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At least 19 recordsLinked to original sources
PubMed1999

Phylogeny, biogeography, and processes of molecular differentiation in Quercus subgenus Quercus (Fagaceae).

Quercus is one of the most abundant and economically important genera of woody plants in the Northern Hemisphere. To infer phylogenetic relationships within Quercus subgenus Quercus, chloroplast DNA (cpDNA) restriction sites and nucleotide sequences of the internal transcribed spacers (ITS) and the 5.8S coding region of the nuclear ribosomal DNA repeat were obtained for 44 individuals, including 25 species, intraspecific samples, and three outgroups. Separate parsimony analyses of each data set showed that individual gene trees were congruent and often complementary in supporting clades that generally corresponded to previously recognized taxonomic groups. Only one instance of strongly supported gene tree incongruence was detected and this anomalous pattern was explained best by ancient introgression of cpDNA across sectional boundaries. Simultaneous parsimony analysis of the pruned data sets supported the recognition of the strictly Eurasian section Cerris and resolved a novel hypothesis for the major infrageneric groups (Cerris- (Lobatae- (Protobalanus + Quercus sensu stricto))). The biogeographic hypothesis that all major oak lineages evolved locally at middle latitudes within the general distribution of their fossil ancestors was fully supported. This set of relationships also suggested a New World origin for the widespread white oaks of the Northern Hemisphere (section Quercus s. s.). For both data sets, inter- and intraspecific sampling within section Protobalanus showed little correspondence to morphological species. Greater cladistic structure among the samples was obtained by cpDNA restriction sites and two well-delimited plastomes types comprising a total of 15 distinct haplotypes were resolved. Haplotypes of 2 of the peripheral species in this species complex occupy terminal portions of one of the plastome clades, suggesting a more recent origin relative to those of more widespread species. The phylogeography of the two divergent plastome types suggested a north-south pattern, consistent with a Late Tertiary disjunction in the ancestral distribution of section Protobalanus.

Cell Nucleus↗
PubMed2003

Effect of tannins from Quercus suber and Quercus coccifera leaves on ethanol-induced gastric lesions in mice.

The gastroprotective effects of 70% acetone extracts of Quercus suber and Quercus coccifera leaves and of tannins (pedunculagin, castalagin, phillyraeoidin A, and acutissimin B) purified from these extracts were examined in the mouse using the ethanol-induced gastric ulcer model. Both extracts (25, 50, and 100 mg/kg), given orally, prevented the formation of ethanol-induced lesions in the stomach. The percent protection varied between 68 and 91%. Purified tannins (50 mg/kg) were also effective in protecting the stomach against ethanol, and the percent protection varied from 66 to 83%. Castalagin was the most potent. Both extracts and all of the tannins tested (10, 25, and 50 microg/mL) strongly inhibited (55-65%) the lipid peroxidation of rabbit brain homogenate. These results suggest that the gastroprotective effects of extracts of Q. suber and Q. coccifera leaves and the purified tannins in this experimental model are related to their anti-lipoperoxidant properties.

Acetone↗
PubMed2002

Dimeric and trimeric hydrolyzable tannins from Quercus coccifera and Quercus suber.

Three new hydrolyzable tannins, cocciferins D(1) (1), D(2) (2), and T(1) (4), were isolated from the leaves of Quercus coccifera. Cocciferin D(2) (2) and two additional new tannins, cocciferins D(3) (3) and T(2) (5), were also obtained from the leaves of Quercus suber. Their oligomeric structures were elucidated on the basis of spectroscopic methods and chemical evidence. Compounds 2, 3, and 5 were rare oligomers possessing glucose cores with both open-chain and pyranose forms.

Algeria↗
PubMed2005

Gene flow and hybridisation in a mixed oak forest (Quercus pyrenaica Willd. and Quercus petraea (Matts.) Liebl.) in central Spain.

Oaks are long-standing models for the study of gene flow and hybridisation. Temperate (Quercus petraea) and sub-Mediterranean (Quercus pyrenaica) oaks coexist in central Spain, showing remarkable differences in population size and structure. Q. petraea has a scattered distribution in central Spain, where it is at one of the southernmost limits of its range, and forms low-density stands; in contrast, Q. pyrenaica is widespread in the region. We selected a mixed population of the two species ( approximately 13 ha, 176 adults and 96 saplings) to compare the patterns of gene flow within each species and the extent of introgression between them. Using five nuclear microsatellite markers, we performed a parentage analysis and found considerable immigration from outside the stand ( approximately 38% for Q. petraea and approximately 34% for Q. pyrenaica), and estimated average seed-dispersal distances of 42 and 14 m for Q. petraea and Q. pyrenaica, respectively. Introgression between species was also estimated using our microsatellite battery. First, we developed a multivariate discriminant approach and, second, we compared our results with a widely used clustering method (STRUCTURE). Both analyses were consistent with a low level of introgression between Q. petraea and Q. pyrenaica. Indeed, only 15 adult trees, approximately 8.5%, were identified as putative hybrids when both methods of analysis were combined. Hybrids may be most common in contact zones due merely to physical proximity.

