The endosperm of a rare tree endemic to Chile, Gomortega keule, has two parts with different chemical composition

Abstract

ABSTRACT‘Queule’ (Gomortega keule) is an endemic and endangered Chilean tree belonging to the monotypic family Gomortegaceae. Inside its edible fruit the usually single seed has an oily endosperm divided in two distinctive parts; this represents a unique organisation of storage tissue in angiosperm seeds. Since this trait has not been previously reported in literature, this study aimed to describe both parts of the storage tissue and to identify the presence of lipid, starch and protein. Seeds were observed using the paraffin method and handmade slices. Specific dyes were applied to identify chemical compounds. Oil content was quantified in both parts of the endosperm. Additionally, seed and embryo size were measured from endocarps collected from the forest floor during an 8 month period. Increased embryo size and absence of germination suggest morphological dormancy. Histological slices showed abundant and larger starch grains in the inner part of the endosperm, and lower presence of proteins compared to the outer part. In terms of oil content, the inner part of the endosperm contained 27% (w/w fresh weight), the embryo 22% and the outer part 20%. Although both parts of the storage tissue are notoriously different, both belong to the endosperm. The presence of oil, proteins and starch in the storage tissue may provide ecological advantages for seedling establishment.