AbstractCatasetum is a neotropical orchid genus of 130 species characterized by its unisexual flowers. They are pollinated by male Euglossini bees. It is widely know that these bees collect volatile compounds in Catasetum from structures called osmophores. However, there is little information on morpho-anatomy and histochemistry of secretory tissues for this neotropical genus and data are lacking. Based on these arguments members of the Catasetum cristatum alliance, namely C. arietinum, C. ariquemense, C. barbatum, C. carolinianum, C. cristatum, C. lanciferum, C. multifidum, C. multifissum, C. rivularium and C. semicirculatum were analyzed. The labellum of male flowers of this alliance is elongate and with fimbriate margins, possessing two protuberances and a median saccate portion. The labellum of female flowers is galeiform and there is no ornamentation. The entire adaxial surface of the labellum is secretory in both sexes, including the fimbriae of male flowers. The structure of the secretory tissue is similar among species, and they are composed of a simple epidermis and five layers of underlying parenchyma. In most species the epidermis is flat, and cells are elongated in the saccate portion. In C. ariquemense and C. carolinianum the epidermal cells are papillous, while in C. semicirculatum they have convex surface (male flowers). The histochemical analysis detected lipophilic droplets and starch grains inside the secretory cells. All characteristics observed are encountered in secretory tissues with high-energy demand, as is common in osmophores.

Resumo A biologia floral e reprodutiva de Echinodorus grandiflorus (Cham. & Schltdl.) Micheli foram estudadas em populações nativas do interior do estado de São Paulo. A espécie floresce no verão e suas flores oferecem tanto néctar quanto pólen como recurso. O néctar é secretado por nectários localizados na base dos carpelos marginais, opostos às pétalas. Os polinizadores (abelhas sociais e solitárias), no entanto, foram observados coletando apenas pólen. As visitas, que podem durar de um a poucos segundos até mais de um minuto, acontecem desde o momento da abertura das flores (ca. 5:30 h) até o fenecimento. Cada flor dura cerca de oito horas. Todos os indivíduos das populações produzem apenas flores hermafroditas. A porcentagem de grãos de pólen viáveis é de 75%. As populações estudadas são autoincompatíveis e, como conseqüência, polinizadores são necessários para transferência de pólen. Em condições naturais e a partir das polinizações cruzadas realizadas manualmente, todos os receptáculos apresentaram aquênios maduros. Através das análises dos tubos polínicos das flores autopolinizadas manualmente, e devido ao fato dos aquênios derivados desse tratamento abortarem cerca de 30 dias a partir das autopolinizações, aparentemente, as populações de E. grandiflorus estudadas apresentam um mecanismo de auto-esterilidade de ação tardia.

Abstract The reproductive biology and the pollination of Echinodorus grandiflorus (Cham. & Schltdl.) Micheli were studied in populations native to interior of the State of São Paulo, Brazil. This species blossoms in summer and its flowers offer both nectar and pollen as rewards to pollinators. Nectar is produced in nectaries located at the base of the marginal carpels, opposite the petals. However, the effective pollinators (social and solitary bees), were recorded collecting pollen only. Visits, which can last from one or a few seconds to more than one minute, occur during the whole flower lifespan. Each flower opens at about 5:30 a.m. and lasts circa eight hours. All plants in the studied populations produce only hermaphrodite flowers. Percentage of pollen viability is 75%. The studied populations are self-incompatible and, as a consequence, pollinators are needed to transfer pollen among individuals. In natural conditions and after hand cross-pollinations, all receptacles presented mature achenes. Based on the analyses of pollen tube growth from hand self-pollinated flowers, and as a consequence of achenes abortion circa 30 days after self-pollinations, the populations of E. grandiflorus studied apparently presents a mechanism of late-acting self-sterility.