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1.
Solute mobilities in cuticular membranes of six species (Hedera helix, Malus domestica, Populus alba, Pyrus communis, Stephanotis floribunda, Strophantus gratus) were measured using plant hormones, growth regulators and other organic model compounds varying in molar volumes from 99
to 349 mL · mol−1 The dependence of mobilities (k*) on molar volume (V
x
) was exponential and could be described with equations of the type log
k*=log
k*0−′
V
x
. The y-intercepts (log
k*0) represent mobilities of a hypothetical solute of zero molar volume. The parameter β′ is a measure of size selectivity of
cuticular membranes and no differences among the six species were observed. At 25 °C the average β′ was 0.0095 mol · mL−1. Solute mobility decreased by about a factor of 8.9 when molar volume increased by 100 mL · mol−1 and the mobility of a compound with V
x
= 100 mL · mol−1 was about 700-fold higher than the mobility of a compound with V
x
= 400 mL · mol−1. Size selectivity decreased with increasing temperatures and for Strophantusβ′-values of 1.6 × 10−2 to 8.0 × 10-4 mol · mL−1 were obtained for 10 and 30 °C, respectively. The-intercepts (log k*0) differed among plant species by 3 orders of magnitude and since size selectivity was the same for all species, solute mobilities
for solutes having zero molar volumes were the sole cause for differences among species in solute mobilities and permeabilities.
We argue that these differences in k*0 are related to tortuosity of the diffusion path. These results were used to derive an equation which predicts rates of cuticular
penetration on the basis of k*0, the average size selectivity of 9.5 × 10−3 mol · mL−1 and the driving forces of penetration.
Received: 25 November 1997 / Accepted: 9 March 1998 相似文献
2.
The mutational synergism of caffeine and acriflavine was studied in five types ofEscherichia coli mutants induced by u. v.-radiation. The following types of mutations were compared: streptomycinrresistance (strain B/r),
streptomycin-independence (strain Sd-4), and reversions to prototrophy (strains WP-14 pro−, WP-2 try−, and WP-2 try− hcr−). In all hcr+ strains tested the presence of caffeine or acriflavine in a post-irradiation plate medium slightly decreases the survival
of u.v.-irradiated cells and increases considerably the frequency of induced mutations. The mutational synergism of caffeine
and acriflavine in the str-r and str-i mutants is observed only within the range of low doses. The abovementioned dose-dependence
of the synergistic effect is discussed from the point of view of qualitative difference between the premutational damage caused
by low and high doses. The post-irradiation treatment by caffeine slightly increases the frequency of induced prototrophs
also in the WP-2 hcr− strain. This finding is explained by the inhibition of the residual HCR-activity of the strain. The post-irradiation mutational
synergism of acriflavine was not found in the WP-2 hcr− strain. 相似文献
3.
We re-visited a seven-stand boreal chronosequence west of Thompson, Manitoba, Canada, in which coarse woody debris (CWD) and
its instantaneous decomposition were measured in 2000. New CWD measurements were performed in 2007, and tree inventories updated
to provide mortality and snag failure data. These data were used to model CWD changes, compare methods of estimating decomposition,
and infer possible fragmentation rates. Measured CWD was between 9.7 (in both the 77- and 43-year-old stands) and 80.4 (in
the 18-year-old stand) Mg ha−1 in 2007. Spatial variability was high; at most stands CWD levels had not changed significantly from 2000 to 2007. Tree mortality
was a significant flux only in older stands, whereas snag fall rate varied by an order of magnitude, from 2.9% y−1 (0.2 Mg ha−1 y−1) in the 9-year-old stand to 9.8% y−1 (2.3 Mg ha−1 y−1) in the 12-year-old stand. A one-pool model based on these inputs underestimated actual 2000–2007 CWD decomposition in the
younger stands, suggesting that fragmentation could be an important part of the carbon flux exiting the CWD pool. We compared
three independent measures of annual decomposition (k): direct measurements of CWD respiration, rates based on the 7-year re-sampling effort described here, and rates inferred
from the chronosequence design itself. Mean k values arrived at via these techniques were 0.06 ± 0.03, 0.05 ± 0.04, and 0.05 ± 0.05 y−1, respectively. The four-pool model suggested that the transition rate between decay classes was 0.14–0.19 y−1; the model was most sensitive to initial CWD values. Although the computed k values implied a problem with chronosequence site selection for at least one site, the overall CWD trend was consistent with
a larger number of sites surveyed in the region. 相似文献
4.
