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1.
This work describes the long-term acclimation of the halotolerant microalga Dunaliella viridis to different photon irradiance, ranging from darkness to 1500 μmol m−2 s−1. In order to assess the effects of long-term photoinhibition, changes in oxygen production rate, pigment composition, xanthophyll
cycle and in vivo chlorophyll fluorescence using the saturating pulse method were measured. Growth rate was maximal at intermediate irradiance
(250 and 700 μmol m−2 s−1). The increase in growth irradiance from 700 to 1500 μmol m−2 s−1 did not lead to further significant changes in pigment composition or EPS, indicating saturation in the pigment response
to high light. Changes in Photosystem II optimum quantum yield (Fv/Fm) evidenced photoinhibition at 700 and especially at 1500 μmol m−2 s−1. The relation between photosynthetic electron flow rate and photosyntetic O2 evolution was linear for cultures in darkness shifting to curvilinear as growth irradiance increased, suggesting the interference
of the energy dissipation processes in oxygen evolution. Carbon assimilation efficiencies were studied in relation to changes
in growth rate, internal carbon and nitrogen composition, and organic carbon released to the external medium. All illuminated
cultures showed a high capability to maintain a C:N ratio between 6 and 7. The percentage of organic carbon released to the
external medium increased to its maximum under high irradiance (1500 μmol m−2 s−1). These results suggest that the release of organic carbon could act as a secondary dissipation process when the xanthophyll
cycle is saturated.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
2.
Pablo A. P. Antiqueira Paula M. de Omena Thiago Gonalves-Souza Camila Vieira Gustavo H. Migliorini Mnica F. Kersch-Becker Tiago N. Bernab Ftima C. Recalde Sandra Benavides- Gordillo Gustavo Q. Romero 《Oecologia》2020,192(3):745-753
Biotic and abiotic factors may individually or interactively disrupt plant–pollinator interactions, influencing plant fitness. Although variations in temperature and precipitation are expected to modify the overall impact of predators on plant–pollinator interactions, few empirical studies have assessed if these weather conditions influence anti-predator behaviors and how this context-dependent response may cascade down to plant fitness. To answer this question, we manipulated predation risk (using artificial spiders) in different years to investigate how natural variation in temperature and precipitation may affect diversity (richness and composition) and behavioral (visitation) responses of flower-visiting insects to predation risk, and how these effects influence plant fitness. Our findings indicate that predation risk and an increase in precipitation independently reduced plant fitness (i.e., seed set) by decreasing flower visitation. Predation risk reduced pollinator visitation and richness, and altered species composition of pollinators. Additionally, an increase in precipitation was associated with lower flower visitation and pollinator richness but did not alter pollinator species composition. However, maximum daily temperature did not affect any component of the pollinator assemblage or plant fitness. Our results indicate that biotic and abiotic drivers have different impacts on pollinator behavior and diversity with consequences for plant fitness components. Even small variation in precipitation conditions promotes complex and substantial cascading effects on plants by affecting both pollinator communities and the outcome of plant–pollinator interactions. Tropical communities are expected to be highly susceptible to climatic changes, and these changes may have drastic consequences for biotic interactions in the tropics. 相似文献
3.
A survey was conducted to determine the levels of fumonisins B1 and B2 in corn and corn-based products available in Colombia
for human and animal consumption. A total of 120 samples were analyzed by acetonitrile-water extraction, cleanup with a strong-anion-exchange
column, and liquid chromatography with o-phthaldialdehyde-2-mercaptoethanol derivatization and fluorescence detection. The
samples of corn and corn-based products for animal intake were taken at different feed manufacturing plants, whereas the samples
used for human foods where purchased from local retail stores. The number of positive samples for fumonisin B1 was 20.0% higher
in corn and corn-based products for animal intake (75.0%) than in corn and corn-based products for human consumption (55.0%).
The levels of fumonisin B1 were also higher in corn and corn-based products for animal intake (mean = 694 μg/kg; range = 32–2964
μg/kg), than in corn and corn-based products for human intake (mean = 218 μg/kg; range = 24–2170 μg/ kg). The incidence and
levels of fumonisin B2 were lower than those for fumonisin B1. Corn and corn-based products for animal consumption had an
incidence of fumonisin B2 of 58.3%, with a mean value of 283 μg/kg, and a range of 44–987 μg/kg. The incidence of fumonisin
B2 in corn-based products for human intake was 35.0%, with a mean value of 118 μg/kg and a range of 21–833 μg/kg. The highest
incidence and levels of fumonisins were found in samples of hominy feed, with concentrations ranging from 86 to 2964 μg/kg
fumonisin B1 and 57 to 987 μg/kg fumonisin B2. 相似文献
4.
