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排序方式: 共有245条查询结果,搜索用时 15 毫秒
191.
Finbarr G. Horgan Thanga Suja Srinivasan Eduardo Crisol‐Martínez Maria Liberty P. Almazan Angelee Fame Ramal Ricardo Oliva Ian L. Quibod Carmencita C. Bernal 《Ecology and evolution》2019,9(20):11911-11929
The microbiomes of phloem‐feeding insects include functional bacteria and yeasts essential for herbivore survival and development. Changes in microbiome composition are implicated in virulence adaptation by herbivores to host plant species or host populations (including crop varieties). We examined patterns in adaptation by the green leafhopper, Nephotettix virescens, to near‐isogenic rice lines (NILs) with one or two resistance genes and the recurrent parent T65, without resistance genes. Only the line with two resistance genes was effective in reducing leafhopper fitness. After 20 generations on the resistant line, selected leafhoppers attained similar survival, weight gain, and egg laying to leafhoppers that were continually reared on the susceptible recurrent parent, indicating that they had adapted to the resistant host. By sequencing the 16s rRNA gene, we described the microbiome of leafhoppers from colonies associated with five collection sites, and continually reared or switched between NILs. The microbiomes included 69–119 OTUs of which 44 occurred in ≥90% of samples. Of these, 14 OTUs were assigned to the obligate symbiont Candidatus sulcia clade. After 20 generations of selection, collection site had a greater effect than host plant on microbiome composition. Six bacteria genera, including C. sulcia, were associated with leafhopper virulence. However, there was significant within‐treatment, site‐related variability in the prevalence of these taxa such that the mechanisms underlying their association with virulence remain to be determined. Our results imply that these taxa are associated with leafhopper nutrition. Ours is the first study to describe microbiome diversity and composition in rice leafhoppers. We discuss our results in light of the multiple functions of herbivore microbiomes during virulence adaptation in insect herbivores. 相似文献
192.
193.
C. A. Glasbey G. W. Horgan G. J. Gibson D. Hitchcock 《Biometrical journal. Biometrische Zeitschrift》1995,37(4):481-495
Landmarks are used to summarize the shapes of ten haddock and nine whiting. Error variance models, after generalized Procrustes analysis, are compared using simulation tests. The power to discriminate between fish species is shown to be increased by permitting non-affine transformations that correct for fish curvature. 相似文献
194.
Finbarr G. Horgan 《Biodiversity and Conservation》2009,18(13):3519-3541
This study examines the effects of deforestation, and the habitat value of coffee and regenerated forest for tropical dung
beetles, a functionally significant insect group. Pitfall trapping was conducted at 22 sites in a montane region of central
Peru during April and November/December of 2002. Sites included primary and secondary forest, shade-coffee, regenerated forest
and open farms (mainly with banana, yuca, and corn). Ordination techniques indicated that beetle assemblages in forests, regenerated
forest and coffee were relatively similar. However, assemblage compositions in forested areas differed even at similar altitudes
under the influence of biogeographical factors, and the assemblages at disturbed sites (farms/coffee) were influenced by beetle
dispersal from adjacent forests. During dry months, when beetle activity is low, communities at all habitat types tended to
converge because fewer unique species were recorded in forests at that time and habitat/season generalists were dominant.
Preliminary results also indicate that beetles in shady crops such as bananas responded to plant growth: as the banana canopy
closed-in, producing more shade, open-habitat specialists retreated and forest/shade specialists invaded the sites. Chronosequence
data at two of the sites demonstrate the rapid and dramatic changes in species richness and assemblage composition caused
by deforestation. As forests become increasingly fragmented, and open farms continue to expand, dung beetles will become more
restricted to the remaining fragments and reserves. In the mosaic landscape studied here, shade crops, like coffee, act as
habitat and corridors for many dung beetle species. Small farm size and the consequent magnitude of edge effects, likely contributed
to beetle movement between habitat types and determined the apparent generalist nature of many of the dung beetle species
in this study. 相似文献
195.
