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61.
Burr Medic (Medicago polymorpha) is awidespread, polymorphic annual legume of Mediterranean origin, and as aself-reseeding, highly effective nitrogen fixer it has important value invarious dryland farming systems. In central Chile, it is naturalized along a1000 km long environmental gradient, from an arid zone(29°–31° S) to a perhumid one(37°–38°24' S). Comparative and experimental studiesof its ecotypic differentiation patterns along this gradient should be usefulinelucidating the evolutionary forces at work along environmental gradients, andalso for efforts to select annual legumes for pastures and fallow fieldimprovement in mediterranean climate areas. In this first paper of atwo-part series, we present results of two common-environmentexperiments conducted at a subhumid site in central Chile to compare vegetativeand reproductive traits in 69 populations of Burr Medic collected in 1988 and1994. Multivariate analyses based on 11 phenological and agronomic characters,including phenology and biomass accumulation, winter vigour and degree ofhard-seededness, showed that three principal components (PCs)explained nearly 70% of total variability, in both collections. For thelarger collection (1988), the diagram of dispersion for the first twoPCs – phenology, winter vigour and above-ground biomass –provided good discrimination between accessions from arid-semiarid andhumid-perhumid mediterranean zones. Onset of flowering was positivelycorrelated with both latitude and longitude, as well as mean annualprecipitation/potential evapotranspiration (PP/ETP) ofcollecting site; days from first flower to pod ripening was negativelycorrelated with PP/ETP. In contrast to reports from Syria and Sardinia, noclear trends in Burr Medic seed or pod-related traits was found along theChilean gradient, apart from the concentration of spiny pod accessions in thesouthern, more mesic end of the gradient. Winter vigour (according to asemi-quantitative analysis of growth) was greater in accessions fromthe warmer, arid and semiarid zones than in those from cooler, subhumid tohumidones. Both winter vigour and harvest index were negatively correlated with daysto first flower. Applied and evolutionary aspects of the results are brieflydiscussed. 相似文献
62.
Javier Prez Margarita Menndez Santiago Larraaga Jesús Pozo 《International Review of Hydrobiology》2011,96(1):105-117
The main goal of this study was to examine the natural variability of alder (Alnus glutinosa (L.) Gaertn.) leaf processing and explore its potentiality as a functional indicator to assess the ecological status of Spanish headwater streams. Breakdown of leaf litter was studied during autumn‐winter in reference headwater streams of two regions of northern Spain: the Basque Country (on the Atlantic) and Catalonia (on the Mediterranean). Spring experiments were also carried out in the Atlantic region in order to study seasonal changes. Leaf mass loss rates were slightly higher in Catalonian streams. Temperature was not the main factor for explaining differences between the two regions. In the Atlantic one, however, water temperature determined the spatial and seasonal variability of leaf litter processing. Because of the high natural variability in breakdown rates, our results highlight the difficulty in detecting moderate impairments on stream functioning through the analysis of leaf litter decomposition if this process is not accompanied by the study of other factors affecting it. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
63.
Del Pozo Alejandro; Ovalle Carlos; Aronson James; Avendano Julia 《Annals of botany》2000,85(6):809-814
The phenological development of nine Chilean accessions of Medicagopolymorpha, collected along a northsouth aridity gradient,and of two commercial cultivars of the same species, were comparedin 12 sequential outdoor sowings at Cauquenes (35°58'S,72°17'W, elev. 177 m), in the sub-humid Mediterranean climatezone of Chile. A glasshouse experiment was also conducted toevaluate the effect of photoperiod on phenophase timing. Therewas a clear gradient in precocity among the Chilean accessionsin both experiments: accessions MPO-9-88 and MPO-7-88, fromthe arid zone, were the earliest-flowering accessions, whereasMPO-36-88 from the humid Mediterranean zone was the latest.Both experiments revealed significant variation among the Chileanaccessions in the response of flowering time to variation inphotoperiod regime. Differences in days to flowering betweenthe least- (8 h) and the most- (16 h) inductive photoperiodswere lower in precocious accessions from arid and semi-aridzones, than in late-flowering accessions from more humid zones.Rate of progress to flowering, defined as the inverse of timefrom emergence to first flower appearance (1/ f), was relatedto mean diurnal temperature, or to both mean diurnal temperatureand mean photoperiod. In two early-flowering accessions fromthe arid zone, and in the Australian cultivar CircleValley, 1/ f was affected significantly (P < 0.05)by both temperature and photoperiod. In the remaining accessions,no significant responses to temperatures were detected; 1/ fwas influenced significantly by photoperiod only. Copyright2000 Annals of Botany Company Annual medic, aridity gradient, Medicago polymorpha, flowering time, rate of development 相似文献
64.