Francisco J.L. Gordillo Carlos Jiménez Félix L. Figueroa F. Xavier Niell 《Journal of applied phycology》1998,10(5):461-469
The consequences of the addition of CO2 (1%) in cultures of S. platensis are examined in terms of biomass yield, cell composition
and external medium composition. CO2 enrichment was tested under nitrogen saturating and nitrogen limiting conditions. Increasing
CO2 levels did not cause any change in maximum growth rate while it decreased maximum biomass yield. Protein and pigments
were decreased and carbohydrate increased by high CO2, but the capability to store carbohydrates was saturated. C:N ratio
remained unchanged while organic carbon released to the external medium was enhanced, suggesting that organic carbon release
in S. platensis is an efficient mechanism for the maintenance of the metabolic integrity, balancing the cell C:N ratio in
response to environmental CO2 changes. CO2 affected the pigment content: Phycocyanin, chlorophyll and carotenoids were reduced
in around 50%, but the photosynthetic parameters were slightly changed. We propose that in S. platensis CO2 could act promoting
degradation of pigments synthetised in excess in normal CO2 conditions, that are not necessary for light harvesting. Nitrogen
assimilation was significantly not affected by CO2, and it is proposed that the inability to stimulate N assimilation by CO2
enrichment determined the lack of response in maximum growth rate.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
5.
6.
Ankit X. Sharma Ezekiel B. Quittner-Strom Young Lee Joshua A. Johnson Sarah A. Martin Xinxin Yu Jianping Li John Lu Zheqing Cai Shiuhwei Chen May-yun Wang Yiyi Zhang Mackenzie J. Pearson Andie C. Dorn Jeffrey G. McDonald Ruth Gordillo Hai Yan Dung Thai William L. Holland 《Cell reports》2018,22(7):1760-1773
7.
8.
Wilfried Veron Nicole Orange Marc GJ Feuilloley Olivier Lesouhaitier 《BMC microbiology》2008,8(1):114
Background
Nervous tissues express various communication molecules including natriuretic peptides, i.e. Brain Natriuretic Peptide (BNP) and C-type Natriuretic Peptide (CNP). These molecules share structural similarities with cyclic antibacterial peptides. CNP and to a lesser extent BNP can modify the cytotoxicity of the opportunistic pathogen Pseudomonas aeruginosa. The psychrotrophic environmental species Pseudomonas fluorescens also binds to and kills neurons and glial cells, cell types that both produce natriuretic peptides. In the present study, we investigated the sensitivity of Pseudomonas fluorescens to natriuretic peptides and evaluated the distribution and variability of putative natriuretic peptide-dependent sensor systems in the Pseudomonas genus. 相似文献9.
Gaelle Rossignol Annabelle Merieau Josette Guerillon Wilfried Veron Olivier Lesouhaitier Marc GJ Feuilloley Nicole Orange 《BMC microbiology》2008,8(1):189
Background
Pseudomonas fluorescens is a ubiquitous Gram-negative bacterium frequently encountered in hospitals as a contaminant of injectable material and surfaces. This psychrotrophic bacterium, commonly described as unable to grow at temperatures above 32°C, is now considered non pathogenic. We studied a recently identified clinical strain of P. fluorescens biovar I, MFN1032, which is considered to cause human lung infection and can grow at 37°C in laboratory conditions. 相似文献10.
Colony foraging allocation is finely tuned to food distance and sweetness even close to a bee colony 下载免费PDF全文
Adolfo León Carlos Arias‐Castro Martha A. Rodríguez‐Mendiola Rocío Meza‐Gordillo Federico A. Gutiérrez‐Miceli James C. Nieh 《Entomologia Experimentalis et Applicata》2015,155(1):47-53
Social bee colonies can allocate their foraging resources over a large spatial scale, but how they allocate foraging on a small scale near the colony is unclear and can have implications for understanding colony decision‐making and the pollination services provided. Using a mass‐foraging stingless bee, Scaptotrigona pectoralis (Dalla Torre) (Hymenoptera: Apidae: Meliponini), we show that colonies will forage near their nests and allocate their foraging labor on a very fine spatial scale at an array of food sources placed close to the colony. We counted the foragers that a colony allocated to each of nine feeders containing 1.0, 1.5, or 2.0 M sucrose solution [31, 43, and 55% sucrose (wt/wt), respectively] at distances of 10, 15, and 20 m from the nest. A significantly greater number of foragers (2.6–5.3 fold greater) visited feeders placed 10 vs. 20 m away from the colony. Foraging allocation also corresponded to food quality. At the 10‐m feeders, 4.9‐fold more foragers visited 2.0 M as compared to 1.0 M sucrose feeders. Colony forager allocation thus responded to both differences in food distance and quality even when the travel cost was negligible compared to normal colony foraging distances (10 m vs. an estimated 800–1 710 m). For a nearby floral patch, this could result in unequal floral visitation and pollination. 相似文献