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1.
In August 1982, a net of 48 stations with altogether 208 samples was investigated in the eastern German Bight with respect
to temperature, salinity, as well as the amount and species composition of the mesozooplankton (>80 μm). The data were arranged
into different structures by means of a cluster analysis. Four different clusters were found: (a) a “Wadden sea water” with
few holoplankton organisms but a higher amount of spionid larvae; (b) a “German Bight water” with a maximum occurrence of
turbellaria (Alaurina composita) and medium concentrations of copepods; (c) a mixing area between these two water masses with highest amounts ofOikopleura dioica, Temora longicornis, Acartia sp., mussel larvae and larvae of the spionid worms; (d) a “North Sea water” mass with highest concentrations ofPseudocalanus elongatus, Paracalanus parvus undOithona similis. The differences in the concentrations of the species mentioned between the four clusters were significant on the 0.1%-level. 相似文献
2.
JONES RUSSELL S.; COE LAURA L.; MONTGOMERY LADONNA; MITCHELL CARY A. 《Annals of botany》1990,66(6):617-622
Physical agitation applied as periodic seismic stress (shaking)reduced stem clongation, leaf expansion, and biomass accumulationby vegetative soybeans. Level of photon flux (PPF) influencedthe type and extent of plant response to mechanical stress.Plant parts responded differently as PPF varied between 135and 592 µmol m2 S1. Stem length was significantlyreduced by seismic stress at 135 µmol m2 s1but this effect was insignificant at higher PPFs. Reduced stemlength resulted from an inhibition of internode elongation.Stem diameter was unaffected by stress at the PPFs tested. Incontrast to effects on stem elongation, leaf area was insensitiveto stress treatments at 135 µmol m2 S1 butwas progressively inhibited by stress as PPF increased. Statisticallysignificant reductions in shoot f. wt and d. wt by seismic stressoccurred only at 295 µmol m2 S1. Root biomassaccumulation was not affected by seismic stress at any PPF usedin this study. Glycine max (L.) Merr. cv. Century 84, mechanical stress, photosynthetic photon flux, seismic stress, soybean 相似文献
3.
Analysis of Odor Discrimination by Multidimensional Scaling at Different Temperatures 总被引:1,自引:0,他引:1
Discrimination of odorants by the turtle olfactory bulb at 25°and 37°C was examined by the cross-adaptation techniqueand analysed by multidimensional scaling. Analysis by multidimensionalscaling suggests that at 25°C odorants are grouped accordingto their odor qualities in the turtle olfactory system. At 37°C,the cluster formation of odorants, which have a similar odorquality, such as minty and floral alcohol odorants and molecularstructure, in the plot of multidimensional scaling was poor,indicating that the ability of odor grouping according to theirodor qualities was low at 37°C. Chem. Senses 20: 565571,1995. 相似文献
4.
Y. P. Kalra 《Plant and Soil》1971,34(1):535-539
Summary Isotopic-dilution technique was used to study the differential phosphate absorption abilities of several field crops. The
response of crops was found to be inversely related to the ratio of phosphorus absorbed from the soil to that absorbed from
the fertilizer. The ‘A’ values ranged from 2.03 ppm for mustard to 21.77 ppm for soybeans. A highly significant correlation
(r=0.77**) was found between per cent yields and the ‘A’ values. 相似文献
5.
A study was made of the influence of grain size variation withinand between diploid, tetraploid and hexaploid wheat, on a numberof seedling growth characters. Differences in grain size within the three ploidy levels appearedto be related to total photosynthetic area and dry weight accretionin the seedling. In the diploids there was a positive correlationbetween seed size and total photosynthetic area (r = +0·99,P < 0·01) and total dry weight (r = +0·84,P < 0·05) of the seedling at 10 weeks after emergence.In the tetraploid and hexaploids, seed size was negatively correlatedwith both total photosynthetic area (r = 0·69,P < 0·05 and r = 0·33, P < 0·05for the tetraploids and hexaploids respectively) and total dryweight (r = 0·69, P < 0·05 and r = 0·59,P < 0·05 for the tetraploids and hexaploids respectively),of the seedlings 10 weeks after emergence. The main physiological distinction between the tetraploids andhexaploids appeared to be the superiority of the hexaploidsin rate of leaf appearance and the lower ratio of expanded tounexpanded leaves in the seedling 10 weeks after emergence.The tetraploids, in turn, appeared to be superior to the diploidsin these two characters. Triticum spp., wheat, polyploidy, grain size, photosynthetic area, net assimilation rate, tiller number 相似文献
6.
