Pollen morphology of Galactia P. Browne and related genera (Papilionoideae, Leguminosae), with emphasis on Brazilian representatives

ABSTRACT Galactia is a pantropical genus, which is part of the Galactia clade, and together with the genera Betencourtia, Caetangil, Cerradicola, Collaea, Lackeya, Nanogalactia, and Rhodopis, it maintains a taxonomic relationship that has already been the focus of previous studies. However, the palynology of these groups has not been extensively studied, with gaps in pollen descriptions. Thus, a palynological study of 30 species belonging to Galactia and related genera was performed. For this purpose, pollen grains were acetolized using the standard methodology, subjected to scanning electron microscopy analysis, and then quantitatively and qualitatively evaluated. Generally, pollen grains of this genera are medium or large size, isopolar or heteropolar, 3-colporate, and may have microreticulate or reticulate exine. Pollen data for Rhodopis and Nanogalactia agree with the most recently proposed circumscription of these genera. Other genera exhibited similar pollen characteristics; however, the diameter of the lumen, associated with other pollen characteristics, proved to be important for the differentiation of the genera. Thus, the pollen morphology provided information that contributes to the description of the genera, mainly Brazilian representatives of Galactia and related genera.

摘要 乳豆属（Galactia）为泛热带分布属，隶属于乳豆演化支（Galactia clade），与Betencourtia、Caetangil、Cerradicola、Collaea、Lackeya、Nanogalactia及Rhodopis共同构成一类群，其分类学关系已成为既往研究的焦点。然而，上述类群的孢粉学研究尚不充分，花粉形态描述存在诸多空白。为此，本研究针对乳豆属及相关类群的30个物种开展了孢粉学分析。实验采用标准方法对花粉粒进行乙酰解处理，随后通过扫描电子显微镜（scanning electron microscopy, SEM）进行观测，并进行定性与定量评估。总体而言，该类群的花粉粒多为中等至大型，等极或异极，具3孔沟，外壁纹饰为微网状或网状。Rhodopis与Nanogalactia的花粉数据与最新提出的该类属分类界定标准相符。其余类群的花粉特征整体相似，但管腔直径结合其他花粉形态特征，可作为属间区分的重要依据。综上，本次研究所得的花粉形态信息，可为乳豆属及其近缘类群（尤其是巴西分布的类群）的分类学描述提供重要参考。