Chromosome counts inCephalotus (Cephalotaceae)

Cephalotus follicularis is uniformly n = 10 in all populations surveyed.     

A new species of Aristolochia (Aristolochiaceae) from Thailand

Aristolochia dinghoui is described from southwestern Thailand. It is morphologically similar toA. harmandiana Pierre ex Lecomte, from Cambodia and Laos, and also bears some resemblance toA. philippinensis Warb. andA. sericea Blanco, both from the Philippines. A key to these four species is included, and some of their diagnostic features are listed.

---

Resumen   Aristolochia dinghoui est décrite à partir de spécimens recueillis dans le sud-buest de la Thailande. Morphologiquement pareille à l'A. harmandiana Pierre ex Lecomte de l'Indochine, elle présente également des ressemblances avecA. philippinensis Warb. etA. sericea Blanco, des iles Philippines. Une clé est proposée pour distinguer ces quatre espèces. Les caractères diagnostiques de l'{btA. dinghoui} sont illustrés.

     

Structure and development of the ovule and seed in Aristolochiaceae, with particular reference to Saruma

All members of Aristolochiaceae have anatropous, bitegmic, crassinucellate ovules, which are endostomic except in Saruma and Asarum arifolium where ovules are amphistomic. The outer integument is two cell-layered and the inner integument is three cell-layered. The chalazal megaspore is the functional one. All these conditions appear to be plesiomorphic for the order Piperales, which consists of five families, Aristolochiaceae, Hydnoraceae, Lactoridaceae, Piperaceae and Saururaceae. The embryo sac in Aristolochiaceae is eight-nucleate and corresponds to the Polygonum type; a hypostase is frequently present in this family. The seed coat of Aristolochia s.l., Asarum, Saruma and some Thottea species consists primarily of a two cell-layered testa, and a three cell-layered tegmen. In some species the cells of the outer epidermis become radially elongated, forming reticulate wall thickenings. Cells of the inner layer of the testa have crystals and thickened inner walls. The three layers of the tegmen are tangentially elongated, and become cross fibres at maturity, as fibres of the outer and inner layers are parallel to the seed axis, whereas those of the middle layer are perpendicular to it. This type of seed coat anatomy is synapomorphic for Aristolochiaceae. In addition, the gross morphology of the seed and elaiosome histology are remarkably similar in Asarum and Saruma, thus supporting a sister-group relationship between them. Embryological and seed characters do not supply any synapomorphy that support a close relationship between Aristolochiaceae, Hydnoraceae and Lactoridaceae. Instead, some seed features such as the absence of seed appendages and the collapsed cells of endotesta may indicate a close relationship of Lactoris with Piperaceae plus Saururaceae, although this is the subject of further analysis.     

Chromosome number of theOxalis tuberosa alliance (Oxalidaceae)

Twelve taxa of theOxalis tuberosa alliance were analysed and found to share the same basic chromosome number x = 8. The karyotypes are composed by small metacentric and submetacentric chromosomes. Different ploidy levels were found among the taxa: there were 9 diploids, 1 tetraploid, 1 hexaploid and 1 octoploid. The last ploidy level corresponds toO. tuberosa, the only tuber bearing taxon found so far in the alliance. Cytotaxonomic evidence and evolutionary considerations suggest to classify theO. tuberosa alliance in sect.Herrerea.     

Chromosome number inHalophytum ameghinoi (Halophytaceae)

The chromsome number and karyotype ofHalophytum ameghinoi (Speg.) Speg. was found to be 2n = 24 and 12m+10sm+2t, respectively. Meiosis was regular and 12 bivalents were observed. The relationships of this monotypic family are briefly discussed.     

Two new species of Aristolochia (Aristolochiaceae) from Brazil and Peru

Aristolochia dalyi, from western Peruvian and Brazilian Amazonia, andA. bahiensis, from Bahia, Brazil, are described and illustrated. The species belong toAristolochia ser.Thyrsicae andA. ser.Hexandrae subser.Anthocaulicae, respectively. A key to the eight western Amazonian species of the seriesThyrsicae is presented.Aristolochia dalyi closely resemblesA. silvatica Barb. Rodr. from the Río Negro basin, andA. bahiensis—the first cauliflorous species ofAristolochia known from the Mata Atlantica—is similar toA. guentheri O. C. Schmidt andA. klugii O. C. Schmidt, from the Western Amazon basin. Characters based primarily on the perianth shape, along with some vegetative features, are used to distinguish the two newly described species from their close relatives.

