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In the cell nucleus several ribonucleoproteins related to gene expression are present The nucleolus coiled bodies and other nuclear particles are among these structures Particles of nanometer size include perichromatin fibrils perichromatin and Balbiani ring granules interchromatin granules and Lacandonia granules All of them are involved in pre messenger RNA intranuclear metabolism Previous and recent research suggests that these particles are involved in transcription and processing of pre messenger RNA within the cell nucleus

The monocot family Triuridaceae is a morphological misfit with respect to several traits of floral morphology, including the uniformly apocarpous polymerous gynoecium and the famous inside-out flowers of Lacandonia. Although Triuridaceae are crucially important for understanding the floral evolution of Pandanales and angiosperms in general, significant knowledge gaps exist which hamper adequate morphological analysis of flowers in this family. The scarcity of morphological data is also reflected in numerous taxonomic inconsistencies. Here we provide a comprehensive study of reproductive organs of four species of Sciaphila occurring in Vietnam (S. arfakiana, S. densiflora, S. nana and S. stellata) including the first investigation of early floral development and gynoecium phyllotaxis. Our observations are mainly based on SEM images. We confirm the perianth (studied in male flowers) to be two-whorled and report a rare sequence of initiation of perianth parts: the outer tepals show a late congenital fusion, as their free lobes appear before the common perianth tube, whereas the inner tepals show an early congenital fusion, with their free lobes initiating on the tube rim. We interpret the stamen appendages as basal adaxial outgrowths of the stamen filaments. We discuss the number of thecae and locules in anthers of Sciaphila, and conclude that 3- and 4-, but not 2-locular anthers are characteristic of this genus. We describe the carpels as consisting of both ascidiate and plicate zones, the former being extremely short and completely obscured by anthesis. The single ovule is attached in the cross-zone. The style is non-plicate. We analyze gynoecium phyllotaxis by estimating its contact parastichies, and by investigating the number and arrangement of the outermost carpels. The carpel arrangement in a given gynoecium is a result of the balance between whorled and irregular (but not spiral) phyllotaxis. We recognize the following figures of gynoecium merism: 6, 9, 10, 10.5, 11 and 12, with the prevalence of those divisible by three. We discuss our results in the light of general diversity of floral structure of monocots. Our data allow to clarify several issues in taxonomy of Asian Sciaphila and indicate directions of further studies. We report a significant range extension for S. densiflora, which is newly recorded for the flora of Vietnam. We describe for the first time staminodes in female flowers of this species. We reveal two distinct morphs of S. nana in Vietnam. We highlight the need of a thorough revision of S. secundiflora species complex in order to verify the species boundaries and, in particular, to test the identity of the Vietnamese S. stellata.

Background: Lacandonia granules are extranucleolar ribonucleoprotein (RNPs) particles, 32 nanometers in diameter that were first described in the nucleus of Lacandonia schismatica . Cytochemical and immunocytochemical studies suggest that these particles are equivalent to perichromatin and Balbiani ring granules described in mammals and salivary glands cells of the insect Chironomus tentans, respectively. Lacandonia granules are also present in the related Triuris brevystilis , and they were later described in the gymnosperm Ginkgo biloba . These findings suggest that Lacandonia granules have a wider distribution in the plant kingdom. Species study: The plant Welwitschia mirabilis, a gymnosperm of the order Gnetales. Hyphotesis: Lacandonia granules are present in the cell nucleus of W. mirabilis . Methods: Plants were cultivated in a germination chamber and samples of leaves were processed for transmission electron microscopy. Thin sections were stained with the EDTA technique preferential for ribonucleoproteins and osmium amine specific for DNA and observed with a microscopy. Results: Light, electronic and atomic force microscopy revealed that cell nuclei of W. mirabilis display a reticulated arrangement of chromatin. Moreover, granules of 32.17 ± 1.7 nm in diameter were observed among strands of reticulated chromatin. Conclusions: Our results indicate that Lacandonia granules are present in the nuclei of the gnetal W. mirabilis.

