More than Scales: Evidence for the Production and Exudation of Mucilage by the Peltate Trichomes of Tillandsia cyanea (Bromeliaceae: Tillandsioideae)

Abstract

Bromeliad scales have been investigated extensively due to their recognition as a key ecological and evolutionary feature of Bromeliaceae. However, much remains unknown about such trichomes and only recently mucilage exudation was described for them in a species of the subfamily Bromelioideae. The present study aimed to investigate the secretion present in inflorescences of Tillandsia cyanea Linden ex K. Koch (Tillandsioideae) to determine whether the scales of this species also produce and release secretions. Samples of young and mature portions of inflorescences were collected and prepared according to standard methods for light and electron microscopy. Anatomical and ultrastructural results indicate that the secretion is produced by the wing portion of typical peltate trichomes on the adaxial surface of bracts. The secretory activity begins in the early stages of trichome expansion and characteristically occurs in cells exhibiting a porous cuticle and dense cytoplasm with numerous mitochondria and dictyosomes. Histochemical tests confirmed mucilage secretion and revealed proteins in the exudate. These data comprise the first record of mucilage exudation by trichomes within Tillandsioideae and indicate that this capacity may be more relevant to bromeliad biology than previously considered. Functional aspects and colleter-like activity are also discussed.

Functional Ecology of External Secretory Structures in Rivea ornata (Roxb.) Choisy (Convolvulaceae)

“…Nevertheless, the positive reaction of the ruthenium red test showed that the calycinal glands of R. ornata likely contain mucilaginous and hygroscopic substances, as was also found in Ipomoea cairica (L.) Sweet [ 26 ], and were defined as colleters (any of the morphologically diverse secretory organs functioning homologously in secreting mucilaginous or resinous fluids [ 13 ]). Based on the properties of the secreted substances, calycinal glands are believed to protect flower buds, from their development until fruiting, from desiccation and insolation [ 26 , 58 , 107 ].…”

Notes on the Newly Identified Asperula cankiriense B. Şahin & Sağıroğlu (Rubiaceae) from Turkey Based on a Light and Scanning Electron Microscopic Study

“…and reported differences in terms of floral tube, anther, and stigma length. Ballego-Campos et al (2020) predicted that dense secretion based on the presence of trichomes in the flower parts of Tillandsia cyanea Linden ex K. Koch (Bromeliaceae) contributes to the development of flower buds and the preservation of the delicate corolla structure. In this study, the hairs on the outer surface of the corolla tube and the corolla lobes may have taken on the task of protecting the sensitive corolla.…”

Phylogenomics of Puya (Bromeliaceae): Evolution in the Andean slopes and sky island ecosystems

“…The leaves of bromeliads are commonly covered with specialized peltate trichomes capable of absorbing water and nutrients that, in some cases, can replace the absorptive function of the roots (Benzing, 2000). The presence and density of these trichomes on leaf blades might reflect different adaptations to water and nutrient intake (Givnish et al, 1984; Martin, 1994; Benz & Martin, 2006), as well as other functions, like light reflectance and secretion of mucilage (Benzing et al, 1985; Benzing, 2000; Ballego‐Campos et al, 2020). To capture this variation, we coded this trait as glabrous to glabrescent (state 0) and clearly covered with peltate scales on either side of the blade (state 1).…”