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1.
F. A. Bliss 《Plant and Soil》1993,152(1):71-79
Common bean (Phaseolus vulgaris L.), which is an important food crop in the Americas, Africa and Asia, usually is thought to fix only small amounts of atmospheric nitrogen. However, field data indicate considerable genetic variability for total N2 fixation and traits associated with fixation. Studies have shown that selection to increase N2 fixation will be successful if: (1) discriminating traits (selection criteria) are measured precisely, (2) variability in germplasm is heritable, (3) selected parents are also agronomically suitable, (4) units of selection facilitate quantification of selection criteria, and (5) a breeding procedure that allows maximum genetic gain for N2 fixation and recombination with essential agronomic traits is chosen. Breeding lines capable of fixing enough atmospheric N2 to support seed yields of 1000–2000 kg ha–1 have been identified and new cultivars with high N2 fixation potential are being released. 相似文献
2.
Does selection on horn length of males and females differ in protected and hunted populations of a weakly dimorphic ungulate?
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Weaponry in ungulates may be costly to grow and maintain, and different selective pressures in males and females may lead to sex‐biased natural survival. Sexual differences in the relationship between weapon growth and survival may increase under anthropogenic selection through culling, for example because of trophy hunting. Selection on weaponry growth under different scenarios has been largely investigated in males of highly dimorphic ungulates, for which survival costs (either natural or hunting related) are thought to be greatest. Little is known, however, about the survival costs of weaponry in males and females of weakly dimorphic species. We collected information on horn length and age at death/shooting of 407 chamois Rupicapra rupicapra in a protected population and in two hunted populations with different hunting regimes, to explore sexual differences in the selection on early horn growth under contrasting selective pressures. We also investigated the variation of horn growth and body mass in yearling males (n = 688) and females (n = 539) culled in one of the hunted populations over 14 years. The relationship between horn growth and survival showed remarkable sexual differences under different evolutionary scenarios. Within the protected population, under natural selection, we found no significant trade‐off in either males or females. Under anthropogenic pressure, selection on early horn growth of culled individuals showed diametrically opposed sex‐biased patterns, depending on the culling regime and hunters’ preferences. Despite the selective bias between males and females in one of the hunted populations, we did not detect significant sex‐specific differences in the long‐term pattern of early growth. The relationship between early horn growth and natural survival in either sex might suggest stabilizing selection on horn size in chamois. Selection through culling can be strongly sex‐biased also in weakly dimorphic species, depending on hunters’ preferences and hunting regulations, and long‐term data are needed to reveal potential undesirable evolutionary consequences. 相似文献
3.
K. Takeda K. J. Frey 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1985,69(4):375-382
Summary The method of independent culling levels was applied for simultaneous improvement in grain yield, protein percentage, and protein yield in a population of oat lines from the BC0–BC5 of the interspecific matingAvena sativa ×A. sterilis. Grain yield and protein percentage were subjected to selection with various combination of culling levels to give samples with 2% of the lines from the original population. — Intense selection for grain yield resulted in samples with high grain and protein yields but low protein percentage. Intense selection for protein percentage resulted in samples with high protein percentage but low grain and protein yields. The sample selected for protein yield only showed no significant difference from the recurrent parent for any trait. The recommended regime for improving protein percentage and grain and protein yields simultaneously was one that initially saved approximately 25–50% of the original population on the basis of protein percentage, and then provided intense selection for grain yield on the lines that remained. At least three backcrosses were necessary to obtain lines with high protein percentage and acceptable agronomic traits.Journal Paper No. J-11439 of the Iowa Agric. and Home Econ. Exp. Stn., Ames, IA 50011. Project No. 2447 相似文献
4.
