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1.
Quantitative trait loci for white blood cell numbers in swine   总被引:2,自引:1,他引:1  
Differential white blood cell counts are essential diagnostic parameters in veterinary practice but knowledge on the genetic architecture controlling variability of leucocyte numbers and relationships is sparse, especially in swine. Total leucocyte numbers (Leu) and the differential leucocyte counts, i.e. the fractions of lymphocytes (Lym), polymorphonuclear leucocytes [neutrophils (Neu), eosinophils (Eos) and basophils (Bas)] and monocytes (Mon) were measured in 139 F2 pigs from a Meishan/Pietrain family, before and after challenge with the protozoan pathogen Sarcocystis miescheriana for genome-wide quantitative trait loci (QTL) analysis. After infection, the pigs passed through three stages representing acute disease, reconvalescence and chronic disease. Nine genome-wide significant and 29 putative, single QTL controlling leucocyte traits were identified on 15 chromosomes. Because leucocyte traits varied with health and disease status, QTL influencing the leucocyte phenotypes showed specific health/disease patterns. Regions on SSC1, 8 and 12 contained QTL for baseline leucocyte traits. Other QTL regions reached control on leucocyte traits only at distinct stages of the disease model. Two-thirds of the QTL have not been described before. Single QTL explained up to 19% of the phenotypic variance in the F2 animals. Related traits were partly under common genetic influence. Our analysis confirms that leucocyte trait variation is associated with multiple chromosomal regions.  相似文献   

2.
Clinical–chemical traits are diagnostic parameters essential for characterization of health and disease in veterinary practice. The traits show significant variability and are under genetic control, but little is known about the fundamental genetic architecture of this variability, especially in swine. We have identified QTL for alkaline phosphatase (ALP), lactate (LAC), bilirubin (BIL), creatinine (CRE) and ionized sodium (Na+), potassium (K+) and calcium (Ca++) from the serum of 139 F2 pigs from a Meishan/Pietrain family before and after challenge with Sarcocystis miescheriana , a protozoan parasite of muscle. After infection, the pigs passed through three stages representing acute disease, subclinical disease and chronic disease. Forty-two QTL influencing clinical–chemical traits during these different stages were identified on 15 chromosomes. Eleven of the QTL were significant on a genome-wide level; 31 QTL were chromosome-wide significant. QTL showed specific health/disease patterns with respect to the baseline values of the traits as well as the values obtained through the different stages of disease. QTL influencing different traits at different times were found primarily on chromosomes 1, 3, 7 and 14. The most prominent QTL for the investigated clinical–chemical traits mapped to SSC3 and 7. Baseline traits of ALP, LAC, BIL, Ca++ and K+ were influenced by QTL regions on SSC3, 6, 7, 8 and 13. Single QTL explained up to 21.7% of F2 phenotypic variance. Our analysis confirms that variation of clinical–chemical traits is associated with multiple chromosomal regions.  相似文献   

3.
Quantitative trait loci for red blood cell traits in swine   总被引:4,自引:1,他引:3  
Haematological traits are essential diagnostic parameters in veterinary practice but knowledge on the genetic architecture controlling variability of erythroid traits is sparse, especially in swine. To identify QTL for erythroid traits in the pig, haematocrit (HCT), haemoglobin (HB), erythrocyte counts (RBC) and mean corpuscular haemoglobin content (MCHC) were measured in 139 F2 pigs from a Meishan/Pietrain family, before and after challenge with the protozoan pathogen Sarcocystis miescheriana . The pigs passed through three stages representing acute disease, reconvalescence and chronic disease. Forty-three single QTL controlling erythroid traits were identified on 16 chromosomes. Twelve of the QTL were significant at the genome-wide level while 31 were significant at a chromosome-wide level. Because erythroid traits varied with health and disease status, QTL influencing the erythroid phenotypes showed specific health/disease patterns. Regions on SSC5, 7, 8, 12 and 13 contained QTL for baseline erythroid traits, while the other QTL regions affected distinct stages of the disease model. Single QTL explained 9–17% of the phenotypic variance in the F2 animals. Related traits were partly under common genetic influence. Our analysis confirms that erythroid trait variation differs between Meishan and Pietrain breeds and that this variation is associated with multiple chromosomal regions.  相似文献   

