Timing of Morphological and Histological Development in Premeiotic Anthers of Nicotiana tabacum cv. Xanthi (Solanaceae)

Abstract

The tobacco stamen has been the object of many developmental studies, and the organ has more recently become a model for molecular genetic studies of anther differentiation. However, the spatial and temporal details of cellular differentiation of early anther development have never been thoroughly characterized. In the present study, the age of 15 tobacco flowers from plants grown under constant light and temperature was estimated using growth analysis. Prior to tissue fixation for light microscopy, moulds of stamen and anther primordia were made with a dental impression polymer so morphological and histological observations could be made on each tissue sample. Flower ages spanned an 8-d interval during which petal and stamen initiation occurred, and sporogenous cells reached the leptonema stage of meiosis. The initial development of the tetrasporangiate anther shape largely preceded periclinal division of archesporial initials. Anatomically, periclinal divisions in the hypodermal ∗∗∗(l2) layer were observed before archesporial initials began to divide. These data indicate differences in the cellular basis of tobacco anther development compared to earlier clonal analyses of Datura. The pattern of mitotic cell division associated with microsporangial development suggested modal peaks in division over time. The ability to estimate developmental time in the tobacco anther has implications for future studies directed at understanding mechanisms of anther evolution via heterochrony.