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1.
GERUZA DE OLIVEIRA CEITA JOSÉ GERALDO DE AQUINO ASSIS MARIA LENISE SILVA GUEDES ANA LÚCIA PIRES COTIAS DE OLIVEIRA 《Botanical journal of the Linnean Society. Linnean Society of London》2008,158(1):189-193
This paper presents the mitotic chromosome numbers of 18 species of Bromeliaceae. The diploid number 2n = 50 was observed in Aechmea comata, A. caudata, A. correia‐araujoi, A. recurvata, A. marauensis, A. bicolor, A. pineliana, Hohenbergia catingae, H. blanchetti, Alcantarea imperialis, Al. nahoumi, Neoregelia tenebrosa, Nidularium lyman‐smithii, N. scheremetiewii, N. innocentii var. innocentii, and N. innocentii × Neoregelia johannis hybrid, whereas 2n = 34 was observed in Cryptanthus maritimus and C. warren‐loosei. All of the determinations presented in this study are previously unpublished, except A. comata and H. catingae. These results confirm x = 25 as the basic number for the family and x = 17 as a secondary basic number probably generated by decreasing dysploidy. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 189–193. 相似文献
2.
The palynological characterisation of 157 honey samples from three northwest regions of Argentina (Prepuna, Yungas and Chaco) are presented to determine their botanical origin and species associations to be able to define their geographic origin. Samples were harvested during 2003–2011 and processed by means of melissopalynological conventional techniques. One-hundred and nine pollen types were identified. Representative pollen types with a frequency of occurrence greater than 50% in descending order of importance are: Salix humboldtiana, Allophylus edulis, Baccharis, Solanaceae, Eucalyptus, Schinus, Brassicaceae, Papilionoideae, Celtis, Scutia/Condalia-type and Parapiptadenia excelsa. The most important monofloral honeys are from the following: Salix humboldtiana, Scutia/Condalia-type, Allophylus edulis, Baccharis, Blepharocalyx salicifolius, Gleditsia amorphoides, Myrtaceae, Sicyos, Ziziphus mistol, Schinopsis-type, Agonandra excelsa, Anadenathera colubrina, Mimosa, all of them native species, and among introduced species are Eucalyptus, Citrus and Tithonia. Three apicultural zones and their corresponding pollen association indicators were determined: Zone I, Prepuna: Arquita trichocarpa, Prosopis ferox, Schinus areira, Baccharis, Buddleja and Mutisieae; Zone II, Yungas: Myrtaceae, Parapiptadenia excelsa, Baccharis, Salix humboldtiana, Allophylus edulis, Scutia/Condalia-type and Zanthoxylum coco; Zone III, transitional area Yungas-Chaco: Prosopis, Salix humboldtiana, Schinus, Anadenanthera colubrina and Allophylus edulis. 相似文献
3.
M. S. Magdoń-Maksymowicz 《Theorie in den Biowissenschaften》2008,127(4):335-342
There are some analytical solutions of the Penna model of biological aging; here, we discuss the approach by Coe et al. (Phys.
Rev. Lett. 89, 288103, 2002), based on the concept of self-consistent solution of a master equation representing the Penna
model. The equation describes transition of the population distribution at time t to next time step (t + 1). For the steady state, the population n(a, l, t) at age a and for given genome length l becomes time-independent. In this paper we discuss the stability of the analytical solution at various ranges of the model
parameters—the birth rate b or mutation rate m. The map for the transition from n(a, l, t) to the next time step population distribution n(a + 1, l, t + 1) is constructed. Then the fix point (the steady state solution) brings recovery of Coe et al. results. From the analysis
of the stability matrix, the Lyapunov coefficients, indicative of the stability of the solutions, are extracted. The results
lead to phase diagram of the stable solutions in the space of model parameters (b, m, h), where h is the hunt rate. With increasing birth rate b, we observe critical b
0 below which population is extinct, followed by non-zero stable single solution. Further increase in b leads to typical series of bifurcations with the cycle doubling until the chaos is reached at some b
c. Limiting cases such as those leading to the logistic model are also discussed. 相似文献
4.