Gene Flow↗
PubMed2003

Rapid temperature acclimation of leaf respiration rates in Quercus alba and Quercus rubra.

We conducted controlled (chamber) and natural (field) environment experiments on the acclimation of respiration in Quercus alba L. and Quercus rubra L. Three-year-old Louisiana, Indiana and Wisconsin populations of Q. alba were placed in growth chambers and exposed to alternating 5-week periods of cool (20 degrees C mean) and warm (26 degrees C mean) temperatures. We measured respiration rates on fully expanded leaves immediately before and approximately every 2 days after a switch in mean temperature. In a second chamber experiment, 3-year-old potted Q. alba seedlings were exposed to alternating warm (26 degrees C mean) and cool (16 degrees C mean) temperatures at 4-day intervals. Leaf dark respiration rates were measured on days 2, 3 and 4 after each change in temperature. In a third, field-based study, we measured leaf respiration rates in the same three sources of Q. alba and in Arkansas, Indiana and Minnesota sources of Q. rubra before and after a natural 16 degrees C change in mean daily ambient temperature. We observed rapid, significant and similar acclimation of leaf respiration rates in all populations of Q. alba and Q. rubra. Cold-origin populations were no more plastic in their acclimation responses than populations from warmer sites. All geographic sources showed lower respiration rates when measured at 24 degrees C after exposure to higher mean temperatures. Respiration rates decreased 13% with a 6 degrees C increase in mean temperature in the first chamber study, and almost 40% with a 10 degrees C increase in temperature in the second chamber study. Acclimation was rapid in all three studies, occurring after 2 days of exposure to changed temperature regimes. Acclimation was reversible when changes in ambient temperature occurred at 4-day intervals. Respiration response functions, ln(R) = ln(beta0) + beta1T, were statistically different among treatments (cool versus warm, first chamber study) and among sources in a pooled comparison. Pair-wise comparisons indicated statistically significant (P<0.05) differences in cool- versus warm-measured temperature/respiration response functions for Indiana and Wisconsin sources of Q. alba. Log-transformed base respiration rates were significantly lower during periods of higher mean temperatures. Indiana Q. alba showed a significantly higher beta1 when plants were grown at 16 degrees C than when grown at 26 degrees C. Acclimation in Q. alba was unaccompanied by changes in leaf nitrogen concentration, but was associated with a change in leaf total nonstructural carbohydrate concentration. Total nonstructural carbohydrate concentration was slightly, but statistically, lower (13.6 versus 12%, P<0.05) after a 10 degrees C increase in temperature.

Acclimatization↗
PubMed2001

Three divergent rDNA clusters predate the species divergence in Quercus petraea (Matt.) Liebl. and Quercus robur L.

Quercus petraea and Quercus robur are two closely related oak species that frequently hybridize. We sequenced 70 clones containing the 5.8S and ITS2 regions of ribosomal DNA (rDNA) from these two species and did not detect a species-specific difference. Surprisingly, three divergent (up to 12.6%) rDNA families were identified in both species, indicating that they predate the speciation event. Despite a large between-rDNA-families divergence, rDNA sequences were very similar within families, suggesting ongoing concerted evolution. Expression analysis, relative-rate tests, and mutation spectrum analyses indicated that only a single rDNA family is functional. We propose that past hybridization events, combined with nucleolar dominance, were the evolutionary processes underlying the contemporary rDNA variability in Q. petraea and Q. robur.

Base Sequence↗
PubMed1999

Photosynthetic acclimation to elevated atmospheric CO(2) concentration in the Florida scrub-oak species Quercus geminata and Quercus myrtifolia growing in their native environment.