The Triuridaceae family is composed of saprophytic plants, chlorophylls, usually unbranched stems, leaves in alternate scales, bisexual or unisex racemous inflorescence, follicle or achene fruits. The species Lacandonia brasiliana A. Melo & M. Alves was described as a new species at the beginning of this decade through its first occurrence in the state of Paraiba, Brazil and South America. The objective was to report the first occurrence of the species Lacandonia brasiliana to Ceara State, the second occurrence for Brazil and South America, contributing to the knowledge of its distribution. The species was collected through expeditions in Cerrado fragments, in the municipality of Vicosa do Ceara-CE, during May/2019, which had fertile structures for later taxonomic identification. The collected material was herborized and later deposited in the Herbarium Prisco Bezerra (EAC) of the Federal University of Ceara. Identification was based on identification keys, specialized bibliography, expert consultation, comparison with herbarium and standard specimens. The species is presented with description, taxonomic and ecological comments, distribution data and images. It is a small, non-branched, mycro-heterotrophous species found in a preserved area of Seasonal Semideciduous Forest, being the first record for a Cerrado phytophysiognomy area. It’s concluded that the new occurrence of Lacadonia brasiliana for the State of Ceara highlights the importance of floristic surveys in Cerrado forest remnants, and it is possible to observe the expansion of its territorial distribution, degree of conservation and richness. Lacandonia brasiliana A. Melo & M. Alves (Triuridaceae), Nova Ocorrencia para o Estado do Ceara, Brasil R E S U M O A familia Triuridaceae e composta de plantas saprofitas, aclorofiladas, caule geralmente nao ramificado, folhas em escamas alternas, inflorescencia racemosa bissexuada ou unissexuada, frutos em foliculo ou aquenio. A especie Lacandonia brasiliana A. Melo & M. Alves foi descrita como nova especie no inicio desta decada atraves de sua primeira ocorrencia no Estado da Paraiba, no Brasil e na America do Sul. Objetivou-se relatar a primeira ocorrencia da especie Lacandonia brasiliana para o Estado do Ceara, a segunda ocorrencia para o Brasil e para a America do Sul, contribuindo para o conhecimento da sua distribuicao. A especie foi coletada atraves de expedicoes em fragmentos de Cerrado, no municipio de Vicosa do Ceara-CE, durante o mes de maio/2019, a qual possuia estruturas ferteis para a posterior identificacao taxonomica. O material coletado foi herborizado e posteriormente depositado no Herbario Prisco Bezerra (EAC) da Universidade Federal do Ceara. A identificacao ocorreu a partir de chaves de identificacao, bibliografia especializada, consulta aos especialistas, comparacao com especimes de herbario e especimes-tipo. A especie e apresentada com descricao, comentarios taxonomicos e ecologicos, dados de distribuicao e imagens. Trata-se de uma especie de pequeno porte, mico-heterotrofa, nao ramificada, encontrada em area preservada de Floresta Estacional Semidecidual, sendo o primeiro registro para uma area de fitofisionomia do Cerrado. Conclui-se que a nova ocorrencia da Lacadonia brasiliana para o Estado do Ceara evidencia a importância dos levantamentos floristicos em remanescentes florestais de Cerrado, sendo possivel observar a expansao da sua distribuicao territorial, o grau de conservacao e a riqueza. Palavras-chave: Nordeste do Brasil, Cerrado, Pandanales, saprofita.

Made available in DSpace on 2018-11-27T10:20:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-02-04 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Background and Aims. A recently described Brazilian species, Lacandonia brasiliana, shares with its longer established putative sister species from Mexico, L. schismatica, inverted floral patterning (carpels surrounding stamens) that is almost unique among angiosperms. We present a detailed ontogenetic study of L. brasiliana for comparison with other members of the tribe Triurideae (Triuridaceae) to explore the possible evolutionary origins of inside-out'' flowers. Methods. Wild-source populations of L. brasiliana were compared morphologically and ontogenetically with related species of Triurideae, using light and scanning electron microscopy. Key Results. Relatively few morphological differences separate flowers of L. brasiliana and L. schismatica. Both species have tepals with late-developing subapical appendages. In both species, the three central (almost sessile) anthers develop precociously with respect to the carpels; the anthers remain closed, and fertilization is achieved via pollen-tube growth from germinating pollen grains of the same cleistogamous flower. Carpels are initiated on fascicles. Conclusions. The close similarity between the two Lacandonia species makes it unlikely that they arose independently from two separate homeotic transformation events; they could either represent sister species or two populations of a single disjunct species. Our study underlines the problematic generic and species boundaries within Triurideae. We present an evolutionary scenario of character evolution in Triuridaceae. The inside-out Lacandonia flower could have resulted from a stabilized homeotic transformation; this hypothesis is not in conflict with constrasting theories of the origin of the Triuridaceae flower, which coincided with a shift to unisexuality. The unisexual yet highly plastic flowers that are typical of Triuridaceae could have pre-adapted the origin of the extraordinary Lacandonia morphology. Royal Bot Gardens, Comparat Plant & Fungal Biol, Richmond, Surrey, England Univ Fed Pernambuco, Dept Bot, Recife, PE, Brazil Univ Estadual Paulista, Inst Biociencias, Sao Paulo, Brazil Univ Estadual Paulista, Inst Biociencias, Sao Paulo, Brazil