Abdel-Hasseb A. Fayed 《Biological trace element research》2010,134(1):64-67
Trace elements such as Zinc (Zn), copper (Cu), iron (Fe), and selenium (Se) are essential for male fertility. The fertilizing
capacity of most animals reduced with advancing age. The objective of the present work was to determine the serum and testicular
levels of Zn, Cu, and Se in young (10 months old) and old (30 months old) rabbits. Blood and testicular samples were obtained
from rabbits after their slaughter. All samples were digested by concentrated acids and analyzed for trace elements by flame
emission atomic absorption spectrophotometer. The results showed that serum Zn and Cu were lower in old rabbits than young
(P < 0.01). Serum Se was higher in old than young rabbits (P < 0.05). Testicular Cu and Se were significantly lower in old than young rabbits (P < 0.01). However, Zn level was higher in old compared to young rabbits (P < 0.01). The serum Zn and Se were higher than the testicular levels (P < 0.01). The testicular Cu in both ages was higher than the serum level (P < 0.01), which suggest a very important role for Cu in the process of spermatogenesis in rabbits. 相似文献
7.
Zhang L Sun YN Li YM Lin LX Ye Y Yan YQ Chen ZP 《Biological trace element research》2011,143(3):1629-1639
The thyroid functions of breastfed infants, as well as (indirectly) the development of their central nervous system, are dependent
on the iodine status of the lactating mother. Purkinje cell protein-2 is a cell-specific marker of the cerebellum Purkinje
cell and is a suitable indicator for observing the postnatal development of the cerebellum after birth. We measured the Purkinje
cell protein-2 mRNA and protein levels in the rat cerebellum in the critical postnatal (14 days after birth) and maturation
periods (28 days after birth) to determine the effect of different nutritional iodine levels on cerebellum growth in the offspring
during lactation. We found that severe iodine deficiency resulted in thyroid dysfunction in lactating rats and their offspring
on both 14 and 28 days, showing maternal total T4 16.7 ± 12.0 vs 36.4 ± 15.0, P < 0.05 (14 days) and 22.6 ± 18.7 vs 53.4 ± 9.4, P < 0.01 (28 days), and neonatal total T4 10.6 ± 2.3 vs 16.4 ± 4.7, P < 0.01(14 days) and 12.8 ± 2.9 vs 16.7 ± 3.4, P < 0.05 (28 days), respectively. The Purkinje cell protein-2 mRNA and its protein levels in offspring rats were significantly
reduced that showed Purkinje cell protein-2 mRNA 1.12 ± 0.04 vs 2.25 ± 0.53, P < 0.05 (14 days) and 1.74 ± 0.94 vs 8.69 ± 2.71, P < 0.01 (28 days). However, mild iodine deficiency and excessive iodine maintained almost normal thyroid function in maternal
and neonatal rats and normal Purkinje cell protein-2 mRNA and protein levels in offspring’s cerebellum. We conclude that severe
iodine deficiency could significantly reduce Purkinje cell protein-2 mRNA and its protein levels, indicating that the cerebellum
development was retarded, but mild iodine deficiency and excessive iodine could maintain them at an approximately normal level
by the mother’s and offspring’s compensations, especially by the mother’s mammary glands. 相似文献
8.
Immature barley embryos (Hordeum distichum var. Julia) of between020 and 080 mm in length, were isolated from thedeveloping grain and cultured in vitro on various culture media.The subsequent development of the embryos was followed overa period of weeks, and where germination ensued the growth rateof shoot and root meristems was compared with in vivo germinationrates. Various growth media were assessed for their abilityto support normal development of immature embryos. A numberof published media failed to support satisfactory developmentof young embryos. The addition of 115 per cent coconutmilk to Norstog's Medium I (mineral + vitamin solns) enhancedembryo development and lowered the threshold of viability fromembryos of 050 mm in length to 035 mm. Althoughin many cases germination ensued, embryo development was largelyabnormal. A slightly greater enhancement of growth was achievedwith 005030 per cent casein hydrolysate asthe growth medium supplement, although abnormal developmentwas not eliminated. A further lowering of the viability thresholdto include embryos of 025 mm in length was obtained bycombining 27 mM glutamine with the casein hydrolysatesupplement. Normal development and germination of embryos assmall as O25 mm was however obtained on Norstog's Medium JJand the results were reproduced in four additional if . distichumvarieties. In each case the critical threshold of viabilitywas found to lie in embryos of 020030 mmin length. 相似文献
9.
