Airborne pollen data of Platanaceae in Santiago de Compostela (Iberian Peninsula)

The pollen count of the Platanus genus in the atmosphere of Santiago de Compostela (Galicia, Spain) was carried out from 1993 to 1998, with the pollen of this taxon representing 6% of total identified pollen. The principal pollination period (P.P.P.) was centred on the months of March and April, with an average duration of 23 days.During the study period we obtained negative correlations with precipitation and humidity and positive ones with temperature and hours of sunshine, with a confidence index of more than 90%. On the basis of the six-year study period, we also calculated the average accumulated temperature required to trigger the onset of flowering, which oscillated between 330 and 456 °C, with this result being confirmed for 1999 (437 °C). We also observed that the values of maximum pollen concentration of this taxon in the last 7 years (1993–1999), were obtained on days during the P.P.P. with maximum temperatures above 18 °C. The model of intradiurnal variation reflects, for the majority of years, a greater representation during the central hours of the day.     

A developmental and evolutionary analysis of embryology in Platanus (platanaceae), abasal eudicot

The Platanaceae are an early derived eudicot lineage and therefore occupy a key position for understanding reproductive character diversification associated with the early evolutionary radiation of flowering plants. We conducted an embryological study of Platanus racemosa in order to provide critical data on defining angiosperm reproductive characters for this important group. Female gametophyte development is monosporic. Embryogenesis occurs in a series of stages including zygote elongation and division, development of a linear proembryo, formation of the embryo proper, histogenesis, organogenesis, and growth. Endosperm development is a complex process that includes four distinct phases: free nuclear proliferation, cellularization of the chalazal zone, centripetal cellularization of the micropylar zone, and cellular differentiation and growth. Only the outer endosperm layer persists at seed maturity. Our findings differ significantly from previously published reports for Platanus, in which endosperm development was described as ab initio cellular. A comparison of endosperm development in Platanus with several closely and distantly related free nuclear taxa reveals considerable developmental variability, consistent with a hypothesis of multiple origins of free nuclear endosperm in angiosperms. Our analysis indicates that much remains to be learned about embryology in basal angiosperms. Additional developmental and comparative studies will likely reveal critical insights into the early evolution of flowering plants.     

Occurrence of Sapindopsis (Platanaceae) in the Cretaceous of Eurasia

Three new species of the genus Sapindopsis Fontaine from Central Asia and western Siberia are described: S. neuburgae (Vachr.) Golovn., comb. nov., S. janschinii (Vachr.) Golovn., comb. nov., and S. kryshtofovichii (I. Lebed.) Golovn., comb. nov. Geographical and stratigraphic analyses have shown that the genus evolved in Eurasia from the Middle Albian to the Cenomanian, and was mostly restricted to the subtropics of the Euro-Sinian phytogeographic area from the Middle East to Russian Primorye and northern China. The are no reliable records of Sapindopsis from Europe. The migration of Sapindopsis from North America to Eurasia through the Bering Land Bridge was most probably related to the Early-Middle Albian climatic optimum.     

A new species of the genus <Emphasis Type="Italic">Platimeliphyllum</Emphasis> N. Maslova from the Paleocene of the Amur Region,Russia

A new species, Platimeliphyllum valentinii, is described from the Paleocene of the Amur Region on the basis of macromorphological and epidermal characters. It was shown that leaves of Platimeliphyllum N. Maslova associate with two fundamentally different types of reproductive structures: platanaceous Archaranthus N. Maslova et Kodrul and Bogutchanthus N. Maslova, Kodrul et Tekleva, which combines characters of the Platanaceae and Hamamelidaceae. The higher evolutionary stability of leaf structures in comparison with reproductive organs is discussed.     

