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Acta Botanica Brasilica

Print version ISSN 0102-3306On-line version ISSN 1677-941X


SILVEIRA JUNIOR, Cristiano Eduardo Amaral; LIMA, Luciene Cristina Lima e  and  SABA, Marileide Dias. Pollen morphology of Waltheria L. (Malvaceae-Byttnerioideae) from Bahia, Brazil. Acta Bot. Bras. [online]. 2017, vol.31, n.4, pp.597-612.  Epub Sep 21, 2017. ISSN 0102-3306.

Waltheria encompasses about 60 species distributed in Brazil and Mexico. To improve the palynology of the genus, we analyzed 14 species occurring in the Brazilian State of Bahia. Pollen grains were acetolyzed and examined using light microscopy and scanning electron microscopy. Non-acetolyzed pollen grains were viewed by transmission electron microscopy. The results revealed two general pollen types based on exine ornamentation, such as reticulate and echinate, which are distinct with regard to (1) size and shape, (2) apertural type and number, (3) relative length of ectoapertures, and (4) thickening of the nexine compared to the sexine. An ultrastructural analysis of the pollen wall revealed a continuous foot layer and a compact and discontinuous endexine in most cases. The sexine consisted of heterogeneous columellae, which support a perforated semitectum (echinate type) or the semitectum was composed of perforations and muri-shaped thickening (reticulate type). These results confirm a high degree of pollen dimorphism in Waltheria associated with heterostyly.

Keywords : heterostyly; palynology; ultrastructure; taxonomy; Waltheria.

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