Bromeliaceae display many water-use strategies, from leaf impounding tanks to CAM photosynthesis and absorbing trichomes. Recent studies show that trichomes in inflorescences of bromeliads can exude viscous secretions, protecting against various stresses, including excessive water loss. In light of this, and considering the knowledge gap regarding inflorescence trichomes in bromeliads, we aimed to investigate the presence, source, and chemical nature of inflorescence secretions in species of the Tillandsioideae (Bromeliaceae) and to describe the anatomy of their floral bracts focusing on trichome structure and position.We conducted a prospection of secretory activity and anatomy in floral bracts in 52 species of Tillandsioideae and one early-divergent Bromeliaceae species. We used histochemical tests to investigate the presence and nature of secretion combined with standard light microscopy methods. Secretion appears in all studied species of tribe Vrieseeae, in Guzmania species, Wallisia cyanea, Tillandsia streptopylla (Tillandsieae), and Catopsis morreniana (Catopsideae). It is absent in Vriesea guttata (Vrieseeae), Racinaea crispa, and various Tillandsia species (Tillandsieae). Secretion is produced by peltate trichomes on the adaxial surface of young bracts and comprises hydrophilic and lipophilic substances. Bract anatomy revealed an internal mucilage-secreting tissue with wide distribution within subtribe Vrieseinae. Our results point to a broad occurrence of secretion associated with bracteal scales in inflorescences of Tillandsioideae. Secretory function is strongly related to trichomes of the adaxial surface, whereas the indumentum of the abaxial side is lacking or likely associated with water absorption; the latter case is especially related to small, xeric plants. Exudates might engage in colleter-like roles, protecting against desiccation, high-radiation, and herbivores. Directions for future research are presented.

中文翻译：

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凤梨科（凤梨科）花苞片分泌的概述，重点是分泌鳞片

凤梨科植物表现出许多用水策略，从叶子蓄水池到 CAM 光合作用和吸收毛状体。最近的研究表明，凤梨科植物花序中的毛状体可以分泌粘性分泌物，防止各种压力，包括过度失水。鉴于此，并考虑到有关凤梨科植物花序毛状体的知识差距，我们旨在研究凤梨科（凤梨科）物种花序分泌物的存在、来源和化学性质，并描述其花苞片的解剖结构，重点是毛状体的结构和位置。我们对52种凤梨科植物和一种早期分化的凤梨科植物的花苞片的分泌活性和解剖结构进行了展望。我们使用组织化学测试结合标准光学显微镜方法来研究分泌物的存在和性质。分泌物出现在 Vrieseeae 部落的所有研究物种、Guzmania 物种、Wallisiacyeae、Tillandsia streptopylla (Tillandsieae) 和 Catopsis morreniana (Catopsideae) 中。它在 Vriesea guttata (Vrieseeae)、Racinaea Cripa 和各种空气凤梨属 (Tillandsieae) 中不存在。分泌物由幼苞片正面的盾状毛产生，包含亲水性和亲脂性物质。苞片解剖显示内部粘液分泌组织在 Vrieseinae 亚族内广泛分布。我们的结果表明，铁兰科花序中广泛存在与苞片相关的分泌物。分泌功能与近轴表面的毛状体密切相关，而远轴侧的毛被缺乏或可能与吸水有关；后一种情况尤其与小型旱生植物有关。渗出物可能起到类似收集器的作用，防止干燥、高辐射和食草动物。提出了未来研究的方向。