Heteranthery has been largely associated with a division of labour between anthers. Most species of Stigmaphyllon (Malpighiaceae) present heteromorphic anthers and glandular connectives of different development; yet, the functional meaning of this condition has never been explored in the genus. The aims of this study were to provide a comparative description of the structure and development of anthers and their connective glands in S. bonariense and S. jatrophifolium and to assess the existence of division of functions. Natural populations were selected to collect flowers at different stages. Anthers were subjected to morpho-anatomical, histochemical and pollen viability studies. For both species, abundance of pollen grains and size of anther and their connective glands were estimated. Three types of stamens are recognized: stamen with small, intermediate and large anthers. Anthers of both species exhibit a similar glandular tissue in the connective, and the histochemical analysis revealed that it produce a mucilagous secretion. The pattern of anther wall development, stainability and release of pollen grains was identical among anther types. For both species, we observed a positive relationship between anther size and abundance of pollen grains, but an inverse relationship between area of anthers and size (area and thickness) of connective glands in small anthers vs. intermediate and large ones. Our results evidence a specialization of anthers related to division of labour between heteromorphic stamens in two species of Stigmaphyllon. Thus, one set of anthers produces large amount of pollen grains for pollination and another sets large quantities of mucilage, which would improve pollen transport (better adherence to pollinator body and dampness maintenance). Nevertheless, heteranthery in both Stigmaphyllon species would represent a transitional state towards the division of labour rather than a stable state.

中文翻译：

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两种 Stigmaphyllon (Malpighiaceae) 花药和结缔腺的结构和发育：异形花药是否与分工有关？

Heteranthery 在很大程度上与花药之间的分工有关。大多数 Stigmaphyllon (Malpighiaceae) 物种呈现出不同发育的异形花药和腺体结缔组织；然而，在该属中从未探索过这种情况的功能意义。本研究的目的是比较描述 S. bonariense 和 S. jatrophifolium 中花药及其结缔腺的结构和发育，并评估功能划分的存在。选择自然种群收集不同阶段的花卉。对花药进行形态解剖学、组织化学和花粉活力研究。对于这两个物种，估计了花粉粒的丰度和花药及其结缔腺的大小。承认三种类型的雄蕊：雄蕊小，中花药和大花药。这两个物种的花药在结缔组织中表现出相似的腺体组织，组织化学分析表明它产生粘液分泌物。花药壁发育、染色和花粉粒释放的模式在不同的花药类型中是相同的。对于这两个物种，我们观察到花药大小与花粉粒丰度之间存在正相关关系，但小花药与中花药和大花药的花药面积与结缔腺大小（面积和厚度）之间呈负相关。我们的结果证明了花药的特殊化与两种柱状花中异形雄蕊之间的分工有关。因此，一组花药产生大量用于授粉的花粉粒，而另一组产生大量粘液，这将改善花粉运输（更好地附着在传粉者身上和保持湿度）。尽管如此，这两种柱状花属物种的异种优势将代表一种向分工过渡的过渡状态，而不是一种稳定状态。