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81.
Geochemical partitioning and bioavailability of copper to aquatic plants in an artificial oxide-organic sediment 总被引:2,自引:0,他引:2
This study investigated the effects of competition between binding substrates (organic matter and iron oxide) and between
metals (cadmium and copper), on the partitioning of sedimentary copper and its subsequent bioavailability to an aquatic plant.
Organic matter and a synthesized iron oxide, ferrihydrite, were added singly and in combination to a series of sand sediments,
which were then dosed with environmentally realistic concentrations of cadmium and copper and planted with rice,Oryza sativa.
Organic matter controlled copper partitioning and bioavailability, whereas the synthetic ferrihydrite bound negligible amounts
of either metal, even in the absence of organic matter. As organic matter concentrations increased, operationally-defined
leachable copper decreased, organic-associated copper increased and the survival of rice plants improved in an approximately
linear fashion. At a nominal starting copper concentration of 5.8 μg g dry wt−1, plant survival after four weeks averaged 0–8% in sediments without organic matter, 25% in a sediment containing 0.18% organic
matter and 58% in a sediment containing 0.36% organic matter. These results suggest that organic-associated forms of copper
are unavailable to plants, and that the operational definition of ‘leachable’ copper (extracted with dilute ammonium acetate)
adequately represents the species of copper that is (are) available to plants. Our study using a well-characterized artificial
sediment supports the copper fractionation patterns and correlations between copper partitioning and bioavailability reported
from the heterogeneous, poorly characterized sediments of natural lake and river sediments. 相似文献
82.
83.
Wytske de Vries Claar Donkers Marian Boellaard A. H. Stouthamer 《Archives of microbiology》1978,119(2):167-174
Veillonella alcalescens contained a membrane-bound lactate oxidase system. Studies on the effect of inhibitors on lactate oxidase showed the participation of non-heme iron, quinone and cytochromesb andd. Superoxide anion radicals (
) and H2O2 were shown to be formed at lactate oxidation and presumably arose from cyanide- and azide-resistant side chains of the respiratory system. The H+/O ratio withL-lactate as a hydrogen donor was 2.3. When an anaerobic culture growing on lactate was shifted to a high dissolved oxygen tension (d.o.t.=15 kPa) rapid inhibition of growth and lactate conversion occurred. This could be correlated with a rapid inactivation of lactate dehydrogenase. The effects of high d.o.t.'s on lactate dehydrogenase, lactate conversion and growth were reversible. After a shift to low d.o.t.'s (<2.5 kPa) growth ofV. alcalescens continued for one or two doublings whereafter lysis did occur. Acetate and pyruvate were the main fermentation products. P/O ratio's were calculated from molar growth yields and fermentation balances. A P/O value of 0.66 was found after a shift to a very low oxygen supply at which the d.o.t. presumably was zero. Shifts to higher d. o. t.'s gave much lower growth yields. Presumably, under these conditions uncoupling between growth and energy production occurred. Accumulation of toxic oxygen compounds was given as an explanation for the behaviour ofV. alcalescens at low d.o.t.'s.Abbreviations HQNO
2-n-heptyl-4-hydroxy-quinoline-N-oxide
- CCCP
carbonyl cyanide m-chlorophenyl-hydrazone
- ABTS
2,2-azino-di-3-ethyl-benzthiazoline sulfonate
- DCPIP
2,6 dichlorophenolindophenol
- PMS
phenazine methosulfate
- NBT
p-nitro blue tetrazolium chloride
- d.o.t.
dissolved oxygen tension
- SOD
superoxide dismutase 相似文献
84.
T. WAYNE SCHULTZ JAMES N. DUMONT LOLA M. KYTE 《The Journal of eukaryotic microbiology》1978,25(4):502-509
SYNOPSIS. Shale oil retort water is obtained by centrifuging the oil/water emulsion produced by oil shale retorting. The ciliate Tetrahymena pyriformis was exposed to retort water; 2, 1, and 0.5% initially increased motility; longer exposures decreased motility. Three, 4, and 5% all decreased motility. Cell lysis was directly related to concentration; after 24 h, population densities were 0, 10, and 25% of controls for 2, 1, and 0.5% retort water, respectively. Oxygen consumption paralleled the motility pattern: at lower concentrations it increased initially but decreased with extended exposures while at higher concentrations it decreased rapidly. The most striking cytologic alteration of cells exposed to the toxicant occurred in the membranes; alterations of mucocysts and glycogen content were also observed, but mitochondrial changes were not. Population growth was affected at much lower concentrations than the other test indices. The growth of test populations reached a plateau at values inversely related to concentration: concentrations <0.4% had no effect on growth rate. 相似文献
85.
Summary Effects of three solution aluminium concentrations (0, 25, and 100M) on nitrogen fixation by well-nodulated plants ofStylosanthes hamata, Stylosanthes humilis andStylosanthes scabra are reported. Plants were inoculated with Rhizobium CB756 and grown for 21 days in an aluminium-free nutrient solution at pH 5.3 before imposition of the aluminium treatments.Nitrogen fixation was measured both by the increase in total nitrogen content of the plants and acetylene reduction in roots of plants harvested at 10 and 20 days after imposition of the aluminium treatments. Solution aluminium concentrations as high as 100M, had no detrimental effect on nitrogen fixation in any species. 相似文献
86.
