Structure and function of the elaiosome in some angiosperm species

Abstract

Summary The structural and functional characteristics of the elaiosomes were studied in various angiosperm species. The elaiosome varies widely in relation to its anatomical origin, and always contains lipid reserves, sometimes accompanied by starch and proteins. In Chelidonium majus the elaiosome originated from raphe cells, whereas in Mercurialis annua and Ricinus communis , it arose from the external integument of the seed in the form of an appendage in the micropyle area. In Ricinus communis the parenchyma cells are larger and have walls with pectin thickenings interrupted by pits. The elaiosome contributes little (4-9%) to the total seed weight. On the other hand, the elaiosome caloric content is high, constituting about a third of the total energy content of the seed. The role of elaiosome is well known in the myrmecochorous dispersal. However, we have seen in the species studied that elaiosomes have also other functions: i) facilitation of dehydration and hydration of the seed, especially when the cuticle is thin ( Chelidonium majus ) or absent ( Ricinus communis ); ii) induction of seed dormancy ( Calendula arvensis, Euphorbia cyparissias and Mercurialis annua ); iii) water reserve by absorbing water from the soil and transferring it to the rest of the seed during germination ( Ricinus communis ).