Floral ontogeny is described in five species—representing four (of 11) genera—of the mycoheterotrophic monocot family Triuridaceae in order to address hypotheses on the evolutionary origin of their reproductive units, in which the inflorescence–flower boundary is ambiguous. This study provides broader ontogenetic sampling across all three tribes of Triuridaceae (Kupeaeae, Triurideae, and Sciaphileae). The observations highlight some radical morphological shifts in floral units of Triuridaceae, marked by associated morphological novelties. These include the presence of carpel fascicles in Lacandonia, Triuris, and Peltophyllum, centrifugal carpel inception in Lacandonia and Triuris, paired carpel arrangement in some species, unusual filamentous structures in atypical positions in several species, and the remarkable inside‐out flowers of Lacandonia. The novel carpel fascicles are relevant to the inflorescence versus flower debate because fascicles are sometimes interpreted as axial structures, analogous to a...

Recent molecular phylogenetic analyses prompted recircumscription of Pandanales into five families—Cyclanthaceae, Pandanaceae, Stemonaceae, and Velloziaceae, plus the mycoheterotrophic Triuridaceae—that were not hitherto regarded as closely related and so have not previously been compared in detail. Some species exhibit anomalous floral features, including apparently secondary apocarpy, loss of trimery, and an imprecise boundary between inflorescence and flower. Most noteworthy are the female reproductive structures of Triuridaceae, especially the “inside-out” flowers of Lacandonia. A phylogenetic cladistic analysis using 39 morphological characters of 23 genera spanning all five families of Pandanales yielded three fairly well-resolved and moderately supported most-parsimonious trees. Velloziaceae were sister to all other Pandanales. Cyclanthaceae and Pandanaceae formed a sister pair that was sister to Stemonaceae plus Triuridaceae. Triuridaceae were embedded within a paraphyletic Stemonaceae. P...

The enigmatic monocotyledon family Triuridaceae is composed of inconspicuous mycoheterotrophs, that have been variously interpreted. We present here the first report of a thorough floral developmental series for any member of the Triuridaceae. The two known Mexican Triuridaceae species were studied with anatomical sections and scanning electron microscopy. While both species have ephemeral and reduced radially symmetric flowers arising in a counterclockwise spiral on racemose inflorescences, Lacandonia schismatica is hermaphroditic with a central androecium and Triuris brevistylis is dioecious. Tepals are connately fused at their bases, and during development the subapical caudal tips continue to elongate, while at maturity the tepals are reflexed. Carpel primordia develop centrifugally from compound primordia in both species, with contrasting androecium development. In Lacandonia schismatica stamen and carpel primordia arise from a common precursor. The two species differ in tepal and carpel number and timing of organ development. This paper provides a developmental framework to understand floral characters in the Triuridaceae. Notably, we addressed if L. schismatica and T. brevistylis bear true flowers or pseudanthia, and our data support the former. The role of particular genes in determining the floral developmental patterns studied and the evolutionary significance of these patterns are discussed.

Homeosis is the result of a developmental process where attributes of one structure are transferred to the position normally occupied by a different structure. The importance of homeotic mutations in the evolution of flowers and their impact on the whole pollination strategy is discussed from a morphological perspective, with special reference to the development of floral organs and the underlying genetics. Three case studies are presented where transformations of organs in flowers have important evolutionary implications, and these are related to the genetic background that is causal for these changes. I hypothesize that petals in the Rosaceae are derived from stamens through homeosis. The petals usually occupy an apical position in a complex multistaminate androecium. Evidence is derived from the similar primordial morphology of petals, their occasional replacement by stamens, obhaplostemonous androecia without petals, and the position of the family next to Rhamnaceae and Urticales. It is postulated tha...

