Development of corded vascular cylinder in Thinouia restingae Ferruci & Somner (Sapindaceae: Paullinieae).
Journal of the Torrey Botanical Society
The Paullinieae tribe (Sapindaceae) has stems with structural variation highly specialized and unique to this tribe: divided vascular cylinder, compound vascular cylinder and corded vascular cylinder. In Brazil, these stems are used in wood marquetry. The present study is the first to explore the ontogeny of the corded stem through the analysis of Thinouia restingae, an endemic species in Brazil. A normal vascular cambium arises as a continuous cylinder and functions for a long time producing secondary phloem centrifugally and secondary xylem centripetally. New cambia are formed by the pericycle giving rise to the peripheral vascular cylinder. The variant cambia are circular and have cambial activity similar to the regular cambium. Morphologically, the corded type is similar to the compound type. However, while the ontogenesis and presence of pith is found in the compound type, these features are absent in the corded vascular cylinder. Overall, we found that the corded stem of Thinouia restingae differs from other cable structures present in Sapindaceae by its macromorphology, tissue structure, and developmental timing. The commercial importance of Sapindaceae wood gives our findings particular significance in that our study serves as a first step toward incorporating developmental data into the identification of the wood of lianas commercially.