The consequences of preferential mating in the presence of partial assortative and sexual selection mechanisms are ascertained for a two-allele one-locus trait involving two phenotype classes C1 = {all homozygotes} and C2 = {heterozygotes}. Relevant biological cases may include Burley (1977, Proc. Nat. Acad. Sci. USA 74, 3476–3479), Wilbur et al. (1978, Evolution 32, 264–270), and Singh and Zouros (1978, Evolution 32, 342–353). When the preference rate for the heterozygote exceeds that for homozygotes, it is established that the unique stable state is the central Hardy-Weinberg equilibrium. The rate of approach is faster with sexual selection than for the corresponding model of assortative mating. When the preference rates favor the homozygotes then in this symmetric model of sexual selection two asymmetric Hardy-Weinberg polymorphisms can evolve, and which succeeds depends on initial conditions. The models are also analyzed with natural selection acting on phenotypes superimposed on assortative mating. In this case we can have up to three coexisting stable states involving both fixation alternatives and a central polymorphism. The corresponding model with sexual selection maintains either the central equilibrium as in assortative mating or two asymmetric polymorphic equilibria. 相似文献
5.
The comparison of the degree of differentiation in neutral marker loci and genes coding quantitative traits with standardized and equivalent measures of genetic differentiation (FST and QST, respectively) can provide insights into two important but seldom explored questions in evolutionary genetics: (i) what is the relative importance of random genetic drift and directional natural selection as causes of population differentiation in quantitative traits, and (ii) does the degree of divergence in neutral marker loci predict the degree of divergence in genes coding quantitative traits? Examination of data from 18 independent studies of plants and animals using both standard statistical and meta‐analytical methods revealed a number of interesting points. First, the degree of differentiation in quantitative traits (QST) typically exceeds that observed in neutral marker genes (FST), suggesting a prominent role for natural selection in accounting for patterns of quantitative trait differentiation among contemporary populations. Second, the FST – QST difference is more pronounced for allozyme markers and morphological traits, than for other kinds of molecular markers and life‐history traits. Third, very few studies reveal situations were QST < FST, suggesting that selection pressures, and hence optimal phenotypes, in different populations of the same species are unlikely to be often similar. Fourth, there is a strong correlation between QST and FST indices across the different studies for allozyme (r=0.81), microsatellite (r=0.87) and combined (r=0.75) marker data, suggesting that the degree of genetic differentiation in neutral marker loci is closely predictive of the degree of differentiation in loci coding quantitative traits. However, these interpretations are subject to a number of assumptions about the data and methods used to derive the estimates of population differentiation in the two sets of traits. 相似文献
6.
Annual inputs of symbiotic N2-fixation associated with 3 species of alpine Trifolium were estimated in four alpine communities differing in resource supplies. We hypothesized that fixation rates would vary according to the degree of N, P, and water limitation of production, with the higher rates of fixation in N limited communities (dry meadow, moist meadow) and lower rates in P and water limited communities (wet meadow, fellfield). To estimate N2-fixation rates, natural abundance of N isotopes (15N) were measured in field collected Trifolium and reference plants and in Trifolium plants grown in N-free medium in a growth chamber. All three Trifolium species relied on a large proportion of atmospherically-fixed N2 to meet their N requirements, ranging from 70 to 100%. There were no apparent differences in the proportion of plant N derived from fixation among the communities, but differences in the contribution of the Trifolium species to community cover resulted in a wide range of annual N inputs from fixation, from 127 mg m–2 year–1 in wet meadows to 810 mg m–2 year–1 in fellfields. Annual spatially integrated input of symbiotic N2-fixation to Niwot Ridge, Colorado was estimated at 490 mg m–2 year–1 (5 kg ha–1 year–1), which is relatively high in the context of estimates of net N mineralization and N deposition. 相似文献
7.
