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排序方式: 共有81条查询结果,搜索用时 171 毫秒
1.
YONG-JIANG ZHANG FREDERICK C. MEINZER GUANG-YOU HAO FABIAN G. SCHOLZ SANDRA J. BUCCI FREDERICO S. C. TAKAHASHI RANDOL VILLALOBOS-VEGA JUAN P. GIRALDO KUN-FANG CAO WILLIAM A. HOFFMANN & GUILLERMO GOLDSTEIN 《Plant, cell & environment》2009,32(10):1456-1466
Size-related changes in hydraulic architecture, carbon allocation and gas exchange of Sclerolobium paniculatum (Leguminosae), a dominant tree species in Neotropical savannas of central Brazil (Cerrado), were investigated to assess their potential role in the dieback of tall individuals. Trees greater than ∼6-m-tall exhibited more branch damage, larger numbers of dead individuals, higher wood density, greater leaf mass per area, lower leaf area to sapwood area ratio (LA/SA), lower stomatal conductance and lower net CO2 assimilation than small trees. Stem-specific hydraulic conductivity decreased, while leaf-specific hydraulic conductivity remained nearly constant, with increasing tree size because of lower LA/SA in larger trees. Leaves were substantially more vulnerable to embolism than stems. Large trees had lower maximum leaf hydraulic conductance ( K leaf ) than small trees and all tree sizes exhibited lower K leaf at midday than at dawn. These size-related adjustments in hydraulic architecture and carbon allocation apparently incurred a large physiological cost: large trees received a lower return in carbon gain from their investment in stem and leaf biomass compared with small trees. Additionally, large trees may experience more severe water deficits in dry years due to lower capacity for buffering the effects of hydraulic path-length and soil water deficits. 相似文献
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3.
EXPERTS VERSUS CONSUMERS: A CRITIQUE 总被引:1,自引:0,他引:1
GUILLERMO HOUGH 《Journal of sensory studies》1998,13(3):285-289
In a recent paper Moskowitz (1996) refuted the notion that consumers are incapable of validly rating the sensory aspects of products. An analysis of this paper reveals that references are not presented to support his introduction, there is lack of experimental detail, parameters to compare panels were questionable, the degree of expertise of the expert panel is put to doubt and the model proposed to relate data between panels was not compared to existing models. 相似文献
4.
Supercooling along an Altitudinal Gradient in Espeletia schultzii, a Caulescent Giant Rosette Species 总被引:1,自引:0,他引:1
RADA FERMIN; GOLDSTEIN GUILLERMO; AZOCAR AURA; TORRES FRESIA 《Journal of experimental botany》1987,38(3):491-497
Rada, F., Goldstein, G., Azocar, A. and Torres, F. 1987. Supercoolingalong an altitudinal gradient in Espeletia schultzii, a caulescentgiant rosette species.J. exp. Bot. 38: 491497. Tropical high Andes plants may be exposed to sub-zero temperaturesany night of the year. These plants have to rely on mechanismswhich protect them from these environmental conditions but atthe same time allow their growth and development. Supercoolinghas been found to be the principal avoidance mechanism in leavesof the caulescent giant rosette genus Espeletia in the Andes.We report here the differences in supercooling capacity andcold injury in several Espeletia schultzii populations growingalong an altitudinal gradient. The relationships between supercooling,water potential and leaf anatomy were also investigated. Thesupercooling capacity increased and injury temperature decreasedfrom lower to higher elevation populations. These changes maybe explained in terms of physiological, morphological and anatomicalcharacteristics of the leaves. Key words: Espeletia schultzii, supercooling, freezing avoidance mechanisms 相似文献
5.
