Complex exudates in inflorescences of Vriesea species reveal evidence of lipophilic secretions by scales of bromeliads

• Published in: Flora. Morphologie, Geobotanik, Oekophysiologie Geobotanik, Oekophysiologie, 2023-03, Vol.300, p.152228, Article 152228
• Main Authors: Ballego-Campos, Igor, Forzza, Rafaela C., Paiva, Élder A.S.
• Format: Article
• Language: English
• Subjects: Bromeliaceae; Colleter; Peltate trichome; Plant-environment interactions; Resin; Terpenoid
• ISSN: 0367-2530; 1618-0585
• DOI: 10.1016/j.flora.2023.152228

•Secretion of lipophilic substances is revealed for the first time in the typical peltate trichome of bromeliads.•The exudates comprise complex mixtures with lipophilic and hydrophilic phases.•Secretory products are likely related with protection against biotic/abiotic stressors. Trichomes are a key feature of bromeliads. These structures absorb water and minerals, potentially constituting an important element in plant-environment interactions. Recent studies have shown a glandular function associated with mucilage-secreting scales in inflorescences of bromeliads. During a prospective study of secretions in bromeliad inflorescences, we observed the presence of an oily exudate in three species of Vriesea sect. Xiphion. To verify whether scales in bromeliads can produce lipophilic secretions, we investigated the secretory activity in these species to identify the source and chemical nature of the secretions which spread over the inflorescences. We used standard methods of histochemistry, light, and electron microscopy applied to samples of floral bracts in two distinct phases of development. The secretions comprised hydrophilic and lipophilic substances secreted by trichomes on the adaxial side of bracts. The exudate was heterogeneous in V. aff. bituminosa and V. fenestralis, with a lipophilic phase composed of terpenoids and lipids. Vriesea aff. bituminosa also presented alkaloids. In V. platynema var. rosea, the lipophilic content was lipids. The secretory activity was restricted to the early stages of organ development and might be characterized by a temporal disjunction between the secretion of hydrophilic and lipophilic contents. The functions of the exudate seem to include protection against herbivores but might also relate to protection against pathogens, water loss and high irradiance. The secretion of lipophilic substances by the typical peltate trichome of bromeliads was reported here for the first time.