ABSTRACT
The mode of reproduction in plants may be sexual, asexual, or by specialized vegetative structures. Sexual reproduction is a complex biological activities that facilitates genetic diversity and speciation. In flowering higher plants, the reproductive organs are in the flower. Meiosis and fertilization are two essential processes in the sexual cycle of higher plants. Sexual reproduction consists of two generations—sporophytic and gametophytic. The disruption of the sexual process may lead to apomixis. Apomictic plants of some species produce seed directly from chromosomally unreduced megaspore mother cells or from somatic cells of the nucellus or ovule without fertilization. In addition, several plants propagate by specialized vegetative structures like bulbs, corms, cuttings, runners, rhizomes, tubers, and by grafting. Development of unreduced embryo sacs is directly from the somatic cells located in the center of the nucellus. There may be multiple embryo sacs in an ovule but only one of them matures into an aposporous embryo sac.
