Gnetophyta - Ecology and Morphology

Ecology and Morphology

The three genera of the gnetophytes are highly specialized to their respective environments, making it difficult to identify homologous characters. The three extant genera of gnetophytes, a "bizarre and enigmatic" trio, are likely aberrant members of the group, which was diverse and dominant in the Tertiary. Some synapomorphies of the gnetophytes include enveloping bracts around the ovules and microsporangia, and a micropylar projection of the outer membrane of the ovule that produces a pollination droplet.

Gnetum species are mostly woody climbers in tropical forests. However, the most well-known member of this group, Gnetum gnemon, is a tree. Its seeds are used to produce a crispy krupuk snack known as emping or krupuk belinjo.

Welwitschia comprises only one species, Welwitschia mirabilis. It grows only in the deserts of Namibia and Angola. This strange species has only two large strap-like leaves that grow continuously from the base throughout the plant's life.

Plants of the genus Ephedra are known as jointfirs because they have long slender branches which bear tiny scale-like leaves at their nodes. Ephedra has been traditionally used as a stimulant, but is a controlled substance today in many jurisdictions because of the risk of harmful or even fatal overdosing.

Knowledge of fossils of the gnetophytes has increased greatly since the 1980s. There are fossils from the Permian, the Triassic, and the Jurassic which may belong to the gnetophytes, but this is uncertain. The fossil record is richer starting in the early Cretaceous, with fossils of plants as well as seeds and pollen which can be clearly assigned to the gnetophytes.