Liu XR Li JH Zhang Y Ge YS Tian FF Dai J Jiang FL Liu Y 《The Journal of membrane biology》2011,244(3):105-112
Zinc is one of the required trace elements in animals, and it serves an important role in biological systems. However, high
levels of zinc are poisonous to organisms. So far, there exist conflicting reports about zinc ions-induced mitochondrial permeability
transition (MPT). We analyzed the effects of Zn2+ on MPT by monitoring mitochondrial swelling with the ultraviolet–visible light absorption spectrum, characterizing the fluidity
of the membrane with fluorescence anisotropy, detecting the transmembrane potential (Δψ) with fluorescence intensity, and
observing mitochondrial ultrastructure with transmission electron microscopy. Data reveal that low concentrations of zinc
ions can trigger MPT while high levels of zinc ions cannot, which implies that zinc ions’ toxicity cannot be the result of
a single simple mechanism. 相似文献
10.
Responses of Quercus ilex L. seedlings from three different localities in Italy to experimentally imposed drought stress were analysed. Predawn (Ψpd) and midday (Ψm) leaf water potential of stressed seedlings decreased on an average until −4.0 and −4.2 MPa, respectively, in the severe
water stress. At the end of the severe water stress the relative water content (RWC) was 72.5 – 83.6 % and the photosynthetic
rates (PN) near zero. The critical threshold value of Ψpd for complete stomatal closure was from −4.0 to −4.5 MPa. The leaf damage after the severe water stress was significantly
greater in seedlings originated from the acorns of climax area (45 % total leaf injured area and 40 % fallen leaves) than
in the other seedlings (on an average 20.5 % total leaf injured area and 21 % fallen leaves).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
11.
Miguel Arroyo Raquel Torres-Guzmán Isabel de la Mata MarÍa Pilar Castillón Carmen Acebal 《Biocatalysis and Biotransformation》2013,31(1):53-56
We have studied the thermal stability of penicillin acylase from Streptomyces lavendulae in water-organic solvent monophasic systems at the range of temperatures between 40 and 60°C. We found a linear correlation between the log u P value of the solvent and the activation free energy for denaturation ( j G d ) at all temperatures tested. Thermodynamic analysis of the results indicates that solvents with log u P h m 2.3 have protective effects, whereas solvents with log u P S m 1.8 are deleterious for penicillin acylase. 相似文献
12.
Nitrous oxide (N2O) emissions from grazed grasslands are estimated to be approximately 28% of global anthropogenic N2O emissions. Estimating the N2O flux from grassland soils is difficult because of its episodic nature. This study aimed to quantify the N2O emissions, the annual N2O flux and the emission factor (EF), and also to investigate the influence of environmental and soil variables controlling
N2O emissions from grazed grassland. Nitrous oxide emissions were measured using static chambers at eight different grasslands
in the South of Ireland from September 2007 to August 2009. The instantaneous N2O flux values ranged from -186 to 885.6 μg N2O-N m−2 h−1 and the annual sum ranged from 2 ± 3.51 to 12.55 ± 2.83 kg N2O-N ha−1 y−1 for managed sites. The emission factor ranged from 1.3 to 3.4%. The overall EF of 1.81% is about 69% higher than the Intergovernmental
Panel on Climate Change (IPCC) default EF value of 1.25% which is currently used by the Irish Environmental Protection Agency
(EPA) to estimate N2O emission in Ireland. At an N applied of approximately 300 kg ha−1 y−1, the N2O emissions are approximately 5.0 kg N2O-N ha−1 y−1, whereas the N2O emissions double to approximately 10 kg N ha−1 for an N applied of 400 kg N ha−1 y−1. The sites with higher fluxes were associated with intensive N-input and frequent cattle grazing. The N2O flux at 17°C was five times greater than that at 5°C. Similarly, the N2O emissions increased with increasing water filled pore space (WFPS) with maximum N2O emissions occurring at 60–80% WFPS. We conclude that N application below 300 kg ha−1 y−1 and restricted grazing on seasonally wet soils will reduce N2O emissions. 相似文献
13.
Germination of three populations of Kochia indica Wight fromcontrasting soil types were studied under various levels ofsalinity, alkalinity and osmotic stress with a view to evaluatetheir potential to establish through seeds in saline and alkalineenvironments of various magnitudes. The seeds were germinatedunder controlled conditions in Petri dishes using salinizedsolutions of NaCl, Na2SO4, MgCI2 and CaSO4 (electrical conductivity,EC, 416 ds m), sodium carbonate solutions (pH8.5100), mannitol solutions ( 2.5 to 100 bar) and de-ionised distilled water (control). Inter-populationdifferences were very marked, showing selective adaptation ofthe populations to a particular stress type. In general, allpopulations exhibited salt tolerance but were rather sensitiveto high osmotic stress. Kochia indica Wight (bui), germination, population, salinity, alkalinity, osmotic stress 相似文献
14.
