Biologia floral e sistema de reprodução de Merostachys riedeliana (Poaceae: Bambusoideae)
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Data
2001-06-01
Autores
GUILHERME, FREDERICO AUGUSTO G. [UNESP]
RESSEL, KAILA [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Sociedade Botânica de São Paulo
Resumo
Merostachys riedeliana Rupr. é uma espécie monocárpica com floração cíclica e muito freqüente em sub-bosques de fragmentos florestais do sul do estado de Minas Gerais, Brasil. Sua biologia floral e seu sistema de reprodução foram estudados e comparados com os de outros bambus. Devido ao complexo sistema de rizomas, formam touceiras vigorosas no interior da floresta, ocorrendo a interrupção na produção de novos colmos meses antes do aparecimento das primeiras inflorescências. O início da floração maciça e da morte da população ocorreu em outubro de 1998 e maio de 1999, respectivamente, com pico de floração durante a estação quente e chuvosa (dezembro e janeiro). As inflorescências espiciformes possuem, em média, 29 espiguetas. Estas são hermafroditas com três anteras poricidas e dois estigmas plumosos que se expõem durante a antese. O pólen é abundante e facilmente liberado das anteras pelo vento ou pelos visitantes. Apis mellifera L. e Trigona spinipes (F.) foram os visitantes mais freqüentes, atuando como pilhadores de pólen e, ocasionalmente, através de movimentos vibratórios, como elementos auxiliares para a dispersão do pólen. A alta pluviosidade durante a floração e a escassez de vento no sub-bosque da floresta, podem diminuir a efetividade da anemofilia. No entanto, vários caracteres morfológicos das espiguetas, queda de folhas e o hábito espacialmente agrupado, apontam para uma polinização pelo vento. Testes de polinização controlada, mostraram que M. riedeliana é autocompatível (ISI 0,99). A auto-incompatibilidade não favorece a formação de frutos em clones vegetais, ao passo que a autocompatibilidade poderia resultar em uma elevada produção de sementes. Assim, a possível ocorrência de clones de M. riedeliana nos fragmentos florestais, originados pelo crescimento vegetativo durante os intervalos reprodutivos de 30-32 anos, poderiam explicar o alto investimento na produção de espiguetas e a formação de frutos provenientes da autocompatibilidade.
Merostachys riedeliana Rupr. is a long-lived monocarp species common in the understorey of tropical semideciduous forest fragments in the south of Minas Gerais, Brazil. Its floral biology and breeding system were studied and compared with others bamboos. Due to its rhizome, it occurs in clumps and has a remarkable capacity for vegetative multiplication, which ceases a few months before the emergence of the first inflorescences. The beginning of the flowering and the death of the entire population occurred respectively on October 1998 and May 1999. The peak of the blooming episode took place during the hot and rainy months of the year (December and January). Each inflorescence produces in average 29 spikelets, which have hermaphrodite florets with three stamens and two plumose stigmas that are exposed during theanthesis. The abundant pollen is easily released by the wind or visitors. Apis mellifera L. and Trigona spinipes (F.) were the commonest visitors and behave as pollen thieves. These bees occasionally act as devices for dispersion of pollen, through vibration produced in the anthers. The excess of rain during flowering and the lack of wind in the understorey of the forest constrain the effectiveness of the anemophily. However, several morphological characters of the flowers, leaf fall and dense clumps tend to expect for wind pollination. Also, the auto-incompatibility index (0.99) showed that M. riedeliana is an autocompatible bamboo. So the auto-incompatibility does not favour the formation of fruits in vegetal clones, and the autocompatibility could result in the high production of seeds. Therefore the possible occurrence of clones of M. riedeliana in the forest fragments, due to the effective vegetative growth and the 30-32 years cyclic flowering intervals, might explain the high investment on spikelets production and autocompatible fruits formation.
Merostachys riedeliana Rupr. is a long-lived monocarp species common in the understorey of tropical semideciduous forest fragments in the south of Minas Gerais, Brazil. Its floral biology and breeding system were studied and compared with others bamboos. Due to its rhizome, it occurs in clumps and has a remarkable capacity for vegetative multiplication, which ceases a few months before the emergence of the first inflorescences. The beginning of the flowering and the death of the entire population occurred respectively on October 1998 and May 1999. The peak of the blooming episode took place during the hot and rainy months of the year (December and January). Each inflorescence produces in average 29 spikelets, which have hermaphrodite florets with three stamens and two plumose stigmas that are exposed during theanthesis. The abundant pollen is easily released by the wind or visitors. Apis mellifera L. and Trigona spinipes (F.) were the commonest visitors and behave as pollen thieves. These bees occasionally act as devices for dispersion of pollen, through vibration produced in the anthers. The excess of rain during flowering and the lack of wind in the understorey of the forest constrain the effectiveness of the anemophily. However, several morphological characters of the flowers, leaf fall and dense clumps tend to expect for wind pollination. Also, the auto-incompatibility index (0.99) showed that M. riedeliana is an autocompatible bamboo. So the auto-incompatibility does not favour the formation of fruits in vegetal clones, and the autocompatibility could result in the high production of seeds. Therefore the possible occurrence of clones of M. riedeliana in the forest fragments, due to the effective vegetative growth and the 30-32 years cyclic flowering intervals, might explain the high investment on spikelets production and autocompatible fruits formation.
Descrição
Palavras-chave
Semideciduous tropical forest, wind pollination, autocompatibility, vegetative growth, Merostachys
Como citar
Brazilian Journal of Botany. Sociedade Botânica de São Paulo, v. 24, n. 2, p. 205-211, 2001.