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1.
In an assay addressing the toxicity of copper to Dictyosphaerium pulchellum, a 48 hours' exposure of axenic cultures of the alga to metal concentrations ranging from 0 to 300 mg L?1 caused a significant decrease in the growth rate and cell chlorophyll content. Extracellular mucilage remotion by controlled sonication before exposure to copper emphasized chlorophyll content reduction, but not cellular density diminution. Because mucilage acts as a cation interchanger, these results suggested that, during at least the first 48 hours, division rates might be affected by lower Cu+2 concentrations than chlorophyll content. Ultrastructural observations showed that the normal organization of the chloroplasts was altered; they presented dilated lamellae, irregularly arranged with practically no stacking. Copper precipitates were mainly observed outside the plasmalemma or within the extracellular mucilage. Electron probe microanalysis confirmed these observations, showing only minor precipitates inside the cells. 相似文献
2.
Abstract: The concentration dependency of the impact of elevated atmospheric CO2 concentrations on Arabidopsis thaliana L. was studied. Plants were exposed to nearly ambient (390), 560, 810, 1240 and 1680 μl I-1 CO2 during the vegetative growth phase for 8 days. Shoot biomass production and dry matter content were increased upon exposure to elevated CO2 . Maximal increase in shoot fresh and dry weight was obtained at 560 μl I-1 CU2 , which was due to a transient stimulation of the relative growth rate for up to 3 days. The shoot starch content increased with increasing CO2 concentrations up to two-fold at 1680 μl I-1 CO2 , whereas the contents of soluble sugars and phenolic compounds were hardly affected by elevated CO2 . The chlorophyll and carotenoid contents were not substantially affected at elevated CO2 and the chlorophyll a/b ratio remained unaltered. There was no acclimation of photosynthesis at elevated CO2 ; the photosynthetic capacity of leaves, which had completely developed at elevated CO2 was similar to that of leaves developed in ambient air. The possible consequences of an elevated atmospheric CO2 concentration to Arabidopsis thaliana in its natural habitat is discussed. 相似文献
3.
Effect of high external NaCl concentration on ion transport within the shoot of Lupinus albus. II. Ions in phloem sap 总被引:1,自引:0,他引:1
RANA MUNNS M. LORRAINE TONNET CAROL SHENNAN P. ANNE GARDNER 《Plant, cell & environment》1988,11(4):291-300
Abstract. Phloem sap was collected from petioles of growing and fully expanded leaves of lupins exposed to 0–150 mol m−3 [NaCl]ext , for various periods of time. Sap bled from growing leaves only after the turgor of the shoot was raised by applying pneumatic pressure to the root. Increased pressure was also needed to obtain sap from fully expanded leaves of plants at high [NaCl]ext . Exposure to NaCl caused a rapid rise in the Na+ concentration in phloem sap to high levels. The Na+ concentration reached 20 mol m−3 within a day of exposure and reached a plateau of about 60 mol m−3 in plants at 50–150 mol m−3 [NaCl]ext , after a week. There was a slower, smaller increase in the Cl− concentration. K+ concentrations in phloem sap were not affected by [NaCl]ext . Cl− concentrations in phloem sap collected from growing leaves were similar to those from old leaves while Na+ concentrations were somewhat increased, suggesting that there was no reduction in the salt content of the phloem sap while it flowed within the shoot to the apex. Calculations of ion fluxes in xylem and phloem sap indicated that Na+ and Cl− fluxes in the phloem from leaves of plants at high NaCl could be equal to those in the xylem. This prediction was borne out by observations that Na+ and Cl− concentrations in recently expanded leaves remained constant. 相似文献
4.