Long-term effects of elevated CO(2) concentration (ambient plus 350 &mgr;mol mol(-1)) on leaf photosynthetic acclimation of two species of a scrub-oak community, Quercus myrtifolia Willd. and Quercus geminata Small, were studied. Plants of both species were grown in open-top chambers in their natural habitat at Kennedy Space Center, Florida, USA. Compared to ambient CO(2), elevated CO(2) stimulated photosynthetic rates by 73 and 51% for Q. geminata and Q. myrtifolia, respectively. Maximum rate of carboxylation (V(cmax)) was significantly reduced by elevated CO(2) in Q. myrtifolia (28%) but not in Q. geminata. Maximum rate of potential electron transport (J(max)) was not significantly reduced by elevated CO(2) in either species. In response to elevated CO(2), specific leaf area decreased in Q. myrtifolia (22%), but not in Q. geminata. Elevated CO(2) caused a significant accumulation of sugars (54%) and starch (264%) in Q. myrtifolia leaves, but not in Q. geminata leaves. Total Rubisco activity in Q. myrtifolia leaves was reduced 40% by elevated CO(2), whereas no significant reduction occurred in Q. geminata leaves. Although both species share a common habitat, they exhibited marked differences in photosynthetic acclimation to elevated CO(2) concentration.

Journal Article↗
PubMedDate not supplied

Cryopreservation of Quercus suber and Quercus ilex embryonic axes: in vitro culture, desiccation and cooling factors.

This study examines different factors included in the cryopreservation protocols for Quercus ilex and Q. suber embryonic axes. In vitro incubation temperature played an important role in the appropriate development of Q. ilex axes, as 15 degrees C was superior to 25 degrees C. Q. suber axes proved to be more sensitive to desiccation and cooling. Poor survival (35%) was observed when axes were included into cryovials and then in liquid nitrogen, and none when immersed in sub-cooled liquid nitrogen (-210 degrees C). Q. ilex axes showed poorly organised development in vitro (c. 50% of non-cooled axes showed shoot development). However, c. 80% survival was observed after cryopreservation (either in liquid nitrogen or sub-cooled liquid nitrogen at 0.34 g water / g dry weight), of which c. 15% showed shoot development.

Cryopreservation↗
PubMedDate not supplied

Shade, leaf growth and crown development of Quercus rubra, Quercus velutina, Prunus serotina and Acer rubrum seedlings.

The study was conducted in an open field to determine the optimum irradiance for establishment and growth of two oak species and two major associated woody species. Half-sib seedlings of black cherry (Prunus serotina Ehrh.), red maple (Acer rubrum L.), northern red oak (Quercus rubra L.) and black oak (Q. velutina Lam.) were grown for two years under shade-cloth tents. Eight shade treatments (94, 70, 57, 45, 37, 27, 20 and 8% of full sunlight) with three replications each were used. Measurements were made on seedlings harvested at the end of the first and second growing seasons. In the second year, shading significantly decreased the number of leaves for all species except black cherry, but only significantly decreased leaf area in northern red oak. Shading significantly decreased average leaf size of red maple. Average leaf size of black cherry was largest in the intermediate shade treatments and decreased significantly with increased and decreased shade. Leaf weight/leaf area (mg cm(-2)) increased significantly in a quadratic pattern with decreasing shade for all four species. Leaf area ratio (cm(2) g(-1)) decreased significantly with decreasing shade for all species except red maple in the first year and black oak in the second year. Total branch development increased significantly with decreasing shade in red maple and northern red oak, whereas indeterminate branches increased significantly with decreasing shade only in black cherry, and short branches increased significantly with decreasing shade only in red maple.

Journal Article↗
PubMed2002

AFLP markers demonstrate local genetic differentiation between two indigenous oak species [ Quercus robur L. and Quercus petraea (Matt.) Liebl.] in Flemish populations.

The nuclear genetic variation within and between four sessile ( Q. petraea) and six pedunculate ( Q. robur) autochthonous Flemish oak populations was investigated with AFLP markers. One sessile and one pedunculate oak population were additionally screened for detailed leaf characteristics using an image analysis system. Principal coordinate analysis on the AFLP data classified the oaks in two main groups, according to their taxonomic status. No species-specific AFLP markers were found using four primer combinations, but marker frequency differences up to 71% were recorded between both species. Analysis of the genetic structure showed that the divergence between species, as observed by ordination, was significant. Both species revealed similar diversity levels. A smaller though significant differentiation was also revealed for both species among populations within species. Molecular and morphology based approaches showed a high degree of consistency. Screening of 60 AFLP primer combinations using a bulking strategy did not allow identifying species-specific markers, which supports the conclusions reached in previous studies. The distribution of genetic variability at the species and at the population level is discussed.

Journal Article↗