---

Resumen   Aristolochia dalyi, del occidente de la amazonía peruana y brasilera, yA. bahiensis, del estado de Acre, en Brasil, son descritas e ilustradas. Las especies pertenecen aAristolochia ser.Thyrsicae yA. ser.Hexandrae subser.Anthocaulicae respectivamente.Aristolochia dalyi es incluída en una clave para diferenciarla de las especies de la serieThyrsicae presentes en la Amazonía occidental, y resulta ser similar aA. silvatica Barb. Rodr, propia de la cuenca del río Negro; por su parte,A. bahiensis, hasta ahora la única especie deAristolochia cauliflora hallada en la Mata Atlántica, es similar aA. guentheri O. C. Schmidt yA. klugii O. C. Schmidt, propias del occidente de la cuenca amazónica. Los caracteres diagnósticos de las nuevas especies se basan principlalmente en la forma del perianto, aunque algunas diferencias vegetativas son también reconocidas.

     

Chromosome number evolution in the tribeBrassiceae (Brassicaceae): Evidence from isozyme number

Variation in isozyme number was used to assess the evolution of haploid chromosome numbers (n=6–75) and systematic relationships in the tribeBrassiceae, which is believed to be one of the few monophyletic tribes in theBrassicaceae. Ten enzyme systems were surveyed among 108 species in 35 genera of tribeBrassiceae and for 11 species from seven other tribes. The data indicated that taxa with n=7–13 and n=14–18 were similar in isozyme number, suggesting that genera with n=14–18 did not arise from polyploidy (i.e. entire duplication) of the n=7–13 genomes. These results suggest that aneuploidy and/or chromosome fusion/splitting have played a more significant role than polyploidy in the evolution of higher base chromosome numbers in the tribe. The detection of widespread isozyme duplication in the tribe is consistent with reports of extensive gene duplication in theBrassica crop species, and suggests that the common ancestor of the tribe already had undergone a polyploid event, i.e. complete genome duplication, prior to aneuploid divergence. Inheritance studies conducted onSinapis arvensis showed that segregation ratios at seven loci (Fbp-2,Gpi-2,Idh-2,Pgm-2,Pgm-2,Tpi-1,Tpi-1) conformed to those expected under Mendelian inheritance. Isozyme duplications were phylogenetically informative at various taxonomic levels in the tribe. In particular, duplications for cytosolic phosphoglucomutase (Pgm-2,Pgm-2) and plastid triosephosphate isomerase (Tpi-1,Tpi-1) were evident in 33 of the 35 genera examined, supporting the monophyletic status of theBrassiceae with the inclusion ofOrychophragmus and the exclusion of controversial membersCalepina andConringia.     

Chromosome counts inPosidonia (Posidoniaceae)

The five species ofPosidonia occuring in Western Australia all have a diploid chromosome number of 20.     

Chromosome counts inCalea (Asteraceae-Heliantheae)

Chromosome numbers are reported for six taxa ofCalea, among them tetraploidC. septuplinervia, the only known polyploid inCalea s. str. The base chromosome number ofCalea is interpreted as x = 19.     

Chromosome number,morphology, pairing,and DNA values of species and hybrids in the genusFallopia (Polygonaceae)

The taxa in this study have in the past been treated together in sect.Tiniaria Meissner ofPolygonum L. s.l., and more recently the large erect rhizomatous herbaceous perennials have been separated from the twining annuals and perennials as the generaReynoutria andFallopia respectively. These taxa range in ploidy level from diploid to octoploid, with base numbers of both 10 and 11 present. The plants are primarily Asiatic in distribution, although many of the large erect perennials are now naturalized in many parts of Europe. Cytological examination has revealed the presence of a number of previously unknown hybrid taxa in the British Isles. The readiness with which hybridisation occurs between taxa of differing base number and ploidy level, and similarities revealed in chromosome morphology, meiotic pairing and in DNA C-value, suggest to the authors that these two genera are best amalgamated underFallopia.     

Chromosome numbers in AustralianEuphrasia (Scrophulariaceae)

Chromosome numbers for six Australian taxa ofEuphrasia have been determined. Improved staining techniques have shown that numbers for four of the taxa published previously by the first author were incorrect. The investigated taxa show high ploidy levels with an apparent base number of x = 11, the same as for the genus outside Australia.Dedicated to Prof. DrElisabeth Tschermak-Woess on the occasion of her 70th birthday.     