Photosynthetic CO2 -fixation, chlorophyll content, growth rate and nitrate reductase activity were used to examine the influence of NH+ 4 -N and NO− 3 -N on Sphagnum magellanicum cultivated under defined conditions in phytotrons. NO− 3 -concentrations up to 322 μ M were found to be favourable. Increased NH+ 4 concentrations, however, resulted in growth inhibition and decreased chlorophyll content at concentrations ≧ 255 μ M ; e.g. 600 μ M NH+ 4 caused a 20% reduction of nitrate reductase activity and net photosynthesis. For raised bog Sphagna an improved standard nutrient solution is proposed with the following ion concentrations (μ M ): 55 Na+ ; 17 K+ ; 95 NH+ 4 ; 22 Ca2+ ; 22 Mg2+ ; 2 Fe3+ ; 20 Cl− ; 100 NO− 3 ; 57 SO2- 4 ; 7.4 H2 PO− 4 ; trace elements: A-Z solution (Hoagland) 50 μl 1000 ml−1 ; pH 5.8. 相似文献
5.
The effects of copper (CuCl2 ) on active and passive Rb+ (86 Rb+ ) influx in roots of winter wheat grown in water culture for 1 week were studied. External copper concentrations in the range of 10–500 μ M in the uptake nutrient solution reduced active Rb+ influx by 20–70%, while passive influx was unaffected (ca 10% of the Rb+ influx in the Cu-free solution). At external Rb+ concentrations of up to 1 m M , Cu exposure (50 μ M decreased Vmax to less than half and increased Km to twice the value of the control. Short Cu exposure reduced the K+ concentration in roots of low K+ status. Pretreatment for 5 min in 50 μ M CuCl2 prior to uptake experiments reduced Rb+ influx by 26%. After 60 min pretreatment with Cu, the corresponding reduction was 63%. Cu in the cultivation solution impeded growth, especially of the roots. The Cu concentration in the roots increased linearly with external Cu concentration (0–100 μ M ) while Cu concentration in the shoots was relatively unchanged. The K+ concentration in both roots and shoots decreased significantly with increased Cu in the cultivation solutions. Possible effects of Cu on membranes and ion transport mechanisms are discussed. 相似文献
6.
Endocrine, osmoregulatory, respiratory and haematological parameters in flounder exposed to the water soluble fraction of crude oil 总被引:2,自引:0,他引:2
A. Y. A. Alkindi J. A. Brown † C. P. Waring ‡ J. E. Collins 《Journal of fish biology》1996,49(6):1291-1305
Flounders Pleuronectes flesus with an implanted vascular catheter were exposed to a 50% dilution of the water soluble fraction (WSF) of Omani crude oil (c. 6ppm total aromatic hydrocarbons) and serial blood samples taken to determine their endocrine status (cortisol, catecholamines and thyroid hormones) and the resultant and/or causal physiological (haematological, ionoregulatory and respiratory) disturbances. This resulted in a progressive increase in plasma cortisol concentrations from 3 h onwards (rising from 18 to 51 ng ml−1 after 48-h exposure), and increased plasma glucose concentrations indicating a generalized stress response. Plasma T3 and T4 concentrations of both control and WSF-exposed groups declined progressively over the experimental period; exposure to the WSF of crude oil further depressed plasma T4 concentrations but not plasma T3 concentrations relative to those of control fish. Plasma osmolality and sodium and chloride concentrations were stable in WSF-exposed fish, however, plasma potassium concentrations were increased significantly at the 24-and 48-h sampling points. The most profound physiological disturbance in WSF-exposed fish was a dramatic decline in blood oxygen content (CvO2 ) (from 2–8 to 0–8 ml 100 ml−1 after 48-h exposure), which is likely to be the cause of the increased plasma noradrenaline concentrations from 3 h onwards. Increased noradrenaline is likely in turn to have been responsible for the significant increase in blood haematocrit and blood haemoglobin at the 3-h sampling point, although the dominant effect in the longer-term was a significant decline in both of these haematological parameters. 相似文献
7.