Aristidis S. Veskoukis Michalis G. Nikolaidis Antonios Kyparos Dimitrios Kouretas 《Free radical biology & medicine》2009,47(10):1371-1374
This study investigated whether selected oxidative stress markers measured in blood adequately reflect redox status in skeletal muscle, heart, and liver. Several markers were determined after implementing two treatments known to affect redox status, namely exercise and allopurinol administration. Xanthine oxidase, thiobarbituric acid-reactive substances (TBARS), protein carbonyls (PC), reduced glutathione (GSH), oxidized glutathione (GSSG), catalase, and total antioxidant capacity were determined in blood, skeletal muscle, heart, and liver. Correlation between blood and tissues in each marker was performed through the Spearman rank correlation coefficient. GSSG in erythrocytes was correlated with all tissues, ranging in the five experimental groups as follows: skeletal muscle rs = 0.656–0.874, heart rs = 0.742–0.981, liver rs = 0.646–0.855. Xanthine oxidase and TBARS measured in blood satisfactorily described the redox status of the heart (0.753–0.964 and 0.705–1.000, respectively) and liver (0.755–0.902 and 0.656–1.000, respectively). Skeletal muscle and heart redox status can be adequately described by PC (0.652–1.000 and 0.656–0.964, respectively), GSH (0.693–1.000 and 0.656–1.000, respectively), and catalase (0.745–1.000 and 0.656–1.000, respectively) measured in blood. In conclusion, this study suggests that a combination of markers measured in blood provides a reliable indication about the redox status in skeletal muscle, heart, and liver. 相似文献
8.
A. N. Kucher N. R. Maksimova A. N. Nogovitsina A. L. Sukhomyasova 《Russian Journal of Genetics》2004,40(5):546-552
Information on the sex, age, and ethnic compositions; reproductive parameters; intensity of natural selection (Crow's indices); and surname diversity of three rural populations (the Byadi, Dyupsya, and Cheriktey villages) of the Ust-Aldan ulus (district) of Sakha Republic (Yakutia) has been analyzed. The rural Yakut population of the Ust-Aldan ulus is demographically young (the mean age 25–31 years) and characterized by low outbreeding, unfavorable sex ratio in both prereproductive and reproductive ages, and high fertility (3.58–5.45 children surviving until the reproductive age per woman that has completed the reproductive period), although the actual reproductively active period is shorter than half its physiological duration. In the structure of index of total selection, the differential-fertility component is considerably greater than the differential-mortality component (I
tot = 0.625, I
m = 0.093, and I
f = 0.487). In the villages studied, some surnames are accumulated (45–65% of the population have five most frequent surnames), which determines the low surname diversity ( = 11.62–25.19) and high random isonymy (I
r= 0.0391–0.0823). 相似文献
9.
Nitrogen concentration of cauliflower organs as determined by organ size,N supply,and radiation environment 总被引:1,自引:0,他引:1
Data from field experiments carried out in three consecutive years under contrasting N supply and radiation environment altered by artificial shading were used to identify (a) the relationship between N concentration and organ size under conditions of unrestricted N supply and (b) critical levels of soil nitrate (Nmincrit), where nitrogen concentration of cauliflower organs begin to decline because of N limitations. The decline of N concentrations in cauliflower was analysed at different levels of morphological aggregation, i.e., the whole shoot level, the organ level (leaves, stem, and curd), and within different leaf groups within the canopy. Nmincrit values (0–60 cm soil depth) for total nitrogen concentration of cauliflower organs leaves, stem and curd were estimated at 85, 93 and 28 kg N ha–1, respectively. Within the canopy, Nmincrit values for total N of leaves increased from the top to the bottom from 44 to 188 kg N ha–1. Nmincrit values for protein N in leaves from different layers of the canopy were much lower at around 30 kg N ha–1, without a gradient within the canopy. It is discussed that these differences in Nmincrit values are most likely a consequence of N redistribution associated with nitrogen deficiency. The decline of average shoot nitrogen concentrations, [Nm] (%N DM), with shoot dry matter, W
sh, (t ha–1) under conditions of optimal N supply was [Nm]= 4.84 (±0.071) W
sh
–0.089(± 0.011), r
2=0.67 (±S.E.). The reduction of radiation intensity by artificial shading (60% of control) had no significant influence on total nitrogen concentrations of leaves and only a small influence on protein nitrogen concentrations in lower layers of the canopy. The leaf nitrate nitrogen fraction of nitrogen, f
nitr (–), within the canopy decreased linearly with increased average incident irradiance in different canopy layers (I
av, W PAR m–2) (f
Nitr. = 0.2456(±0.0188) – 0.0023(±0.0004)I
av, r
2 = 0.67. 相似文献
10.
