Seed germination of Ricinus communis in predicted settings after autochorous and myrmecochorous dispersal1

Abstract

Seeds of Ricinus communis are primarily dispersed by autochory and secondarily dispersed by ants, which are attracted to their lipid-rich elaiosome. The aim of this study was to determine how the conditions to which Ricinus seeds are submitted after these two types of dispersal affect their germination. We examined the germination responses of freshly harvested and one-year-old seeds to combinations of light (present or absent), temperature (alternating or constant), and elaiosome (present or absent). We also checked the soil for persistent seed banks. The seeds presented different germination responses but germinated in all conditions to which they were submitted. More specifically, germination of fresh seeds was higher in the environmental conditions to which they are submitted after being dispersed by ants, although seeds with elaiosome germinated in greater number. Germination of old seeds was not enhanced in alternating temperatures and/or presence of light, as would be expected for seeds that make up persistent soil seed banks. This, and the fact that we found only a few viable seeds in the soil, indicates that Ricinus does not form seed banks. Nevertheless, we observed massive seedling emergence after soil disturbance and, therefore, the existence or not of seed banks is not yet clear and deserves further investigation. This study shows that the generalist germination behavior of Ricinus seeds guarantees that they germinate under various environmental conditions.