YONG‐JIANG ZHANG FREDERICK C. MEINZER JIN‐HUA QI GUILLERMO GOLDSTEIN KUN‐FANG CAO 《Plant, cell & environment》2013,36(1):149-158
Midday depressions in stomatal conductance (gs) and photosynthesis are common in plants. The aim of this study was to understand the hydraulic determinants of midday gs, the coordination between leaf and stem hydraulics and whether regulation of midday gs differed between deciduous and evergreen broadleaf tree species in a subtropical cloud forest of Southwest (SW) China. We investigated leaf and stem hydraulics, midday leaf and stem water potentials, as well as midday gs of co‐occurring deciduous and evergreen tree species. Midday gs was correlated positively with midday stem water potential across both groups of species, but not with midday leaf water potential. Species with higher stem hydraulic conductivity and greater daily reliance on stem hydraulic capacitance were able to maintain higher stem water potential and higher gs at midday. Deciduous species exhibited significantly higher stem hydraulic conductivity, greater reliance on stem capacitance, higher stem water potential and gs at midday than evergreen species. Our results suggest that midday gs is more associated with midday stem than with leaf water status, and that the functional significance of stomatal regulation in these broadleaf tree species is probably for preventing stem xylem dysfunction. 相似文献
6.
SABINA L. MAHUAD GUILLERMO R. PRATTA GUSTAVO R. RODRIGUEZ ROXANA ZORZOLI LILIANA A. PICARDI 《Journal of genetics》2013,92(2):195-203
Five recombinant inbred lines obtained from the F2 generation of an interspecific cross between cultivar, Caimanta (Cai, Solanum lycopersicum) and wild accession, LA722 (P, S. pimpinellifolium) were crossed to obtain the second cycle hybrids (SCH). Eleven fruit quality traits were assessed in evaluating phenotypic variability among genotypes P, Cai, F1 (Cai × P), five RILs, and 10 SCH. One of the five recombinant inbred lines and three SCH had higher values than P, as the best genotype for shelf life. Sequence-related amplified polymorphism was used as the molecular method for detecting polymorphism among these 18 genotypes. The percentage of polymorphism in RILs and SCH was 61% and 66% respectively. Moreover, some bands detected in P were present in SCH. Several multivariate analyses were performed to find agreement between the phenotypic variability observed for fruit quality traits and the polymorphism obtained from sequence-related amplified polymorphism markers. A general Procrustes analysis estimated that there was a consensus proportion of 75% between phenotypic and molecular data. There was considerable preservation of some bands from the wild genotype, which could increase the variability in fruit quality traits in populations where the genetic diversity is limited. 相似文献
7.
ABSTRACT. Horizontal gene transfer (HGT) and common descent interact in space and time. Because events of HGT co‐occur with phylogenetic evolution, it is difficult to depict evolutionary patterns graphically. Tree‐like representations of life's diversification are useful, but they ignore the significance of HGT in evolutionary history, particularly of unicellular organisms, ancestors of multicellular life. Here we integrate the reticulated‐tree model, ring of life, symbiogenesis whole‐organism model, and eliminative pattern pluralism to represent evolution. Using Entamoeba histolytica alcohol dehydrogenase 2 (EhADH2), a bifunctional enzyme in the glycolytic pathway of amoeba, we illustrate how EhADH2 could be the product of both horizontally acquired features from ancestral prokaryotes (i.e. aldehyde dehydrogenase [ALDH] and alcohol dehydrogenase [ADH]), and subsequent functional integration of these enzymes into EhADH2, which is now inherited by amoeba via common descent. Natural selection has driven the evolution of EhADH2 active sites, which require specific amino acids (cysteine 252 in the ALDH domain; histidine 754 in the ADH domain), iron‐ and NAD+ as cofactors, and the substrates acetyl‐CoA for ALDH and acetaldehyde for ADH. Alternative views invoking “common design” (i.e. the non‐naturalistic emergence of major taxa independent from ancestry) to explain the interaction between horizontal and vertical evolution are unfounded. 相似文献
8.