Marie-France Champliaud Ismo Virtanen Car-Fredrik Tiger Matti Korhonen Robert Burgeson Donald Gullberg 《Experimental cell research》2000,259(2):326
Laminins assemble into trimers composed of α, β, and γ chains which posttranslationally are glycosylated and sometimes proteolytically cleaved. In the current paper we set out to characterize posttranslational modifications and the laminin isoforms formed by laminin α1 and α5 chains. Comparative pulse–chase experiments and deglycosylation studies in JAR cells established that the Mr 360,000 laminin α1 chain is glycosylated into a mature Mr 400,000 band while the Mr 370,000 laminin α5 chain is glycosylated into a Mr 390,000 form that upon secretion is further processed into a Mr 380,000 form. Hence, despite the shorter peptide length of α1 chain in comparison with the α5 chain, secreted α1 assumes a larger size in SDS–PAGE due to a higher degree of N-linked glycosylation and due to the lack of proteolytic processing. Immunoprecipitations and Western blotting of JAR laminins identified laminin α1 and laminin α5 chains in laminin-1 and laminin-10. In placenta laminin α1 chain (Mr 400,000) and laminin α5 chain (Mr 380,000/370,000 doublet) were found in laminin-1/-3 and laminin-10/-11. Immunohistochemically we could establish that the laminin α1 chain in placenta is deposited in the developing villous and trophoblast basement membrane, also found to contain laminin β2 chains. Surprisingly, a fraction of the laminin α1 chain from JAR cells and placenta could not be precipitated by antibodies to laminin β1–β3 chains, possibly pointing to an unexpected complexity in the chain composition of α1-containing laminin isoforms. 相似文献
11.
Linkages between phosphorus transformations and carbon decomposition in a forest soil 总被引:6,自引:1,他引:5
Noam Gressel John G. McColl Caroline M. Preston Roger H. Newman Robert F. Powers 《Biogeochemistry》1996,33(2):97-123
Phosphorus mineralization is chemically coupled with organic matter (OM) decomposition in surface horizons of a mixed-conifer forest soil from the Sierra Nevada, California, and is also affected by the disturbance caused by forest harvesting. Solution13C nuclear magnetic resonance (NMR) spectroscopy of NaOH extracts revealed a decrease of O-alkyl and alkyl-C fractions with increasing degree of decomposition and depth in the soil profile, while carbonyl and aromatic C increased. Solid-state13C-NMR analysis of whole soil samples showed similar trends, except that alkyl C increased with depth. Solution31P-NMR indicated that inorganic P (P1) increased with increasing depth, while organic-P (Po) fractions decreased. Close relationships between P mineralization and litter decomposition were suggested by correlations between P1 and C fractions (r = 0.82, 0.81, –0.87, and –0.76 for carbonyl, aromatic, alkyl and O-alkyl fractions, respectively). Correlations for diester-P and pyrophosphate with O-alkyl (r = 0.63 and 0.84) and inverse correlations with aromatics (r = –0.74 and –0.72) suggest that mineralization of these P fractions coincides with availability of C substrate. A correlation between monoester P and alkyl C (r = 0.63) suggests mineralization is linked to breakdown of structural components of the plant litter. NMR analyses, combined with Hedley-P fractionation, suggest that post-harvest buildup of labile P in decomposed litter increases the potential for leaching of P during the first post-harvest season, but also indicates reduced biological activity that transports P from litter to the mineral soil. Thus, P is temporarily stored in decomposed litter, preventing its fixation by mineral oxides. In the mineral horizons,31P-NMR provides evidence of decline in biologically-available P during the first post-harvest season. 相似文献
12.