Ortega E Bosković RI Sargent DJ Tobutt KR 《Molecular genetics and genomics : MGG》2006,276(5):413-426
Cross-compatibility relationships in almond are controlled by a gametophytically expressed incompatibility system partly mediated by stylar RNases, of which 29 have been reported. To resolve possible synonyms and to provide data for phylogenetic analysis, 21 almond S-RNase alleles were cloned and sequenced from SP (signal peptide region) or C1 (first conserved region) to C5, except for the S
29
allele, which could be cloned only from SP to C1. Nineteen sequences (S
4
, S
6
, S
11
–S
22
, S
25
–S
29
) were potentially new whereas S
10
and S
24
had previously been published but with different labels. The sequences for S
16
and S
17
were identical to that for S
1
, published previously; likewise, S
15
was identical to S
5
. In addition, S
4
and S
20
were identical, as were S
13
and S
19
. A revised version of the standard table of almond incompatibility genotypes is presented. Several alleles had AT or GA tandem repeats in their introns. Sequences of the 23 distinct newly cloned or already published alleles were aligned. Sliding windows analysis of Ka/Ks identified regions where positive selection may operate; in contrast to the Maloideae, most of the region from the beginning of C3 to the beginning of RC4 appeared not to be under positive selection. Phylogenetic analysis indicated four pairs of alleles had ‘bootstrap’ support > 80%: S
5
/S
10
, S
4
/S
8,
S
11
/S
24
, and S
3
/S
6
. Various motifs up to 19 residues long occurred in at least two alleles, and their distributions were consistent with intragenic recombination, as were separate phylogenetic analyses of the 5′ and 3′ sections. Sequence comparison of phylogenetically related alleles indicated the significance of the region between RC4 and C5 in defining specificity.An erratum to this article can be found at 相似文献
5.
Analysis of the rnc locus of Coxiella burnetii 总被引:4,自引:0,他引:4
Mohammed Zuber Timothy A. Hoover Bradford S. Powell Donald L. Court 《Molecular microbiology》1994,14(2):291-300
A 3.2 kb EcoRI genomic DNA fragment of Coxiella burnetii was isolated by virtue of Its ability to suppress mucoidy in Eschertchia coli. Nucleotide sequence analysis revealed the presence of the genes homologous to rnc, era and recO of E. coli. Suppression of capsule synthesis, measured by β-galactosidase expression in Ion cps-lac fusion strains of E. coli, is caused by gene-dosage effects of the plasmid-borne rnc genes of either C. burnetii or E. coli. The rnc gene of C. burnetii complemented rn– E. coli hosts for lambda plaque morphology and stimulation of lambda N gene expression. We also demonstrated heterologous complementation of an E coli strain defective for the expression of Era, an essential protein in E. coli, using the plasmid-borne C. burnetii era. Under the control of the bacteriophage lambda PL promoter, this 3.2 kb EcoRI DNA fragment directed the synthesis in E. coli of three proteins with approximate molecular masses of 35,27 and 25 kDa. Antibodies against purified E. coli Era protein cross-reacted with the 35 kDa protein of C. burnetii on Western blots. 相似文献
6.
