Pollen morphology of Acalypha L. (Euphorbiaceae) with emphasis on Brazilian species from Bahia

ABSTRACT We investigated the pollen morphology of eight species of Acalypha occurring in Bahia State, Brazil. Flower buds were collected from specimens deposited in the CEPEC and HUEFS herbaria. Pollen samples were acetolyzed and analyzed using both light and scanning electron microscopy. The pollen grains examined using optical microscopy were found to be small and brevicolporate, with three to six apertures and elevations and fastigium, and had a psilate to scabrate exine. Scanning electron microscopy revealed the presence of supratectal elements and Ubisch bodies, and evidenced three pollen types based mainly on exine ornamentation: microrugulate-scabrate (slightly rugulate-scabrate), areolate-rugulate, and microechinate. This study provides new data and new interpretations of pollen morphology for the genus Acalypha, with comments on the palynological relationships between Acalypha and its sister group Mareya, and the next most closely related genus (Spathiostemon).

摘要 本研究针对巴西巴伊亚州分布的8种铁苋菜属（Acalypha）植物的花粉形态展开调查。研究材料取自保存于CEPEC标本馆与HUEFS标本馆的馆藏标本的花蕾。花粉样品经乙酰解处理后，分别利用光学显微镜与扫描电子显微镜进行观察分析。经光学显微镜观察的花粉粒均为小型短沟孔花粉，具3至6个萌发孔，表面带有隆起与穹状结构，外壁纹饰呈光滑至糙面状。扫描电子显微镜观察显示，花粉表面存在盖层外附属结构与乌氏体，并基于外壁纹饰特征划分出3种花粉类型：微皱糙状（略呈皱糙状）、网胞皱状以及微刺状。本研究为铁苋菜属的花粉形态学研究提供了全新的数据与解读，并探讨了铁苋菜属与其姊妹群Mareya以及近缘属Spathiostemon之间的孢粉学关系。