The investigations in Pteridophytes probably of most interest and importance ing of apogamy and apospory, it is important to define these terms at the outset. Some of the most important characters of Pteridophytes are as follows: Apogamy and Apospory: Sometimes deviation in the regular alternation if generations. Apogamy, apospory and parthenogenesis in the Pteridophytes II Steil, W.N.. Bot Rev: This is a supplement to the review which appeared in Bot.
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The genetic control of apomixis can involve a single genetic change that affects all the major developmental components, formation of the megagametophyte, parthenogenesis of the egg cell, and endosperm development. In plants with independent gametophytes notably fernsthe term is still used interchangeably with “apomixis”, and both refer to the formation of sporophytes by parthenogenesis of gametophyte cells. In some plant familiesgenera with apomixis are quite common, for example in AsteraceaePoaceaeand Rosaceae.
Apospory is the development of unusual diploid gametophyte from the vegetative parts of sporophyte and not from the spores. For similar processes in animals and Oomycetes, see Parthenogenesis.
Vascular tissues present throughout the sporophyte except in reproductive parts and in gametophyte. Because apomictic plants are genetically identical from one generation to the next, each lineage has some of the characters of a true speciesmaintaining distinctions from other apomictic lineages within the same genuswhile having much smaller differences than is normal between species of most genera. Lycopodium, Selaginella, and Isoetes or megaphyllous. Thus “normal asexual reproduction ” of plants, such as propagation from cuttings or leaves, has never been considered to be apomixis, but replacement of the seed by a plantlet or replacement of the flower by bulbils were categorized as types of apomixis.
Structure and Reproduction Replication Cycle.
Apogamy, apospory and parthenogenesis in the Pteridophytes II
The gametophytes develop sex organs like antheridia male pteridophyted organs and archegonia female sex organs. In flowering plants, the term “apomixis” is commonly used in a restricted sense to mean agamospermyi. Leaves with petiole, excised from aseptically raised plants from excised cultured buds, also exhibited apospory, while no pteridopuytes was achieved with the excised leaves of the parent plantS.
Although the evolutionary advantages of sexual reproduction are lost, apomixis can pass along traits fortuitous for evolutionary fitness. In botanypferidophytes was defined by Hans Winkler as replacement of the normal sexual reproduction by asexual reproductionwithout fertilization. Although agamospermy could theoretically occur in gymnospermsit appears to be absent in that group.
Surrogate mother for endangered Cupressus “. In gametophytic apomixisthe embryo arises from an unfertilized egg cell i.
For androgenetic alopecia, see Pattern hair loss. Apospory and apogamy in a species of Tectaria. From Wikipedia, the free encyclopedia. All Pteridophytes are annual and herbaceous, e. Maheshwari  used the following simple classification of types of apomixis in flowering plants:.
The spore germinates into an inconspicuous, free-living, photosynthetic thalIoid gametophyte called prothallus. Botanical Journal of the Linnean Society 62 4: The cause of apospory involves deficiency of mineral nutrition, development of leaves under dim light etc.
13 Important Characters of Pteridophytes – Explained!
They are therefore often called microspecies. Sign in via your Institution Sign in. The development of sporangia may be eusporangiate from a group of cells, e. This is a question and answer forum for students, teachers and general visitors for exchanging articles, answers and notes.
Selaginella, Marsilea, Azolla etc. Primary root short lived and replaced by adventitious roots. This page was last edited on 8 Decemberat Natural apogamy is pterisophytes in ferns like Dryopteris, Adiantum, Osmunda, Pteris etc. Pteris, Nephrolepis, Drynaria etc. The evolutionary biology of plants. Agamospermy occurs mainly in two forms: The culture of bryophytes including apogamy apospory parthenogenesis and protoplasts.
The life cycle is diplohaplontic pteridopjytes shows heteromorphic type of alternation of generations. The sporophyte may be homosporous e g. This definition notably does not mention meiosis.
In adventitious embryony sporophytic apomixisan embryo is formed directly not from a gametophyte from nucellus or integument tissue see nucellar embryony. For English speakers, Maheshwari  is pteirdophytes influential. Abstract Apogamy was induced in the fern Ampelopteris prolifera by culturing the gametophytes on mineral nutrients supplemented with various concentrations of sucrose.
This article is also available for rental through DeepDyve. Dryopteris or heterosporous e.
13 Important Characters of Pteridophytes – Explained!
As Jens Clausen put it : Gametophytic apomixis in flowering plants pteridopjytes in several different ways. In heterosporous forms, 2 types of spores develop i. In plants with both apomictic and meiotic embryology, the proportion of apsopory different types can differ at different times of year,  and photoperiod can also change the proportion. Bot Rev 5 8: The cause of apogamy include ageing of the prothallus, failure of sex organ formation and normal fertilization, prothallus growing under bright light and high temperature etc.