During a one year period, 944 dogs from the Municipal kennel of Barcelona were examined to detect animals with suspected dermatophytosis. Only a few animals (1.8%) presented skin lesions but none of them had dermatophytosis. A representative number of dogs without visible skin lesions (n=172), selected at random, were used to carry out a seasonal study of the mycobiota of their fur. Fifteen isolates belonging to the genera Microsporum and Trichophyton were isolated from 14 of the 172 (8.1%) dogs without lesions. The identity of these fungi was Microsporum gypseum (6/15), Trichophyton terrestre (4/15), M. canis (2/15), M. cookei (2/15) and Trichophyton ajelloi (1/15) (one strain each of M. gypseum and T. ajelloi were isolated from one dog). Species of Penicillium (% prevalence=89.5%), Alternaria (86.6%), Cladosporium (84.9%), Aspergillus (77.3%), Scopulariopsis (65.7%) and Chrysosporium (64.5%) were the most prevalent. No significant differences in the fungal biota were observed with respect to age, gender, hair length or between mixed and pure breed dogs. A large number of isolates, including species belonging to the genera Beauveria, Chrysosporium, Malbranchea and Scopulariopsis, that macroscopically and/or microscopically resemble dermatophytes and may be mistaken for them, produced a red color change in Dermatophyte Test Medium. No significant seasonal difference was detected among the isolates belonging to the the most frequently encountered genera, with the exception of Scopulariopsis (higher in summer and autumn) and Chrysosporium (higher in summer). Species from other genera, with lower occurrence also presented significant differences in their seasonal distribution. Arthrinium, Aureobasidium, Chaetomium and Phoma spp. presented maximum prevalence peaks in spring, Fusarium, Paecilomyces, Phoma and Rhizopus spp. in summer and Geotrichum and Mucor spp. in autumn. The Microsporum and Trichophyton species were more frequently isolated in summer. 相似文献
7.
8.
Five mutants of Escherichia coli K12 (lam 24, lam 25, lam 26, lam 27 and lam 646) that block head formation of λ are described. In vitro complementation tests and electron microscopy demonstrated that in these bacteria phage tails were produced normally, whereas head formation was abnormal, aberrant head-related structures being produced. In lysates prepared from lam 24, lam 25 and lam 26, monsters and empty heads without tail were the predominant structures, whereas in lysates from lam 27 and lam 646, petit λ and empty heads were the most common structures. The five lam mutations were located in two regions on the bacterial chromosome; lam 24, lam 25 and lam 26 were near the dnaB gene and lam 27 and lam 646 near the lac gene. It was suggested that the former three mutants are new isolates that belong to GroE mutants, whereas the latter two comprise a new group of mutants. Analyses of phage mutants (ov mutants) that overcome the interference by the lam 646 mutation revealed that this mutation blocks normal expression of the gene E of λ. 相似文献
9.
Katarína Olšavská Marián Perný Carsten J. Löser Rosemarie Stimper Iva Hodálová 《Botanical journal of the Linnean Society. Linnean Society of London》2013,173(2):230-257
To reveal the general cytogeographical pattern of Cyanus section Protocyanus in Europe, DNA ploidy and/or chromosome numbers were newly examined for 160 populations by flow cytometry (450 plants) and/or chromosome counting (30 plants). Furthermore, previously published karyological data were revised (236 records). Our analyses confirmed chromosome counts of 2n = 22 for all newly investigated samples of the C. triumfetti group (the records for C. semidecurrens and C. ternopoliensis are new), C. diospolitanus and C. achtarovii; 2n = 44 for C. montanus and C. mollis; and 2n = 20 for C. lingulatus, C. napulifer, C. nissanus, C. orbelicus, C. thirkei, C. tuberosus and C. velenovskyi. The chromosome count of 2n = 20 is the first report for C. epirotus. The cytotype 2n = 40 was newly recorded for the Crimean endemic C. fuscomarginatus and Calabrian and Greek populations of C. graminifolius. The cytotypes 2n = 20 and 2n = 40 were confirmed for C. pindicola. For the first time triploidy (2n~3x~30) was found in C. nissanus, C. thirkei and in a newly discovered hybrid, C. epirotus × C. graminifolius. Two contrasting ecogeographical patterns emerged: cytotypes derived from the base chromosome number x = 11 (2n = 22, 44) are widespread in northern latitudes and ecologically diverse, whereas cytotypes with x = 10 (2n = 20, 30, 40) are confined to mountains in southern Europe. In general, tetraploids have smaller ranges than diploids. The new combinations Cyanus section Protocyanus (Dobrocz.) Ol?avská comb. nov. and Cyanus ternopoliensis (Dobrocz.) Ol?avská comb. nov. are provided. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173 , 230–257. 相似文献
10.