4.
White blood cell count and platelets are implicated as risk factors for common complex diseases. Genetic factors substantially affect these traits in humans and mice. However, little is known about the genetic architecture of these traits in pigs. To identify quantitative trait loci (QTL) for leucocyte- and platelet-related traits in pigs, the total leucocyte number and differential leucocyte counts including the fraction of basophils, eosinophils, lymphocytes, monocytes, neutrophils, and a series of platelet parameters including platelet count, mean platelet volume, platelet distribution width and plateletcrit were measured in 1033 F2 animals on 240 days from a White Duroc × Erhualian intercross resource population. A total of 183 informative microsatellites distributed across 19 pig chromosomes (SSC) were genotyped across the entire resource population. Thirty-three QTL were identified for the examined traits, including eight genome-wide significant QTL for white blood cells and differential leucocyte counts on SSC2, 7, 8, 12 and 15 and six significant QTL for platelet-related traits on SSC2, 8, 13 and X. Erhualian or White Duroc alleles were not systematically associated with increased phenotypic values. These results not only confirmed many QTL identified previously in the mouse and swine, but also revealed a number of novel QTL for the traits recorded. Moreover, it is the first time that QTL for platelet-related traits in pigs have been reported.  相似文献   

5.
Behavioural indices in vertebrates are under genetic control at least to some extent. In spite of significant behavioural problems in farm animals, information on the genetic background of behaviour is sparse. The aim of this study was to map QTL for behavioural indices in swine under healthy conditions and after infection with Sarcocystis miescheriana , as behaviour can be significantly influenced by disease . This well-described parasite model subsequently leads to acute (day 14 p.i.), subclinical (day 28 p.i.) and chronic disease (day 42 p.i.), allowing the study and comparison of the behaviour of pigs under four different states of health or disease. The study was based on a well-described Pietrain/Meishan F2 family that has recently allowed the detection of QTL for disease resistance. We have mapped six genome-wide significant and 24 chromosome-wide significant QTL for six behavioural indices in swine. Six of these QTL (i.e. 20% of total QTL) showed effects on behavioural traits of the healthy pigs (day 0). Some of them (QTL on SSC11 and 18) lost influence on behavioural activities during disease, while the effects of others (QTL on SSC5, SSC8) partly remained during the whole experiment, although with different effects on the distinct behavioural indices. The disease model has been of high relevance to detect effects of gene loci on behavioural indices. Considering the importance of segregating alleles and environmental conditions that allow the identification of the phenotype, we conclude that there are indeed QTL with interesting effects on behavioural indices in swine.  相似文献   

6.
Atlantic salmon Salmo salar with amoebic gill disease (AGD) were exposed to a graded hypoxia (135–40 mmHg water P O2) and blood samples analysed for respiratory gases and pH at 119, 79·5 and 40 mmHg water P O2. There were no differences in the rate of oxygen uptake between infected and control fish. However, arterial P O2, and pH were significantly lower in the infected fish whereas P CO2 was significantly higher in infected fish compared with controls prior to hypoxia and at 119 mmHg water P O2. At 79·5 and 40 mmHg water P O2 saturation, there were no significant differences in blood P O2 or pH although blood P CO2 was elevated in AGD affected fish at 50% hypoxia (79·5 mmHg water P O2). The elevated levels of P CO2 in fish affected by AGD resulted in a persistent respiratory acidosis even during hypoxic challenge. These data suggest that even though the fish were severely affected by AGD, the presence of AGD while impairing gas transfer under normoxic conditions, did not contribute to respiratory failure during hypoxia.  相似文献   

7.
Carcass and meat quality traits are economically important in pigs. In this study, 17 carcass composition traits and 23 meat quality traits were recorded in 1028 F2 animals from a White Duroc × Erhualian resource population. All pigs in this experimental population were genotyped for 194 informative markers covering the entire porcine genome. Seventy-seven genome-wide significant quantitative trait loci (QTL) for carcass traits and 68 for meat quality were mapped to 34 genomic regions. These results not only confirmed many previously reported QTL but also revealed novel regions associated with the measured traits. For carcass traits, the most prominent QTL was identified for carcass length and head weight at 57 cM on SSC7, which explained up to 50% of the phenotypic variance and had a 95% confidence interval of only 3 cM. Moreover, QTL for kidney and spleen weight and lengths of cervical vertebrae were reported for the first time in pigs. For meat quality traits, two significant QTL on SSC5 and X were identified for both intramuscular fat content and marbling score in the longissimus muscle, while three significant QTL on SSC1 and SSC9 were found exclusively for IMF. Both LM and the semimembranous muscle showed common QTL for colour score on SSC4, 5, 7, 8, 13 and X and discordant QTL on other chromosomes. White Duroc alleles at a majority of QTL detected were favourable for carcass composition, while favourable QTL alleles for meat quality originated from both White Duroc and Erhualian.  相似文献   

