gnetophytes

Gnetophytes are a small, ancient lineage of gymnosperms classified in the division Gnetophyta. They comprise three living genera—Ephedra, Gnetum, and Welwitschia—with roughly 70–100 species in total. Ephedra species are mostly desert shrubs with reduced, scale-like leaves and photosynthetic stems; Gnetum includes tropical vines and trees with broad, leathery leaves; Welwitschia mirabilis is a distinctive desert plant that bears a pair of long, strap-shaped leaves and a central reproductive structure.

Morphology and traits of gnetophytes are notable for their diversity and some angiosperm-like features. They possess vessel elements in their xylem, a trait uncommon among gymnosperms. Reproduction involves separate male and female plants in many species (dioecy), with pollen and ovules borne on different shoots or cones. Seeds are typically naked, though some species exhibit fleshy coverings or arillate structures.

Ecology and distribution vary by genus. Ephedra is widespread in arid and semi-arid regions of the northern hemisphere and southern Africa. Gnetum occurs in tropical forests of Africa and Asia. Welwitschia survives in the Namib Desert of southwestern Africa, thriving in extreme, dry conditions and exhibiting very slow growth.

Phylogeny and evolution remain topics of research. Molecular data have placed gnetophytes in different positions relative to other gymnosperms, but they are generally regarded as an ancient lineage whose exact relationships to conifers and other gymnosperms are still debated.

Economy and conservation: Ephedra species yield ephedrine and related alkaloids used in medicine and decongestants. Gnetum leaves are eaten as vegetables in some cultures. Welwitschia is primarily of conservation and scientific interest, with several populations threatened by habitat change and desertification.