![]() ![]() In hemidimorphic ferns, just a portion of the fertile leaf is different from the sterile leaves. In monomorphic ferns, the fertile and sterile leaves looks morphologically the same, and both are able to photosynthesize. The arrangement of the sporangia is important in classification. The sporangia may be covered with a protective coating called an indusium. Fern spores are borne in sporangia which are usually clustered to form sori. Sporophylls produce spores tropophylls do not. ![]() Leaves are divided into two types: sporophylls and tropophylls. 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. The green, photosynthetic part of the plant is technically a megaphyll and in ferns, it is often called a frond. 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 spermatophytes in that they reproduce by spores rather than having flowers and producing seeds. Like the sporophytes of seed plants, those of ferns consist of stems, leaves and roots. Their foliage may be deciduous or evergreen, and some are semi-evergreen depending on the climate. When woody growth is present, it is found in the stem. They also play certain roles in folklore.Įxtant ferns are herbaceous perennials and most lack woody growth. ![]() 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. 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, whisk ferns, marattioid ferns, and ophioglossoid ferns.įerns first appear in the fossil record about 360 million years ago in the late Devonian period, but Polypodiales, the group that makes up 80% of living fern diversity, did not appear and diversify until the Cretaceous, contemporaneous with the rise of flowering plants that came to dominate the world's flora.įerns are not of major economic importance, but some are used for food, medicine, as biofertilizer, as ornamental plants, and for remediating contaminated soil. The group includes about 10,560 known extant species. They produce coiled fiddleheads that uncoil and expand into fronds. They differ from mosses 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.įerns have complex leaves called megaphylls, that are more complex than the microphylls of clubmosses. The ferns ( Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. ![]()
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