Physiological effects of long-term exposure to low and moderate concentrations of atmospheric NH3 on poplar leaves 总被引:2,自引:0,他引:2
L. W. A. VAN HOVE O. VAN KOOTEN E. H. ADEMA W. J. VREDENBERG G. A. PIETERS 《Plant, cell & environment》1989,12(9):899-908
Abstract. Poplar shoots ( Populus euramericana L.) obtained from cuttings were exposed for 6 or 8 weeks to NH3 concentrations of 50 and 100 μgm−3 or filtered air in fumigation chambers. After this exposure the rates of NH3 uptake, transpiration, CO2 assimilation and respiration of leaves were measured using a leaf chamber. During the long-term exposure also modulated chlorophyll fluorescence measurements were carried out to obtain information about the photosynthetic performance of individual leaves. Both fluorescence and leaf chamber measurements showed a higher photosynthetic activity of leaves exposed to 100 μg NH3 m−3 . These leaves showed also a larger leaf conductance and a larger uptake rate of NH3 than leaves exposed to 50 μg m−3 NH3 or filtered air. The long-term NH3 exposure did not induce an internal resistance against NH3 transport in the leaf, nor did it affect the leaf cuticle. So, not only at a short time exposure, but also at a long-term exposure NH3 uptake into leaves can be calculated from data on the boundary layer and stomatal resistance for H2 O and ambient NH3 -concentration. Furthermore, the NH3 exposure had no effect on the relation between CO2 -assimilation and stomatal conductance, indicating that NH3 in concentrations up to 100 μg m−3 has no direct effect on stomatal behaviour; for example, by affecting the guard or contiguous cells of the stomata. 相似文献
8.
Enzymatic desulfurization of dibenzothiophene by a cell-free system of Rhodococcus erythropolis D-1 总被引:1,自引:0,他引:1
Abstract Pseudomonas syringae cells were exposed to Cu2+ alone or in the precence of acetate, proline or cysteine, at concentrations that reduced free Cu2+ to 1/10 of the total copper. Ligand concentrations (designated as isoeffective) were determined experimentally using a Cu2+ -selective electrode and confirmed by computer calculations using published stability constants. Exposure of P. syringae cells to Cu2+ alone resulted in rapid and pronounced cell death, and binding of most of the copper in solution. The addition of acetate, proline or cysteine, a few minutes after Cu2+ treatment, resulted in a significant reduction in cell death, and in the amount of copper bound to the cells. For short exposures to Cu2+ , cysteine was more effective than acetate or proline, but after 60 min of treatment, similar results were observed with these ligands. The addition of ligands before Cu2+ resulted in even more reduced copper toxicity. The results showed that, at isoeffective concentrations, weak and moderate copper-ligands can effectively antagonize copper toxicity, and that this protective effect does not require previously equilibrated copper-ligand solutions and is not very dependent of the nature of the ligand. 相似文献
9.
Z. Krupa 《Physiologia plantarum》1988,73(4):518-524
Five-day-old etiolated radish ( Raphanux salivux L. cv. Saxa) seedlings exposed to white continuous light in the presence of Cd2+ (0.2 mM) showed characteristic changes in their light-harvesting chlorophyll a/b protein complex II after 48 h of greening. The content of its oligomeric supramolecular form was greatly diminished with a concomitant increase in the level of the monomer. The isolation of highly purified light-harvesting chlorophyll a/b protein complex II from control and Cd2+ treated radish cotyledons and a detailed analysis of its structure and composition revealed that first of all, Cd2+ altered the content of the specific phosphatidylglycerol fatty acid - trans -Δ3 -hexadecenoic acid, widely accepted as a component responsible for the oligomerization of this chlorophyll-protein complex. This fatty acid in the thylakoid membrane phosphatidylglycerol pool seems to be very sensitive to different environmental stresses lowering its content, which indicates the vital significance of this component for the supramolecular organization and proper functioning of the light-harvesting chlorophyll a/b protein complex II. 相似文献
10.
