyll concentrations decreased in the former but not in the latter. Those differences were
not observed anymore in adult plants. Exclusion processes were more efficient at the adult stage than at the young seedling
stage and were more marked in response to Zn than to Cd. It is concluded that D. pentaphyllum could be used for phytostabilization of heavy metal-contaminated areas. The physiological strategies of tolerance, however,
differ according to the age of the plants and the nature of the metal. 相似文献
8.
Jian Wu Henk Schat Rifei Sun Maarten Koornneef Xiaowu Wang Mark G. M. Aarts 《Plant and Soil》2007,291(1-2):167-180
Brassica rapa L. is an important vegetable crop in eastern Asia. The objective of this study was to investigate the genetic variation in
leaf Zn, Fe and Mn accumulation, Zn toxicity tolerance and Zn efficiency in B. rapa. In total 188 accessions were screened for their Zn-related characteristics in hydroponic culture. In experiment 1, mineral
assays on 111 accessions grown under sufficient Zn supply (2 μM ZnSO4) revealed a variation range of 23.2–155.9 μg g−1 dry weight (d. wt.) for Zn, 60.3–350.1 μg g−1 d. wt. for Fe and 20.9–53.3 μg g−1 d. wt. for the Mn concentration in shoot. The investigation of tolerance to excessive Zn (800 μM ZnSO4) on 158 accessions, by using visual toxicity symptom parameters (TSPs), identified different levels of tolerance in B. rapa. In experiment 2, a selected sub-set of accessions from experiment 1 was characterized in more detail for their mineral accumulation
and tolerance to excessive Zn supply (100 μM and 300 μM ZnSO4). In this experiment Zn tolerance (ZT) determined by relative root or shoot dry biomass varied about 2-fold. The same six
accessions were also examined for Zn efficiency, determined as relative growth under 0 μM ZnSO4 compared to 2 μM ZnSO4. Zn efficiency varied 1.8-fold based on shoot dry biomass and 2.6-fold variation based on root dry biomass. Zn accumulation
was strongly correlated with Mn and Fe accumulation both under sufficient and deficient Zn supply. In conclusion, there is
substantial variation for Zn accumulation, Zn toxicity tolerance and Zn efficiency in Brassica rapa L., which would allow selective breeding for these traits. 相似文献
9.
Effects of zinc (12–180 μM) alone and in mixtures with 12 μM Cd on metal accumulation, dry masses of roots and shoots, root
respiration rate, variable to maximum fluorescence ratio (FV/FM), and content of photosynthetic pigments were studied in hydroponically cultivated chamomile (Matricaria recutita) plants. The content of Zn in roots and shoots increased with the increasing external Zn concentration and its accumulation
in the roots was higher than that in the shoots. While at lower Zn concentrations (12 and 60 μM) the presence of 12 μM Cd
decreased Zn accumulation in the roots, treatment with 120 and 180 μM Zn together with 12 μM Cd caused enhancement of Zn content
in the root. Presence of Zn (12–120 μM) decreased Cd accumulation in roots. On the other hand, Cd content in the shoots of
plants treated with Zn + Cd exceeded that in the plants treated only with 12 μM Cd. Only higher Zn concentrations (120 and
180 μM) and Zn + Cd mixtures negatively influenced dry mass, chlorophyll (Chl) and carotenoid content, FV/FM and root respiration rate. Chl b was reduced to a higher extent than Chl a. 相似文献
10.
Copper-induced changes in the growth, oxidative metabolism, and saponin production in suspension culture roots of Panax ginseng in bioreactors 总被引:3,自引:0,他引:3
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. 相似文献
11.
Dynamics of zinc uptake and accumulation in the hyperaccumulating and non-hyperaccumulating ecotypes of Sedum alfredii Hance 总被引:2,自引:0,他引:2
X. E. Yang T. Q Li X. X. Long Y. H. Xiong Z. L. He P. J. Stoffella 《Plant and Soil》2006,284(1-2):109-119
Sedum alfredii Hance has been identified as a Zn-hyperaccumulating plant species native to China. The characteristics of Zn uptake and accumulation
in the hyperaccumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE) of S. alfredii were investigated under nutrient solution and soil culture conditions. The growth of HE was normal up to 1000 μM Zn in nutrient solution, and 1600 mg Zn kg−1 soil in a Zn-amended soil. Growth of the NHE was inhibited at Zn levels ≥250 μM in nutrient solution. Zinc concentrations in the leaves and stems increased with increasing Zn supply levels, peaking at
500 and 250 μM Zn in nutrient solution for the HE and the NHE, respectively, and then gradually decreased or leveled off with further increase
in solution Zn. Minimal increases in root Zn were noted at Zn levels up to 50 μM; root Zn sharply increased at higher Zn supply. The maximum Zn concentration in the shoots of the HE reached 20,000 and
29,000 mg kg−1 in the nutrient solution and soil experiments, respectively, approximately 20 times greater than those of the NHE. Root Zn
concentrations were higher in the NHE than in the HE when plants were grown at Zn levels ≥50 μM. The time-course of Zn uptake and accumulation exhibited a hyperbolic saturation curve: a rapid linear increase during the
first 6 days in the long-term and 60 min in the short-term studies; followed by a slower increase or leveling off with time.
