02720nas a2200193   4500008004100000245014300041210006900184300001200253490000800265520207300273100001602346700001702362700002002379700003102399700001202430700002202442700001802464856004402482       2015                        eng d00aA new positive relationship between pCO2 and stomatal frequency in Quercus guyavifolia (Fagaceae): a potential proxy for palaeo-CO2 levels0 anew positive relationship between pCO2 and stomatal frequency in  a777-7880 v1153 a<p>Background and Aims The inverse relationship between atmospheric CO2 partial pressure (pCO2) and stomatal frequency in many species of plants has been widely used to estimate palaeoatmospheric CO2 (palaeo-CO2) levels; however, the results obtained have been quite variable. This study attempts to find a potential new proxy for palaeo-CO2 levels by analysing stomatal frequency in Quercus guyavifolia (Q. guajavifolia, Fagaceae), an extant dominant species of sclerophyllous forests in the Himalayas with abundant fossil relatives.Methods Stomatal frequency was analysed for extant samples of Q. guyavifolia collected from17 field sites at altitudes ranging between 2493 and 4497&thinsp;m. Herbarium specimens collected between 1926 and 2011 were also examined. Correlations of pCO2&ndash;stomatal frequency were determined using samples from both sources, and these were then applied to Q. preguyavaefolia fossils in order to estimate palaeo-CO2 concentrations for two late-Pliocene floras in south-western China.Key Results In contrast to the negative correlations detected for most other species that have been studied, a positive correlation between pCO2 and stomatal frequency was determined in Q. guyavifolia sampled from both extant field collections and historical herbarium specimens. Palaeo-CO2 concentrations were estimated to be approx. 180&ndash;240&thinsp;ppm in the late Pliocene, which is consistent with most other previous estimates.Conclusions A new positive relationship between pCO2 and stomatal frequency in Q. guyavifolia is presented, which can be applied to the fossils closely related to this species that are widely distributed in the late-Cenozoic strata in order to estimate palaeo-CO2 concentrations. The results show that it is valid to use a positive relationship to estimate palaeo-CO2 concentrations, and the study adds to the variety of stomatal density/index relationships that available for estimating pCO2. The physiological mechanisms underlying this positive response are unclear, however, and require further research.</p>
1 aHu, Jin-Jin1 aXing, Yao-Wu1 aTurkington, Roy1 aJacques, Frédéric, M. B.1 aSu, Tao1 aHuang, Yong-Jiang1 aZhou, Zhe-Kun  uhttps://quercus.myspecies.info/node/17300566nas a2200157   4500008004100000245015700041210006900198260000900267300001400276490000700290100001600297700001800313700001700331700001700348856004300365       2000                        eng d00aMorphological and molecular differentiation between Quercus petraea (Matt.) Liebl. and Quercus pubescens Willd. (Fagaceae) in Northern and Central Italy0 aMorphological and molecular differentiation between Quercus petr  c2000  a325 - 3330 v851 aBruschi, P.1 aVendramin, G.1 aBussotti, F.1 aGrossoni, P.  uhttps://quercus.myspecies.info/node/5801674nas a2200169   4500008004100000245015600041210006900197260000900266300001200275490000700287520107900294100001601373700002001389700001701409700001701426856006101443       2000                        eng d00aMorphological and Molecular Differentiation between Quercus petraea(Matt.) Liebl. and Quercus pubescens Willd. (Fagaceae) in Northern and Central Italy0 aMorphological and Molecular Differentiation between Quercus petr  c2000  a325-3330 v853 aQuercus petraea(Matt.) Liebl. and Q. pubescens Willd. are two closely related taxa. No specific single marker, either morphological or molecular, has been identified to distinguish the two species until now. In the present study morphoanatomical and molecular traits (simple sequence repeats = SSR loci) were investigated in an attempt to characterize and to discriminate between these two oak species. At the morphological level, the applied statistics (nested ANOVA and discriminant analysis) suggest that the micromorphological features are the most effective for this purpose. The wide range of macromorphological variation observed can confound the classification of many individuals into either Q. petraea and Q. pubescens. Analysis of microsatellite data indicates that most of the genetic variation is contained within, rather than between, species. The lack of molecular divergence could be attributed to either relatively rapid and recent differentiation or to extensive hybridization following secondary contact of the taxa.Copyright 2000 Annals of Botany Company1 aBruschi, P.1 aVendramin, G.G.1 aBussotti, F.1 aGrossoni, P.  uhttp://aob.oupjournals.org/cgi/content/abstract/85/3/325