Potassium (K+) and chloride (Cl−) are two essential elements for plant growth and development. While it is known that plants possess specific membrane transporters
for transporting K+ and Cl−, it remains unclear if they actively use K+-coupled Cl− cotransporters (KCC), as used in animals, to transport K+ and Cl−. We have cloned an Oryza sativa cDNA encoding for a member of the cation–Cl− cotransporter (CCC) family. Phylogenetic analysis revealed that plant CCC proteins are highly conserved and that they have
greater sequence similarity to the sub-family of animal K+–Cl− cotransporters than to other cation–Cl− cotransporters. Real-time PCR revealed that the O. sativa cDNA, which was named OsCCC1, can be induced by KCl in the shoot and root and that the expression level was higher in the leaf and root tips than in any
other part of the rice plant. The OsCCC1 protein was located not only in onion plasma membrane but also in O. sativa plasma membrane. The OsCCC1 gene-silenced plants grow more slowly than wild-type (WT) plants, especially under the KCl treatment regime. After 1 month
of KCl treatment, the leaf tips of the gene-silenced lines were necrosed. In addition, seed germination, root length, and
fresh and dry weight were distinctly lower in the gene-silenced lines than in WT plants, especially after KCl treatment. Analysis
of Na+, K+, and Cl− contents of the gene-silenced lines and WT plants grown under the NaCl and KCl treatment regimes revealed that the former
accumulated relatively less K+ and Cl− than the latter but that they did not differ in terms of Na+ contents, suggesting OsCCC1 may be involved in K+ and Cl− transport. Results from different tests indicated that the OsCCC1 plays a significant role in K+ and Cl− homeostasis and rice plant development. 相似文献
5.
Ozone- and ethylene-induced regulation of a grapevine resveratrol synthase promoter in transgenic tobacco 总被引:1,自引:0,他引:1
Bernhard Grimmig Roland Schubert Regina Fischer Rüdiger Hain Peter H. Schreier Christian Betz Christian Langebartels Dieter Ernst Heinrich Sandermann 《Acta Physiologiae Plantarum》1997,19(4):467-474
Stilbene synthases (STSs) are enzymes that play a critical role in the biosynthesis of stilbene, phytoalexins in a small number
of unrelated plant species, and are induced by various biotic and abiotic stressors like pathogen attack, UV-irradiation or
ozone exposure. To investigate the molecular basis for ozone-induced plant stress responses, we have examined the promoter
of the grapevine resveratrol synthase (Vst1). In this report we summarize the influence of ozone on gene regulation. In transgenic tobacco a chimeric gene construct,
containing the Vst1 promoter combined with the β-glucuronidase (GUS) reporter gene, is rapidly induced by ozone (0.1 μl·l−1, 12 h). The same construct is also strongly induced by ethylene (20 μl·l−1, 12 h). Promoter deletion analysis of the 5′ flanking sequence identified a positive regulatory element between −430 bp and
−280 bp. This region contains ethylene-responsive enhancer elements, as well as an elicitor-responsive sequence in inverse
orientation. 相似文献
6.
Barrera-Cortés J Manilla-Pérez E Poggi-Varaldo HM 《Bioprocess and biosystems engineering》2006,29(5-6):391-398
The objective of this work was to determine (1) the effect of rotational speed (N) and lifters on the oxygen transfer coefficient (k
L) of a mineral solution and (2) the effect of solids concentration of a slurry soil-mineral solution on k
L, at a fixed value N (0.25 s−1); in both cases the treatment was carried out in an aerated rotating drum reactor (RDR) operated at atmospheric pressure. First, the k
L for the mineral solution was in the range 6.38 × 10−4–7.69 × 10−4 m s−1, which was of the same order of magnitude as those calculated for closed rotating drums supplied with air flow. In general, k
L of RDR implemented with lifters was superior or equal to that of RDR without lifters. For RDR implemented with lifters, k
L increased with N in the range 6.65 × 10−4–10.51 × 10−4 m s−1, whereas k
L of RDR without lifters first increased with N up to N = 0.102 s−1, and decreased beyond this point. Second, regarding soil slurry experiments, an abrupt fall of k
L (ca. 50%) at low values of the solid concentration (C
v) and an asymptotic pattern at high C
v were observed at N = 0.25 s−1. These results suggest that mass transfer phenomena were commanded by the slurry properties and a semi-empirical equation of the form Sh = f(Re, Sc) seems to corroborate this finding. 相似文献
7.