Joann P. Roskoski 《Microbial ecology》1980,6(4):349-355
Nitrogen fixation (C2H2 reduction) by epiphylls on coffee,Coffea arabica, grown in sites with different degrees of shade, was determined. Coffee leaves with nitrogen-fixing epiphylls were found in all sites in approximately equal numbers. Rates of C2H2 reduction were similar for all sites and throughout the year, averaging 3.21 nmoles C2H2 reduced leaf with epiphylls–1 day–1. Apparently, neither rates of activity nor abundance of leaves with nitrogen-fixing epiphylls is related to the degree of shade in a site. No correlation was found between percent epiphyll cover and the presence or magnitude of nitrogen-fixing activity. Calculated annual fixation by epiphylls on coffee was low, ranging from 0.7 g N2 ha–1 year–1 for the shadeless site to 1.4 g N2 ha–1 year–1 for the site withIngajinicuil shade trees. These results suggest that epiphyll fixation is not an important source of nitrogen for the coffee ecosystem studied. 相似文献
13.
Vast areas of southern Chile are now covered by second-growth forests because of fire and logging. To study successional patterns after moderate-intensity, anthropogenic fire disturbance, we assessed differences in soil properties and N fluxes across a chronosequence of seven successional stands (2–130 years old). We examined current predictions of successional theory concerning changes in the N cycle in forest ecosystems. Seasonal fluctuations of net N mineralization (Nmin) in surface soil and N availability (Na; Na=NH
4
+
–N+NO
3
–
–N) in upper and deep soil horizons were positively correlated with monthly precipitation. In accordance with theoretical predictions, stand age was positively, but weakly related to both Na (r
2=0.282, P<0.001) and total N (Ntot; r
2=0.192, P<0.01), and negatively related to soil C/N ratios (r
2=0.187, P<0.01) in surface soils. A weak linear increase in soil Nmin (upper plus deep soil horizons) was found across the chronosequence (r
2=0.124, P<0.022). Nmin occurred at modest rates in early successional stands, suggesting that soil disturbance did not impair microbial processes. The relationship between N fixation (Nfix) in the litter layer and stand age best fitted a quadratic model (r
2=0.228, P<0.01). In contrast to documented successional trends for most temperate, tropical and Mediterranean forests, non-symbiotic Nfix in the litter layer is a steady N input to unpolluted southern temperate forests during mid and late succession, which may compensate for hydrological losses of organic N from old-growth ecosystems. 相似文献
14.
Frédéric Fabre Josselin Montarry Jér?me Coville Rachid Senoussi Vincent Simon Beno?t Moury 《PLoS pathogens》2012,8(4)
Uncovering how natural selection and genetic drift shape the evolutionary dynamics of virus populations within their hosts can pave the way to a better understanding of virus emergence. Mathematical models already play a leading role in these studies and are intended to predict future emergences. Here, using high-throughput sequencing, we analyzed the within-host population dynamics of four Potato virus Y (PVY) variants differing at most by two substitutions involved in pathogenicity properties. Model selection procedures were used to compare experimental results to six hypotheses regarding competitiveness and intensity of genetic drift experienced by viruses during host plant colonization. Results indicated that the frequencies of variants were well described using Lotka-Volterra models where the competition coefficients βij exerted by variant j on variant i are equal to their fitness ratio, rj/ri. Statistical inference allowed the estimation of the effect of each mutation on fitness, revealing slight (s = −0.45%) and high (s = −13.2%) fitness costs and a negative epistasis between them. Results also indicated that only 1 to 4 infectious units initiated the population of one apical leaf. The between-host variances of the variant frequencies were described using Dirichlet-multinomial distributions whose scale parameters, closely related to the fixation index F
ST, were shown to vary with time. The genetic differentiation of virus populations among plants increased from 0 to 10 days post-inoculation and then decreased until 35 days. Overall, this study showed that mathematical models can accurately describe both selection and genetic drift processes shaping the evolutionary dynamics of viruses within their hosts. 相似文献
15.