Stem CO2 efflux in six co‐occurring tree species: underlying factors and ecological implications 下载免费PDF全文
JESÚS RODRÍGUEZ‐CALCERRADA ROSANA LÓPEZ ROBERTO SALOMÓN GUILLERMO G. GORDALIZA MARÍA VALBUENA‐CARABAÑA JACEK OLEKSYN LUIS GIL 《Plant, cell & environment》2015,38(6):1104-1115
Stem respiration plays a role in species coexistence and forest dynamics. Here we examined the intra‐ and inter‐specific variability of stem CO2 efflux (E) in dominant and suppressed trees of six deciduous species in a mixed forest stand: Fagus sylvatica L., Quercus petraea [Matt.] Liebl, Quercus pyrenaica Willd., Prunus avium L., Sorbus aucuparia L. and Crataegus monogyna Jacq. We conducted measurements in late autumn. Within species, dominants had higher E per unit stem surface area (Es) mainly because sapwood depth was higher than in suppressed trees. Across species, however, differences in Es corresponded with differences in the proportion of living parenchyma in sapwood and concentration of non‐structural carbohydrates (NSC). Across species, Es was strongly and NSC marginally positively related with an index of drought tolerance, suggesting that slow growth of drought‐tolerant trees is related to higher NSC concentration and Es. We conclude that, during the leafless period, E is indicative of maintenance respiration and is related with some ecological characteristics of the species, such as drought resistance; that sapwood depth is the main factor explaining variability in Es within species; and that the proportion of NSC in the sapwood is the main factor behind variability in Es among species. 相似文献
9.
GUILLERMO DEBANDI VALERIA CORBALÁN JOSÉ ALEJANDRO SCOLARO SERGIO ALBERTO ROIG‐JUÑENT 《Austral ecology》2012,37(3):392-400
The genus Phymaturus (Reptilia: Liolaemidae) is distributed in the mountains and rocky plateaux of Argentina and Chile and comprises two groups of species, palluma and patagonicus. The two lineages have diverged early in the evolution of the genus and up to today, there is very little geographical overlap between them. We worked with records of localities from the literature, herpetological collections and field data to evaluate habitat suitability of the genus Phymaturus. We used 11 environmental variables to develop environmental niche models (ENMs) for each group within the genus using the Maxent software, and to determine those variables that best explain the distribution of each group. We also estimated measures of niche similarity using ENMTools to determine whether niche differentiation is real or apparent. The geographical overlap between the groups was very low considering the large geographical range of the genus. Some variables, such as mean annual temperature, soil type and bare soil cover, have a high contribution to the models for both groups. The current niche overlap between Phymaturus groups indicates that the environmental niches of the palluma and patagonicus groups are not equivalent. Based on background analysis, we cannot reject the hypothesis that similarity (or divergence) between groups of Phymaturus is no more than expected based on the availability of habitat. The results of this study are a first approximation to the knowledge of the environmental variables associated with the palluma and patagonicus groups, and reveal that the ecological differences found between these groups are more likely due to habitat availability in their respective regions than to differences in habitat preferences. 相似文献
10.
CLAUDIO PEREIRA CRISTINA PAVETO JOAQUIN ESPINOSA GUILLERMO ALONSO MIRTHA M. FLAWÁ HECTOR N. TORRES 《The Journal of eukaryotic microbiology》1997,44(2):155-156
ABSTRACT. Trypanosoma cruzi epimastigote motility can be enhanced by addition of L-arginine, to the culture. This effect is blocked by N-methyl-L-arginine, a competitive inhibitor of the nitric oxide synthase. N-methyl-D-aspartate and L-glutamate, two agonists of the NMDALglutamate receptor, also enhanced motility. This stimulation is blocked by MK-801 a noncompetitive antagonist of the NMDA receptor. In addition, sodium nitroprusside, a guanylyl cyclase stimulator and 8-Br-cyclic GMP, an analog of cyclic GMP, also stimulated epimastigote motility. It is suggested that an increase of intracellular cyclic GMP levels mediated by nitric oxide may be responsible for the increase in epimastigote motility. 相似文献