Temperature is one of the main factors that determine sexual reproduction in terrestrial and emergent aquatic plant species. The effect of temperature on sexual reproduction and seed production of Glyceria maxima (Hartm.) Holmb. in the southern hemisphere is unknown. Glyceria maxima collections in February 2010 at three isolated infestations in KwaZulu-Natal failed to yield a single seed, only empty panicles. Laboratory experiments showed that vernalisation had no consistent effect on seed production. Field- and laboratory-grown plants produced seeds in the 2010/2011 season, because of having sufficient time at optimum temperatures required for seed production (1 491 and 1 585 hours, respectively), compared to a shorter period (1 352 hours) of suitable temperatures during the 2009/2010 growing season. An inadequate period of optimum temperatures (15–25°C) during seed production resulted in the lack of seeds in the field in the 2009/2010 growing season. This study showed that temperature and duration of exposure thereto during the seed-production period play vital roles in G. maxima sexual reproduction. 相似文献
65.
Rosa Belén Mohedano del Pozo Margarita Rubio Alonso Mª Soledad Cuétara García 《Revista iberoamericana de micología》2018,35(3):117-122
Background
The role of culture-independent techniques (galactomannan, (1-3)-β-d-glucan) in the early diagnosis of invasive fungal diseases (IFD) is well assessed in hematological patients, but there are no clear conclusions in patients with chronic obstructive pulmonary disease (COPD).Aims
To study the usefulness of nonculture-based techniques in the diagnosis of IFD in COPD-patients at risk for IFD.Methods
A prospective observational study based on monitoring COPD patients at risk for IFD during 2007–2010 was carried out. The presence of galactomannan, (1-3)-β-d-glucan and an indirect immunofluorescence of Candida albicans germ tube specific antibodies (CAGTA) were performed.Results
Among 43 COPD patients, 16 (37.2%) were diagnosed with IFD: seven cases were proven IFD (five invasive candidemia – IC, one invasive aspergillosis – IA and a rhinocerebral zygomycosis) and nine probable IFD (seven IA and two IC). In the diagnosis of IC and IA, the negative predictive value (NPV) of (1-3)-β-d-glucan was 100%. Regarding CAGTA in IC, NPV was 96.2%. Finally, NPV of galactomannan in IA was 91.2%. The area under the ROC curve for (1-3)-β-d-glucan in IC and for the rest of the IFD cases was 0.86 (95% CI, 0.79–0.93) and 0.60 (95% CI, 0.43–0.77), for CAGTA in IC was 0.83 (95% CI, 0.74–0.91) and for galactomannan in IA was 0.71 (95% CI, 0.56–0.85). Positive (1-3)-β-d-glucan preceded the growth of Candida (average of 1.7 days) in blood culture.Conclusions
In COPD patients at risk for IFD the assayed techniques are especially useful to rule out the presence of IFD. 相似文献66.
Marmoset phylogenetics, conservation perspectives, and evolution of the mtDNA control region 总被引:3,自引:1,他引:2
Tagliaro CH; Schneider MP; Schneider H; Sampaio IC; Stanhope MJ 《Molecular biology and evolution》1997,14(6):674-684
Marmosets (genus Callithrix) are a diverse group of platyrrhine primates
with 13-15 purported taxa, many of them considered endangered.
Morphological analyses constitute most of the basis for recognition of
these forms as distinct taxa. The purpose of this study was to provide a
molecular view, based on mitochondrial control region sequences, of the
evolutionary history of the marmosets, concomitant with a molecular
phylogenetic perspective on species diversity within the group. An
additional purpose was to provide the first comparative examination of a
complete New World monkey control region sequence with those of other
mammals. The phylogenetic analyses provide convincing support for a split
between the Atlantic forest and Amazonian marmosets, with the inclusion of
the pygmy marmoset (Cebuella pygmaea) at the base of the Amazonian clade.