N. B. Jelodar N. W. Blackhall T. P. V. Hartman D. S. Brar G. Khush M. R. Davey E. C. Cocking J. B. Power 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,99(3-4):570-577
Somatic hybrid plants were obtained following the electrofusion of rice (Oryza sativa L. cv ’Taipei 309’, 2n = 2x = 24) cell suspension–derived protoplasts with non-dividing leaf protoplasts of Porteresia coarctata (2n = 4x = 48), a saline-tolerant wild species. Fusion-treated protoplasts were plated on the surface of cellulose nitrate
filter membranes, overlaying Lolium multiflorum nurse cells. The nurse cells were embedded in KPR medium containing 0.5 mg l−1 2,4–dichlorophenoxyacetic acid and semi-solidified with SeaPlaque agarose. Putative somatic hybrid cell colonies were selected
on the basis of their growth, whereby faster growing colonies were transferred preferentially to MS-based medium with 2.0
mg l−1 kinetin, 0.5 mg l−1α-naphthaleneacetic acid, 30 g l−1 sucrose and 4.0 g l−1 SeaKem agarose to induce shoot regeneration. One hundred and nineteen regenerated plants were micropropagated clonally on
MS-based medium containing 2.0 mg l−1 6–benzylaminopurine, 50 g l−1 sucrose and 4.0 g l−1 SeaKem agarose, prior to DNA extraction of plant samples. Putative somatic hybrids were initially identified by RAPD analysis,
and 8 plant lines were selected for further investigation by flow cytometric ploidy determination and cytology. Plants of
one line had an allohexaploid chromosome complement (2n = 6x = 72) and, following examination of its vegetative clones by
GISH, were confirmed as somatic hybrids containing full chromosome complements of both O. sativa and P. coarctata.
Received: 27 July 1998 / Accepted: 19 December 1998 相似文献
8.
The effect of several plant growth regulators on the number of tumors developing on potato tuber discs (Solatium tuberosum L. cv. Radka) inoculated withAgrobacterium tumefaciens, strain C 58 was studied. The plant growth regulators used in appropriate range of concentrations stimulated the formation
of tumors byA. tumefaciens.
Naphthaleneacetic acid (NAA) was most active in concentration of 10−4 mg ml−1. Kinetin gave a biphasic response with optimal promotions of tumor initiation at 10−4 − 2 × 10−3 mg ml−1. High kinetin concentration (10−1 mg ml−1) inhibited the formation of tumors completely. Indoleacetic acid (IAA) stimulated the initiation of tumors in the same range
of concentrations as kinetin, except that very high concentrations did not inhibit but enhanced tumor formation. 2,4-diehlorphenoxyacetic
acid (2,4-D) showed a biphasic response with maxima in 10−4 mg ml−1 and 10−1 mg ml−1. All the tumors scored for nopaline production showed nopaline synthase activity independently whether their formation was
stimulated by l0−1 mg ml−1 IAA or they were initiated without any treatment by plant growth regulators. 相似文献
9.
The DR2356 nudix hydrolase gene from Deinococcus radiodurans has been cloned and the product expressed as an 18 kDa histidine-tagged protein. The enzyme hydrolysed adenosine and diadenosine polyphosphates, always generating ATP as one of the initial products. ATP and other (deoxy)nucleoside triphosphates were also substrates, yielding (d)NDP and Pi as products. The DR2356 protein was most active at pH 8.6–9.0 and showed a strong preference for Mn2+ as activating cation. Mg2+ ions at 15 mM supported only 5% of the activity achieved with 2 mM Mn2+. K
m and k
cat values for diadenosine tetra-, penta- and hexaphosphates were 2.0, 2.4 and 1.1 μM and 11.4, 28.6 and 12.0 s−1, respectively, while for GTP they were 20.3 μM and 1.8 s−1, respectively. The K
m for adenosine 5′-pentaphosphate was <1 μM. Expression analysis showed the DR2356 gene to be induced eight- to ninefold in stationary phase and in cells subjected to slow dehydration plus rehydration. Superoxide (but not peroxide) treatment and rapid dehydration caused a two-to threefold induction. The Mn-requirement and induction in stationary phase suggest that DR2356 may have a specific role in maintenance mode metabolism in stationary phase as Mn2+ accumulates. 相似文献
10.