K. Okazaki M. Kusaba D. J. Ockendon T. Nishio 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,98(8):1329-1334
Forty three S tester lines of Brassica oleracea were characterized using DNA and protein gel-blotting analyses. DNA gel-blot analysis of HindIII-digested genomic DNA with class-I and class-II SLG probes revealed that 40 lines could be classified as class-I S haplotypes while three lines could be classified as class-II S haplotypes. The band patterns in the S tester lines were highly polymorphic. Although the S tester lines typically showed two bands corresponding to SLG and SRK in the analysis with the class-I SLG probe, only one band was observed in the S
24
homozygote. This band was identified as SRK, suggesting that this haplotype has no class-I SLG band. In the analysis using the class-II SLG probe, one plant yielded a different band pattern from the known class-II haplotypes, S
2
, S
5
and S
15
. Unexpectedly, this plant was reciprocally cross-incompatible with the S
2
haplotype. Therefore, it was designated as S
2-b
. We found an S
13
haplotype having a restriction fragment length polymorphism different from that of the S
13
homozygotes of the S tester line. These findings indicate that S homozygous lines with the same S specificity do not necessarily show the same band pattern in the DNA gel-blot analysis. Soluble stigma proteins of 32 S homozygotes were separated by isoelectric focusing and detected using anti-S
22
SLG antiserum. S haplotype-specific bands were detected in 27 S homozygotes but not in five S homozygotes, including the S
24
homozygote. This is consistent with the observation that the S
24
haplotype had no SLG band.
Received: 13 July 1998 / Accepted: 29 September 1998 相似文献
11.
The Family Thelastomidae (Thelastomatoidea; Oxyurida; Nematoda) is revised, genera are diagnosed and a complete list of species
is given. The following genera, normally classified in the family, are not included: Linstowiella Basir is considered a member of the Pharyngodonidae and perhaps a synonym of Pharyngodon Diesing; Klossinema Lal is considered a synonym of Cephalobellus Cobb; Schubartnema Kloss is considered a taxonomic chimaera, the male corresponding to Carnoya Gilson and the female probably to Binema Basir. Two new species are proposed: Gryllophila bainae and G. klossae for material assigned to G. skrjabini (Sergiev) by Bain (1965) and Kloss (1959) respectively. The following new synonyms are proposed: Blattellicola Basir and Blatellicoloides Farooqui synonyms of Blatticola Schwenck; Basiriella Ahmed & Jabin synonym of Blattophila Cobb; Leidynema (Basiria) Farooqui synonym of Cranifera Kloss; Posterovulva Van Waerebeke synonym of Desmicola Basir; Oryctophila Van Waerebeke synonym of Johnstonia Basir; Panaesthiana Kloss synonym of Leidynemella Chitwood & Chitwood; Psilocephala Rao synonym of Cameronia Basir; Welchiella Gupta & Kaur synonym of Hammerschmidtiella Chitwood. The following new combinations are proposed: Blattophila basiri for Basiriella basiri Ahmed & Jabin, leaving Blattophila basiri Farooqui pre-occupied (and renamed B. farooquii); Cameronia psilocephala and C. aspiculata for Psilocephala psilocephala Rao and P. aspiculata Farooqui respectively; Corydiella mamba (Van Waerebeke) for Thelastoma mamba; Desmicola moramangi for Posterovulva moramangi Van Waerebeke; Johnstonia morondovae for Oryctophila morondovae; Leidynemella sphaeropoei for Oxyuris sphaeropoei Parona; Thelastoma aurangabadense, T. indica (preoccupied), T. mackenziei, T. thapari, T. unicoloris and T. welchi for Schwenkiella aurangabadense Farooqui, S. indica Rao & Rao, Suifunema mackenziei Zervos, Bulhoesia thapari Singh & Singh, Cephalobellus unicoloris Van Waerebeke and Schwenkiella welchi Farooqui, respectively. 相似文献
12.