More than 80% of Zn accumulated in the shoots of the HE at half time (day 16) of the long-term uptake in 500 μM Zn, and also at half time (120 min) of the short-term uptake in 10 μM 65Zn2+. These results indicate that Zn uptake and accumulation in the shoots of S. alfredii exhibited a down-regulation by internal Zn accumulated in roots or leaves under both nutrient solution and soil conditions.
An altered Zn transport system and increased metal sequestration capacity in the shoot tissues, especially in the stems, may
be the factors that allow increased Zn accumulation in the hyperaccumulating ecotype of S. alfredii.
Section Editor: F. J. Zhao 相似文献
12.
Ozone depletion is highest during spring and summer in Antarctica, coinciding with the seasonal reproduction of most macroalgae.
Propagules are the life-stage of an alga most susceptible to environmental perturbations therefore, reproductive cells of
three intertidal macroalgal species Adenocystis utricularis (Bory) Skottsberg, Monostroma hariotii Gain, and Porphyra endiviifolium (A and E Gepp) Chamberlain were exposed to photosynthetically active radiation (PAR), PAR + UV-A and PAR + UV-A + UV-B radiation
in the laboratory. During 1, 2, 4, and 8 h of exposure and after 48 h of recovery, photosynthetic efficiency, and DNA damage
were determined. Saturation irradiance of freshly released propagules varied between 33 and 83 μmol photons m−2 s−1 with lowest values in P. endiviifolium and highest values in M. hariotii. Exposure to 22 μmol photons m−2 s−1 PAR significantly reduced photosynthetic efficiency in P. endiviifolium and M. hariotii, but not in A. utricularis. UV radiation (UVR) further decreased the photosynthetic efficiency in all species but all propagules recovered completely
after 48 h. DNA damage was minimal or not existing. Repeated exposure of A. utricularis spores to 4 h of UVR daily did not show any acclimation of photosynthesis to UVR but fully recovered after 20 h. UVR effects
on photosynthesis are shown to be species-specific. Among the tested species, A. utricularis propagules were the most light adapted. Propagules obviously possess good repair and protective mechanisms. Our study indicates
that the applied UV dose has no long-lasting negative effects on the propagules, a precondition for the ecological success
of macroalgal species in the intertidal. 相似文献
13.
Experiments on the effect of Cd, Cu, Ni, Pb and Zn, suppliedas single salt solutions between 10 µM and 0·1M, on the moss Rhytidiadelphus squarrosus showed little alterationto respiratory rates but reduced photosynthetic rates, and somemembrane damage as assessed by K leakage. Two distinct morphologicalforms of the moss showed different responses to supplied heavymetal. Storage of material, after 30 mins exposure to heavymetals, resulted in a further decrease in the photosyntheticrate. Expressing the photosynthetic decline relative to thetotal heavy metal recovered from the moss showed a similar pattern.Transfer of metal from extracellular exchange sites into theprotoplast was also demonstrated with storage after exposure.An approximately linear relationship was demonstrated betweenphotosynthetic decline and intracellular heavy-metal concentration,irrespective of the duration of exposure or morphological natureof the material used. Photosynthetic decline on storage is concludedto be a response to additional metal stress rather than a progressivedeterioration of the physiological process. Cadmium, copper, lead, nickel, zinc, photosynthesis, respiration, membrane damage, intracellular metals, Rhytidiadelphus squarrosus (Hedw.) Warnst 相似文献
14.
