Structure and development of the elaiosome in Myrtus communis L. (Myrtaceae) seeds

Myrtus communis L. (Myrtaceae) is a fleshy-fruited shrub occurring in the Mediterranean area, whose seeds are snail shaped, with a very thick coat and a central elaiosome. This structure is a fleshy and edible appendage responsible of seed dispersal by ants, a phenomenon known as myrmecochory. The elaiosome develops very early from the external integument cells near the funicular and micropylar area, through cell enlargement and cell divisions. At the latest stages of development, some internal integument cells participate to its formation so that myrtle elaiosome can be classified among those originating from both epidermal and inner tissues. The low content of lipids, starch and proteins revealed by histochemical and biochemical analyses on M. communis elaiosomes suggests that the myrtle is a plant with a multiple pattern of seed dispersal. Myrmecochory seems to play a secondary role.