The aim of this study was to isolate and cultivate protoplasts of the green alga Ulva fasciata Delile and subsequently induce them to form a microthallus suspension for algal seed stock. The protoplasts were covered with secreted mucilage following 6 h of culture when viewed with SEM. The mucilage fused to form thick layers during day 1 of culture. Microfibrillar cell walls were deposited into the thick layers of mucilage on the 5th day of culture. An average of about 10% of the freshly isolated protoplasts began to divide at 6–14 days. These protoplasts subsequently developed varied morphologies, depending on the time of collection during the year. Protoplasts isolated from U. fasciata collected in March to June developed frond thalli or microthalli when they were cultured in low or high densities (cells/area), respectively. The microthallus suspension was cultured for more than two years at 10–40 μ mol·m− 2 ·s− 1 . Frond thalli formed when the suspension was cultivated at 100–160 μ mol·m− 2 ·s− 1 . Therefore, microthallus suspension can serve as a seed stock of U. fasciata . 相似文献
11.
Abstract— Myelin, synaptosomal and mitochondrial fractions obtained from homogenates of whole mouse brain contain K+ which can exchange with 42 K+ at 2º in 0·32 m -sucrose. The content and rates of exchange of K+ were greater at pH 8·2 than at 6·1. In the synaptosomal preparations, the rates of exchange and content of 42 K+ and K+ declined progressively with decreasing pH.
Of the total synaptosomal K+ , 95 per cent could exchange with external 42 K+ . At pH 7·5, 20 per cent of the K+ and 78 per cent of the Na+ appeared to reside in osmotically insensitive pools. Synaptosomal K+ at 2º was slowly displaced by NaCl (0·18 m ) and the rate of exchange between 42 K+ and K+ was retarded. KCI (0·18 m ) did not readily displace endogenous Na+ . Synaptosomal K+ exchanged with exogenous K+ more rapidly than with exogenous Na+ .
These observations have been discussed in terms of possible roles for ion exchange as the principal means by which K+ traverses the plasma membrane at 2º. 相似文献
Of the total synaptosomal K
These observations have been discussed in terms of possible roles for ion exchange as the principal means by which K
12.
Effects of mixtures of chloride salts of cadmium, copper and zinc on survival, whole body residues, and histopathology of mummichog, Fundulus heteroclitus (L.), were investigated in synthetic sea water at 20‰ salinity and 20°C. Mixtures of Cu2+ and Zn2+ as indicated by 96 h bioassay studies produced more deaths than expected on the basis of toxicities of individual components. Concentrations of Cd2+ not ordinarily lethal exerted a negative effect on survival of fish intoxicated by salts of copper, zinc, or both.
Atomic absorption determinations of Cd, Cu, and Zn residues in mummichog which survived 96 h exposures to each of these toxicants provided useful indices of total body burdens for these metals. Residues from survivors held in mixtures, especially Cd2+ and Zn2+ mixtures, did not conform to patterns observed for single elements. Whole body aggregates of Cd, Cu, and Zn from dead mummichogs were of limited worth owing to possible accumulation of these metals from the medium after death.
Renal and lateral line canal lesions were noted in all fish subjected to copper concentrations of 1 mg/1 and higher. Renal lesions observed in fish immersed in mixtures of Cu2+ and Cd2+ assumed a damage pattern characteristic of Cd2+ ; with mixtures of Cu2+ and Zn2+ , lesion were typical of Cu2+ -induced damage. Lesions induced in lateral line epithelium by Cu2+ were not affected by either Cd2+ or Zn2+ . Epithelia lining the oral cavity were necrotized by the caustic action of high levels of Zn2+ (60 mg/1) and of Cu2+ (8 mg/1). 相似文献
Atomic absorption determinations of Cd, Cu, and Zn residues in mummichog which survived 96 h exposures to each of these toxicants provided useful indices of total body burdens for these metals. Residues from survivors held in mixtures, especially Cd
Renal and lateral line canal lesions were noted in all fish subjected to copper concentrations of 1 mg/1 and higher. Renal lesions observed in fish immersed in mixtures of Cu
13.