8.
Stomatal traits are important to cope with changes in levels of atmospheric carbon dioxide (CO2) and with changing availability of water. Thus, they are expected to be involved in the reactions of plants to climate change. They are known to show a plastic physiological response to environmental factors such as elevated CO2 concentrations, but they are also under genetic control and should undergo evolutionary change if selection differs among environments. Stomatal development is regulated by several environmental and genetic signals suggesting a polygenic inheritance. In the present study, F1 progeny derived from a cross between Quercus robur and Q. robur subsp. slavonica were used to map QTLs (quantitative trait loci) for stomatal densities and growth parameters under nonwater stress conditions in 2 and 3 consecutive years, respectively. The positions of QTLs for stomatal density and growth coincided on six linkage groups. The QTL allele associated with the higher stomatal density was generally associated with taller plants and size increment indicating pleiotropic gene effects or close linkage. The phenotypic effects of the individual QTLs were mostly moderate in terms of phenotypic variance explained. However, a considerable amount of the genetically determined variation was explained by QTLs for stomatal density (from 63.6% to 94.4%). Especially, the QTL on linkage group 11 had a strong and highly significant effect on stomatal densities and growth parameters in all years suggesting a major QTL on this linkage group. The importance to analyse the genetic variation controlling complex adaptive traits in keystone species as oaks is discussed with regard to a better understanding of the reactions of ecosystems to global change.  相似文献   

9.
Chlamydomonas acidophila Negoro is a green algal species abundant in acidic waters (pH 2–3.5), in which inorganic carbon is present only as CO2. Previous studies have shown that aeration with CO2 increased its maximum growth rate, suggesting CO2 limitation under natural conditions. To unravel the underlying physiological mechanisms at high CO2 conditions that enables increased growth, several physiological characteristics from high- and low-CO2-acclimated cells were studied: maximum quantum yield, photosynthetic O2 evolution (Pmax), affinity constant for CO2 by photosynthesis (K0.5,p), a CO2-concentrating mechanism (CCM), cellular Rubisco content and the affinity constant of Rubisco for CO2 (K0.5,r). The results show that at high CO2 concentrations, C. acidophila had a higher K0.5,p, Pmax, maximum quantum yield, switched off its CCM and had a lower Rubisco content than at low CO2 conditions. In contrast, the K0.5,r was comparable under high and low CO2 conditions. It is calculated that the higher Pmax can already explain the increased growth rate in a high CO2 environment. From an ecophysiological point of view, the increased maximum growth rate at high CO2 will likely not be realised in the field because of other population regulating factors and should be seen as an acclimation to CO2 and not as proof for a CO2 limitation.  相似文献   

10.
Rainbow trout Oncorhynchus mykiss were exposed acutely to chloramine-T at a therapeutic concentration (9mg l−1) under moderately hypoxic (water P o2: l00 mmHg) or hyperoxic (water P o2: 430mmHg) conditions and arterial blood gas tensions ( P ao2 and P aco2) and pH were monitored using an extracorporeal circulation. Hypoxia, alone, resulted in an increased ventilation frequency, a decrease in both arterial P co2 and P o2 and an increase in arterial pH. There was no effect of chloramine-T exposure on the measured variables as compared with pre-exposure (hypoxia baseline) values. Hyperoxia, alone, resulted in a decrease in ventilation frequency, an increase in arterial P co2 and P o2, and a decrease in arterial pH. Chloramine-T exposure under these conditions caused a significant increase in ventilation frequency, but no significant effect on arterial blood gases or pH as compared with the hyperoxia baseline values. Despite the increase in ventilation caused by chloramine-T during hyperoxia, there was no reduction in P co2 or increase in P o2. Although these results were of little pathological significance, this study suggests that chloramine-T, although stimulating ventilation, was impairing the diffusion of co2 across the gill probably by the secretion of branchial mucus and enhancing the gill boundary layer.  相似文献   

