Agamospermy is much more common than conceived: A hypothesis

Abstract

This study supports the hypothesis that agamospermy in general and casual agamospermy in particular occur in many plant species. Direct and indirect tests have been applied on multi-seeded species of the Cuscutaceae, Orobanchaceae (both families of holoparasites), and the Apiaceae. The results show that many of the species did manifest agamospermy, to various degrees: Fruits and seeds were formed from pistils with pre-cut stigmas, the number of seeds exceeded by far the number of microgametophytes, and some mature fruits with seeds did not have pollen tubes. It is therefore assumed that most plants do have the potential to experience at least occasional agamospermy (termed as "casual agamospermy"). The evolutionary implications of casual or facultative agamospermy in opportunistic plants and higher parasitic plants are briefly discussed.