Shoot and Inflorescence Architecture of the Neotropical Genus Sinningia (Gesneriaceae)

The neotropical genus Sinningia, comprising about 60 species, exhibits a vast diversity with regard to plant size and plant architecture. The size ranges from miniature rosette plants less than 5 cm high to 2-3 m tall shrubs. All species are perennial, the flowering shoots emerge either from an exposed or underground tuber or, less frequently, from a perennial basal shoot portion. Analysis of shoot and inflorescence architecture results in the recognition of c. 20 closely interconnected types which can be roughly categorised into 5 groups (A-E). Caulescent plants with a distinct vegetative region and a frondose, frondo-bracteose or bracteose florescence are considered to represent the central group (A) (e.g. S. schiffneri, S bulbosa, S. cochlearis). This is also the most prominent one with regard to species number. The frondose type, found in species of forest habitats with high rainfall and showing +/- continuous growth throughout the year, is perhaps the phylogenetically most primitive one in the genus. The other groups can be regarded as advanced or terminal points of development. They include rosulate or rosette species (B) (e.g. S. speciosa, S. pusilla), ‘verticillate’ plants with an elevated pseudowhorl of foliage leaves and several variants of inflorescence architecture (C) (e.g. S. douglasii), ‘candle-stick’ plants with extensive elongated, spicate florescence (D) (e.g. S. allagophylla), unifoliate plants with the shoots separated into bracteose floral shoots and very short vegetative shoots that develop only a single, large leaf (E) (e.g. S. tuberosa). Radiation of the partial-florescences (pair-flowered cymes) is considerable, relating to branching pattern, flower number (including frequent reduction to solitary flowers), bracteole presence and texture, presence of [gamma]-bracts, and length of peduncle and pedicels. Loss of front-flowers in the cymes apparently does not occur in the genus. Inflorescence characters are considered significant in ecological respects and form an important part of the pollination syndrome.