Developmental synchronization of male and female gametophytes in Ginkgo biloba and its neck mother cell division prior to fertilization

Abstract

This study investigated male and female gametophytes in Ginkgo biloba, while a droplet of fluid was present in the fertilization chamber and found that the central cell, the generative cell and the neck mother cell divided simultaneously prior to fertilization. In male gametophytes, the generative cell divided to yield two sperm cells. Concomitantly, the two neck mother cells of the archegonium increased in size then divided asymmetrically resulting in two big cover cells and two small base cells. Each cell had a fixed end in direct contact with an adjacent jacket cell and a free end overlapping its counterpart. This unique arrangement could allow for their free ends to swing into the fertilization chamber as a result of the force from the interior of the archegonium where a polar periclinal division had occurred to produce a canal cell and an egg. The subsequent withdrawal of the content of the archegonium may facilitate the entry of sperm into the archegonium. The neck apparatus closed after the fertilization occurred. The concurrence of the above divisions and the delicate structure of neck apparatus suggest that the gametophytes undergo a synchronization process to become receptive at the time of fertilization. However, the formation of neck cells and the opening time of neck apparatus of the archegonia within the same ovule were slightly different, which could lead to the formation of zygotes at a temporally distinct interval. The earlier formed zygote may progress as the only mature embryo in the ovule.

Changes in Seed Germination Ability, Lipid Peroxidation and Antioxidant Enzyme Activities of Ginkgo biloba Seed during Desiccation

“…The process from pollination to fertilization takes approximately 120 days [4][5][6]. Mature seeds have a large thousand kernel weight, and are composed of fleshy sarcotesta …”

Composition of Sexual Fluids in Cycas revoluta Ovules During Pollination and Fertilization

“…These megagametophyte-derived fluids are produced in cycads (Chamberlain 1910;Lawson, 1926;Takaso et al, 2013) and Ginkgo biloba (Hirase, 1898;Lee, 1955;Friedman, 1987). Archegonia-derived fluids are known from both clades (Herzfeld, 1927;Takaso et al, 2013;Zhang et al, 2013). In conclusion, during zoidogamous reproduction there are stages in which the female produces complex sexual fluids that regulate the male.…”

“…In cycads and in Ginkgo biloba this material lies in the immediate vicinity of the archegonium at the bottom of archegonial chambers. This rope-like flocculent mass has been referred to as an “egg projection” (Lee, 1955 ), a “protrusion” (Wang et al, 2014 ) and a “fertilization droplet” (Zhang et al, 2013 ). Similar to what we found in C. revoluta , Lee ( 1955 ) noted in Ginkgo biloba that the material is ejected into liquid already present in the archegonial chamber.…”

Morphological Characteristics, Ultrastructure, and Chemical Constituents of the Endotesta in Ginkgo (Ginkgo biloba L.)

“…Subsequently, the macrospore membrane underwent gradual disintegration and degradation. This transformation was facilitated by the growth of primordial neck cell divisions within the female gametophyte, the emergence of tent columns, the formation of bead core tissue enveloping tent columns, and interactions with the macrospore membrane [27][28][29][30][31].…”