Comparative anatomy of the fig wall (Ficus, Moraceae)

Abstract

The genus Ficus is unique in that it has a closed inflorescence (fig) holding all of the flowers inside its cavity, which is isolated from the outside world by a fleshy barrier: the fig wall. The fig wall is the main structure of the fig, giving its shape, but the wall has also important ecological functions such as protection of fig seeds and fig wasp larvae. Nevertheless, the fig wall anatomy is poorly understood. This study aims to examine the fig wall anatomy of 22 Ficus taxa (21 species, one species having two varieties) in Taiwan to reveal the diversity in anatomy of the fig wall. We found that these 21 fig species exhibited a great variety in fig wall anatomy, from the simplest parenchymatic wall to complex fig walls. The walls of the figs from 12 sampled taxa developed aerenchyma and sclerenchyma formations whereas seven taxa had fig walls containing tanniferous cells. Five anatomical types of fig walls have been identified according to the presence or absence of the different differentiated tissues. These types are distributed among the Ficus subgenera. Further studies on tissue differentiations of the fig wall should be investigated in other Ficus species as well as the ecological functions of the fig wall.