The stoichiometric composition of autotrophs can vary greatly in response to variation in light and nutrient availability,
and can mediate ecological processes such as C sequestration, growth of herbivores, and nutrient cycling. We investigated
light and nutrient effects on phytoplankton stoichiometry, employing five experiments on intact phytoplankton assemblages
from three lakes varying in productivity and species composition. Each experiment employed two nutrient and eight irradiance
levels in a fully factorial design. Light and nutrients interactively affected phytoplankton stoichiometry. Thus, phytoplankton
C:N, C:P, and N:P ratios increased with irradiance, and slopes of the stoichiometric ratio versus irradiance relationships
were steeper with ambient nutrients than with nutrients added. Our results support the light–nutrient hypothesis, which predicts
that phytoplankton C:nutrient ratios are functions of the ratio of available light and nutrients; however, we observed considerable
variation among lakes in the expression of this relationship. Phytoplankton species diversity was positively correlated with
the slopes of the C:N and C:P versus irradiance relationships, suggesting that diverse assemblages may exhibit greater flexibility
in the response of phytoplankton nutrient stoichiometry to light and nutrients. The interactive nature of light and nutrient
effects may render it difficult to generate predictive models of stoichiometric responses to these two factors. Our results
point to the need for future studies that examine stoichiometric responses across a wide range of phytoplankton communities. 相似文献
196.
Seed development was investigated in kernels of developing wild-type and viviparous (vp-1) Zea mays L. Embryos and endosperm of wild-type kernels began to dehydrate at approx. 35 d after pollination (DAP); viviparous embryos did not desiccate but accumulated fresh weight via coleoptile growth in the caryopses. Concentrations of endogenous abscisic acid (ABA) in the embryo were relatively high early in development, being approx. 150 ng·g-1 fresh weight at 20 DAP. The ABA content declined thereafter, falling to approx. 50 ng·g-1 at 30 DAP. Endosperm ABA content was always low, being less than 20 ng·g-1. There were no differences between wild-type and vp-1 tissues. Immature kernels did not germinate when removed from the ear until late in development. The ability to germinate was correlated with decreasing moisture content in the endosperm at the time of removal; premature drying of immature kernels resulted in greatly increased germination following imbibition. Excised embryos germinated precociously when removed from the endosperm as early as 25 DAP. Such germination could be prevented by treatment with 10-5 M ABA or by lowering the solute potential (s) of the medium with 0.3 M mannitol. Treatment of excised embryos with ABA led to internal ABA concentrations comparable to those in embryos in which germination was inhibited in situ. Mannitol treatment did not have this effect, although water-deficit stress of excised embryos resulted in substantial ABA production. Germinated vp-1 embryos were less sensitive to growth inhibition by ABA or mannitol than germinating wild-type embryos. The vp-1 seedlings were not wilty and their transpiration rates were reduced in response to ABA or water shortage.Abbreviations and symbols ABA
abscisic acid
- DAP
days after pollination
- FW
fresh weight
-
vp-1
viviparous genotype
- s
solute potential 相似文献
197.
Deuterium-labelled indole-3-acetic acid, abscisic acid and phthalimido-1-aminocyclopropane-1-carboxylic acid were found to separate from the unlabelled compounds on reverse-phase high-performance liquid chromatography (HPLC). A similar separation was found for the methyl esters of these compounds on normal-phase HPLC. Such separations may lead to substantial errors when these compounds are used as internal standards for quantitation by gas chromatography-mass spectrometry/selective ion detection, unless the complete chromatographic peaks are collected.Abbreviations ABA
abscisic acid
- ACC
1-aminocyclopropane-1-carboxylic acid
- IAA
indole-3-acetic acid
- GC-MS
gas chromatography-mass spectrometry
- HPLC
high-performance liquid chromatography
- Pht-ACC
phthalimido-ACC
- SIM
selected ion monitoring 相似文献
198.
A new cytokinin was isolated from mature leaves of poplar. Its structure was determined by UV and MS and confirmed by synthesis as 6-(o-hydroxybenzylamino)-9-β-d-ribofuranosylpurine. This cytokinin has medium activity in the soybean callus test but shows high activity in the radish leaf senescence test. 相似文献
199.
200.
cis-Zeatin riboside was identified in transfer-RNA hydrolysates from both normal and crown-gall tissue of Vinca rosea L. The trans-isomer was associated exclusively with the crowngall transfer-RNA. The importance of these observations is discussed in relation to biosynthesis of free cytokinins.Abbreviations GC-MS
gas chromatography-mass spectrometry
- HPLC
high-performance liquid chromatography
- TLC
thin-layer chromatography
- TMSi
trimethylsilyl
- tRNA
transfer RNA
- ZR
zeatin riboside 相似文献