Summary The possible use of particle size separation of soils in water was tested for preparing fractions rich in ‘unknown’-N, which
constitutes between 41 and 46% of the total N. Ten particle size fractions ranging from <0.2 to>1,000.0 μm were separated
from the A horizon of the Bainsville soil, an Orthic Humic Gleysol, and from the Bh horizon of the Armadale soil, a poorly
drained Podzol. The distribution of N (hydrolyzable-, amino acid-, protein-, amino sugar-, ammonia-, ‘unknown’-and unidentified-N)
in the initial soils and in each size fraction was determined. While particle size separation did not yield fractions which
contained essentially only ‘unknown’-N and few known N-components, it was possible to isolate fractions which were either
rich in amino acid-or protein-N or in NH3-N. In general, the finer size fractions tended to be enriched in amino acid-N while NH3-N was more prominent in the coarser fractions. The amino sugar-N content of all size fractions was low. 相似文献
15.
Mitochondria from 1-day-old bean cotyledons were isolated bya slow isolation procedure involving a wash andby a rapid procedure. The mitochondria isolatedby the rapid procedure were more tightly coupledthan those isolated by the slow procedure. Anexogenous supply of cytochrome c or NAD was shown to improvethe activity of mitochondria isolated by the slowprocedure, but not those isolated by the rapidprocedure. The phosphorylative abilities of the latter weremuch greater than the former and were retained for longer periods.It was found that there was a leakage of NAD out of the mitochondria. 相似文献
16.
Osman, M. E-A. H. and El-Shentenawy, F. 1988. Photosyntheticelectron transport under phosphorylating conditions as influencedby different concentrations of various salts.J. exp.Bot. 39: 859863. The rate of light-induced electron transport by isolated spinachthylakoids under phosphorylating conditions, as affected bydifferent concentrations of Br, Cl, NO3,HCO3, SO42 and CO32 has been investigated.The results show that both low and high concentrations of HCO32stimulated the oxygen evolution capacity under phosphorylatingconditions, whereas only low concentrations of CO32,SO42 and Cl stimulated the oxygen evolution capacity.However, irrespective of concentration, both Br and NO3reduced this capacity. The rate of photosynthetic electron transportwas generally stimulated by addition of ADP, even in cases whereelectron transport was inhibited by addition of bromide andnitrate. The different concentrations of these anions also causedreduction of the power generated by proton pumping and usedfor phosphorylation. The greatest level of reduction was observedin the presence of high concentrations of Cl and HCO3. Key words: Spinach thylakoids, photosynthetic electron transport, phosphorylation 相似文献
17.
A bacterial phylogenetic survey of three environmentally distinct Antarctic Dry Valley soil biotopes showed a high proportion of so-called “uncultured” phylotypes, with a relatively low diversity of identifiable phylotypes. Cyanobacterial phylotypic signals were restricted to the high-altitude sample, whereas many of the identifiable phylotypes, such as the members of the Actinobacteria, were found at all sample sites. Although the presence of Cyanobacteria and Actinobacteria is consistent with previous culture-dependent studies of microbial diversity in Antarctic Dry Valley mineral soils, many phylotypes identified by 16S rDNA analysis were of groups that have not hitherto been cultured from Antarctic soils. The general belief that such “extreme” environments harbor a relatively low species diversity was supported by the calculation of diversity indices. The detection of a substantial number of uncultured bacterial phylotypes showing low BLAST identities (<95%) suggests that Antarctic Dry Valley mineral soils harbor a pool of novel psychrotrophic taxa. 相似文献
18.
