Morfo-anatomia da flor do cacto epífito Schlumbergera truncata (Haw.) Moran (Rhipsalidae: Cactaceae), com ênfase na ontogenia do nectário floral.
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Data
2022-04-29
Autores
Apolonio, Veronica Rubim
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Universidade Estadual Paulista (Unesp)
Resumo
Schlumbergera é um gênero composto por seis espécies de cactos epífitos, nativo do sudeste brasileiro. Possui interesse ornamental e por esta razão é cultivada em muitas partes do mundo. As flores de Schlumbergera truncata são adaptadas à ornitofilia e possuem nectários de morfologia conspícua dentro da família. Buxbaum descreveu três tipos morfológicos de nectários para Cactaceae, sendo (1) em fenda, (2) em disco (anelar) e (3) em câmara. Há apenas dois trabalhos relacionados à arquitetura do nectário floral de Schlumbergera e nenhum deles é conclusivo sobre a sua natureza. Neste trabalho buscou-se estudar a morfologia floral enfatizando a ontogenia do nectário em S. truncata. Para tal, usamos técnicas de histologia vegetal e imagens de microscopia eletrônica de varredura, desde os estágios iniciais de desenvolvimento até a antese. O nectário se forma a partir de células meristemáticas, no tubo floral, entre o primeiro ciclo de estames e a base do estilete. A cobertura sobre o nectário, que o torna excêntrico, é formada por apêndices encontrados na base do filete, que também têm origem no tubo floral. O nectário com a estrutura de cobertura evita que a água do néctar evapore para o ambiente, fazendo com que o néctar fique menos viscoso por mais tempo. Estudos com beija-flores apontam que esses animais preferem estas configurações de néctar. Além das novidades ontogenéticas, as informações presentes neste trabalho contribuem para elucidar outros estudos morfológicos e sistemáticos dentro de Rhipsalideae.
Schlumbergera is a genus composed of six species of epiphytic cacti, native to southeastern Brazil. It has ornamental interest and for this reason it is cultivated in many parts of the world. The flowers of Schlumbergera truncata are adapted to ornithophily and have nectaries of conspicuous morphology within the family. Buxbaum described three morphological types of nectaries for Cactaceae, being (1) cleft, (2) disc (annular) and (3) chamber. There are only two works related to the architecture of the Schlumbergera floral nectary and neither is conclusive about its nature. In this work we sought to study the floral morphology emphasizing the ontogeny of the nectary in S. truncata. To this end, we used plant histology techniques and scanning electron microscopy images, from the early stages of development to anthesis. The nectary forms from meristematic cells, in the floral tube, between the first cycle of stamens and the base of the style. The covering over the nectary, which makes it eccentric, is formed by appendages found at the base of the fillet, which also originate from the floral tube. The nectar with the cover structure prevents the nectar water from evaporating into the environment, making the nectar less viscous for longer. Studies with hummingbirds indicate that these animals prefer these nectar settings. In addition to the ontogenetic novelties, the information presented in this work contributes to elucidate other morphological and systematic studies within Rhipsalideae.
Schlumbergera is a genus composed of six species of epiphytic cacti, native to southeastern Brazil. It has ornamental interest and for this reason it is cultivated in many parts of the world. The flowers of Schlumbergera truncata are adapted to ornithophily and have nectaries of conspicuous morphology within the family. Buxbaum described three morphological types of nectaries for Cactaceae, being (1) cleft, (2) disc (annular) and (3) chamber. There are only two works related to the architecture of the Schlumbergera floral nectary and neither is conclusive about its nature. In this work we sought to study the floral morphology emphasizing the ontogeny of the nectary in S. truncata. To this end, we used plant histology techniques and scanning electron microscopy images, from the early stages of development to anthesis. The nectary forms from meristematic cells, in the floral tube, between the first cycle of stamens and the base of the style. The covering over the nectary, which makes it eccentric, is formed by appendages found at the base of the fillet, which also originate from the floral tube. The nectar with the cover structure prevents the nectar water from evaporating into the environment, making the nectar less viscous for longer. Studies with hummingbirds indicate that these animals prefer these nectar settings. In addition to the ontogenetic novelties, the information presented in this work contributes to elucidate other morphological and systematic studies within Rhipsalideae.
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Palavras-chave
Botanica, Morfologia vegetal, Anatomia vegetal, Cactos, Nectários, Development, Floral anatomy, Floral tube, Flower, Nectar, Christmas cactus