11.
J. Ma  W. Qi  D. Ren  Y. Duan  R. Qiao  Y. Guo  Z. Yang  L. Li  D. Milan  J. Ren  L. Huang 《Animal genetics》2009,40(4):463-467
Chinese Erhualian pigs have larger and floppier ears compared with White Duroc pigs (small, half- or fully-pricked ears). To identify quantitative trait loci (QTL) for ear weight and area as well as erectness, a genome-wide scan with 194 microsatellites was performed in a White Duroc × Chinese Erhualian resource population (>1000 F2 animals). Twenty-three genome-wide significant QTL and 12 suggestive QTL were identified. All QTL for ear erectness and size detected in two previous studies, bar two on SSC6 and 9, were confirmed here. The 1% genome-wide significant QTL at 70 cM on SSC5 and at 58 cM on SSC7 have profound and pleiotropic effects on the three ear traits, with Erhualian alleles increasing weight and area but decreasing erectness. Notably, the 95% confidence interval of the QTL for weight and area on SSC7 spanned only 3 cM. New QTL reaching 1% genome-wide significance were found on SSC8 (at 37 cM) for all three ear traits, on SSC4 and 16 for weight and area, and on SSCX for area. Unexpectedly, Erhualian alleles at these loci were associated with lighter and smaller or erect ear. Some new suggestive QTL were also found on other chromosome regions. Almost all the QTL for weight and area had essentially additive effects, while the QTL for erectness on SSC2, 5 and 7 showed not only additive effects but also partial dominance effects of Erhualian alleles. The two most significant QTL on SSC7 and SSC5 could be promising targets for fine mapping and identification of the causative mutations.  相似文献   

12.
Cho IC  Park HB  Yoo CK  Lee GJ  Lim HT  Lee JB  Jung EJ  Ko MS  Lee JH  Jeon JT 《Animal genetics》2011,42(6):621-626
Haematological traits play important roles in disease resistance and defence functions. The objective of this study was to locate quantitative trait loci (QTL) and the associated positional candidate genes influencing haematological traits in an F2 intercross between Landrace and Korean native pigs. Eight blood‐related traits (six erythrocyte traits, one leucocyte trait and one platelet trait) were measured in 816 F2 progeny. All experimental animals were genotyped with 173 informative microsatellite markers located throughout the pig genome. We report that nine chromosomes harboured QTL for the baseline blood parameters: genomic regions on SSC 1, 4, 5, 6, 8, 9, 11, 13 and 17. Eight of twenty identified QTL reached genome‐wide significance. In addition, we evaluated the KIT locus, an obvious candidate gene locus affecting variation in blood‐related traits. Using dense single nucleotide polymorphism marker data on SSC 8 and the marker‐assisted association test, the strong association of the KIT locus with blood phenotypes was confirmed. In conclusion, our study identified both previously reported and novel QTL affecting baseline haematological parameters in pigs. Additionally, the positional candidate genes identified here could play an important role in elucidating the genetic architecture of haematological phenotype variation in swine and in humans.  相似文献   

13.
Transport of gases into leaves   总被引:14,自引:10,他引:4  
Abstract. Transport of gases between the intercellular spaces of plant leaves and the surrounding air is analysed in terms of multicomponent collision processes through an isothermal, porous septum. Interaction of diffusing species with each other and with the pore walls is described using a modified Stefan–Maxwell equation and an equation relating the pressure gradient to the sum of the diffusive fluxes, weighted by their appropriate Knudsen diffusivities. Viscous How arising from an excess pressure within the leaf is also considered.
Equations are derived which describe the flux densities of water vapour and CO2 through the stomata. The analysis is general and is applicable to trace gases other than CO2. A simple conductance is defined for water vapour to relate the flux and mol fraction difference across the stomata, viz. Nw =− gw , δ xw / xa . A simple conductance cannot be defined for CO2 because the flux of water vapour has a significant influence on the CO2 gradient. The equation derived for the intercellular mol fraction of CO2 is in terms of the fluxes of CO2 and water vapour and represents a 'large-pore' ( d > μm) approximation which requires no information about stomalal geometry. Analogous equations are developed for transfer of gases through the leaf boundary layer. Sample calculations are presented to illustrate the effect of neglecting the interaction of water vapour and CO2 on the calculated intercellular and surface concentrations of CO2. Equations for computing water vapour and CO2 flux densities from leaf chamber measurements are also presented.  相似文献   