Photosynthetic inorganic carbon utilization and growth of Porphyra linearis (Rhodophyta) 总被引:2,自引:0,他引:2
Alvaro Israel Shlomit Katz Zvy Dubinsky John E. Merrill Michael Friedlander 《Journal of applied phycology》1999,11(5):447-453
Photosynthetic (oxygen evolution) and growth (biomass increase) responses to ambient pH and inorganic carbon (Ci) supply were
determined for Porphyralinearis grown in 0.5 L glass cylinders in the laboratory, or in 40 L fibreglass outdoor tanks with running seawater. While net photosynthetic
rates were uniform at pH 6.0–8.0, dropping only at pH 8.7, growth rates were significantly affected by pH levels other than
that of seawater (c. pH 8.3). In glass cylinders, weekly growth rates averaged 76% at external pH 8.0, 13% at pH 8.7 and 26%
at pH 7.0. Photosynthetic O2 evolution on a daily basis(i.e. total O2 evolved during day time less total O2 consumed during night time) was similar to the growth responses at all experimental pH levels, apparently due to high dark
respiration rates measured at acidic pH. Weekly growth rates averaged 53% in algae grown in fibreglass tanks aerated with
regular air (360 mg L-1 CO2) and 28% in algae grown in tanks aerated with CO2-enriched air (750 mg L-1 CO2). The pH of the seawater medium in which P. linear is was grown increased slightly during the day and only rarely reached 9.0. The pH at the boundary layer of algae submerged
in seawater increased in response to light reaching, about pH 8.9 within minutes, or remained unchanged for algae submerged
in a CO2-free artificial sea water medium. Photosynthesis of P. linearissaturated at Ci concentrations of seawater (K0.5560 μM at pH 8.2) and showed low photosynthetic affinity for CO2(K0.5 61 μM) at pH 6.0. It is therefore concluded that P. linearisuses primarily CO2 with HCO3
- being an alternative source of Ci for photosynthesis. Its fast growth could be related to the enzyme carbonic anhydrase whose
activity was detected intra- and extracellularly.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
15.
Physiological responses of wheat genotypes grown in chelator-buffered nutrient solutions with increasing concentrations of excess HEDTA 总被引:1,自引:0,他引:1
The chelator-buffered nutrient solutions containing excess chelator have been used frequently in the micronutrient research,
but potential toxicity of the excess chelator has not been ascertained. The present study was conducted to test effects of
four concentrations of excess HEDTA [ N-(2-hydroxyethyl)ethylenedinitrilotriacetic acid] and two levels of total Zn on growth,
root exudation, and nutrient uptake and transport by Triticum aestivum L. (cv. Aroona) and Triticum turgidum L. conv. durum
(Desf.) MacKey (cv. Durati) genotypes differing in tolerance to Zn deficiency. Excess HEDTA at 50 μM reduced root and shoot
growth and caused visual toxicity symptoms (necrotic lesions) on leaves; these effects were generally absent at lower concentrations
of excess HEDTA. Root exudation of phytosiderophores increased with increasing concentrations of excess HEDTA at deficient
and sufficient Zn levels, and was higher in Zn-deficiency-tolerant Aroona than in Zn-deficiency-sensitive Durati wheat. Shoot
and root Zn concentrations showed a saturable response to increasing Zn2+ activities in solution. Excess HEDTA at 50 μM caused an increase in shoot concentrations of Fe and a decrease in concentrations
of Mn and Cu. An average rate of Zn uptake increased with an increase in Zn2+ ionic activity in solution, with Zn-deficiency-tolerant Aroona having a higher rate of Zn uptake than Zn-deficiency-sensitive
Durati in the deficiency range of Zn2+ activities. Average uptake rates of Mn and Cu decreased with an increase in concentration of excess HEDTA. Similar observations
were noted for transport of Mn and Cu to shoots, while Zn transport to shoots was proportional to Zn2+ activities in solution. It was concluded that excess HEDTA at 50 μM adversely affects wheat growth and physiology, while
excess of 25 μM or less does not cause measurable toxicity.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
16.
Organic Acids Accumulation and Antioxidant Enzyme Activities in Thlaspi caerulescens under Zn and Cd Stress 总被引:2,自引:0,他引:2
Growth, organic acid and phytochelatin accumulation, as well as the activity of several antioxidative enzymes, i.e. superoxide
dismutase (SOD), ascorbate peroxidase (APX) guaiacol peroxidase (POX) and catalase (CAT) were investigated under Zn and Cd
stress in hydroponically growing plants of Thlaspi caerulescens population from Plombières, Belgium. Tissue Zn and Cd concentration increased (the highest concentration of both was in roots)
as the concentration of these metals increased in the nutrient solution. Increasing Zn concentration enhanced plant growth,
while with Cd it declined compared to the control. Both metals stimulated malate accumulation in shoots, Zn also caused citrate
to increase. Zn did not induce phytochelatin (PC) accumulation. In plants exposed to Cd, PC concentration increased with increasing
Cd concentration, but decreased with time of exposure. Under Zn stress SOD activity increased, but APX activity was higher
at 500 and 1000 μM Zn and CAT activity only at 500 μM Zn in comparison with the control. CAT activity decreased in Cd- and Zn-stressed plants. The results suggest that relative
to other populations, a T. caerulescens population from Plombières, when grown in hydroponics, was characterized by low Zn and Cd uptake and their translocation
to shoots and tolerance to both metals. The accumulation of malate and citrate, but not PC accumulation was responsible for
Zn tolerance. Cd tolerance seems to be due to neither PC production nor accumulation of organic acids. 相似文献
17.