John C. Thomas Farah K. Malick Charles Endreszl Elizabeth C. Davies Kent S. Murray 《Physiologia plantarum》1998,102(3):360-368
Selective gene expression allows the halophyte Mesembryanthemum crystallinum to survive a salt stress. To broaden our understanding of the environmental cues initiating diverse stress responses in this higher plant, unstressed and 0.4 M NaCl‐stressed plants were compared to plants treated with several concentrations of copper (CuSO4 ), an increasingly relevant environmental heavy metal pollutant. Comparisons of control and copper‐stressed plants included germination, chlorophyll content, accumulation of proline, heat shock protein (HSP) 60 and a Crassulacean acid metabolism (CAM)‐specific marker enzyme, phospho enol pyruvate carboxylase (PEPCase). In germination and whole plant tests, M. crystallinum was significantly more tolerant to copper than Arabidopsis thaliana. Mature M. crystallinum plants stressed with 50 ppm CuSO4 for 48 h became dehydrated. These plants produced a 4‐fold increase in proline concentration and accumulated both the CAM‐specific PEPCase and HSP 60 compared to controls. Higher levels of copper stress resulted in a 10‐fold increase in leaf proline content, 10‐fold HSP 60 accumulation but no detectable PEPCase protein compared to unstressed controls. HSP 60 did not accumulate under NaCl stress. Concurrent with copper‐induced genetic responses to stress, copper was accumulated and concentrated in leaves (3 500 ppm). Together, these results suggest that this halophyte copes with copper metal exposure through distinct genetic mechanisms. 相似文献
14.
Anne Ojala 《Nordic Journal of Botany》1993,13(6):697-705
The effects of light and temperature on cell size and cellular composition (chlorophyll, protein, carbohydrate) of two freshwater cryptophytes were studied with batch cultures. Neither of the species had a constant cell size but the size varied with growth conditions. At each temperature the smallest cells were recorded at the lowest experimental photon flux density. The smallest cells of Cryptomonas 979/67 had an average volume of 232 μm3 and the largest ones 1 020 μm3 . In Cryptomonas 979/62 the smallest and largest cells measured 4 306 μm3 and 12 450 μm3 . Both species increased their cellular chlorophyll content when PFB dropped below 110–120 μmol m-2 s-1 . The highest and lowest chlorophyll contents of 979/67 were 7.45 fg μm-3 and 0.55 fg μm-2 respectively. For 979/62 the corresponding values were 10.23 fg μm-3 and 0.93 fg μm-3 . In both species the protein content remained stable at PFDs higher than 110–120 μmol m-2 S-1 . The highest content of protein measured in 979/67 was 638 fg μm-3 and the lowest 147 fg μm-3 . For 979/62 these values were 1 036 fg μm-3 and 148 fg μm-3 respectively. The carbohydrate results were less clear and no pattern either in response to photon flux density or temperature was obvious. The lowest and highest contents recorded for 979/67 were 62 fg μm-3 and 409 fg μ-3 and for 979162, 36 fg μm-3 and 329 fg μm-3 相似文献
15.
The present study investigates the light acclimation potential of photoautotrophic suspension culture cells of Chenopodium rubrum L. grown in 16 h light/8 h dark cycles. Typical features of sun/shade acclimation could be demonstrated in cultures grown at photon flux densities of 30 and 150 μmol m−2 s−1 . Low light grown cells had lower chlorophyll a/b ratios, lower respiration rates and lower light compensation points than high light grown cells. Maximum photosynthetic rate per cell dry weight was highest in low light conditions, indicating that the cells did not enlarge their photosynthetic machinery upon exposure to high light. Transfer of cultures to 800 μmol m−2 s−1 caused photoinhibition as indicated by a decrease in photosynthetic efficiency and by the occurrence of a slowly reversible quenching of variable chlorophyll fluorescence. Extension of the photoinhibitory treatment over six light dark cycles did not result in further dramatic changes of these parameters, whereas the chlorophyll content per dry weight and the chlorophyll a/b ratio decreased. Measurements of photochemical quenching showed that the capability of the cells to dissipate excessive energy had increased during the acclimation process. The presence of the xanthophyll cycle pigments and the operation of the cycle could be demonstrated. In agreement with the putative photoprotective function of antheraxanthin and zeaxanthin these pigments could only be detected under photoinhibitory conditions. Prolonged photoinhibitory treatment resulted in increases in the xanthophyll pigment concentration but not of the potential to deepoxidate violaxanthin. The limited potential of the cells to accumulate zeaxanthin and antheraxanthin might indicate that the xanthophyll cycle is not the main factor determining their resistance to high light stress. 相似文献
16.