Critical levels of selenium in raya (Brassica juncea Czern L.), maize (Zea mays L.), wheat (Triticum aestivum L.) and rice (Oryza sativa L.) were worked out by growing these crops in an alkaline silty loam soil treated with different levels of selenite-Se ranging
from 1 to 25 μg g−1 soil. Significant decrease in dry matter yield was observed above a level of 5 μg Se g−1 soil in raya and maize; 4 μg Se g−1 soil in wheat and 10 μg Se g−1 soil in rice shoots. The critical level of Se in plants above which significant decrease in yield would occur was found to
be 104.8 μg g−1 in raya, 76.9 μg g−1 in maize, 41.5 μg g−1 in rice and 18.9 μg g−1 in wheat shoots. Significant coefficients of correlation were observed between Se content above the critical level and dry
matter yield of raya as well as rice (r = −0.99, P ≤ 0.01), wheat (r = −0.97, P ≤ 0.01) and maize ((r = −0.96, P ≤ 0.01). A synergistic relationship was observed between S and Se content of raya (r = 0.96, P ≤ 0.01), wheat (r = 0.89, P ≤ 0.01), rice (r = 0.85, P ≤ 0.01) and maize (r = 0.84, P ≤ 0.01). Raya, maize and rice absorbed Se in levels toxic for animal consumption (i.e. > 5 mg Se kg−1) when the soil was treated with more than 1.5 μg Se g−1. In case of wheat, application of Se more than 3 μg g−1 soil resulted in production of toxic plants. 相似文献
19.
Selenium Distribution in Camel Blood and Organs After Different Level of Dietary Selenium Supplementation 总被引:1,自引:0,他引:1
Rabiha Seboussi Bernard Faye Ghaleb Alhadrami Mustafa Askar Wissam Ibrahim Baaha Mahjoub Khalil Hassan Tarik Moustafa Ahmed Elkhouly 《Biological trace element research》2010,133(1):34-50
Eight young female camels shared in four groups of two 2 years received a basal diet enriched respectively with 0, 2, 4, and
8 mg selenium under sodium selenite form for 64 days. Feed intake was assessed daily; blood samples were taken on weekly basis.
One camel from each group was killed at the end of the experiment. Se concentration in serum was increased significantly in
the supplemented groups with an average of 176.3 ± 18.0 ng/mL in the control group, 382.7 ± 107.6 in the group receiving 2 mg
Se, 519.8 ± 168.4 in the group receiving 4 mg Se, and 533.4 ± 158.6 in the group receiving 8 mg Se daily. For glutathione
peroxidase (GSH-Px) activity, the control group (51.0 IU/g Hb) and the group receiving 2 mg (50.5 IU/g Hb) were significantly
different than groups receiving 4 and 8 mg (respectively, 65.9 and 76.1 IU/g Hb). No significant variation occurred for vitamin
E (mean, 0.56 ± 0.23 ng/mL). Significant correlation between serum Se and GSH-Px was reported. Kidney was the richest organ
in selenium followed by lung, spleen, and liver, but the increase in supplemented groups was more marked in liver and kidney.
The hair seemed to be the best indicator of selenium intake in camel. 相似文献
20.
CO2-exchange rates (CER) of the sixth and the flag leaves oftwo spring-wheat varieties, Kolibri and Famos, were comparedusing an open-circuit infrared gas analysing system. Measurementswere repeated every two weeks starting when leaf blades werefully expanded. Single plants were grown in a controlled environmenthaving a photopuiod of 15 h and a day/night temperature of 24/19°C(H), 18/13 °C (M), and 12/7 °C (L) respectively untilapprox. 2 weeks after anthesis and at 18/13 °C until maturity.The photosynthetic photon-flux density (PPFD) at the top ofthe plants was 500 µE m2 sec1. During themeasurements PPFD was gradually reduced from 2000 to 0 µEm2 sec1 whereas the temperature was maintainedat the respctive growth-temperatures during the light period.The CER of the sixth leaf declined fairly similarly for bothvarieties, except for Kolibri where a faster decline was observedduring the first two weeks after full leaf expansion. The CERof the flag leaf declined more slowly than that of the sixthleaf. With the flag leaf of Famos, the decline was nearly linear,whereas with Kolibri it was very slow during the first few weeksbut rapid as the leaves further senesced. This pattern becamemore pronounced as the growth temperature decreased. The declinein relation to leaf age was much smaller at low PPFD than athigh PPFD during the same period. At full leaf expansion Kolibrireached higher maximum CER than Famos except at H. As the PPFDwas reduced the difference became smaller and at very low PPFDsuch as 50 µE m2 sec1 was reversed for thesixth leaf. Under optimum growth conditions maximum values ofCER were greater than 50mg CO2 dm2h1 and PPFDfor light saturation was close to 2000 µE m2 sec1.A comparison between the actual CER and a fitted curve widelyused, PN=(a+b/l)1DR, showed that the goodnessof fit strongly depends on cultivar, treatment and leaf ageas well as on the number and the level of PPFD from which datafor calculations are taken. Triticum aestivum, L., wheat, photosynthesis, photon-flux density, light response, carbon, dioxide exchange 相似文献