Floral Morphology and Organogenesis in Tinantia pringlei, Along with a Review of Floral Developmental Variation in the Spiderwort Family, Commelinaceae

Abstract

Floral organogenesis had previously been investigated thoroughly in 11 species from three of nine subtribes or their equivalent in the Commelinaceae. Here flower morphology and development is described from a member of a fourth subtribe, Tinantia pringlei from the Thyrsantheminae, and comparisons are made. Although the calyx is only weakly monosymmetric at maturity, development is of the monosymmetric-type known from or resembling that of the monosymmetric flowers of Cochliostema, Dichorisandra, and Plowmanianthus (subtribe Dichorisandrinae; tribe Tradescantieae) and Commelina (tribe Commelineae). Whereas the corolla also is weakly monosymmetric at maturity, development is of the polysymmetric-type known from the polysymmetric flowers of Callisia, Gibasis, and Tradescantia (subtribe Tradescantiinae). In the androecium, the long, inconspicuous blue stamens of the lower floral hemisphere emerge first during development, while the shorter, showy yellow, upper stamens emerge last. The overall pattern of stamen development is centripetal, thereby resembling that reported for the majority of confamilial taxa, and contrasting with the centrifugal pattern known from Callisia and Tradescantia. Relative to the majority of confamilial taxa investigated, the carpels emerge relatively late in development, resembling the timing known for the carpels of Callisia and Tradescantia. Overall, however, carpel emergence in Tinantia pringlei is unique in the comparatively small size of the remnant floral apical primordium on which the carpels emerge. Other variations in floral development are discussed and further such studies within the family are encouraged based on the potential for using such developmental variations in the assessment of morphological homologies and phylogenetic relationships within the Commelinaceae.