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Three of these independent gametophyte cells degenerate and the one that remains is the gametophyte mother cell which normally contains one nucleus. [24] In general, it will then divide by mitosis until it consists of 8 nuclei separated into 1 egg cell, 3 antipodal cells , 2 synergid cells , and a central cell that contains two nuclei.
Prothallus of the tree fern Dicksonia antarctica (note new moss plants for scale) Spore-bearing plants, like all plants, go through a life-cycle of alternation of generations. The fully grown sporophyte, what is commonly referred to as the fern, produces genetically unique spores in the sori by meiosis.
Each male gametophyte typically consists of two to four cells enclosed within the protective wall of a pollen grain. The sporophyte of a flowering plant is often described using sexual terms (e.g. "female" or "male") based on the sexuality of the gametophyte it gives rise to. For example, a sporophyte that produces spores that give rise only to ...
Within each ovule, a megaspore develops by mitosis into a megagametophyte. An archegonium develops within the megagametophyte and produces an egg. The whole of the gametophytic generation remains within the protection of the sporophyte except for pollen grains (which have been reduced to just three cells contained within the microspore wall).
The gametophyte of ferns is a free-living organism, whereas the gametophyte of the gymnosperms and angiosperms is dependent on the sporophyte. The life cycle of a typical fern proceeds as follows: A diploid sporophyte phase produces haploid spores by meiosis (a process of cell division which reduces the number of chromosomes by a half).
The gametophyte is the multicellular structure (plant) that is haploid, containing a single set of chromosomes in each cell. The gametophyte produces male or female gametes (or both), by a process of cell division, called mitosis. In vascular plants with separate gametophytes, female gametophytes are known as mega gametophytes (mega=large, they ...
Heterospory stops self-fertilization from occurring in a gametophyte, but does not stop two gametophytes that originated from the same sporophyte from mating. [8] This specific type of self-fertilization is termed as sporophytic selfing, and in extant plants it occurs most commonly among angiosperms .
Flowchart depicting the phenomenon discovered in Ceratoperis richardii in which antheridiogen exposure influences the growth of a gametophyte starting in its very early stages. The way in which antheridiogen determines sex in ferns is a "spatiotemporally split gibberellin synthesis pathway". [ 7 ]