The gametophytes of ferns, however, are very different from those of seed plants. Like all other vascular plants, the diploid sporophyte is the dominant phase or generation in the life cycle. They are always fibrous and structurally are very similar to the roots of seed plants. Roots: The underground non-photosynthetic structures that take up water and nutrients from soil. The leafy structures that grow from the stipe are known as pinnae and are often again divided into smaller pinnules. In tree ferns, the main stalk that connects the leaf to the stem (known as the stipe), often has multiple leaflets. The anatomy of fern leaves can either be simple or highly divided. In some groups, the fertile leaves are much narrower than the sterile leaves, and may even have no green tissue at all (e.g., Blechnaceae, Lomariopsidaceae). In most ferns, fertile leaves are morphologically very similar to the sterile ones, and they photosynthesize in the same way. A sporophyll frond is a fertile leaf that produces spores borne in sporangia that are usually clustered to form sori.
A trophophyll frond is a vegetative leaf analogous to the typical green leaves of seed plants that does not produce spores, instead only producing sugars by photosynthesis. Leaves are divided into two types a trophophyll and a sporophyll. This uncurling of the leaf is termed circinate vernation. New leaves typically expand by the unrolling of a tight spiral called a crozier or fiddlehead into fronds. Leaf: The green, photosynthetic part of the plant is technically a megaphyll and in ferns, it is often referred to as a frond. These can reach up to 20 meters (66 ft) tall in a few species (e.g., Cyathea brownii on Norfolk Island and Cyathea medullaris in New Zealand). Epiphytic species and many of the terrestrial ones have above-ground creeping stolons (e.g., Polypodiaceae), and many groups have above-ground erect semi-woody trunks (e.g., Cyatheaceae). Stems: Fern stems are often referred to as rhizomes, even though they grow underground only in some of the species. Also unlike bryophytes, fern sporophytes are free-living and only briefly dependent on the maternal gametophyte. However they also differ from spore-producing bryophytes in that, like seed plants, they are Polysporangiophytes, their sporophytes branching and producing many sporangia. Ferns differ from seed plants in reproducing by spores. Like the sporophytes of seed plants, those of ferns consist of stems, leaves and roots. Tree ferns, probably Dicksonia antarctica, growing in Nunniong, Australia They also play certain roles in folklore. Some fern genera, such as Azolla, can fix nitrogen and make a significant input to the nitrogen nutrition of rice paddies. Some fern species, such as bracken ( Pteridium aquilinum) and water fern ( Azolla filiculoides) are significant weeds worldwide. They have been the subject of research for their ability to remove some chemical pollutants from the atmosphere. The fern Osmunda claytoniana is a paramount example of evolutionary stasis paleontological evidence indicates it has remained unchanged, even at the level of fossilized nuclei and chromosomes, for at least 180 million years.įerns are not of major economic importance, but some are used for food, medicine, as biofertilizer, as ornamental plants and for remediating contaminated soil. Ferns are defined here in the broad sense, being all of the Polypodiopsida, comprising both the leptosporangiate ( Polypodiidae) and eusporangiate ferns, the latter group including horsetails or scouring rushes, whisk ferns, marattioid ferns, and ophioglossoid ferns.įerns first appear in the fossil record about 360 million years ago in the middle Devonian period, but many of the current families and species did not appear until roughly 145 million years ago in the early Cretaceous, after flowering plants came to dominate many environments. The group includes about 10,560 known extant species. They produce coiled fiddleheads that uncoil and expand into fronds.
Ferns have complex leaves called megaphylls, that are more complex than the microphylls of clubmosses. They differ from mosses and other bryophytes by being vascular, i.e., having specialized tissues that conduct water and nutrients and in having life cycles in which the branched sporophyte is the dominant phase. A fern ( Polypodiopsida or Polypodiophyta / ˌ p ɒ l i ˌ p ɒ d i ˈ ɒ f ə t ə ˌ- ə ˈ f aɪ t ə/) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers.