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

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.

Morphological investigation of glandular hairs on Drosera capensis leaves with an ultrastructural study of the sessile glands

Electron and light microscopy were employed to elucidate the types of glandular hairs on Drosera capensis L. leaves. Eight types of stalked and sessile hairs were found. One type of long-stalked red hair is present only along the margin of the adaxial surface of the leaf, and five types of short-stalked hairs exist mainly on the central part of the adaxial surface of the leaf. Two types of sessile glands are abundantly distributed on both the adaxial and abaxial leaf surfaces. The sessile glands of two head cells are described for the first time in D. capensis, and the sessile glands of four head cells are illustrated for the first time in the genus Drosera. The presence of a secretion from the two head cells of the sessile glands and the dark large vesicles inside them suggests a secretory function. Numerous wall ingrowths are present in the outer tangential and radial cell walls of the head cells of the sessile glands, increasing the surface area to facilitate mucilage secretion.

Observaciones micromorfológicas y anatómicas en núnulas de Prunella L. y Cleonia L. (Lamiaceae) del suroeste de España.

RESUMEN.Observaciones micromorfológicas y anatómicas en núnulas de Prunella L. y Cleonia L. (Lamiaceae) del suroeste de España. Se han estudiado las núculas de tres especies del género Prunella y una del género Cleonia, tanto al microscopio óptico como al electrónico de barrido. Los taxones de ambos géneros se diferencian fácilmente tanto mediante caracteres morfológicos como el contorno o la ornamentación, como por caracteres anatómicos como la morfología de las células esclerenquimáticas del mesocarpo. La excreción del mucílago también contribuye a esta diferenciación. Otros caracteres como el color, la presencia o ausencia de glándulas, o algunas diferencias en el mesocarpo o endocarpo permiten diferenciar las tres especies examinadas del género Prunella. Por último, se discute brevemente la utilidad del mucílago, así como los sistemas de dispersión más frecuentes.Palabras clave. Núcula, morfología, anatomía, mucílago, Prunella, Cleonia, LamiaceaeABSTRACT. Micromorphological and anatomical observations on nutlets of Prunella L. and Cleonia L. (Lamiaceae), from the SW of Spain. The nutlets of three species of Prunella and another of Cleonia have been studied with light and scanning electron microscopy. The taxa of both genera can be easily differentiated through both morphologic features, such as the outline or the ornamentation, and anatomic features as the morphology of mesocarp’s sclerenchymatic cells. The mucilage secretion also contribute to this differentiation. Other features such as colour, presence/absence of glands, or some differences in the mesocarp or in the endocarp allow to distinguish the three examined species of genus Prunella. Lastly, the usefulness of mucilage and the most frequent dispersal systems are briefly discussed.Key words. Nutlet, morphology, anatomy, mucilage, Prunella, Cleonia, Lamiaceae