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Sporocarp (ferns)
Encyclopedia
A sporocarp is a specialised type of structure found in some ferns whose primary function is the production and release of spores.
Among fern
s, sporocarps are found only in the three families
of the order
Salviniales, a group that is both aquatic and heterosporous. The term actually refers to two very different structures. In the Azollaceae and Salviniaceae
, the sporocarp is nothing more than a modified sorus
, a single cluster of spore-producing tissues enclosed by a thin sphere of tissue
and attached to the leaves.
In the Marsileaceae
(water-clover family), however, the sporocarp is a more elaborate structure formed from an entire leaf
whose development and form is greatly modified. These are hairy, short-stalked, bean
-shaped structures (usually 3 to 8 mm in diameter) with a hardened outer covering. This outer covering is tough and resistant to drying out, allowing the spores inside to survive unfavorable conditions such as winter frost or summer desiccation. Despite this toughness, the sporocarps will open readily in water if conditions are favorable, and specimens have been successfully germinated after being stored for more than forty years. Each growing season, only one sporocarp develops per node along the rhizome near the base of the other leaf-stalks.
The sporocarps are functionally and developmentally modified leaves, although they have much shorter stalks than the vegetative leaves. Inside the sporocarp, the modified leaflets bear several sori
, each of which consists of several sporangia
covered by a thin hood of tissue (the indusium). Each sorus includes a mix of two types of sporangium, each type producing only one of two kinds of spores. Toward the center of each sorus and developing first are the megasporangia, each of which will produce a single large female megaspore
. Surrounding them at the edge of the sorus and developing later are the microsporangia, each of which will produce many small male microspore
s.
Fern
A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...
s, sporocarps are found only in the three families
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
of the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
Salviniales, a group that is both aquatic and heterosporous. The term actually refers to two very different structures. In the Azollaceae and Salviniaceae
Salviniaceae
Salviniaceae , is a family of ferns....
, the sporocarp is nothing more than a modified sorus
Sorus
A sorus is a cluster of sporangia .In fungi and lichens, the sorus is surrounded by an external layer. In some red algae it may take the form of a depression into the thallus....
, a single cluster of spore-producing tissues enclosed by a thin sphere of tissue
Tissue (biology)
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
and attached to the leaves.
In the Marsileaceae
Marsileaceae
The Marsileaceae are a small family of heterosporous aquatic and semi-aquatic ferns, though at first sight they do not physically resemble other ferns. The group is commonly known as the "pepperwort family" or as the "water-clover family" because the leaves of the genus Marsilea superficially...
(water-clover family), however, the sporocarp is a more elaborate structure formed from an entire leaf
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
whose development and form is greatly modified. These are hairy, short-stalked, bean
Bean
Bean is a common name for large plant seeds of several genera of the family Fabaceae used for human food or animal feed....
-shaped structures (usually 3 to 8 mm in diameter) with a hardened outer covering. This outer covering is tough and resistant to drying out, allowing the spores inside to survive unfavorable conditions such as winter frost or summer desiccation. Despite this toughness, the sporocarps will open readily in water if conditions are favorable, and specimens have been successfully germinated after being stored for more than forty years. Each growing season, only one sporocarp develops per node along the rhizome near the base of the other leaf-stalks.
The sporocarps are functionally and developmentally modified leaves, although they have much shorter stalks than the vegetative leaves. Inside the sporocarp, the modified leaflets bear several sori
Sorus
A sorus is a cluster of sporangia .In fungi and lichens, the sorus is surrounded by an external layer. In some red algae it may take the form of a depression into the thallus....
, each of which consists of several sporangia
Sporangium
A sporangium is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. All plants, fungi, and many other lineages form sporangia at some point in their life cycle...
covered by a thin hood of tissue (the indusium). Each sorus includes a mix of two types of sporangium, each type producing only one of two kinds of spores. Toward the center of each sorus and developing first are the megasporangia, each of which will produce a single large female megaspore
Megaspore
Megaspores, also called macrospores, are a type of spore that is present in heterosporous plants. These types of plants have two spore types, megaspores and microspores. Generally speaking, the megaspore, or large spore, germinates into a female gametophyte, which is fertilized by sperm produced...
. Surrounding them at the edge of the sorus and developing later are the microsporangia, each of which will produce many small male microspore
Microspore
In biology, a microspore is a small spore as contrasted to the larger megaspore.In botany, microspores develop into male gametophytes, whereas megaspores develop into female gametophytes. The combination of megaspores and microspores is found only in heterosporous organisms...
s.