The pulvinus is the thickening at the base of leguminous plant leaves responsible for rapid or slow leaf movements. The structural characteristics of pulvini have usually been studied in plants with rapid leaf movements, especially Mimosa species and information on the pulvini of species with slow leaf movement is scarce. We investigated whether the anatomical characteristics of pulvini from a Mimosa species presenting slow nyctinastic leaf movements were different from those of the species in this genus with rapid leaf movements and if these structural aspects differed from those in the petioles. Primary and secondary pulvini and petioles of Mimosa caesalpiniifolia Benth. (Leguminosae, Caesalpinioideae) were cross and longitudinal sectioned and analyzed using a light microscopy. Calcium oxalate crystals were analyzed under polarized light. Histochemical tests were performed for detection of starch, phenolic compounds, polysaccharides, lignin and calcium oxalate. Primary and secondary pulvini had characteristics common to the pulvini of other legume species with different types of leaf movements, such as large parenchyma cortex, reduced vascular system and lack of lignification, which explains the pulvinus’ greater flexibility compared with the petiole. The petiole exhibited reduced cortex, peripheral vascular system and wide pith. Starch grains and calcium oxalate prismatic crystals were observed in the endodermis of pulvini and petioles. The detection of calcium oxalate crystals in the pulvinus endodermis of a Mimosa species is a novelty. However, this feature is common in pulvini with slow movements, corroborating the idea that the pulvinus endodermis content is related to the type of leaf movement, regardless of taxonomic considerations. Septate pericyclic fibers with pectocellulosic walls containing primary pit fields occurred in the pulvini and indicates symplastic communication between cortex and vascular cylinder; in the petiole, the pericyclic fibers were lignified. Internal phloem occurred in both the pulvini and petioles; this is uncommon in leguminous species and a novelty for this genus.

叶枕是豆科植物叶子基部的增厚部分，负责快速或缓慢的叶子运动。通常在叶片快速运动的植物中研究叶斑的结构特征，特别是含羞草物种，而关于叶片运动缓慢的物种的叶斑的信息很少。我们研究了含羞草属物种中表现出缓慢的夜间叶运动的pulvini 的解剖特征是否与该属中具有快速叶运动的物种不同，以及这些结构方面是否与叶柄中的不同。含羞草的初生和次生叶脉和叶柄本斯。（豆科、Caesalpinioideae）进行横向和纵向切片并使用光学显微镜进行分析。在偏振光下分析草酸钙晶体。进行组织化学测试以检测淀粉、酚类化合物、多糖、木质素和草酸钙。初生叶枕和次生叶枕具有与其他具有不同叶运动类型的豆科植物叶枕共同的特征，如薄壁组织皮层大、维管系统减少和缺乏木质化，这解释了叶枕比叶柄具有更大的灵活性。叶柄皮质、外围维管系统减少，髓部较宽。在叶枕和叶柄的内皮层中观察到淀粉粒和草酸钙棱柱晶体。含羞草物种是一个新奇物种。然而，这一特征在运动缓慢的枕叶属中很常见，这证实了枕叶属内皮层含量与叶子运动类型相关的观点，无论分类学考虑如何。枕骨处出现间隔的周环纤维，其果胶纤维素壁含有初级凹坑区，表明皮层和维管柱之间存在共生通讯；在叶柄中，周环纤维木质化。内部韧皮部出现在叶枕和叶柄上；这在豆科物种中并不常见，并且对于该属来说是新颖的。