Hiroshi Takashima Ayako Araki Keiko Takemoto Naokazu Yoshikawa Keiichi Tsukahara 《Journal of biological inorganic chemistry》2006,11(3):316-324
In order to understand the detailed mechanism of the stereoselective photoinduced electron-transfer (ET) reactions of zinc-substituted
myoglobin (ZnMb) with optically active molecules by flash photolysis, we designed and prepared new optically active agents,
such as N,N′-dimethylcinchoninium diiodide ([MCN]I2) and N,N′-dimethylcinchonidinium diiodide ([MCD]I2). The photoexcited triplet state of ZnMb, 3(ZnMb)*, was successfully quenched by [MCN]2+ and [MCD]2+ ions to form the radical pair of ZnMb cation (ZnMb·+) and reduced [MCN]·+ and [MCD]·+, followed by a thermal back ET reaction to the ground state. The rate constants (k
q) for the ET quenching at 25 °C were obtained as k
q(MCN)=(1.9±0.1)×106 M−1 s−1 and k
q(MCD)=(3.0±0.2)×106 M−1 s−1, respectively. The ratio of k
q(MCD)/k
q(MCN)=1.6 indicates that the [MCD]2+ preferentially quenches 3(ZnMb)*. The second-order rate constants (k
b) for the thermal back ET reaction from [MCN]·+ and [MCD]·+ to ZnMb·+ at 25 °C were k
b(MCN)=(0.79±0.04)×108 M−1 s−1 and k
b(MCD)=(1.0±0.1)×108 M−1 s−1, respectively, and the selectivity was k
q(MCD)/k
q(MCN)=1.3. Both quenching and thermal back ET reactions are controlled by the ET step. In the quenching reaction, the energy
differences of ΔΔH
≠(MCD–MCN) and ΔΔS
≠(MCD–MCN) at 25 °C were obtained as −1.1 and 0 kJ mol−1, respectively. On the other hand, ΔΔH
≠(MCD–MCN)=11±2 kJ mol−1 and TΔΔS
≠(MCD–MCN)=−10±2 kJ mol−1 were given in the thermal back ET reaction. The highest stereoselectivity of 1.7 for [MCD]·+ found at low temperature (10 °C) was due to the ΔΔS
≠ value obtained in the thermal back ET reaction.
Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users. 相似文献
11.
The binding and unbinding constants describing interaction of ω-CTx-GVIA with N-type Ca2+ channels were calculated based on the time course of the blocking action of the toxin. The experiments were carried out on
pyramidal neurons freshly dissociated from theCA3 region of the rat hippocampus using a “concentration-clamp” technique and a patch-clamp technique in the whole-cell configuration.
The bindingk
1 and unbindingk
−1 constants were evaluated as 0.32 (μM·sec)−1 and 0.004 sec−1, respectively. The dissociation constantK
D kinetically derived from the ratiok
−1/k
1 was 0.012 μM. These values allow us to interpret the apparent “irreversibility” of the toxin action. 相似文献
12.
Guggulsterone, a hypolipidemic natural agent, is produced in resin canals of the plant Commiphora wightii. In this study, the stimulatory effects of growth retardants [ALAR (N,N-dimethylaminosuccinamic acid) and CCC (chlormequat chloride)] and fungal elicitor on guggulsterone accumulation in cell cultures
of C. wightii are reported. CCC at 1 mg l−1 enhanced guggulsterone content (~123 μg l−1) when added on the fifth day after inoculation, while ALAR at 2.5 mg l−1 increased guggulsterone content (~116 μg l−1) when added on the tenth day. In a two-stage fed-batch process, combined treatment with fungal elicitor and growth retardant
caused a significant increase (~353 μg l−1) in guggulsterone content in cell cultures after 17 days of growth. This represents an approximately fivefold increase over
the guggulsterone contents in initial cultures of this plant. 相似文献
13.
