Abstract
ABSTRACT Flowers with heterodynamous stamens can present differences in the pollen grains of each stamen size group. Species of Aeschynomene L. present didynamous stamens (five long and five short) but little is known about their pollen dimorphism. The objective of this study was to increase the knowledge about the pollen characteristics in Aeschynomene and emphasize the possible morphological differences between the pollen grains of long and short stamens in order to contribute to ecological and taxonomic studies. Pollen grains from the two groups of stamens size of ten species were analyzed separately, according to the standard methodology for studies of pollen morphology. In addition, analyses of variance, comparison of means and base index were performed. The results showed that the amb, shape, endoaperture type and sexine ornamentation did not vary in the pollen grains of the long and short stamens in the same specimen, but they varied among the species. However, in relation to the size of the pollen grains of the two groups of stamens, four species presented significant differences regarding the size of the polar and equatorial axes. The pollen morphological data obtained considering the heteromorphism of the stamens can contribute to the knowledge of the repro ductive dynamics of the genus, and to the systematic studies.
Highlights
The tribe Dalbergieae sensu latu Klitgaard and Lavin (2005) in Papilionoideae subfamily of Fabaceae comprises 49 genera, wich Aeschynomene L. as the third most representative of the tribe
Aeschynomene presents papilionoid corolla, which is related to the co-evolution between the hymenopterans and the Papilionoideae (Arroyo 1981, Judd et al 2007), whose flowers’ androecium has heterodynamous stamens and uniform anthers (Rudd 1955)
The aim of this research was to carry out an unprecedented analysis of the pollen morphology of ten species from the genus Aeschynomene L.; with attention to the possible morphological differences between long and short stamens of the same specimen to contribute to the studies of reproductive biology, pollination and taxonomy to the genus
Summary
The tribe Dalbergieae sensu latu Klitgaard and Lavin (2005) in Papilionoideae subfamily of Fabaceae comprises 49 genera, wich Aeschynomene L. as the third most representative of the tribe. The Aeschynomene genus presents pantropical distributions, with approximately 180 species in the. 1. Instituto de Botânica, Programa de Pós-Graduação em Biodiversidade Vegetal e Meio Ambiente, Avenida Miguel Stéfano, 3687, 04301-902 São Paulo, SP, Brasil. 2. Instituto de Botânica, Núcleo de Pesquisa em Palinologia, Avenida Miguel Stéfano, 3687, 04301-902 São Paulo, SP, Brasil 3. Aeschynomene presents papilionoid corolla, which is related to the co-evolution between the hymenopterans and the Papilionoideae (Arroyo 1981, Judd et al 2007), whose flowers’ androecium has heterodynamous stamens (five long and five short) and uniform anthers (Rudd 1955). Tucker (1996) studied many species of Leguminosae and pointed out that stamens with dimorphisms are commonly found in this family, possibly differing in size, filament length, anther shape and moment of dehiscence. The presence of different stamen sizes was diagnosed in Aeschynomene in research carried out by Burkart (1939), Fernandes (1996), Sampaio (2005), Silva & Antunes (2014)
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