The association of many environmentally sensitive chemicals and their transformation products with mineral and organic substrates is of considerable importance for environmental monitoring, prediction and management purposes in rivers and their basins. Our understanding of these relationships is poor. This paper reviews processes of particular concern, including the physical behaviour of fine-grained (< 63 µm) sediment in freshwater; the role of flocculation as a transport vector; the processes that control freshwater flocculation including microbiological factors; the uncertainty in conventional sediment transport models for predicting pathways of sediment-associated chemistry; the relationship between suspended sediment and toxicity in the water column; and the partitioning of chemicals between the sediment, organic and water phase, including the significance of these in predicting chemical transport on suspended matter. 相似文献
87.
88.
The effect of Al on the growth of plants derived from the F3 generation of a cross between Al tolerant (Waalt) and Al sensitive (Warigal) wheat cultivars, grown in low ionic strength nutrient solutions, were assessed by a number of methods viz; root length and haematoxylin stain after 3 days exposure to Al and plant top and root yields, and root length and visual assessment for Al damage after 4 weeks growth.Of these methods haematoxylin stain (3 days) and visual assessment at 4 weeks identified the same plants as being sensitive or tolerant to Al and clearly segregated the 2 populations. Consequently these 2 methods were used as standard techniques to determine the ability of the other methods to distinguish between tolerant and sensitive plants.The ratio of plant top: root yields clearly segregated the 2 populations. The 2 populations could not be clearly distinguished based on plant top or root yields, or on root length either after 3 days or 4 weeks exposure to Al.Within the population of tolerant plants, root length was significantly correlated with root weight (r2=0.86) and top weight (r2=0.71). None of these relationships were significant for the population of sensitive plants.These techniques were applied in a number of separate experiments on the F2 and F3 populations from a Waalt × Warigal cross. The results indicate that Al tolerance in wheat is inherited by a single gene and that this gene has incomplete dominance. 相似文献
89.
The etiology of selenium-vitamin E (Se-E) deficiency diseases may be complex. Many of the syndromes involve combined deficiency
of selenium and vitamin E. Selenium moves into the animal and human food chain from soil and plants, which may contain inadequate
amounts of the nutrient in many areas of the world. Vitamin E may be in low concentration in many animal feeds unless supplements
are added. Some syndromes, such as steatitis in cats, result from an increased requirement of vitamin E in diets that contain
large amounts of polyunsaturated fatty acids, and these diseases will only respond to vitamin E administration. Deficiency
syndromes in animals owing to pure Se deficiency are infrequent and have been produced mainly by laboratory studies utilizing
extreme deficiency conditions. Other factors that may affect the occurrence of these deficiency diseases are concurrent dietary
deficiency of S-containing amino acids, bioavailability of different forms of dietary Se, intake of compounds that antagonize
Se (e.g., silver salts), and exposure to various prooxidant substances (e.g., iron compounds, oxygen, ozone, and various drugs).
A wide variety of pathologic alterations occur in animals and humans with Se-E deficiency. Myocardial lesions are seen most
frequently in calves, lambs, pigs, turkey poults, and ducklings. In humans, Keshan disease, an endemic cardiomyopathy in China,
is attributed to Se deficiency. Necrosis of skeletal muscle is the most frequent lesion observed in animal species. Necrosis
of smooth muscle of the gizzard and intestine may be a prominent lesion in turkey poults, ducklings, and quail. Other Se-E
deficiency lesions include hepatic necrosis, gastric ulceration, intestinal and uterine lipofuscinosis, pancreatic damage,
steatitis, exudative diathesis, encephalomalacia, and testicular necrosis. Selenium toxicosis is well characterized in animals
and humans by neurological, hoof, and hair alterations. 相似文献
90.
Wayne Chris Hawkes Calvin C. Willhite Kimberly A. Craig Stanley T. Omaye Douglas N. Cox Wai Nang Choy Andrew G. Hendrickx 《Biological trace element research》1992,35(3):281-297
Forty pregnant long-tailed macaques were treated daily for 30 d with 0, 25, 150 or 300 μg selenium as L-selenomethionine/kg
body weight. Erythrocyte and plasma selenium and glutathione peroxidase specific activities, hair and fecal selenium, and
urinary selenium excretion were increased by and were linearly related to L-selenomethionine dose. Hair selenium was most
sensitive to L-selenomethionine dose, with an 84-fold increase in the 300 μg selenium/(kg-d) group relative to controls (r=0.917). Daily urinary selenium excretion (80-fold,r=0.958), plasma selenium (22-fold,r=0.885), erythrocyte selenium (24-fold,r=0.920), and fecal selenium (18-fold,r=0.911) also responded strongly to L-selenomethionine. Erythrocyte and plasma glutathione peroxidase specific activities increased
154% and 69% over controls, respectively. Toxicity was associated with erythrocyte selenium >2.3 μg/mL, plasma selenium >2.8
μg/mL, and hair selenium >27 μg/g. Plasma, erythrocyte, and hair selenium concentrations may be useful for monitoring and
preventing the toxicity of L-selenomethionine administered to humans in cancer chemoprevention trials. 相似文献