How are gnetophytes different from conifers, cycads, and ginkgoes?

Gnetophytes (division Gnetophyta) are distinguished from other gymnosperms—including conifers, cycads, and ginkgoes—primarily by their unique internal anatomy and reproductive features.12

The most significant anatomical difference is that gnetophytes possess vessel elements in their xylem, whereas all other gymnosperms rely solely on tracheids for water and mineral conduction.12

Additionally, gnetophytes exhibit specialized reproductive structures that differ from their counterparts:

• Reproductive Morphology: Gnetophytes have compound pollen- and seed-producing strobili, which some botanists have historically interpreted as being similar to the flowers of angiosperms.2
• Comparison to other groups:
  • Conifers: Unlike the typically needle- or scale-leaved, cone-bearing conifers, gnetophytes include diverse forms such as the desert-dwelling Ephedra, the broad-leaved tropical Gnetum, and the highly unusual Welwitschia.13
  • Cycads: While cycads are palmlike with large, pinnately compound leaves and distinct cones, gnetophytes do not share this uniform appearance.1
  • Ginkgoes: The ginkgo is a single surviving species with fan-shaped leaves and no true cones, whereas gnetophytes comprise three distinct genera with varied growth habits.14

While gnetophytes were once thought to be a direct evolutionary link to flowering plants due to their vessel elements and double fertilization, modern molecular research indicates these traits evolved independently.24