JUDD W.S. Et. Al. (1999) Plant Systematics
CHAPTER8 Phylogenetic Relationships of Angiosperms he angiosperms (or flowering plants) are the dominant group of land Tplants. The monophyly of this group is strongly supported, as dis- cussed in the previous chapter, and these plants are possibly sister (among extant seed plants) to the gnetopsids (Chase et al. 1993; Crane 1985; Donoghue and Doyle 1989; Doyle 1996; Doyle et al. 1994). The angio- sperms have a long fossil record, going back to the upper Jurassic and increasing in abundance as one moves through the Cretaceous (Beck 1973; Sun et al. 1998). The group probably originated during the Jurassic, more than 140 million years ago. Cladistic analyses based on morphology, rRNA, rbcL, and atpB sequences do not support the traditional division of angiosperms into monocots (plants with a single cotyledon, radicle aborting early in growth with the root system adventitious, stems with scattered vascular bundles and usually lacking secondary growth, leaves with parallel venation, flow- ers 3-merous, and pollen grains usually monosulcate) and dicots (plants with two cotyledons, radicle not aborting and giving rise to mature root system, stems with vascular bundles in a ring and often showing sec- ondary growth, leaves with a network of veins forming a pinnate to palmate pattern, flowers 4- or 5-merous, and pollen grains predominantly tricolpate or modifications thereof) (Chase et al. 1993; Doyle 1996; Doyle et al. 1994; Donoghue and Doyle 1989). In all published cladistic analyses the “dicots” form a paraphyletic complex, and features such as two cotyle- dons, a persistent radicle, stems with vascular bundles in a ring, secondary growth, and leaves with net venation are plesiomorphic within angio- sperms; that is, these features evolved earlier in the phylogenetic history of tracheophytes.
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