Structure and histochemistry of the stigmatic and transmitting tissues of Rodriguezia venusta (Orchidaceae) during flower development

Abstract

Stigma and transmitting tissue are floral structures essential for sexual reproduction of angiosperms and can be useful features in taxonomic studies. Rodriguezia venusta (Lindl.) Rchb. f. is an epiphytic orchid belonging to the large subfamily Epidendroideae. The present study describes the structure and histochemistry of the stigmatic and transmitting tissues of R. venusta during flower development. The differentiation and the secretory activity of the stigmatic and transmitting tissues are already visible in the initial stages of development of the flower bud studied. These tissues, which have a reticulated appearance, predominantly secrete mucilaginous material that is accumulated in the intercellular spaces. The stigma is covered by a cuticle that extends over the internal surface of the central canal in the transmitting tissue in this apical portion. In the stigma, the cuticle appears to have micropores, and in the intercellular spaces, there are small spherical bodies that stain for lipids, proteins and total carbohydrates. The functions of these bodies still remain unknown.