A. L. Huber 《Hydrobiologia》1986,131(3):193-203
Variations in nitrogen fixation (acetylene reduction) by Nodularia spumigena blooms in the Peel-Harvey estuarine system were examined with respect to spatial (sampling station location, and depth) and temporal (seasonal and diurnal) distribution. The annual contributions of nitrogen fixation by the blooms to the nitrogen budget of the estuary were estimated to range from 309 to 713t. Contributions by nitrogen fixation were similar to the riverine inputs in the Harvey Estuary, but lower in the Peel Inlet.The Harvey Estuary had higher biomass and total fixation rates (to 0.4 nmol C2H2 · ml–1 h–1), but the heterocyst nitrogen fixation rates were greater in the Peel Inlet (to 9 × 10–1 nmol C2H2 · heterocyst–1 · h–1). Nitrogen fixation decreased with depth in response to light, though other factors also appeared to be involved. The rates of fixation decreased concurrently with increasing bloom age, total soluble inorganic nitrogen and salinities. Maximum daily fixation rates occurred in the early morning. 相似文献
16.
Common bean (Phaseolus vulgaris L.) is able to fix 20–60 kg N ha–1 under tropical environments in Brazil, but these amounts are inadequate to meet the N requirement for economically attractive seed yields. When the plant is supplemented with N fertilizer, N2 fixation by Rhizobium can be suppressed even at low rates of N. Using the 15N enriched method, two field experiments were conducted to compare the effect of foliar and soil applications of N-urea on N2 fixation traits and seed yield. All treatments received a similar fertilization including 10 kg N ha–1 at sowing. Increasing rates of N (10, 30 and 50 kg N ha–1) were applied for both methods. Foliar application significantly enhanced nodulation, N2 fixation (acetylene reduction activity) and yield at low N level (10 kg N ha–1). Foliar nitrogen was less suppressive to nodulation, even at higher N levels, than soil N treatments. In the site where established Rhizobium was in low numbers, inoculation contributed substantially to increased N2 fixation traits and yield. Both foliar and soil methods inhibited nodulation at high N rates and did not significantly increase bean yield, when comparing low (10 kg N ha–1) and high (50 kg N ha–1) rates applied after emergence. In both experiments, up to 30 kg N ha–1 of biologically fixed N2 were obtained when low rates of N were applied onto the leaves. 相似文献
17.
Michael G. Ryan Stith T. Gower Robert M. Hubbard Richard H. Waring Henry L. Gholz Wendell P. Cropper Jr Steven W. Running 《Oecologia》1995,101(2):133-140
We estimate maintenance respiration for boles of four temperate conifers (ponderosa pine, western hemlock, red pine, and slash pine) from CO2 efflux measurements in autumn, when construction respiration is low or negligible. Maintenance respiration of stems was linearly related to sapwood volume for all species; at 10°C, respiration per unit sapwood volume ranged from 4.8 to 8.3 mol CO2 m–3 s–1. For all sites combined, respiration increased exponentially with temperature (Q
10
=1.7, r
2=0.78). We estimate that maintenance respiration of aboveground woody tissues of these conifers consumes 52–162 g C m–2 y–1, or 5–13% of net daytime carbon assimilation annually. The fraction of annual net daytime carbon fixation used for stem maintenance respiration increased linearly with the average annual temperature of the site. 相似文献
18.
Density-dependent regulation of abundance is fundamentally important in the dynamics of most animal populations. Density effects, however, have rarely been quantified in natural populations, so population models typically have a large uncertainty in their predictions. We used models generated from time series analysis to explore the form and strength of density-dependence in several natural rotifer populations. Population growth rate (r) decreased linearly or non-linearly with increased population density, depending on the rotifer species. Density effects in natural populations reduced r to 0 at densities of 1–10 l–1 for 8 of the 9 rotifer species investigated. The sensitivities of these species to density effects appeared normally distributed, with a mean r=0 density of 2.3 l–1 and a standard deviation of 1.9. Brachionus rotundiformis was the outlier with 10–100× higher density tolerance. Density effects in laboratory rotifer populations reduced r to 0 at population densities of 10–100 ml–1, which is 104 higher than densities in natural populations. Density effects in laboratory populations are due to food limitation, autotoxicity or to their combined effects. Experiments with B. rotundiformis demonstrated the absence of autotoxicity at densities as high as 865 ml–1, a much higher density than observed in natural populations. It is, therefore, likely that food limitation rather than autotoxicity plays a major role in regulating natural rotifer populations. 相似文献
19.
