Se presentan seis especies de orquídeas epífitas no citadas anteriormente para Uruguay, de los géneros Acianthera Scheidw., Capanemia Barbosa Rodrigues con una nueva variedad, Gomesa R. Brown, Trichocentrum Poeppig & Endl. y Campylocentrum Bentham. Se proveen descripciones, ilustraciones, datos de distribución geográfica, claves de identificación, referencias de herbario y status de conservación.

Six species and a new variety of epiphytic orchid genera: Acianthera Scheidw, Capanemia Barbosa Rodrigues, Gomesa R. Brown, Trichocentrum Poeppig & Endl. and Campylocentrum Bentham have not been cited before for Uruguay. Descriptions, illustrations, geographical distribution data, identification keys, herbarium references, and information regarding their conservation status are presented.

Se analiza y confirma la presencia de cinco especies de orquídeas en Uruguay, para las que se presentan las descripciones, ilustraciones, distribución geográfica y referencias de herbario. Cuatro de ellas pertenecen a los géneros Malaxis Solander ex Swartz (2 especies), Galeandra Lindley (1 especie) y Cyrtopodium R. Brown (1 especie) y son citas nuevas. La presencia de una especie del género Eulophia R. Brown ex Lindley ha sido redescubierta en el litoral oeste luego de una única colección en el siglo pasado en el este del país, registrada en ese entonces como Pteroglossaspis Reichenbach f.. Todas ellas se consideran prioritarias para su conservación.

The presence, descriptions, illustrations, geographical distributions and herbarium references are provided for five orchid species in Uruguay. Four of them, of the genera Malaxis Solander ex Swartz (2 species), Galeandra Lindley (1 species) and Cyrtopodium R. Brown (1 species), are new records for Uruguay. Another species of the genus Eulophia R. Brown ex Lindley was rediscovered in the western part of the country after a single collection of a misclassified Pteroglossaspis Reichenbach f., in the eastern department of Maldonado during the past century. All five species are considered of priority preservation.

Trifolium polymorphum is recognized as one of the best adapted legume in field conditions. It combines different reproductive strategies such as stoloniferous vegetative reproduction and seed reproduction by two types of fruits produced in underground and aerial flowers. These last ones are chasmogamous and underground flowers are cleistogamous. A higher seed production has empirically been detected in underground flowers rather than in aerial ones. In the present work, embryological studies in aerial and underground flowers were carried out in order to determine the existence of ontogenetic causes which may promote productivity differences in both types of seeds. No embryological pre-zygotic cause explaining aerial flowers low productivity was detected. Aerial and underground seeds share ontogenetic characteristics as both types of flowers showed normal ovule and embryo sac development. Similar nutritional pathways for embryo sacs, embryos and endosperms were also observed. In general, flowering represents a high energetic inversion for plant species. Aerial flowering in T. polymorphum, though subjected to a strong herbivorous pressure, incorporates genetic variability to populations through cross-pollination and succeeds in facilitating long distance dispersion.

Trifolium polymorphum es una leguminosa de pradera con buena adaptación y persistencia en este tipo de vegetación. Combina diferentes estrategias reproductivas como la reproducción vegetativa por estolones y la reproducción por semillas producidas en dos tipos de frutos y flores, subterráneas y aéreas. Las subterráneas son cleistógamas y las aéreas son casmógamas. Empíricamente se ha detectado mayor formación de semillas en los frutos subterráneos que en los aéreos. En el presente trabajo se realizan estudios embriológicos y de desarrollo de semillas en ambos tipos de flores para dilucidar si existen causas ontogenéticas que determinan la productividad diferencial de semillas en ambos tipos de frutos. No se detectaron causas embriológicas pre-cigóticas que expliquen el menor número de semillas en los frutos de las flores aéreas. Ambos tipos de semillas comparten características ontogenéticas y presentan apropiado desarrollo de los óvulos, sacos embrionarios y establecimiento de vías nutricionales para saco embrionario, embrión y endosperma. En general las floraciones insumen un costo energético importante para las especies vegetales. La floración aérea de T. polymorphum, aunque sometida a una fuerte presión de herbivoría del ganado, incorpora variabilidad genética a sus poblaciones a través de la polinización cruzada y permite la dispersión a distancia.

Trifolium polymorphum é uma espécie que cresce no Uruguai, Argentina, Brasil, Paraguai e Chile. As flores subterrâneas são cleistógamas, autógamas obrigatórias e altamente modificadas na sua estrutura e funcionalidade. As flores aéreas são casmógamas e foram descritas como alógamas e autógamas. Este trabalho tem como objetivo identificar as características florais que facilitam ou evitam os processos de autogamia ou alogamia. A fenologia floral foi correlacionada com os modelos estimados do desenvolvimento das flores aéreas, a viabilidade do pólen e a receptividade estigmática, em três populações uruguaias de T. polymorphum. As variáveis analisadas foram: longevidade e desenvolvimento da flor (comprimento, largura e distância entre anteras e estigma); momento de início da antese e deiscência das anteras; viabilidade do pólen e receptividade estigmática. As flores aéreas têm características que facilitam processos de autogamia ainda em pré-antese e outras características fenológicas que os evitam. Os eventos reprodutivos importantes que ocorrem durante o desenvolvimento da flor e facilitam processos de autogamia ou alogamia são discutidos neste trabalho.

Trifolium polymorphum is an amphicarpic species that grows in Uruguay, Argentina, Brazil, Paraguay and Chile. Underground flowers are cleistogamous, obligately autogamous and morphologically highly modified in structure and function. Aerial flowers are chasmogamous, and as mentioned in earlier literature, either allogamous or autogamous. The aim of this study is to identify flower characteristics that facilitate or prevent autogamous or allogamous processes. Floral phenology stages are thus studied in correlation with estimated models of aerial flower development, pollen viability and stigmatic receptivity in three Uruguayan T. polymorphum populations. Flower longevity and development (length, width, and anther-stigma distance), anthesis and anther dehiscence initiation, pollen viability and stigmatic receptivity are the variables correlated with floral phenology. Morphological characteristics of aerial flowers favor autogamy processes - even in pre-anthesis - but phenological characteristics tend to prevent it. The most important reproductive events occurring during flower development, that facilitate autogamous or allogamous processes, are discussed here.