Early fertilization events in the sexual and aposporous egg apparatus of Pennisetum ciliare (L.) Link

Abstract

While detailed descriptions exist on the fine structural characteristics of double fertilization in sexual angiosperms, few studies have described fertilization in apomictic species. The results of this study with buffelgrass ( Pennisetum ciliare (L.) Link syn= Cenchrus ciliaris L.) show that differences exist between the early fertilization events in sexual and apomictic (aposporous) female gametophytes. In unpollinated sexual female gametophytes, the egg cell did not show signs of parthenogenetic activity. In contrast, autonomous egg embryony was observed in unpollinated aposporous female gametophytes. Compared with the sexual genotype, degeneration of the synergids in the aposporous female gametophyte was precocious and rapid. During the first 4 h after pollination, the chalazal end of the sexually functional egg cell remained covered by the plasma membrane. In the aposporous embryo sac, a cell wall covered the plasma membrane of the egg cell several hours before penetration of the pollen tube into the female gametophyte.