This paper describes the frequency of occurrence and biodiversity of fungi from mangroves of the Godavari and Krishna deltas, on the east coast of India. Seventy three species were identified from Godavari and 67 from the Krishna mangroves. Fifty five species were common to both sites, 18 were found only at Godavari and 12 at Krishna mangroves. Verruculina enaliawas found to be very frequent at both sites with a higher frequency of occurrence at Godavari. Eutypa bathurstensis was very frequent at Godavari but only frequent at Krishna. Cirrenalia pygmea and Cryptosphaeria mangrovei were frequent at the Godavari mangrove, but were recorded occasionally at Krishna. Decaying samples of Rhizophora and Avicennia were studied in detail. Forty three species were common to both hosts, while 22 species were recorded only from Avicennia and 20 only from Rhizophora. Verruculina enalia was the only very frequent fungus recorded on both hosts with a lower percentage occurrence (14.8%) on R. apiculata as compared to Avicennia spp. (24.3%). Eutypa bathurstensis was the next most frequent fungus on Avicennia, while Rhizophila marina was next most frequent on Rhizophora. Dactylospora haliotrepha which was recorded frequently on Rhizophorawas infrequent on Avicennia. 相似文献
13.
Christian Baumann Martin Judex Harald Huber R. Wirth 《Extremophiles : life under extreme conditions》1998,2(2):101-108
Genomes of various hyperthermophilic and extremely thermophilic prokaryotes were analyzed with respect to size, physical
organization, and 16S rDNA copy number. Our results show that all the genomes are circular, and they are in the size range
of 1.6–1.8 Mb for Pyrodictium abyssi, Methanococcus igneus, Pyrobaculum aerophilum, Archaeoglobus fulgidus, Archaeoglobus lithotrophicus, and Archaeoglobus profundus (the two bacteria Fervidobacterium islandicum and Thermosipho africanus possess genomes of 1.5-Mb size). A systematic study of all validly described species of the order Sulfolobales revealed the existence of two classes of genome size for these archaea, correlating with phylogenetic analyses. The Metallosphaera–Acidianus group, plus Sulfolobus metallicus, have genomes of ca. 1.9 Mb; the other members of the order Sulfolobales group possess genomes >2.7 Mb. The special case of Stygiolobus azoricus is discussed.
Received: August 10, 1997 / Accepted: January 1, 1998 相似文献
14.
Three distinct clusters of crustacean cardioactive-peptide-immunoreactive neurones occur in the terminal abdominal ganglion of the crayfish species Orconectes limosus, Astacus leptodactylus, Astacus astacus and Procambarus clarkii, as revealed by immunocytochemistry of whole-mount preparations and sections. They exhibit similar topology and projection patterns in all four studied species. An anterior ventral lateral and a posterior lateral cluster contain one small, strongly stained perikaryon and two large, less intensely stained perikarya, each showing contralateral projections. A posterior medial lateral cluster of up to six cells also contains these two types of perikarya. Whereas the small type perikarya belong to putative interneurones, the large type perikarya give rise to extensive neurohaemal plexuses in perineural sheaths of the third roots of the fifth abdominal ganglia, the connectives, the dorsal telson nerves, the ganglion itself, its roots and arteriolar supply. Thin fibres from these plexuses reach newly discovered putative neurohaemal areas around the hindgut and anus via the intestinal and the anal nerves, and directly innervate the phasic telson musculature. A comparison with earlier investigations of motoneurones and segmentation indicates that these three cell groups containing putative neurosecretory neurones may be members of at least three neuromeres in this ganglion. Crustacean cardioactive peptide released from these neurones may participate in the neurohumoral and modulatory control of different neuronal and muscle targets, thereby exceeding its previously established hindgut and heart excitatory effects.Abbreviations
