An informal set of flowering plant orders that contains Laurales, Magnoliales, Piperales, and Winterales, plus the monocotyledons, and in total contains roughly one-third of angiosperm species. Formerly, many have equated this group (minus the monocotyledons) to the subclass Magnoliidae, but studies of sequences of deoxyribonucleic acid (DNA) have demonstrated that orders such as Nymphaeales and Ranunculales are distantly related to the others and that the monocotyledons are much closer. A formal taxonomy for this group is not yet feasible because until more data are collected the exact relationships of the eumagnoliids to the eudicots are not clear, and before formal names are proposed it is preferable to understand these taxa better. The eumagnoliids, including the monocotyledons, exhibit a set of characteristics that reflect their relatively close relationships; these include a tendency to trimerous flowers and a suite of chemical compounds restricted to the group. They also have a set of traits that are “primitive” by most estimations; these include vesselless wood, laminar stamens, and laminar placentation. It now seems quite clear that although the eumagnoliids exhibit some primitive traits they are neither the most archaic nor the earliest of angiosperms, and they contain some of the most advanced taxa, such as many of the monocotyledons (grasses, palms, and orchids).
- 词性: noun
- 行业/领域: 科学
- 类别 普通科学
- Company: McGraw-Hill
创建者
- Francisb
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