The floral units of Triuridaceae, commonly regarded as flowers, may equally plausibly be interpreted as pseudanthia, i.e., modified and highly reduced partial inflorescences. This hypothesis is new for Triuridaceae, but earlier authors have noted strong similarities between the inflorescences of Cyclanthaceae and Pandanaceae (Pandanales) and the putatively pseudanthial floral units of some Alismatales (e.g., Potamogeton). The morphology of the floral units of Triuridaceae, particularly the female and hermaphrodite structures, closely resembles a smaller version of a Pandanus pistillate inflorescence. In some species of Pandanus, the female flower consists of a single uniovulate carpel with a single stigma, as in Triuridaceae. This striking morphological similarity is remarkable in the context of recent evidence from a single 18S nuclear rDNA sequence for Sciaphila that placed it as sister to Pandanaceae within Pandanales. However, because pseudanthia have been reported in both Alismatales and Pandanales, ...

Lacandonia granules are abundant non-typical extranucleolar ribonucleoprotein particles found in the nucleus of Lacandonia schismatica, a rare plant showing spatial inversion of sex organs. In the present study, changes in the number of Lacandonia granules during flower development, and the presence of SR proteins and poly(A)+ RNA in the nuclei of L. schismatica were analyzed by electron microscopy, immunoelectron microscopy and ultrastructural in situ hybridization. Our results show an important reduction in the number of Lacandonia granules in the nuclei of cells of opened (post-anthesis) in relation to unopened (pre-anthesis) flowers, where granules are very abundant. The SR family of splicing factors and poly(A)+ RNA are present in both perichromatin fibers and Lacandonia granules. The developmental behavior, the presence of SR proteins, recently involved in post-splicing events, poly(A)+ RNA and the reported absence of snRNPs splicing factors in Lacandonia granules, suggest that these particles are involved in postranscriptional events as storage and/or transport of mRNAs. A similar situation is present in other nuclear RNP as perichromatin granules present in mammals and Balbiani ring granules of salivary glands of Chironomus. Based on similarities in morphological, developmental behavior, immunocytochemistry and in situ hybridization results, we conclude that Lacandonia, perichromatin and Balbiani ring granules may be also functionally similar structures.

To assess the conservation status of Lacandonia, a megadiversity area in Mexico, rates of deforestation were calculated for the periods 1974–1981 and 1981–1991, using a random sample of 38 5 × 5 km sites. We evaluated: (i) the overall magnitude of, and spatial and temporal variation in deforestation; (ii) how spatial variation relates to human population density, terrain slope and the presence of the Montes Azules Biosphere Reserve; (iii) the magnitude of potential plant species loss associated with deforestation. Overall deforestation was greater in the former than in the second period (1412 vs. 744 ha/year), although mean rates (2.1 and 1.6%/year) were statistically indistinguishable due to a considerable spatial variation. The greatest spatial variation was related to the presence of the Montes Azules Reserve: deforestation outside the reserve was 20 and 6 times greater in the first and second period, respectively. Population density and terrain slope were related to deforestation but the relationship was considerably poor. Estimates of plant species committed to extinction (out of the expected total flora of 4314 species) were as high as 22% by year 2035, and 55% by year 2135. Such levels of potential species extinction associated to deforestation, and the great biological diversity of Lacandonia provide evidence to declare it as the northernmost tropical hot-spot and a priority goal in conservation efforts.

