Pollen development and orbicule and pollen grain morphology in species of Cephalanthus (Rubiaceae-Naucleeae) from the Americas

MARÍA FLORENCIA ROMERO; ROBERTO SALAS; ANA MARIA GONZALEZ

Congreso; VII International Rubiaceae and Gentianales Conference; 2017

This paper is the first embryological report on the genus Cephalanthus L. and contributes tofuture studies in other genera of the tribe Naucleeae. The development of the anther wall inCephalanthus glabratus (Spreng.) K. Schum. corresponds to the dicot type andmicrosporogenesis is simultaneous. The young wall of the anther has four layers; epidermis,endothecium, one middle layer and the secretory tapetum. The tissue of the septum hasidioblasts with crystalline sand. In the wall of the mature anther, only the endothecium andremnants of epidermal cells were preserved. The occurrence and morphology of orbiculeswere observed in the mature anthers of all three species of Cephalanthus with scanningelectron microscopy. The orbicules have taxonomic value at species level, since thesestructures allow us to distinguish between the species analyzed. The presence of a protrudingoncus was observed for the first time in Cephalanthus in non-acetolysed pollen grains.According to our observations, this structure is not affected by the state of anther dehiscencein C. glabratus, because the oncus is visible and prominent in the mature pollen grains in bothindehiscent and dehiscent anthers. Several authors have described that pollen grains in theNaucleeae tribe are always released in monads, we find permanent tetrads in C. glabratus andmonads, but in a smaller proportion. This finding represents the first record for this speciesand the Naucleeae tribe.