JÜRG FUHRER 《Plant, cell & environment》1982,5(4):263-270
Abstract. Seedlings of Phaseolus vulgaris were exposed to solutions containing Cd2+ in the range 0 to 1 molm−3 . Ethylene formation started following 3 h of exposure to 10−2 , 10−1 and 1 mol m−3 Cd2+ , peaked at 18 h and returned to a relatively low rate after 24 h. Cadmium-induced ethylene formation depended on the formation of 1-aminocyclopropane-1-carboxylic acid (ACC). Aminoethoxyvinylglycine (AVG, 0.1 mol m−3 ) inhibited ACC accumulation and ethylene production during exposure to 0.2 mol m−3 Cd2+ .
Activity of soluble and ionically-bound peroxidase increased after 18 h of exposure to Cd2+ concentrations above 10−3 mol m−3 due to an increase in activity of cathodic isoperoxidases. Stimulation of soluble and ionically-bound peroxidase by 0.2 mol m−3 Cd2+ was reduced in the presence of 0.1 mol m−3 AVG.
Accumulation of soluble and insoluble ('ligninlike') phenolics was found in plants exposed to Cd2+ (10−2 mol m−3 or above) in the presence or absence of AVG. Deposition of insoluble (autofluorescing) material occurred in cell walls around vessels and was associated with reduced expansion and water content of leaves. 相似文献
Activity of soluble and ionically-bound peroxidase increased after 18 h of exposure to Cd
Accumulation of soluble and insoluble ('ligninlike') phenolics was found in plants exposed to Cd
17.
Some classes of marine phytoplankton are believed to be more tolerant of high concentrations of trace metals than others, but the results of experimental tests of this hypothesis are ambiguous. Eleven species of phytoplankton representing five classes were grown in Aquil medium containing Cd concentrations between 10−8 and 10−5 M ([Cd2+ ]= 10−9.85 to 10−6.84 M), and growth rates and intracellular concentrations of Cd, C, N, and S were measured. The mean Cd2+ concentration (pCd50 ) that reduced the growth rate of each species to 50% of its maximum varied by 2.5 orders of magnitude, from 10−6.23 for Emiliania huxleyi to 10−8.79 for Synechococcus sp. Taxonomic trends in Cd resistance were not apparent in these data. Cadmium quotas (mol Cd·L−1 cell volume) were lowest in species of Bacillariophyceae (ANOVA, P < 0.001), suggesting that they might regulate Cd transport differently than other taxa. Cellular S:C molar ratios increased in four of seven phytoplankton grown at high pCd (7.37–6.84) compared to low Cd ion concentrations (no added Cd), a result of increases in S·L−1 cell volume. Nitrogen:carbon molar ratios were also higher in Cd-exposed phytoplankton, as changes in N and S were highly correlated ( r = 0.98, P < 0.0001). In two species that were examined, S:C ratios increased as a linear function of increasing Cd concentration. The results demonstrate large variability in Cd resistance among phytoplankton that is primarily a function of interspecific differences in Cd detoxification. 相似文献
18.