The earliest branch of the Atlantic forest group was C. aurita. In the
Amazonian group, the analyses do not support the recognition of C.
humeralifer and the recently described C mauesi as distinct taxa. They do,
however, support a clear distinction between C. argentata and a strongly
supported mixed clade of C. humeralifer and C. mauesi. In the Atlantic
forest group, the phylogenetic tree suggests mixing between C. penicillata,
C. kuhli, and possibly C. jacchus. Most of the sequence features
characteristic of other mammal control regions were also evident in
marmosets, with the exception that conserved sequence blocks (CSBs) 2 and 3
were not clearly identifiable. Tandem repeat units often associated with
heteroplasmy in a variety of other mammals were not evident in the marmoset
sequences.
相似文献
67.
Persistent nuclear ribosomal DNA sequence polymorphism in the Amelanchier agamic complex (Rosaceae) 总被引:5,自引:0,他引:5
Campbell CS; Wojciechowski MF; Baldwin BG; Alice LA; Donoghue MJ 《Molecular biology and evolution》1997,14(1):81-90
Individual plants of several Amelanchier taxa contain many polymorphic
nucleotide sites in the internal transcribed spacers (ITS) of nuclear
ribosomal DNA (nrDNA). This polymorphism is unusual because it is not
recent in origin and thus has resisted homogenization by concerted
evolution. Amelanchier ITS sequence polymorphism is hypothesized to be the
result of gene flow between two major North American clades resolved by
phylogenetic analysis of ITS sequences. Western North American species plus
A. humilis and A. sanguinea of eastern North America form one clade (A),
and the remaining eastern North American Amelanchier make up clade B. Five
eastern North American taxa are polymorphic at many of the nucleotide sites
where clades A and B have diverged and are thought to be of hybrid origin,
with A. humilis or A. sanguinea as one parent and various members of clade
B as the other parent. Morphological evidence suggests that A. humilis is
one of the parents of one of the polymorphic taxa, a microspecies that we
refer to informally as A. "erecta." Sequences of 21 cloned copies of the
ITS1- 5.8S gene-ITS2 region from one A. "erecta" individual are identical
to A. humilis sequence or to the clade B consensus sequence, or they are
apparent recombinants of A. humilis and clade B ITS repeats. Amelanchier
"erecta" and another polymorphic taxon are suspected to be relatively old
because both grow several hundred kilometers beyond the range of one of
their parents. ITS sequence polymorphisms have apparently persisted in
these two taxa perhaps because of polyploidy and/or agamospermy (asexual
seed production), which are prevalent in the genus.
相似文献
68.
Tvbgn3, a β-1,6-Glucanase from the Biocontrol Fungus Trichoderma virens, Is Involved in Mycoparasitism and Control of Pythium ultimum
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Even though β-1,6-glucanases have been purified from several filamentous fungi, the physiological function has not been conclusively established for any species. In the present study, the role of Tvbgn3, a β-1,6-glucanase from Trichoderma virens, was examined by comparison of wild-type (WT) and transformant strains in which Tvbgn3 was disrupted (GKO) or constitutively overexpressed (GOE). Gene expression analysis revealed induction of Tvbgn3 in the presence of host fungal cell walls, indicating regulation during mycoparasitism. Indeed, while deletion or overexpression of Tvbgn3 had no evident effect on growth and development, GOE and GKO strains showed an enhanced or reduced ability, respectively, to inhibit the growth of the plant pathogen Pythium ultimum compared to results with the WT. The relevance of this activity in the biocontrol ability of T. virens was confirmed in plant bioassays. Deletion of the gene resulted in levels of disease protection that were significantly reduced from WT levels, while GOE strains showed a significantly increased biocontrol capability. These results demonstrate the involvement of β-1,6-glucanase in mycoparasitism and its relevance in the biocontrol activity of T. virens, opening a new avenue for biotechnological applications. 相似文献
69.
Hormonal control of the plant cell cycle 总被引:7,自引:0,他引:7
Juan Carlos del Pozo M. Angeles Lopez-Matas Elena Ramirez-Parra Crisanto Gutierrez 《Physiologia plantarum》2005,123(2):173-183
Plant organogenesis is essentially a post-embryonic process that requires a strict balance between cell proliferation and differentiation. This is subject to a complex regulatory network which, in some cases, depends on the action of a variety of plant hormones. Of these, auxins and cytokinins are those best documented as impinging directly on cell cycle control. However, increasing evidence is accumulating to indicate that other hormones also have an impact on cell cycle control by influencing the availability of cell cycle regulators. In this article, we review the results that point to the variety of situations in which cell cycle progression is controlled by phytohormones. 相似文献
70.