14.
Few studies have investigated the interaction of ultraviolet (UV)-B radiation and CO2 concentration on plants. We studied the combined effects of UV-B radiation and CO2 concentration on canola ( Brassica napus cv. 46A65) under four growth conditions – ambient CO2 with UV-B (control), elevated CO2 with UV-B, ambient CO2 without UV-B, and elevated CO2 without UV-B – to determine whether the adverse effects of UV-B are mitigated by elevated CO2. Elevated CO2 significantly increased plant height and seed yield, whereas UV-B decreased them. Elevated CO2 ameliorated the adverse effects of UV-B in plant height. UV-B did not affect the physical characteristics of leaf but CO2 did. Certain flower and fruit characteristics were affected negatively by UV-B and positively by CO2. UV-B did not affect net photosynthesis, transpiration and stomatal conductance but decreased water use efficiency (WUE). Elevated CO2 significantly increased net photosynthesis and WUE. Neither UV-B nor CO2 affected chlorophyll (Chl) fluorescence. UV-B significantly decreased Chl b and increased the ratio of Chl a / b . Elevated CO2 decreased only the ratio of Chl a / b . UV-B significantly increased UV-absorbing compounds while CO2 had no effect on them. Both UV-B and CO2 significantly increased epicuticular wax content. Many significant relationships were found between morphological, physiological, and chemical parameters. This study showed that elevated CO2 can partially ameliorate some of the adverse effects of UV-B radiation in B . napus .  相似文献   

15.
Baseline erythroid indices are increasingly involved as risk factors for common complex diseases in humans. However, little is known about the genetic architecture of baseline erythroid traits in pigs. In this study, hematocrit (Hct), hemoglobin (Hgb), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), mean corpuscular volume (MCV), red blood cell (RBC), and red cell distribution width (RDW) were measured in 1420 (day 18), 1410 (day 46), and 1033 (day 240) F(2) pigs from a White Duroc x Erhualian intercross resource population. The entire resource population was genotyped for 183 microsatellite loci across the pig genome, and the quantitative trait loci (QTL) analysis was performed for all erythroid-related traits measured with QTL Express based on a least-squares method. A total of 101 QTL, including 46 genome-wide significant QTL and 55 chromosome-wide significant QTL, regulating erythroid traits were found on all pig chromosomes (SSC) except for SSC15 and SSC18. The genome-wide significant QTL were mainly localized on SSC1, 7, 8, 10, and X. These results confirmed most of QTL previously identified in the swine. More importantly, this study detected age-specific QTL for baseline erythroid traits in pigs for the first time. Notably, the QTL for MCV and MCH on day 18 on SSC8 with small intervals of 3 and 4 cM, respectively, provided a good starting point for identifying causal genes underlying MCV and MCH in the future.  相似文献   

16.
Ananas comosus L. (Merr.) (pineapple) was grown at three day/night temperatures and 350 (ambient) and 700 (elevated) μ mol mol–1 CO2 to examine the interactive effects of these factors on leaf gas exchange and stable carbon isotope discrimination ( Δ ,‰). All data were collected on the youngest mature leaf for 24 h every 6 weeks. CO2 uptake (mmol m–2 d–1) at ambient and elevated CO2, respectively, were 306 and 352 at 30/20 °C, 175 and 346 at 30/25 °C and 187 and 343 at 35/25 °C. CO2 enrichment enhanced CO2 uptake substantially in the day in all environments. Uptake at night at elevated CO2, relative to that at ambient CO2, was unchanged at 30/20 °C, but was 80% higher at 30/25 °C and 44% higher at 35/25 °C suggesting that phosphoenolpyruvate carboxylase was not CO2-saturated at ambient CO2 levels and a 25 °C night temperature. Photosynthetic water use efficiency (WUE) was higher at elevated than at ambient CO2. Leaf Δ -values were higher at elevated than at ambient CO2 due to relatively higher assimilation in the light. Leaf Δ was significantly and linearly related to the fraction of total CO2 assimilated at night. The data suggest that a simultaneous increase in CO2 level and temperature associated with global warming would enhance carbon assimilation, increase WUE, and reduce the temperature dependence of CO2 uptake by A. comosus .  相似文献   

17.
The effects of high O3 (200 nl l−1 during the light period) and high CO2 (650 μl l−1 CO2, 24 h a day) alone and in combination were studied on 45-day-old sugar maple ( Acer saccharum Marsh.) seedlings for 61 days in growth chambers. After 2 months of treatment under the environmental conditions of the experiment, sugar maple seedlings did not show a marked response to the elevated CO2 treatment: the effect of high CO2 on biomass was only detected in the leaves which developed during the treatment, and assimilation rate was not increased. Under high O3 at ambient CO2, assimilation rate at days 41 and 55 and Rubisco content at day 61 decreased in the first pair of leaves; total biomass was reduced by 43%. In these seedlings large increases (more than 2-fold) in glucose 6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) activity and in anaplerotic CO2 fixation by phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) were observed, suggesting that an enhanced reducing power and carbon skeleton production was needed for detoxification and repair of oxidative damage. Under high O3 at elevated CO2, a stimulation of net CO2 assimilation was observed after 41 days but was no longer observed at day 55. However, at day 61, the total biomass was only reduced by 21% and stimulation of G6PDH and PEPC was less pronounced than under high O3 at ambient CO2. This suggests that high CO2 concentration protects, to some extent, against O3 by providing additional carbon and energy through increased net assimilation.  相似文献   

