Flower and fruit anatomy of Cordia nodosa Lam. and Varronia bonplandii Desv. (Cordiaceae, Boraginales) with phylogenetic implications

Abstract

Despite their ecological importance and wide distribution, Cordiaceae have not been subject to detailed anatomical study yet. We examined flower and fruit anatomies of Cordia nodosa and Varronia bonplandii (using paraffin sectioning and light microscopy) in comparison with other woody members of Boraginales. The internal architecture of the superior bicarpellate ovary resulted from the development of secondary septa including apical, basal and false septa, as reported also from other Boraginales. Novel characters of Cordiaceae were identified such as an extensive tissue surrounding the gynoecium of C. nodosa and a lignified cap on top of the endocarp in V. bonplandii. Fruits containing a single seed may have originated several times independently in Cordiaceae deriving from the four-seeded condition present today in most other non-capsular Boraginales. Distyly of V. bonplandii does not appear genetically fixed but may result from different ecological conditions. Hemianatropous ovules are now considered the derived character state in Cordiaceae, originating from anatropous ovules present in other Boraginales. Studies like this improve the knowledge about generative organs in general and identify phylogenetically informative characters. However, better knowledge of functional morphology and ecological importance regarding many traits identified require further investigations on the diversity of Cordiaceae.