To understand how plants from the Fabaceae family maintain zinc (Zn) homeostasis, we have characterized the kinetics of three
Zn transporting proteins from the ZIP family of divalent metal transporters in the model legume Medicago truncatula. Of six ZIP’s studied, MtZIP1, MtZIP5 and MtZIP6 were the only members from this family determined to transport Zn and were
further characterized. MtZIP1 has a low affinity for Zn with a Km of 1 μM as compared to MtZIP5 and MtZIP6 that have a higher affinity for Zn with Km of 0.4 μM and 0.3 μM, respectively. Zn transport by MtZIP1 was more sensitive to inhibition by copper (Cu) concentrations
than MtZIP5 and MtZIP6, because 3 μM Cu inhibited Zn transport by 80% in MtZIP1 while 5 μM Cu was required to achieve the
same inhibition of Zn transport in MtZIP5 and MtZIP6. Cadmium (Cd) had a greater effect on the ability of MtZIP1 to transport
Zn than MtZIP5 and MtZIP6, because at a concentration of 3 μM Cd, the Zn transport by MtZIP1 was inhibited 55% and the transport
of Zn by MtZIP5 and MtZIP6 was inhibited by 20–30%. However, only MtZIP6 transported Cd at higher rates than those observed
in the control plasmid pFL61, demonstrating a low affinity for Cd based on a Km of 57 μM. These results suggest that Medicago truncatula has both high and low affinity Zn transporters to maintain Zn homeostasis and that these transporters may function in different
compartments within the plant. 相似文献
18.
Zinc (Zn) is an essential nonredox metal that has been regarded as having antioxidant properties. Some epidemiological indications
and therapeutic results point to a role of Zn in restricting the development and the progression of some diseases. Redox-active
metals like iron and copper are involved in oxidative injury mechanisms, and a decrease in the Zn∶Cu ratio may be associated
with certain pathologies. We studied the effect of Zn on the copper-induced lipid peroxidation in diluted human plasma. Lipid
peroxidation was evaluated by measuring the formation of conjugated dienes and of thiobarbituric acid reactive products. We
found that 20 μM Zn reduced the 125-μM copper-dependent formation of conjugated dienes by 27% and of thiobarbituric acid reactive products by 49%, during a 3-h
incubation period. The inhibition of lipid peroxidation by 125 μM Zn is almost total in the same conditions. The time-course study of the inhibitory effect of 125 μM Zn showed that it lasted for 7 h, which was the maximum incubation period tested. We also found that Zn had an inhibitory
effect on the spontaneous lipid peroxidation in rat brain whole homogenates. Our results support the antioxidant properties
of Zn, which may be potentially relevant to the protection of human plasma constituents, competing with the transition metals
for redox reactions. 相似文献
19.
Spruce seedlings [ Picea abies (L.) Karst.] were exposed to a range of concentrations of Zn, Cd, Hg and methyl-Hg for 5 weeks. The chlorophyll and water content of the needles were then estimated. The rates of photosynthesis, transpiration and dark respiration of the intact plant were determined using a Li-cor portable photosynthesis measuring system. Chlorophyll and water contents of needles decreased in response to all metal treatments, as did CO2 uptake. At 1 μ M Cd, 0.1 μ M Hg and 30 and 60 μ M Zn, the decrease in CO2 uptake could be accounted for by decreased chlorophyll concentrations. Decreased transpiration was only found at 5 μ M Cd and 0.01 μ M methyl-Hg. At 5 μ M Cd most of the decrease in CO2 uptake could be explained by decreased chlorophyll levels and stomatal closure induced by water stress. At 0.01 μ M methyl-Hg, besides a decrease in chlorophyll concentration and partial stomatal closure, photosynthetic reactions may have been directly affected. Respiration rates were not influenced by exposure to heavy metals. 相似文献
20.
The effects of season, genotype and their interaction on haploid production were evaluated on four genotypes responsive to
gynogenesis. Naked mature unfertilised ovules, collected from April to October, were cultivated on modified MS basal medium
plus 0.88 μM 6-benzyladenine and 0.57 μM indol-3-acetic acid. After 30–60 days, recovered calli were transferred to a MS basal
medium with 8.8 μM BA and 0.57 μM IAA for regeneration. Genotype and season of ovule collection substantially interact in
the recovery of haploid calli. Between the four genotypes analysed, two gave more calli in the spring, one in the autumn and
the fourth showed only weak differences between seasons. Shoot recovery depended upon both the season of ovule collection
and the genotype but no significant interaction was shown by our data. The ability to produce haploid callus is not predictive
for efficient shoot regeneration.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献