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#basal angiosperms

2 public questions tagged with this topic.

Plant Classification

Amborella trichopoda lacks

Amborella wood anatomy exhibits exclusively tracheid conducting system lacking vessel elements, retaining torus-less circular bordered pits reminiscent of gymnosperms and pteridophytes, considered primitive. This vessellessness represents plesiomorphic retention not secondary loss, as phylogenetic placement suggests vessels evolved independently after Amborella lineage split within core angiosperms. Nonetheless, Amborella possesses angiospermous phloem with companion cells, enclosed ascidiate carpels and double fertilization yielding triploid endosperm confirming flowering plant affinity despite wood. Carpel, flower, endosperm features present, only vessel elements absent, challenging traditional definition of angiosperms requiring vessels and highlighting mosaic evolution.

Ref: Campbell Biology, 12th ed., Chapter 35: Amborella vesselless wood tracheid only plesiomorphy

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Plant Classification

The earliest diverging living angiosperm lineage is

Plastid phylogenomics incorporating rbcL, atpB, matK plus mitochondrial nad and nuclear concatenated genes robustly resolves Amborella trichopoda, shrub endemic New Caledonia with creamy white flowers spirally arranged, as earliest diverging living angiosperm sister to all others with maximal bootstrap support 100 percent. Its placement predates divergence of Nymphaeales water lilies and Austrobaileyales including star anise. Traits like vesselless wood, single aperturate pollen, spirally arranged ascidiate carpels reflect ancestral states useful for reconstructing protoflower ancestral morphology. Magnolia, Nymphaea, Illicium diverge later within mesangiosperms, not basal, making Amborella model organism genome project.

Ref: APG IV 2016, Botanical Journal Linnean Society, Amborella sister to all angiosperms

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