Effects of phenolic acids on ammonia oxidation by terrestrial autotrophic nitrifying microorganisms 总被引:2,自引:0,他引:2
Abstract It has been hypothesized that vegetation in certain ecosystems inhibits nitrification in soil by producing phenolic compounds that inhibit oxidation of ammonia by nitrifying microorganisms. This hypothesis is based largely on a report that very low concentrations (10−6 M–10−8 M) of several phenolic acids (notably ferulic acid) completely inhibited NO2 − production in an aqueous suspension of soil treated with (NH4 )2 SO4 and a nutrient solution suitable for growth of Nitrosomonas and other autotrophic nitrifying microorganisms. To evaluate this hypothesis, we determined the effects of three ohenolic acids (ferulic acid, caffeic acid, and p -coumaric on nitrite production by representatives of three genera of terrestrial autotrophic nitrifying microorganisms ( Nitrosospira, Nitrosomonas , or Nitrosolubos ) grown on a defined medium containing NH4 + . We found that nitrite production by the Nitrososspira was not inhibited by ferulic acid, caffeic acid, or p -coumaric acid at concentrations of 10−6 or 10−5 M and was only slightly inhibited when these acids were at a concentration of 10−4 M. We also found that ferulic acid did not markedly inhibit nitrite production by the three genera of nitrifying microorganisms studied, even when its concentration was as high as 10−3 M. These observations invalidate the hypothesis tested because the phenolic acids studied did not significantly retard ammonia oxidation by autotrophic microorganisms even when their concentration in cultures of these microorganisms greatly exceeded their concentrations in soils. 相似文献
19.
The effect of short-term H2 S fumigation on water-soluble sulphydryl and glutathione levels in spinach 总被引:2,自引:0,他引:2
Abstract. Short-term fumigation of Spinacia oleracea with 380 μg m−3 H2 S (250 ppb) resulted in a rapid accumulation of water-soluble SH-compounds in the shoots. After 1 h exposure a substantial increase in the SH-content was already detectable and maximal accumulation, three- to four-fold that in control plants, was observed after 24 h of exposure. Irradiation during H2 S exposure only slightly affected the rate and level of SH-accumulation. H2 S fumigation did not affect the water-soluble SH-content of the roots. Glutathione was the sole water-soluble SH-compound accumulating upon exposure to H2 S. It was calculated that during the first hour of exposure to 380 μg m−3 H2 S 39% of the possible absorbed H2 S was converted into glutathione. The SH-content of the water-soluble proteins of the shoots was not affected by H2 S exposure. When fumigation was stopped, a rapid decrease in glutathione content was observed and after 48 h the content was comparable to that of the control plants. Contrary to H2 S, SO2 fumigation did not result in a rapid accumulation of glutathione in spinach shoots. The possible role of glutathione accumulation during H2 S fumigation is discussed. 相似文献
20.
The effect of Cu toxicity on photosynthetic function, chlorophyll and Ca2+ content of Cu-tolerant Silene compacta plants grown in nutrient solution was studied. Since, in plants grown under 8 μ M Cu, the chlorophyll and Ca2+ concentration as well as the photosystem II (PSII) photochemistry were increased, compared to the control, the development of an adaptive mechanism of the Cu-tolerant ecotype of S. compacta to 8 μ M Cu is suggested. Increased Cu tolerance of the S. compacta ecotype reflects modulation of the photosynthetic apparatus to optimize photosynthesis. However, exposure of plants to 160 μ M Cu resulted in a marked increase of the fraction of closed PSII centres and decreased quantum yield of PSII electron transport (ΦPSU ) which was accompanied by a significant decline of relative quantum yield for O2 evolution (Aox /Apt ). The concentration of chlorophyll and Ca2+ in leaves also decreased significantly under 160 μ M Cu treatment. Photochemical quenching (qp ) displayed a reduction as a result of perturbation of the photosynthetic electron transfer chain, while non-photochemical quenching (qN ) increased. High Cu treatment reduced photosynthetic productivity of S. compacta plants which can be attributed, in part, to pertubation of photosynthetic process and photosynthetic pigments as well as to Ca2+ loss. 相似文献