Previous modelling of the pullulan fermentation is discussed and found to lack any mechanistic basis. It is concluded that predictive ability can only be conferred by a structured model with at least two compartments, based upon the best available knowledge of the physiology of the microorganism. Such a model is constructed and compared with experimental data.List of Symbols
A (gdm–3)(g/l)
Ammonium ion concentration
-
B (gdm–3)(g/l)
Concentration of balanced growth compartment of biomass
-
G (gdm–3)(g/l)
Glucose concentration
-
k
A
(gdm–3)(g/l)
Saturation constant for ammonium
-
k
G
(gdm–3)(g/l)
Saturation constant for glucose
-
k
S
(gdm–3)(g/l)
Saturation constant for sucrose
-
P (gdm–3)(g/l)
Pullulan concentration
-
Q
Quality of biomass=U/(U+B)
-
r
G
(gdm–1h–1)(g/l/h)
Rate of removal of glucose from broth
-
r
GB
(gdm–3h–1)(g/l/h)
Rate of incorporation of glucose into balanced compartment
-
r
GB
(gdm–3h–1)(g/l/h)
Rate of utilisation of glucose for energy production and cell maintenance
-
r
GP
(gdm–3h–1)(g/l/h)
Rate of conversion of glucose to pullulan
-
r
GU
(gdm–3h–1)(g/l/h)
Rate of incorporation of glucose into unbalanced compartment
-
r
s
(gdm–3h–1)(g/l/h)
Rate of conversion of sucrose to glucose
-
S (gdm–3)(g/l)
Concentration of sucrose
-
U (gdm–3)(g/l)
Concentration of unbalanced growth compartment of biomass
-
X (gdm–3)(g/l)
Biomass concentration
-
Y
G/A
Grams of glucose consumed per gram of ammonium consumed
-
Y
G/B
Grams of glucose consumed per gram of balanced biomass produced
-
Y
G/U
Grams of glucose consumed per gram of unbalanced biomass produced
-
Y
G/P
Grams of glucose consumed per gram of pullulan produced
-
Rate constant for conversion of sucrose to glucose
-
Rate constant for uptake of glucose by the cells
-
Model parameter governing inhibition of sucrose conversion and glucose utilisation
-
Model parameter denoting fraction of glucose uptake devoted to cell maintenance and energy production
-
Model parameter governing apportionment of glucose between pseudo-growth and pullulan production
This work was funded by the National Engineering Laboratory (NEL) through the Bioreactor Design Club. The authors would like to express their gratitude to the NEL for this generous support. 相似文献
20.
N2 fixation in lines of Phaseolus vulgaris was measured by 15N-isotope dilution to determine whether a programme of crossing and recurrent selection had resulted in enhanced nitrogen fixation. In field experiments on an isohyperthermic Aquic Hapludoll soil the amount of N2 fixed by the different lines ranged from 18 to 36 kg ha–1 (32 to 47% of plant N) in 56 days. The quantity of N2 fixed and the proportion of plant N derived from fixation was not significantly greater in the lines selected for N2 fixation (RIZ lines) than parental lines. Total shoot N ranged from 53 to 77 kg ha–1 and partitioning of N to pods differed from 28 to 52% among the lines which all had similar growth habit and duration. Nodulation patterns were also distinct. Nodules formed early (10 to 15 plant–1 at 13 days) in many lines, and smallest amounts of fixation were observed in those lines which nodulated slowly and did not form substantial nodule mass until after 40 days. The screening criteria used in the selection of the RIZ lines had been largely indirect with other factors such as disease resistance also being included. Progress for increasing N2 fixation over good-fixing parental lines such as BAT76 was not significant and it is recommended that more attention be paid to early nodulation, to the use of soils with lower available N and to inter-crossing of lines having different good N2 fixation traits in order to further enhance the potential for N2 fixation in beans. 相似文献