Sporophyll

Not to be confused withSporophyte.

The sporophyll of a fern. It is a fertile leaf bearing reproductive structures.

Asporophyllis aleafthat bearssporangia.Bothmicrophylls and megaphyllscan be sporophylls. Inheterosporousplants, sporophylls (whether they are microphylls or megaphylls) bear either megasporangia and thus are calledmegasporophylls,ormicrosporangiaand are calledmicrosporophylls.The overlap of the prefixes and roots makes these terms a particularly confusing subset of botanical nomenclature.

Sporophylls vary greatly in appearance and structure, and may or may not look similar to sterile leaves. Plants that produce sporophylls include:

Alaria esculenta,a brown alga which shows sporophylls attached near the base of the alga.

Lycophytes,where sporophylls may be aggregated intostrobili(Selaginellaand someLycopodiumand related genera) or distributed singly among sterile leaves (Huperzia). Sporangia are borne in the axil or on the adaxial surface of the sporophyll. In heterosporous members, megasporophylls and microsporophylls may be intermixed or separated in a variety of patterns.

Ferns,which may produce sporophylls that are similar to sterile fronds or that appear very different from sterile fronds. These may be non-photosynthetic and lack typical pinnae, e.g.Onoclea sensibilis.

Cycadsproduce strobili, both pollen-producing and seed-producing, that are composed of sporophylls.

Ginkgoproduces microsporophylls aggregated into a pollen strobilus. Ovules are not born on sporophylls.

Gymnosperms,likeGinkgoand cycads, produce microsporophylls, aggregated into pollen strobili. However, unlike these other groups, ovules are produced on cone scales, which are modified shoots rather than sporophylls.

Some plants do not produce sporophylls. Sporangia are produced directly on stems.Psilotumhas been interpreted as producing sporangia (fused in a synangium) on the terminus of a stem.Equisetumalways produce strobili, but the structures bearing sporangia (sporangiophores) have been interpreted asmodified stems.The sporangia, despite being recurved are interpreted as terminal.

Gnetophytesproduce both compound pollen and seed strobili.

References

• C.Michael Hogan. 2010.Fern.Encyclopedia of Earth. National council for Science and the Environment.Washington, DC