This article reports rate constants for thiol–thioester exchange (k
ex), and for acid-mediated (k
a), base-mediated (k
b), and pH-independent (k
w) hydrolysis of S-methyl thioacetate and S-phenyl 5-dimethylamino-5-oxo-thiopentanoate—model alkyl and aryl thioalkanoates, respectively—in water. Reactions such as
thiol–thioester exchange or aminolysis could have generated molecular complexity on early Earth, but for thioesters to have
played important roles in the origin of life, constructive reactions would have needed to compete effectively with hydrolysis
under prebiotic conditions. Knowledge of the kinetics of competition between exchange and hydrolysis is also useful in the
optimization of systems where exchange is used in applications such as self-assembly or reversible binding. For the alkyl
thioester S-methyl thioacetate, which has been synthesized in simulated prebiotic hydrothermal vents, k
a = 1.5 × 10−5 M−1 s−1, k
b = 1.6 × 10−1 M−1 s−1, and k
w = 3.6 × 10−8 s−1. At pH 7 and 23°C, the half-life for hydrolysis is 155 days. The second-order rate constant for thiol–thioester exchange
between S-methyl thioacetate and 2-sulfonatoethanethiolate is k
ex = 1.7 M−1 s−1. At pH 7 and 23°C, with [R″S(H)] = 1 mM, the half-life of the exchange reaction is 38 h. These results confirm that conditions
(pH, temperature, pK
a of the thiol) exist where prebiotically relevant thioesters can survive hydrolysis in water for long periods of time and
rates of thiol–thioester exchange exceed those of hydrolysis by several orders of magnitude. 相似文献
14.
The eco-physiological responses of three nitrogen-fixing cyanobacteria (N-fixing cyanobacteria), Aphanizomenon gracile, Anabaena minderi, and Ana. torques-reginae, to light were assessed under nutrient saturation. The N-fixing cyanobacteria were isolated into monocultures from a natural
bloom in a shallow colored lake and their growth irradiance parameters and pigment composition were assessed. The different
ecological traits related to light use (μmax, α, I
k) suggest that these N-fixing cyanobacteria are well adapted to low light conditions at sufficient nutrients, yet interspecific
differences were observed. Aphanizomenon gracile and Anabaena minderi had high relative growth rates at low irradiances (ca. 70% of those in high light), low half saturation constant for light-limited
growth (I
k < 9.09 μmol photon m−2 s−1) and high efficiency (α < 0.11 day−1 μmol photon−1 m2 s). Conversely, Ana. torques-reginae showed poorer light competitiveness: low relative growth rates at low irradiances (ca. 40% of those in high light), low α
(0.009 day−1 μmol photon−1 m2 s) and higher I
k (35.5 μmol photon m−2 s−1). Final densities in Aphanizomenon gracile and Anabaena minderi reached bloom densities at irradiances above 30 μmol photon m−2 s−1 with different hierarchy depending on irradiance, whereas Ana. torques-reginae never achieved bloom densities. All species had very low densities at irradiances ≤17 μmol photon m−2 s−1, thus no N-fixing blooms would be expected at these irradiances. Also, under prolonged darkness and at lowest irradiance
(0 and 3 μmol photon m−2 s−1) akinetes were degraded, suggesting that in ecosystems with permanently dark sediments, the prevalence of N-fixing cyanobacteria
should not be favored. All species displayed peaks of phycocyanin, but no phycoeritrin, probably due to the prevailing red
light in the ecosystem from which they were isolated. 相似文献
15.
Kim HT Ko HJ Kim N Kim D Lee D Choi IG Woo HC Kim MD Kim KH 《Biotechnology letters》2012,34(6):1087-1092
A gene, alg7D, from Saccharophagus degradans, coding for a putative alginate lyase belonging to the family of polysaccharide lyase-7, was overexpressed in Escherichia coli. The properties of the recombinant Alg7D were characterized. The enzyme endolytically depolymerized alginate by β-elimination
into oligo-alginates with degrees of polymerization of 2–5. Its activity was maximal at 50°C and pH 7 and was slightly increased
in the presence of Na+. The K
M
, V
max
, k
cat
, and k
cat
/K
M
values were: 3 mg ml−1, 6.2 U mg−1, 1.9 × 10−2 s−1, and 6.3 × 10−3 mg−1 ml s−1, respectively. 相似文献
16.
