Seed-bearing plants were traditionally divided into angiosperms, or flowering plants, and gymnosperms, which includes the gnetophytes, cycads, ginkgo, and conifers.
more Ephedra, Gnetum, and Welwitschia constitute the gymnosperm order Gnetales of still unclear phylogenetic relationships within seed plants.
Here we review progress over the past 10 years in our understanding of their species diversity, morphology, reproductive biology, chromosome numbers, and genome sizes, highlighting the unevenness in the sampling of species even for traits that can be studied in preserved material, such as pollenmorphology.
Unlike other gymnosperms, they possess vessel elements in the xylem.
Some species have been proposed to have been the first plants to be insect-pollinated as their fossils occur in association with extinct pollinating scorpionflies.
The so-called "seed ferns" (Pteridospermae) were one of the earliest successful groups of land plants, and forests dominated by seed ferns were prevalent in the late Paleozoic.
Glossopteris was the most prominent tree genus in the ancient southern supercontinent of Gondwana during the Permian period.Gnetol (IC50, 4.5 micro M) was stronger than kojic acid (IC50, 139 micro M) as a standard inhibitor for murine tyrosinase activity.Moreover, gnetol significantly suppressed, melanin biosynthesis in murine B16 melanoma cells.We include distribution maps and original illustrations of key features, and specify which speciesgroups or geographic areas are undersampled.• Gnetum (Gnetales) species are suggested to be unique extant gymnosperms that have acquired high photosynthetic and transpiration capacities as well as greater xylem hydraulic capacity and efficiency compared with all other extant...more• Gnetum (Gnetales) species are suggested to be unique extant gymnosperms that have acquired high photosynthetic and transpiration capacities as well as greater xylem hydraulic capacity and efficiency compared with all other extant gymnosperms.These results on Gnetum ecophysiology indicate that the coupling of vessels, broad pinnate-veined leaves and the liana habit do not signal the evolution of a highly opportunistic, light-demanding life history in gymnosperms.