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The main, ultimate, gamete-bearing stage in the haploid (n chromosomes) phase of a taxon's life cycle. Two morphologically and genetically distinct and alternate stages together constitute the complete life cycle in sexually reproducing taxa, the other phase (sporophytic) being diploid (2n chromosomes). Any taxon whose life cycle is confined to one or the other phase is limited to asexual means of reproduction, since sexual reproduction and consequent genetic recombination are impossible without alternation between haploid and diploid states via meiosis and fertilization. The term gametophytic applies to any part of the haploid phase, including all unicellular to multicellular entities belonging to it, whereas gametophyte is reserved for the principal and directly gamete-producing stage of that phase. In all vascular plant taxa the sporophyte is the dominant and most conspicuous phase of the life cycle. The gametophytes of "lower" vascular plants (ferns and "fern-allies") are physically independent of the sporophytes and, though inconspicuous, merit description in their own rights. Those of gymnosperms and angiosperms are minute and physically dependent upon (contained within) sporophytic structures and are not usually included in morphological descriptions. In the flowering plants at least, the haploid phase is (presumably evolutionarily) reduced to such a degree that the existence of gametophytes per se is debatable.
[1]The given value was not understood.
The given value was not understood.
Example(s): Example sentences from FNA : [1] female gametophyte tissue slightly wrinkled, not ruminate. [2] female gametophyte tissue deeply ruminate within.
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References
- ↑ Categorical Glossary for the Flora of North America Project, by Robert W. Kiger and Duncan M. Porter. 2001. Hunt Institute for Botanical Documentation.