Sanjay Gupta V. K. Khanna Rameshwar Singh G. K. Garg 《Plant Cell, Tissue and Organ Culture》2006,86(3):379-388
Development of suitable strategy to overcome genotypic limitations of in vitro regeneration in sorghum would help utilize high yielding but poor tissue culture responsive genotypes in genetic manipulation programmes. A factorial experiment was conducted with two explants (immature embryos and inflorescences), eight genotypes (five Sorghum sudanense and three Sorghum bicolor genotypes), three levels of 2,4-D (1 mg l−1, 3 mg l−1, and 5 mg l−1), and two levels of kinetin (0.0 mg l−1 and 0.5 mg l−1). The induced callus was transferred to the regeneration media with factorial combinations of IAA (1.0 mg l−1 and 2.0 mg l−1) and kinetin (0.5 mg l−1 and 1.0 mg l−1). S. sudanense regenerated at significantly higher frequency (38.91%) and produced shoots more intensely (2.2 shoots/callus) than S. bicolor (26.93%, 1.26 shoots/callus). Immature inflorescences regenerated at a much higher frequency (46.48%) and produced significantly more number of shoots (2.71 shoots/callus) than immature embryos (22.35%, 0.99 shoots/callus). Moreover, differences for plant regeneration between genotypes of the same species were minimal when using immature inflorescences. Increase in the 2,4-D concentration in callus induction media exhibited inhibitory effect on callus induction, growth, shoot induction and number of shoots/callus but inclusion of kinetin in callus induction media improved these responses. Use of immature inflorescence explant and inclusion of kinetin in callus induction media could overcome genotypic limitations of plant regeneration to a large extent. The extent of variability, heritability and expected genetic advance was more in plant regeneration traits than in callus induction traits. This indicated that the variability in respect of these attributes in the genotypes may be due to the additive gene action and selection of genotypes for these characters would be rewarding. 相似文献
17.
Legume tissue quality is a key factor for enhancement of feed resources and contribution to soil fertility in mixed crop-livestock
production systems. To compare methods used by soil scientists and animal-nutritionists to assess quality of plant materials,
three woody tropical legumes with contrasting qualities were used: Indigofera zollingeriana Miq. (Indigofera), Cratylia argentea Benth. (Cratylia) and Calliandra houstoniana (Mill.) Stan. var. calothyrsus (Meiss.) Barn. CIAT 20400 (Calliandra). Plant material of each legume was used either fresh,
freeze-dried, frozen, oven-dried (60 °C) or air-dried in order to estimate extents and rates of aerobic degradation in litterbags
on the soil during 140 days and anaerobic degradation in an in-vitro gas production experiment during 144 h. Results showed, that aerobic decomposition rates of leaf tissues were highest for
Indigofera (k = 0.013 day−1), followed by Cratylia (k = 0.004 day−1) and Calliandra (k = 0.002 day−1). Gas production rates evaluated under anaerobic conditions, were highest for Indigofera (k = 0.086 h−1), intermediate for Cratylia (k = 0.062 h−1) and lowest for Calliandra (k = 0.025 h−1). Decomposition and gas production rates differed (P < 0.001) among species. Differences between post harvest treatments were not statistically significant (P > 0.05). The extent of decomposition was highest for Indigofera (82.5%, w/w), followed by Cratylia (44.6%) and Calliandra
(26.4%). The extent of gas production was highest for Indigofera (218.8 ml), followed by Cratylia (170.1ml) and Calliandra
(80.1 ml). Extent of decomposition and extent of gas production were significantly different (P < 0.001) among species. In contrast to the extent of decomposition, the extent of gas production was affected (P < 0.001) by sample post harvest treatments. Highest gas production was observed for the fresh and frozen treatments. The
forage quality parameters that best correlated with aerobic and anaerobic degradation were lignin+bound condensed tannins,
lignin+total condensed tannins/N, indigestible acid detergent fibre (IADF) and in-vitro dry matter digestibility (IVDMD). Results showed that differences in decomposition and digestibility were more related to
intrinsic plant quality parameters than to changes in tissue quality induced by post harvest treatments. In addition, we found
that rate of aerobic degradation of legume leaves on the soil was highly correlated (r > 0.80, P < 0.001) to IVDMD and gas production (r = 0.53, P < 0.001). These results indicate that plant measurements (IADF, IVDMD and gas production) used to assess forage quality in
animal nutrition studies are more rapid and resource saving predictors for aerobic decomposition of tropical legumes than
initial plant quality ratios (lignin+polyphenols/N and lignin+total condensed tannins/N) commonly used by many researchers.
Furthermore, this study confirms the potential usefulness of IVDMD for screening tropical legumes for soil fertility management. 相似文献
18.