Lacandonia brasiliana A.Melo & M.Alves, sp. nov., Figs. 1 A-B, 2 A���E Type: ��� BRAZIL. Para��ba: Mamanguape, 06��43'' S, 35��05���W, Guaribas Biological Reserve, 25 September 2010, A . Melo, M. Alves, M.R.V. Barbosa, S.O. Santos, J.L. Viana, G. Gomes-Costa & E.C.O. Chagas 487 (fl., fr.) (holotype JPB, isotypes NY, UFP). Myco-heterotrophic, monoecious herbs, up to 9 cm tall, hyaline, glabrous; stem unbranched. Roots filiform. Leaves absent. Inflorescence racemose, terminal, bracteate, up to six flowered, or solitary flower; bracteoles 1.0���1.5 �� 0.5���1.0 mm, ensiform to triangular, apex acute; flowers 2���3 �� 2���3 mm, actinomorphic, bisexual; pedicel 1���3 mm long, tepals 4���6, persistent, 1���2 �� 0.5���1.0 mm, isomorphic, deltoid, with a central vein prominent, caudate, 0.5���1.5 mm long; ovary> 35, papillose, apocarpic, surrounding the androecium, style up to 1 mm long., lateral; stamens 3���4, persistent, inserted at the edge of receptacle, anthers 0.2���0.5 mm, globoid. Fruits achenes, up to 1mm long. Notes:���Previous to this study, Lacandonia was considered to be a monotypic genus, represented by L. schismatica, which is known only from the Lacandon region in Chiapas, Mexico (Mart��nez & Ramos 1989, Ambrose et al. 2006). It was previously placed in a separate family, Lacandoniaceae, because it is the only angiosperm in which the ovaries surround the androecium. It also has an apocarpic ovary, three to four central stamens, and bilocular, transversely dehiscent anthers (Mart��nez & Ramos 1989). Later, the species was placed in Triuridaceae (Maas-van de Kamer & Weustenfeld 1998, APG II 2003). The atypical position of the gynoecium and androecium is suggested by Mabberley (2008) as a possible case of homeotic mutation. The genus was previously known only from Mexico and was considered endemic to that country (Mart��nez & Ramos 1989, Ambrose et al. 2006). Our record of populations of a taxon belonging to the same genus in Brazil is therefore the first in South America. It is a remarkable case of disjunction between Mesoamerica and the Brazilian Coastal Forest. The Brazilian specimens, here described as the new species L. brasiliana, fit within the morphological characterization of L. schismatica, albeit at the lower range of number of ovaries and plant size as cited by Mart��nez & Ramos (1989) and Vergara-Silva et al. (2003). Lacandonia brasiliana differs from L. schimatica in having solitary flowers or inflorescences with up to six flowers, and more than 35 papillose ovaries. Molecular studies, comparing Mexican and Brazilian specimens could resolve the question if these geographically isolated populations should actually be treated as different species. Lacandonia brasiliana was found in the extreme north of the Atlantic Forest in northeastern Brazil, in the state of Para��ba, about 20 km from the coast, a region with an average maximum annual temperature of 26��C and rainfall of 1,700 mm /year. It grows in sandy soil in semideciduous forest with a canopy around 15 m high. The forest fragments in the study area are distinguished by the high diversity of trees. Neither selective wood cutting nor other kind of human disturbance was observed in the area. Lacandonia brasiliana was collected in moist, organic, and decomposing substrate and found fertile in August and September. According to Mart��nez & Ramos (1989), L. schismatica blooms throughout the year in Mexico, but most numerously so in November and December. Lacandonia brasiliana blooms in August and September. They are distinguished from other species of Triuridaceae mainly by its bisexual flowers with apocarpic ovaries surrounding the androecium, and the hyaline stem. It occurs in sympatry with other myco-heterotrophic species such as Gymnosiphon divaricatus (Benth.) Benth. & Hook. f. (Burmanniaceae), Voyria caerulea Aubl. and V.tenella Hook. (Gentianaceae). Additional specimen (paratype):��� BRAZIL. Para��ba: Mamanguape, Guaribas Biological Reserve, 17 August 1988, L. P. F��lix & C. A. B. Miranda 3607 (fl., fr.) (EAN!, JPB!)., Published as part of Melo, Aline & Alves, Marccus, 2012, The discovery of Lacandonia (Triuridaceae) in Brazil, pp. 21-25 in Phytotaxa 40 on pages 22-24, DOI: 10.11646/phytotaxa.40.1.3, http://zenodo.org/record/4894777, {"references":["Martinez, E. & Ramos, C. H. (1989) Lacandoniaceae (Triuridales): Una nueva familia de Mexico. Annals of the Missouri Botanical Garden 76: 128 - 135.","Ambrose, B. A., Espinosa-Matias, S., Vazquez-Santana, S., Vergara-Silva, F., Martinez, E., Marquez-Guzman, J. & Alvarez-Buylla, E. R. (2006) Comparative developmental series of the Mexican triurids support a euanthial interpretation for the unusual reproductive axes of Lacandonia schismatica (Triuridaceae). American Journal of Botany 93: 15 - 35.","APG II (2003) An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG II. Botanical Journal of the Linnean Society 141: 399 - 436.","Mabberley, D. J. (2008) Mabberley's Plant-book, a portable dictionary of plants, their classifications, and uses. Cambridge University Press, New York, 1040 p.","Vergara-Silva, F., Espinosa-Matias, S., Ambrose, B. A., Vazquez-Santana, S., Martinez-Mena, A., Marquez-Guzman, J., Martinez, E. Meyerowitz, E. M. & Alvarez-Buylla, E. R. (2003) Inside-out flowers characteristic of Lacandonia schismatica evolved at least before its divergence from a closely related taxon, Triuris brevistylis. International Journal of Plant Sciences 164: 345 - 357."]}