18.
1. Six- to eight-week greenhouse experiments with independent control of pH and dissolved CO2 evaluated the potential for CO2 enrichment to stimulate the accumulation of Al, Fe, P and N in shoots of Vallisneria americana , particularly at pH 5. These minerals were provided only as they occurred in natural lake sediments.
2. The effect of CO2 enrichment at pH 5 v pH 7.3 on growth and tissue N concentration was also determined.
3. CO2 enrichment at pH 5 effected 5.5- and 7-fold increases in total shoot accumulation of Al and Fe, respectively. In a two-way factorial experiment, CO2 enrichment yielded 6- to 11-fold greater total shoot P accumulation in plants grown on less and more fertile sediments, respectively.
4. In a three-way factorial experiment, CO2 enrichment stimulated Vallisneria growth, especially at pH 5, and resulted in a 31–58% reduction in tissue [N] for different pH × sediment combinations. These are greater reductions than previously reported. It also increased total shoot N accumulation up to 6-fold, and there were significant interactions with pH and sediment source: the CO2 enrichment effect on shoot N accumulation was greater at pH 5 than at pH 7.3, and it was greater with the more fertile sediment at pH 5.
5. Water chemistry (pH and/or [CO2]) and sediment fertility thus both indirectly influenced the accumulation of sediment-derived minerals in macrophyte shoots within the water column.  相似文献   

19.
1. Six- to eight-week greenhouse experiments with independent control of pH and dissolved CO2 evaluated the potential for CO2 enrichment to stimulate the accumulation of Al, Fe, P and N in shoots of Vallisneria americana , particularly at pH 5. These minerals were provided only as they occurred in natural lake sediments.
2. The effect of CO2 enrichment at pH 5 v pH 7.3 on growth and tissue N concentration was also determined.
3. CO2 enrichment at pH 5 effected 5.5- and 7-fold increases in total shoot accumulation of Al and Fe, respectively. In a two-way factorial experiment, CO2 enrichment yielded 6- to 11-fold greater total shoot P accumulation in plants grown on less and more fertile sediments, respectively.
4. In a three-way factorial experiment, CO2 enrichment stimulated Vallisneria growth, especially at pH 5, and resulted in a 31–58% reduction in tissue [N] for different pH × sediment combinations. These are greater reductions than previously reported. It also increased total shoot N accumulation up to 6-fold, and there were significant interactions with pH and sediment source: the CO2 enrichment effect on shoot N accumulation was greater at pH 5 than at pH 7.3, and it was greater with the more fertile sediment at pH 5.
5. Water chemistry (pH and/or [CO2]) and sediment fertility thus both indirectly influenced the accumulation of sediment-derived minerals in macrophyte shoots within the water column.  相似文献   

20.
The objective of this investigation was to examine the effect of an elevated atmospheric CO2 partial pressure ( p CO2) on the N-sink strength and performance of symbiotic N2 fixation in Trifolium repens L. cv. Milkanova. After initial growth under ambient p CO2 in a nitrogen-free nutrient solution, T. repens in the exponential growth stage was exposed to ambient and elevated p CO2 (35 and 60 Pa) and two levels of mineral N (N-free and 7·5 mol m–3 N) for 36 d in single pots filled with silica sand in growth chambers. Elevated p CO2 evoked a significant increase in biomass production from day 12 after the start of CO2 enrichment. For plants supplied with 7·5 mol m–3 N, the relative contribution of symbiotically fixed N (%Nsym) as opposed to N assimilated from mineral sources (15N-isotope-dilution method), dropped to 40%. However, in the presence of this high level of mineral N, %Nsym was unaffected by atmospheric p CO2 over the entire experimental period. In plants fully dependent on N2 fixation, the increase in N yield reflects a stimulation of symbiotic N2 fixation that was the result of the formation of more nodules rather than of higher specific N2 fixation. These results are discussed with regard to physiological processes governing symbiotic N2 fixation and to the response of symbiotic N2 fixation to elevated p CO2 in field-grown T. repens .  相似文献   

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