AG
abdominal ganglion
-
adpl
arteria dorsalis pleica
-
Ala
arreria lateralis abdominalis
-
Asub
arteria subneuralis
-
CCAP
crustacean cardioactive peptide
-
CNS
central nervous system
-
IR
immunoreactive
-
LG
lateral giant axon
-
LTr
lateral tract
-
MDT
medial dorsal tract
-
MG
medial giant axon
-
M Tr
medial tract
-
mcan
musculus compressor ani
-
mfltp
museulus flexor telsonos posterior
-
nan
nervus ani (AG6 N5)
-
nant
nervus anterior (AG6 N1, N2)
-
nia
nervus intestinal anterior
-
nin
nervus intestinalis (AG6 N7)
-
nip
nervus intestinalis posterior
-
nteld
nervus telsonos dorsalis (AG6 N6)
-
nielv
nervus telsonos ventralis (AG6 N4)
-
nur
nervus uropedalis (AG6 N3)
-
nven
nervus ventralis (AG5 N3)
-
PIR
peri-intestinal ring
-
PTF
posterior telson flexor
-
VLT
ventral lateral tract
-
VMT
ventral medial tract
-
VNC
ventral nerve cord
-
VIF
ventral telson flexor
-
AVLC, PLC, PMLC
anterior ventral lateral, posterior lateral, posterior medial lateral CCAP-immunoreactive cell cluster
-
A6AVC, A7AVC
anterior ventral commissures
-
A7DCI
dorsal commissure I
-
A7PVC
posterior ventral commissure
-
A7SCII
sensory commissure II
-
A7VCII, A7VCIII
ventral commissures II and III of the sixth (A6) and seventh (A7) abdominal neuromer 相似文献
15.
16.
Substrate selectivity of lipases in the esterification of cis/trans-isomers and positional isomers of conjugated linoleic acid (CLA) 总被引:4,自引:0,他引:4
The substrate selectivity of several microbial lipases has been examined in the esterification of the conjugated linoleic acid (CLA) isomers cis-9,trans-11-, cis-9,cis-11-, trans-9,trans-11- and trans-10,cis-12-octadecadienoic acid with n-butanol in n-hexane. Lipases from Candida cylindracea and Mucor miehei had a preference for the cis-9,trans-11-octadecadienoic acid, while Chirazyme L-5, a Candida antarctica lipase A, accepted the trans-9,trans-11-fatty acid with a high selectivity. Moreover, lipase from Candida cylindracea and Chirazyme L-5 catalysed the esterification of the cis-9,trans-11-octadecadienoic acid with n-butanol faster than the corresponding reaction of the trans-10,cis-12-fatty acid. 相似文献
17.
Yoshiaki Iwamuro Michiko Murata Koichiro Kanamaru Yoichi Mikami Takuro Kisaki 《Bioscience, biotechnology, and biochemistry》2013,77(2):525-526
The aroL gene, encoding shikimate kinase of Brevibacterium lactofermentum, a coryneform glutamic acid-producing bacterium, was cloned. Recombinant plasmids containing the aroL gene caused elevated levels of shikimate kinase synthesis in B. lactofermentum. It was found that in addition to the aroL gene, the aroB and aroE genes, encoding dehydroquinate synthase and shikimate dehydrogenase, respectively, also existed on these recombinant plasmids, in complementation tests with various Escherichia coli and B. lactofermentum aromatic amino acid auxotrophs. The aroL, aroB and aroE genes of B. lactofermentum are located closely on the cloned DNA fragment, in that order. It was shown that at least these three aro genes form a cluster on the chromosome of B. lactofermentum. 相似文献
18.