Chromosome numbers of Western Australian species ofVillarsia (Menyanthaceae)

Chromosome numbers are reported for eight of the nine Western AustralianVillarsia species.Villarsia albiflora, V. calthifolia, V. capitata, V. congestiflora, V. lasiosperma, V. latifolia, andV. violifolia are diploid with n=9. Five populations ofV. parnassiifolia are diploid and three are tetraploid (n=18). The morphological, ecological, and breeding-system diversity of the Western Australian species is largely not associated with the tetraploidy or hexaploidy that characterizes otherVillarsia species in eastern Australia and South Africa. The majority of Western AustralianVillarsia species are restricted to the high rainfall zone of southwestern Western Australia, where favorable climatic and edaphic conditions may have existed since mid-late Tertiary times.     

Concordant clines and significant correlation between floral and pollen characters in Asarum heterotropoides var. heterotropoides (Aristolochiaceae)

To examine geographic differentiation in Asarum heterotropoides var. heterotropoides in Hokkaido Is. in the northern Japan, in which two putative cryptic species have been suspected to exist, extensive and detailed morphological research on 794 individuals from 44 populations throughout Hokkaido Is. was performed. Among the characters examined, the angle between and tip shape of the calyx lobes and the supratecta of the pollen grains were significantly correlated and were found in similar geographic clines. Among them, the pollen showed two discrete states in almost distinct distribution. Multidimensional scaling analysis showed that individuals within each of the two pollen types had different trends in flower characters. Consequently, we assumed a cline from south to north on Hokkaido Is. For the causes of the cline, the two hypotheses were proposed, primary geographic differentiation or extensive introgressive hybridization between two distinct geographical species existing in the past.     

A new species ofThottea (Aristolochiaceae) from India

Thottea ponmudiana sp. nova from Kerala (India) can readily be distinguished from its closest allyTh. siliquosa and all the other known species of the genus by its yellow flowers with purple eyes, deeply lobed perianth with strongly reflexed margins, uniseriate stamens united in three bundles and strongly 4-angled, green, glabrescent fruits.     

Chromosome evolution in Himalayan Impatiens (Balsaminaceae)

AKIYAMA, S., WAKABAYASHI, M. & OHBA, H., 1992. Chromosome evolution in Himalayan Impatiens (Balsaminaceae). Chromosome numbers and karyotypes have been investigated in species of Himalayan Impatiens . In addition to confirming previous chromosome counts, the presence of a tetraploid taxon ( I. exilis) is revealed. In central and east Nepal species with x = 9 are more common than those with other basic numbers and this number is shown to be one of the most frequent numbers in the genus. Most species with x = 9 have a bimodal karyotype. The species relationships are discussed.     

Chromosome cytology and karyotype change inGalaxia (Iridaceae)

Basic chromosome number inGalaxia is believed to be x = 9, and this number, or multiples, occurs in all species of subgenusGalaxia. In subgenusEurystigma, G. barnardii has n = 8,G. versicolor n = 8 and 7,G. citrina n = 8, 7 and 17 whileG. variabilis has n = 7 exclusively. Karyotypes in forms ofG. versicolor with n = 7 and inG. variabilis are quite different and clearly originated independently. Karyotypic features provide evidence for the hypothesis that changes in chromosome number were accomplished through chromosome fusion either by classical Robertsonian translocation, or unequal reciprocal translocation.     

Aristolochia gorgona (Aristolochiaceae), a new species with giant flowers from Costa Rica and Panama

Aristolochia gorgona is described from the Atlantic watershed of Costa Rica and central and eastern Panama. It is similar toA. grandiflora Sw., with which it has been confused in the past. The extensive reported synonymy ofA. grandiflora is reviewed and compared with the new entity. Some new terms are proposed for better describing floral structure in this species complex, and suggestions are made for its collection and study.Aristolochia gorgona is one of the largest-flowered plant species (in terms of perianth area) in the Neotropics.

---

Resumen   Aristolochia gorgona se describe de la vertiente Atlántica de Costa Rica y del centro y este de Panamá. Es similar aA. grandiflora Sw., con la cual se ha confundido en el pasado. La extensa sinonimia reportada paraA. grandiflora es revisada, y comparada con la nueva entidad. Se proponen algunos términos nuevos para describir mejor la estructura floral en éste complejo de especies, y se ofrecen sugerencias para su recolección y estudio.Aristolochia gorgona es una de las especies vegetales con flores más grandes (en cuanto al área del perianto) en el Neotrópico.