Survival and germination of three hard-seeded Acacia species after simulated cattle ingestion: The importance of the seed coat structure

Abstract

Endozoochory has been suggested as an important mechanism for long-distance plant dispersal that facilitates seed arrival to new and more favorable habitats. The hardness (mechanical strength) and thickness of the seed coat are important characteristics for seed survival and germination after passage through an herbivore gut. We studied the effects of seed passage through cattle gut on seed coat structure in three hard-seeded Acacia species that have physical dormancy, A. aroma, A. atramentaria and A. caven, occurring in the semiarid woodlands and shrublands of central Argentina. Histology of the seed coat was examined and a simulated cattle consumption experiment was conducted. Only A. aroma, which has the thinnest seed coat (in terms of epidermis and sclerified parenchyma) of the three species, showed a high germination percentage after seed passage through the digestive tract of cattle, whereas seeds of A. atramentaria and A. caven remained hard and viable. We conclude that the structure of the seed coat in hard-seeded species is crucial in determining the success of endozoochory.