A review of the platanaceous woods from the Eocene paratropical rainforest of south-east England

Small diameter pyritized axes, commonly referred to as 'twigs', of fossil platanaceous wood are described from the Lower Eocene London Clay Formation of south-east England. These twigs are characterized by solitary vessels with scalariform perforation plates, opposite intervessel pits, and tall, multiseriate rays that dilate in the phloem region. The wood anatomy supports close relationship to members of extant Platanaceae and the material is placed in the organ genus Plataninium Unger erected for fossil woods with close anatomical similarity to Platanus L. This material supplements the fossil record of platanaceous type wood from the Eocene London Clay and documents the first record of Plataninium decipiens Brett in the twig flora.  © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 139 , 181–191.     

Karyomorphology and evolution in some Hamamelidaceae and Platanaceae (Hamamelididae; Hamamelidales)

Karyomorphology in 14 species of 12 genera representing a variation of Hamamelidaceae and in one species of Platanaceae (Platanus only) is investigated in an effort to contribute to an understanding of chromosome evolution and inter- and intrafamilial relationships. All genera investigated show similar chromosome features at resting stage and prophase, excepting that at resting stageRhodoleia shows the simple, rather than the simple-complex, chromocenter type as in other genera. At metaphase all the genera investigated of Hamamelidaceae, like other ‘lower’ Hamamelididae, have chromosomes with median centromeres (m-chromosomes), those with submedian centromeres (sm-chromosomes) and those with subterminal (or terminal) centromeres (st-t-chromosomes) at different frequencies, although frequencies ofst-t-chromosomes are always less than 33%. InPlatanus,m-chromosomes are lacking and insteadst-t-chromosomes are predominant (86%), a feature seemingly very specialized. We confirmedx=7 in Platanaceae,x=12 in Hamamelidoideae and Rhodoleioideae, andx=8 in Exbucklandioideae and Altingioideae (Hamamelidaceae). An analysis of chromosome morphology supports the hypothesis thatx=12 in the former two subfamilies is of tetraploid origin fromx=6, rather than of triploid origin fromx=8. We further give brief comments on the suprageneric classification of Hamamelidaceae that was recently proposed by Endress.     

A new platanaceous genus Tasymia (Angiosperms) from the Turonian of Siberia

A new extinct genus of arborescent angiosperms, Tasymia gen. nov., is described from the Turonian deposits of the upper part of the Simonovo Formation on the Kas River (left-bank tributary of the Yenisei River, Krasnoyarsk Region). The epidermal characters of leaves of the new genus testify to its platanaceous affinity. A comparison with other extinct taxa of the Platanaceae from the Chulym-Yenisei Depression and other regions of the Northern Hemisphere is accomplished.     

Isomorphic polymorphism in the Platanaceae and Altingioideae and the problem of their relationship

Isomorphic polymorphism is demonstrated by modern and fossil members of the Platanaceae and Hamamelidaceae (subfamily Altingioideae) and is considered as evidence of structural parallelism in the evolution of the Platanaceae and Altingioideae. The supposed relationship between Platanaceae and Altingioideae is discussed from a paleobotanical perspective.     

Entwicklungsgeschichte und Ultrastruktur von Pollenkitt und Exine bei nahe verwandten entomophilen und anemophilen Angiospermensippen:Ranunculaceae,Hamamelidaceae, Platanaceae undFagaceae

Transfer of fresh pollen either by wind or by insects is strongly related to the degree of its stickiness. The sticky substances involved should be understood as pollenkitt. Ultrastructural investigations indicate that the sticky pollen of entomophilous angiosperms (in this publicationHamamelis vernalis andH. virginiana, Corylopsis platypetala) results from the deposition of usually electron-dense, homogeneous pollenkitt mainly on the outside layer of the exine. In contrast, the pollen of anemophilous angiosperms (in this publicationParrotia persica, Platanus orientalis, Thalictrum flavum andQuercus robur), but also of some entomophilous angiosperms with special pollination ecology (e.g.Aquilegia vulgaris) is rather dry and powdery. In these cases the pollenkitt often is electron-transparent and inhomogeneous and is mainly removed into the cavities of the exine. Ultrastructure and deposition of pollen and pollenkitt in ambophilous angiosperms (in this publicationThalictrum minus, Castanea sativa) are ± intermediate.