ANTHER STRUCTURE AND POLLEN DEVELOPMENT IN SPECIES OF RUBIACEAE AND ANATOMICAL EVIDENCE OF PATHWAY TO MORPHOLOGICAL DIOECY

JUDKEVICH, M.D.; SALAS, R.M.; GONZALEZ, A.M.

ANAIS DA ACADEMIA BRASILEIRA DE CIENCIAS.

ACAD BRASILEIRA DE CIENCIAS

Lugar: Rio de Janeiro; Año: 2022 vol. 93

0001-3765

We conducted anatomical analysis of anthers with the aim to establish the differences in the development pattern of microsporophytes and microgametophytes between bisexual perfect and unisexual imperfect flowers in the tribe Gardenieae (Rubiaceae). The species studied were: Tocoyena formosa (hermaphrodite monoecious with bisexual perfect flowers), Cordiera concolor, Genipa americana, Randia calycina, and Randia sp. (dioecious with unisexual imperfect flowers). Flowers in successive stages of development were collected and fixed. The material was processed and examined using optical light microscopy and scanning electron microscopy. The present study revealed the stage when pollen is arrested in the functionally female pistillate flowers of the dioecious taxa. Based on these observations an evolutionary sequence of changes towards thereduction of non-functional anthers in Rubiaceae is proposed. In addition, we describe and discuss characters that might be of importance in future phylogenetic studies in Rubiaceae (e.g. pollen morphology and its dispersal unit, the presence of orbicules, and a new type of placentoid).