Oils are atypical floral rewards in Orchidaceae and are produced by epidermal glands called elaiophores. Flowers of many members of the subtribe Oncidiinae either produce oil or mimic oil-producing flowers of Malpighiaceae. We focus our research on 3 species of Gomesa, namely, G. flexuosa, G. riograndensis, and G. varicosa in order to investigate the presence of elaiophores, their micromorphology and internal structure, and the process of oil secretion. Elaiophores were located using Sudan III and their internal and external features examined using light and scanning electron microscopy, respectively. The presence of elaiophores was confirmed for regions of calli that are prominent and exposed. In all 3 species the secretory tissue comprised a single layer of epidermal cells, together with some parenchymatous, subsecretory cells. Epidermal cells were isodiametric or palisade-like, with dense cytoplasm, small vacuoles, and prominent nuclei. Gomesa flexuosa differs from the other species investigated in that it bears intermediate elaiophores (i.e. epithelial and possessing unicellular, secretory trichomes). Based on the absence of a distended cuticle, we propose that oil may pass through the wall and cuticle as small lipid moieties. In addition, some evolutionary trends in the elaiophores in the genus Gomesa are suggested.

No abstract

ResumenGómiz, N.E., Torretta, J.P. & Aliscioni, S.S. 2014. Zygostates alleniana (Orchidaceae: Epidendroideae: Cymbidieae: Oncidiinae): estructura floral relacionada con la polinización. Anales Jard. Bot. Madrid 71(1): e002.El género Zygostates Lindl. (Orchidaceae) comprende aproximadamente 20 especies de pequeñas plantas epífitas con distribución neotropical, representado en su límite más austral por la especie Z. alleniana. En el presente trabajo se estudian morfológica y anatómicamente las características florales de esta especie relacionadas con el mecanismo de polinización. Se confirma la presencia de tricomas unicelulares en la base del labelo y lóbulos laterales que actúan secretando aceite, constituyendo un elaióforo tricomatoso. El aceite se deposita por debajo de la cutícula en el ápice de los tricomas formando pequeñas ampollas. El aceite podría representar una recompensa para la especie Lophopedia nigrispinis, la cual sería un posible polinizador de Z. alleniana en un área natural dentro del rango de distribución geográfica de esta especie vegetal. Por otro lado, se comprueba que la reconfiguración del polinario se debe a la deshidratación de las paredes celulares. Esta reconfiguración podría favorecer la polinización cruzada, mecanismo ya descrito para otras especies de la familia Orchidaceae. Por último, se discuten los caracteres florales presentes en Z. alleniana con otras especies estrechamente emparentadas.Palabras clave: aceites florales, abejas colectoras de aceite, Argentina, callo, estípite, recompensa, visitante floral, polinización, elaióforo. The genus Zygostates Lindl. (Orchidaceae) comprises about 20 species of small Neotropical epiphytic plants, represented in its southernmost limit by the species Z. alleniana. In this paper, we studied morphological and anatomical floral characteristics of this species related to pollination mechanism. We confirmed the presence of the unicellular trichomes on the base of the lip and side lobes secreting oil, constituting a trichomal elaiophore. The oil is deposited beneath the cuticle at the apex of the trichomes forming small blisters. The oil could represent a reward for the species Lophopedia nigrispinis, which would be a potential pollinator of Z. alleniana in a natural area within the geographic range of this plant species. Moreover, we prove that the reconfiguration of the pollinaruim is due to the dehydration of the walls cell. This reconfiguration could favor cross-pollination mechanism already described for other species of the family Orchidaceae. Finally, we discuss the floral characters present in Z. alleniana with closely related species.

No abstract

The genus Setaria is economically important because many species are cultivated for grains or forage. Setaria magna is an American species, native to North America and introduced in South America. The morphological aspect of this species is similar to S. italica (foxtail millet), suggesting its potential value as a crop. The purpose of this work was to understand the breeding system (selfpollination vs. open pollination) of S. magna; additionally, the floral development was described. The results of the breeding system analysis indicated that S. magna is mainly autogamous and does not appear to have a self-incompatibility mechanism. The floral development observed was similar to that described for other Paniceae; in most of the spikelets only the upper anthecium developed fruit, but a small number of spikelets presented bisexual lower florets. These spikelets produced two caryopses per spikelet. Thus, S. magna can produced two types of dispersal units; a few whitish naked caryopses from the lower anthecium that fall without their lemma and palea at maturity; and a high number of brown caryopses protected by the lemma and palea from the upper anthecium. The presence of a normal embryo sac in the upper anthecium suggests that S. magna would present normal sexual reproduction, although we can not reject the formation of apomitic seeds in the lower anthecium.