Summary The interphase nucleus of the cells of several tissues of Lacandonia schismatica was studied using electron microscopy cytochemical and immunocytochemical methods. The EDTA staining procedure, preferential for RNP, contrasted the Lacandonia granules and perichromatin fibrils. These granules were found to be relatively resistant to RNAse hydrolysis, but they were easily digested if RNAse treatment was carried out after a short hydrolysis with pronase. Bismuth oxynitrate stained granular structures about 17 nm in diameter and the periphery of a few Lacandonia granules. The anti=snURNPs bound to RNP-containing fibrils in the perichromatin and interchromatin space and also to the periphery of some Lacandonia granules. Immunolabeling of DNA demonstrated numerous filaments of extended chromatin in the perichromatin and interchromatin spaces which were closely related to Lacandonia granules. These observations suggested that Lacandonia granules are equivalent to Balbiani ring granules of nuclei with polytene chromosomes and to perichromatin granules of other plant and animal nuclei. The small number of Lacandonia granules labeled in their periphery by anti-snURNP mAb were interpreted as being immature granules in the process of formation. The external or annular part of the ring-shaped structures is heavily labeled by anti-URNP mAbs but scarcely stained by the EDTA procedure. These features indicate that this region contains abundant proteins associated with snURNAs but probably little snURNAs. The synaptonemal-like complexes previously found in the interphase nuclei of Lacandonia are formed by two parallel masses of compact chromatin, which react with anti-DNA, and a central clear space crossed by fiber. Most of these fibers do not react with tests for DNA or RNA and are probably composed of proteins. The EDTA procedure contrasts some fibrils at the internal aspect of the masses of compact chromatin, suggesting the presence of remnants of the lateral element of a synaptonemal complex.

By light and electron microscope cytochemistry we characterized the interphase nucleus ofLacandonia schismatica, the only known species of the new plant family Lacandoniaceae, whose most peculiar feature is the inverted position of the sexual organs, an aspect never found before among flowering plants. Furthermore, we compare it toTriuris alata, a related species, toVoyria aphylla (a dicotyledon), toGymnosiphon divaricatus (a monocotyledon) and also to saprophytes. The reticulated chromatin ofL schismatica andT alata is similar to that of other monocotyledons. In addition, we describe a unique type of RNP granules in the interchromatin space which are about 32 ± 3 nm SD in diameter and occur as huge clusters. They are intermediate in size and spatial distribution between inter- and peri-chromatin granules. We term them ‘Lacandonia granules’. The granules were also found inT alata. They are 31 ± 2 nm in diameter. No significant differences in size were observed between them (P > 0.05). Synaptonemallike complexes and ring-shaped structures were seen in interphase nuclei of somatic cells of these species. Coiled and nucleolus-associated bodies, as well as centromeres were also found in these two organisms. On the contrary,Vaphylla andG divaricatus display a chromocentric nuclear organization. The nuclear similarities betweenL schismatica andT alata suggest extremely close phylogenetic relationships between them.

Lacandonia schismatica is a rare flowering plant with the sex organs spatially inverted. Several aspects of its cell biology are now known. Interestingly, within the cell nucleus, the chromatin is reticulated and it is associated to a novel structure named Lacandonia granules, a very abundant ribonucleoprotein particle showing similarities to perichromatin and Balbiani ring granules, which are involved in nuclear mRNA metabolism. To see whether these particles are present in other plants, we study the nucleus of Ginkgo biloba, a non-flowering plant. Light, electron and atomic force microscopy show that the cell nuclei of G. biloba are reticulated. Ultrastructural analysis showed that in the nucleoplasm, abundant intranuclear particles 32 nm in diameter are present. The EDTA regressive staining suggested that they contain RNA. Ultrastructural in situ hybridization confirmed the presence of RNA in these particles. Therefore, we conclude that the nuclei of G. biloba are reticulated and contain Lacandonia granules. We suggest that these particles may also be present in other plants.

Lacandonia schismatica (Triuridaceae) is a species only known from Mexico. Recently a very similar plant was discovered in a fragment of the Atlantic Forest in northeastern Brazil and it is described here as a new species. This is the first record of Lacandonia in South America.