All land plants display alternating multicellular generations – the sexual, haploid gametophyte and the asexual, diploid sporophyte.
In early land plant fossils the gametophytic and sporophytic generation share about equal morphological complexity, making it likely that the gametophyte was reduced and the sporophyte became the dominant generation in vascular plants  while in “bryophytes” (mosses, hornworts and liverworts) the sporophyte generation was reduced and the gametophyte became dominant.
In total, 199 genes, (26%) belong to these categories.
Genes of biological process categories that are under-represented within the genome duplication peak are "protein biosynthesis", "organelle organization and biogenesis", "cytoskeleton organization and biogenesis" and "cytoplasm organization and biogenesis".
 based on the calibration of molecular clocks for eudicots.Sequences that were evolving too fast or too slow were removed, after which linearized trees, in which branch lengths are directly proportional to time, were constructed for each gene family [. dating danmark Tønder As can be clearly observed, a majority of the gene duplicates seem to have been created between 30–60 MYA (average 45 MYA), indicating that a large-scale gene duplication or a whole-genome duplication is indeed likely to have occurred around this time.For example, genes involved in signal transduction and transcriptional regulation were preferentially retained after the three whole genome duplication events within the ancestor of ] and compared to the associations of an equally sized random sample.The biological process categories "biosynthesis" and "generation of precursor metabolites and energy" are significantly over-represented (q ).
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Angiosperms (flowering plants) are paleopolyploids, i.e. the genome of their common ancestor was subject to a large-scale or even genome-wide duplication event during the Late Jurassic or Early Cretaceous, 100–160 MYA .There is evidence for several more large-scale or genome-wide duplication events among the angiosperms.The moss underwent polyploidization during the Eocene, potentially becoming hermaphroditic through this process. However, subsequently the plant became functionally haploid again (haploidization) while keeping the duplicated chromosomes.However, these substitution rates have to be interpreted with caution, since there are many theoretical and empirical concerns about the accuracy of molecular clocks and the rate of substitutions in different lineages.
Some of the major issues are rate heterogeneity in and between lineages caused by evolutionary factors (e.g.
Genome duplication, due to its effects on gene regulation and developmental processes, might also be a foundation for speciation and adaptation through genetic divergence in plants .
In the case of the haploid “bryophytes”, however, other effects appear more relevant.
The allopolyploidization of dioecious gametophytes might yield a monoecious plant (thus rendering the dispersal of breeding populations easier).
A second advantage might be that the duplication of the genome would free the formerly haploid plant from the necessity to preserve the function of crucial single copy genes under all circumstances, thus enhancing the potential for development of new functions.