• Fern Sporophyte
• Fern Gametophyte Sporophyte
• Fern Gametophyte Development
• The Fern Gametophyte Is Typically One

This haploid gametophyte bears male and female sex organs (antheridia and archegonia). With respect to populations of gametophytes, ferns are typically monoecious with both male and female sex organs on the same gametophytes. Unlike the unisexual gametophytes of a moss, a fern gametophyte is bisexual. The gametophyte of the fern is monoecious since both the male and female sexual parts (termed antheridia and archegonia) are both on the same plant. I don't think there are any extant dioecious ferns. The Fern Life Cycle, Revisited. Ferns have two main stages of development: the gametophyte stage and the sporophyte stage. The adult, sporophyte plant will release a spore that germinates into the gametophyte stage that participates in sexual reproduction. A gametophyte is a small heart-shaped plant that is only one cell layer thick.

Fern Sporophyte

The gametophyte phase is the primary phase in non-vascular plants, such as mosses and liverworts. Most plants are heteromorphic, meaning that they produce two different types of gametophytes. One gametophyte produces eggs, while the other produces sperm. The spores germinate to produce the haploid gametophyte or prothallus. For the typical homosporous fern the gametophyte is bisexual. It produces archegonia, each containing a single egg-cell and antheridia which release many motile sperm.

In all plants and some algae, an alteration of generations exists in which the species have diploid and haploid phases. Sexual reproduction results in gametes that combine two cells from different individuals. Meiosis also produces gametes. Haploids contain one set of chromosomes in each of their cells. Diploids cells contain two chromosome sets. For plants, haploid and diploid cells divide via mitosis. The plants’ haploid phase is called the gametophyte, and the diploid phase is called the sporophyte. Offspring alternate from diploid sporophytes to haploid gametophytes and back again in generations. This means plants generate two different kinds of plants with the same genetic material.

TL;DR (Too Long; Didn't Read)

Plants exist in alternation generations called sporophytes and gametophytes. Sporophytes represent the diploid phase of plants. Gametophytes represent the haploid phase of plants.

The sexual form, called the gametophyte or prothallium, is a tiny kidney-shaped haploid (N) plant that is difficult to find in the wild. The asexual form, or sporophyte form, is represented by the fern plant as it is commonly known and is diploid (2N). Sporophytes can reproduce either by vegetative cloning via their rhizomes or through spore. Mar 06, 2015  Most ferns species are homosporous and produce only one type of spore. While textbook drawings of homosporous fern gametophytes typically show a heart-shaped hermaphrodite, fern gametophytes can be male, female, male then female, female then male, hermaphroditic or asexual, depending on the species.

Characteristics of Sporophytes

Sporophytes are diploid plants that use meiosis to produce spores. These spores are haploid cells that grow into haploid gametophytes. Megaspores grow into female gametophytes, and microspores grow into male gametophytes. Meiosis occurs in the sporangium of a sporophyte and results in haploid spores. These spores contain one cell that can become another new plant without mating. Sporophytes have evolved in vascular plants to become larger, more dominant and longer-lived compared to gametophytes.

Characteristics of Gametophytes

Gametophytes are haploid plants that use mitosis to make haploid gametes. These gametes are female in the form of an ovum (egg) or male in the form of sperm. Gametophytes contain the archegonium, or female sex organ, or they contain the antheridium, or male sex organ. The sperm and egg unite in the archegonium to produce a diploid zygote cell. That zygote becomes a sporophyte. Vascular plant gametophytes tend to be much smaller than sporophytes, sometimes even only a few cells in size. A pollen grain represents an example of a male gametophyte in vascular plants.

Non-vascular vs. Vascular Plants

Vascular and non-vascular plants display interesting differences between their sporophytes and gametophytes. Vascular plants do not require as much water to thrive, and they display their large, long-lived sporophyte phase as the actual plant. Gymnosperms such as conifers contain a bit of female gametophyte tissue in their cones, such as pine nuts. Those nuts contain the embryonic diploid sporophyte. The male conifer gametophyte exists as pollen, which is wind-dispersed. For flowering plants such as fruit trees and flowers, female gametophytes contain a few cells and reside inside the ovary of the flower; the male exists as pollen. The small gametophytes of vascular plants only live for a season. Vascular plants that make two kinds of spores and gametophytes are called heterosporic.