J. Quinteiro J. Rodríguez-Castro J. Castillejo J. Iglesias-Piñeiro M. Rey-Méndez 《Journal of Zoological Systematics and Evolutionary Research》2005,43(2):139-148
The Iberian Peninsula contains the majority of the Paleartic land slug species of the genus Arion, which exhibits diverse taxonomic problems. The present study investigated Arion taxonomy on the basis of analyses of the mitochondrial ND1 gene and nuclear internal transcribed spacer 1 (ITS1) sequences. The Iberian endemic species were monophyletically clustered in two divergent sister clades. The topotype specimens of Arion lusitanicus and the closely related species Arion nobrei and Arion fuligineus, as well as Arion hispanicus and Arion flagellus, were grouped into an ‘Atlantic’ clade, whereas Arion baeticus, Arion gilvus, Arion anguloi, Arion wiktori and Arion paularensis were included in a ‘Continental–Mediterranean’ clade. Calibration of mutation rate in the ND1 gene suggested that the divergence of these two clades occurred around the Pliocene–Pleistocene boundary, with subsequent speciation events during the Pleistocene. A group of ancestral and divergent endemic species with distribution centred in the Pyrenean mountain range (Arion molinae, Arion lizarrusti, Arion antrhacius and Arion iratii) arose in the Pliocene and survived through the Pleistocene in geographically confined small populations. Arion lusitanicus showed up to be polyphyletic: specimens, sampled outside the geographic range of the topotype in the north‐western Iberian Peninsula, were included in a non‐monophyletic clade together with the widely distributed species Arion ater and Arion rufus. The divergent species with a wide European distribution (Arion subfuscus, Arion hortensis, Arion fagophilus and Arion intermedius) were located in basal positions in all topologies. The evolutionary history of these slug species (highly sensitive to climatic factors, with capacity for both outcrossing and selfing, and with low dispersal ability) appears to have been moulded by Pliocene–Pleistocene climate events and by the rugged topography of southern Europe, giving rise to repeated cycles of population isolation during periods of glaciation alternating with interglacial expansions limited by geographic barriers. 相似文献
19.
在黄河中游郑州荥阳段,选择了5种河滨湿地植物群落进行根系和土壤性状特征研究,以期阐明不同植物群落的根系分布规律与土壤性状的关系,为河滨湿地植物群落组成以及土壤质量恢复提供科学参考。结果表明(1)在0—40 cm土层,根生物量密度与根长密度的平均值均表现为:芦苇群落(Phragmites australis)和芦苇-狗牙根(Cynodon dactylon)群落均大于芦苇-拂子茅(Calamagrostis epigeios)-狗牙根群落、拂子茅-狗牙根群落、拂子茅-狗牙根-水莎草(Juncellus serotinus)群落。拂子茅-狗牙根、芦苇-拂子茅-狗牙根、拂子茅-水莎草-狗牙根三种植物群落类型下根生物量密度、根长密度在0—20 cm表层土壤较大,芦苇群落和芦苇-狗牙根群落的根生物量密度、根长密度在10—40 cm的土层较大。(2)黄河河滨湿地芦苇群落、芦苇-狗牙根群落的土壤以粉粒为主,拂子茅-狗牙根群落、芦苇-拂子茅-狗牙根群落、拂子茅-狗牙根-水莎草群落的土壤主要以砂粒为主。在0—40 cm土层,芦苇群落、芦苇-狗牙根群落的土壤含水率、土壤有机质、有效氮和有效磷含量均显著高于... 相似文献
20.
Leirla Salazar Hafida Fsihi Edda de Rossi Giovanna Riccardi Carmen Rios Stewart T. Cole Howard E. Takiff 《Molecular microbiology》1996,20(2):283-293
The genus Mycobacterium is composed of species with widely differing growth rates ranging from approximately three hours in Mycobacterium smegmatis to two weeks in Mycobacterium leprae. As DNA replication is coupled to cell duplication, it may be regulated by common mechanisms. The chromosomal regions surrounding the origins of DNA replication from M. smegmatis, M. tuberculosis, and M. leprae have been sequenced, and show very few differences. The gene order, rnpA-rpmH-dnaA-dnaN-recF-orf-gyrB-gyrA, is the same as in other Gram-positive organisms. Although the general organization in M. smegmatis is very similar to that of Streptomyces spp., a closely related genus, M. tuberculosis and M. leprae differ as they lack an open reading frame, between dnaN and recF, which is similar to the gnd gene of Escherichia coli. Within the three mycobacterial species, there is extensive sequence conservation in the intergenic regions flanking dnaA, but more variation from the consensus DnaA box sequence was seen than in other bacteria. By means of subcloning experiments, the putative chromosomal origin of replication of M. smegmatis, containing the dnaA-dnaN region, was shown to promote autonomous replication in M. smegmatis, unlike the corresponding regions from M. tuberculosis or M. leprae. 相似文献