New findings to be be published online this week in the Proceedings of the National Academy of Sciences help resolve long-debated questions about the origin and evolution of land plants. …
Qiu’s group used three complementary sets of genetic data, involving more than 700 gene sequences, to resolve relationships among the four major lineages of land plants: liverworts, mosses, hornworts and vascular plants (which include ferns, pines and flowering plants).
Their analysis showed that liverworts—tiny green, ribbon-like plants often found along river banks—represent the first lineage that diverged from other land plants when charophyte algae first came onto land, and an obscure group called hornworts, often found in abandoned cornfields, represents the progenitors of the vascular plants.
Cretaceous fossil trees from North America: here.
Plant evolution: here.
A collaborative research group has succeeded in identifying an important transcription factor, GCAM1, which allows liverwort plants to asexually reproduce through creating clonal progenies (vegetative reproduction). Furthermore, this transcription factor was revealed to have the same origin as those which regulate secondary bud formation in angiosperms. That this transcription factor was found in liverwort suggests that it was an important ancient development in the common ancestor of land plants at least 430 million years ago: here.