Cytological Observations in Citrus: III. Megasporogenesis, Fertilization, and Polyembryony

Abstract

A general review is presented of megasporogenesis, fertilization, endosperm formation and polyembryony in Citrus, most of the findings of Strasburger and Osawa having been confirmed through investigation of C. paradisi and C. aurantium. A new form of polyembryony is presented, caused by the existence in some instances of 2 gametophytes in the same ovule. The origin of 2 non-identical hybrids from the same seed is thus explained. 3 forms of polyembryony are therefore known in Citrus: a) nucellar embryony, giving rise to a variable number of identical "maternal" seedlings derived from the nucellus; b) cleavage polyembryony originating through fission of the generative embryo; and c) polyembryony caused by the occurrence of more than one normal gametophyte in the same ovule. The endosperm in Citrus is free.