Purple Loosestrife is rapidly displacing native vegetation in North American wetlands. Associated changes in wetland plant
communities are well understood. Effects of Loosestrife invasion on nutrient cycling and decomposition rates in affected wetlands
are unknown, though potentially of significance to wetland function. We used litter bag methods to quantify decomposition
rates and phosphorus concentrations of purple Loosestrife (Lythrum salicaria) and native cattails (Typha spp.) in fourteen Minnesota wetlands. A 170-day study that began in autumn modeled decomposition of Loosestrife leaves. Loosestrife
stems andTypha shoots that had overwintered and fragmented were measured in a 280- day study that began in spring. In general, Loosestrife
leaves decomposed most rapidly of the three;Typha shoots decomposed faster than Loosestrife stems. Significant decay coefficients (k-values) were determined by F-testing single
exponential model regressions of different vegetation types in the fourteen wetlands. Significant decay coefficients were:k = 2.5 × 10−3 and 4.32 × 10−3 for all Loosestrife leaves (170 d);k = 7.2 × 10−4 and 1.11 × 10−3 for overwintered Loosestrife stems (280-d) andk = 7.9 × 10−4, 1.42 × 10−3 and 2.24 × 10−3 for overwinteredTypha shoots (280-d). Phosphorus concentrations of plant tissue showed an initial leaching followed by stabilization or increase
probably associated with microbial growth. Loosestrife leaves had twice the phosphorus concentration of Loosestrife stems
andTypha shoots. Our results indicate that conversion of wetland vegetation from cattails to Loosestrife may result in significant
change in wetland function by altering timing of litter input and downstream phosphorus loads. Conversion of a riverine, flow-
through wetland fromTypha to Loosestrife may effectively accelerate eutrophication of downstream water bodies. Impacts of Loosestrife invasion must
be considered when wetlands are managed for wildlife or for improvement of downstream water quality. 相似文献
19.
Lakkana Laopaiboon Pornthap Thanonkeo Prasit Jaisil Pattana Laopaiboon 《World journal of microbiology & biotechnology》2007,23(10):1497-1501
Sweet sorghum juice supplemented with 0.5% ammonium sulphate was used as a substrate for ethanol production by Saccharomyces cerevisiae TISTR 5048. In batch fermentation, kinetic parameters for ethanol production depended on initial cell and sugar concentrations.
The optimum initial cell and sugar concentrations in the batch fermentation were 1 × 108 cells ml−1 and 24 °Bx respectively. At these conditions, ethanol concentration produced (P), yield (Y
ps) and productivity (Q
p
) were 100 g l−1, 0.42 g g−1 and 1.67 g l−1 h−1 respectively. In fed-batch fermentation, the optimum substrate feeding strategy for ethanol production at the initial sugar
concentration of 24 °Bx was one-time substrate feeding, where P, Y
ps and Q
p
were 120 g l−1, 0.48 g g−1 and 1.11 g l−1 h−1 respectively. These findings suggest that fed-batch fermentation improves the efficiency of ethanol production in terms of
ethanol concentration and product yield. 相似文献
20.
Enhanced nitrogen (N) deposition at high latitudes is a circumpolar phenomenon. Low soil phosphorus (P), however, may limit
vegetation responses to increased N inputs. From 2000 to 2002, the effects of N at 0, 0.5 (a rate occurring in Greenland and
Iceland) and 5 (equivalent to deposition in areas of Europe) g N m−2 a−1 and P (0.1 g m−2 a−1) treatments on plant species’ cover and diversity were determined at a polar semidesert site (ambient deposition c 0.1 g N m−2 a−1) in Svalbard (79°N). The largest response was to combined 5 g N plus 1 g P m−2 a−1, where cover of Saxifraga oppositifolia increased c fourfold, density of Salix polaris leaves c ninefold, seedlings of several ‘new’ species (Draba oxycarpa, Saxifraga caespitosa, Sagina nivalis) were established and ‘immigration’ of Bryum arcticum and ‘extinction’ of Schistidium apocarpum were observed. There were fewer, less pronounced, effects on the plant community at 0.5 g N m−2 a−1. Low P availability did indeed appear to restrict vegetation response to N. There was a trend for plant species’ richness
and diversity to increase with 1 g P m−2 a−1 at 0 and 0.5 g N m−2 a−1, but not at 5 g N m−2. Plant species showed individualistic responses so that generalisation by functional type was not possible. Such increased
colonisation by moss species of bare soil, and greater densities of previously unrecorded angiosperm seedlings, are not usually
observed in more closed (subarctic) tundra as a response to N and P additions. These changes are likely to influence significantly
nutrient cycles, whole system carbon budgets and surface energy and water balances.
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