Changes in sclerenchyma cell walls related to stem twining in Dioscorea balcanica

Abstract

Dioscorea balcanica Košanin, family Dioscoreaceae, is an endemic, endangered liana species and a Tertiary relict of Balkan Peninsula. Gelatinous fibers, specialized sclerenchyma cells and well-known components of tension wood, are responsible for stem twining in liana plants. The aim of this investigation was to determine changes in sclerenchyma cell walls correlated with the twining process in liana plants. Our results showed that the differences in cell walls of sclerenchyma cells between straight and twisted internodes are not visible by light microscopy, but they are visible by SEM microscopy. In twisted internodes, cell walls of sclerenchyma cells in the region of contact with the support (‘‘tension’’ side of twisted internodes) appear smooth on the cross sections, suggesting cellulose microfibrils oriented almost parallel to the fiber axis. In contrast, cell walls of the entire ring of sclerenchyma cells in straight internodes, as well as cell walls of sclerenchyma cells on the “opposite” side of twisted internodes, appear jagged on the cross sections, suggesting cellulose microfibrils oriented at very high microfibril angle to the fiber axis. This result suggests that gelatinous fibers in D. balcanica stem have lignified G-layer, and thus could contribute to the understanding of ‘‘late lignification of the G-layer’’.