The xylem of Amborella is unique because it
Amborella xylem lacks vessel elements; water conduction exclusively via narrow tracheids with bordered pits circular lacking torus-margo complex simple, providing hydraulic safety against freeze-thaw embolism in cloud forest understory montane habitat. Absence perforation plates contrasts with most angiosperms possessing simple perforation plates significantly reducing resistance and increasing efficiency. Companion cells present in phloem but not xylem, secondary growth limited diffuse porous. Possession tracheids only interpreted as ancestral retention predating vessel evolution arising mult
Ref: Campbell Biology, 12th ed., Chapter 35: Amborella xylem trait tracheid only no vessels
