Anther Ontogeny and Microsporogenesis in <i>Helianthus annuus</i> L. (Compositae)

Abstract

In this study, anther ontogeny and microsporogenesis were analysed in Helianthus annuus L. The undifferentiated anther is ovoid-shaped and the differentiation starts with the appearance of archesporial cells. Mature anthers are tetrasporangiate. The anther wall is composed of epidermis, endothecium, middle layer and plasmodial tapetum. Endothecial cells show no fibrous thickening. Tapetum is amoeboid type with binucleate cells. Epidermal layer remains intact until anther dehiscence; however, middle layer, endothecium and tapetum disappear during development. At the end of regular meiotic division tetrahedral microspore tetrads are formed. Pollen grains are triporate, suboblate and angulaperturate.