Fern Gametophyte Sporophyte

Non-vascular plants such as bryophytes (which include mosses, liverworts and hornworts) display different characteristics for their gametophytes and sporophytes. Bryophytes comprise the oldest land plants on the planet, having existed for over 400 million years. They require wetter locales for their reproductive success. Their sporophytes are not visibly dominant. However, their gametophyte generation is the noticeable, photosynthetic part of the plant (like green moss) that attaches to substrates via rhizoids rather than the diploid sporophyte. In fact, their sporophytes are not as long-lived as in vascular plants. The sporophyte forms from a fertilized egg inside the flask-like archegonium and attaches to the gametophyte via a penetrating foot. The sporophyte receives nourishment from the gametophyte. The sporophyte forms a very small stalk called a seta and a single sporangium. A protective covering called a calyptra surrounds this embryonic sporophyte. Single-celled spores travel via wind and germinate only in a moist area; water is required for fertilization. Then they form a new gametophyte plant, which creates more spores in the sporophyte cycle. Because they make just one type of spore and gametophyte, these non-vascular plants are called homosporic.

Genetic Controls of Generation Processes

Scientists continue to learn more alternating generations in plants. Genetic studies of mosses reveal that a group of proteins called KNOX help drive development of sporophytes. In the angiosperm Arabidopsis thaliana, the PKL gene is needed for maternal sporophytes to promote male and female gametophyte development. Continued research yields even more fascinating aspects of the complex nature of sporophyte and gametophyte generation processes.

Optiplex 990 pci serial port driver. A gametophyte (/ɡəˈmiːtoʊfaɪt/) is one of the two alternating phases in the life cycle of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the sexual phase in the life cycle of plants and algae. It develops sex organs that produce gametes, haploid sex cells that participate in fertilization to form a diploidzygote which has a double set of chromosomes. Cell division of the zygote results in a new diploid multicellular organism, the second stage in the life cycle known as the sporophyte. The sporophyte can produce haploid spores by meiosis.

• 2Land plants
  • 2.2Vascular plants

Algae[edit]

In some multicellulargreen algae (Ulva lactuca is one example), red algae and brown algae, sporophytes and gametophytes may be externally indistinguishable (isomorphic). In Ulva the gametes are isogamous, all of one size, shape and general morphology.^[1]

Land plants[edit]

In land plants, anisogamy is universal. As in animals, female and male gametes are called, respectively, eggs and sperm. In extant land plants, either the sporophyte or the gametophyte may be reduced (heteromorphic).^[2]

Bryophytes[edit]

In bryophytes (mosses, liverworts, and hornworts), the gametophyte is the most visible stage of the life cycle. The bryophyte gametophyte is longer lived, nutritionally independent, and the sporophytes are typically attached to the gametophytes and dependent on them.^[3] When a moss spore germinates it grows to produce a filament of cells (called the protonema). The mature gametophyte of mosses develops into leafy shoots that produce sex organs (gametangia) that produce gametes. Eggs develop in archegonia and sperm in antheridia.^[4]

In some bryophyte groups such as many liverworts of the order Marchantiales, the gametes are produced on specialized structures called gametophores (or gametangiophores).

Vascular plants[edit]

All vascular plants are sporophyte dominant, and a trend toward smaller and more sporophyte-dependent female gametophytes is evident as land plants evolved reproduction by seeds.^[5]Vascular plants such as ferns that produce only one type of spore are said to be homosporous. They have exosporic gametophytes—that is, the gametophyte is free-living and develops outside of the spore wall. Exosporic gametophytes can either be bisexual, capable of producing both sperm and eggs in the same thallus (monoicous), or specialized into separate male and female organisms (dioicous).

In heterosporous vascular plants (plants that produce both microspores and megaspores), the gametophyte develops endosporically (within the spore wall). These gametophytes are dioicous, producing either sperm or eggs but not both.

Ferns[edit]

In most ferns, for example, in the leptosporangiate fernDryopteris, the gametophyte is a photosynthetic free living autotrophic organism called a prothallus that produces gametes and maintains the sporophyte during its early multicellular development. However, in some groups, notably the clade that includes Ophioglossaceae and Psilotaceae, the gametophytes are subterranean and subsist by forming mycotrophic relationships with fungi.

Lycophytes[edit]

Extant lycophytes produce two different types of gametophytes. In the homosporous families Lycopodiaceae and Huperziaceae, spores germinate into bisexual free-living, subterranean and mycotrophic gametophytes that derive nutrients from symbiosis with fungi. In Isoetes and Selaginella, which are heterosporous, microspores and megaspores are dispersed from sporangia either passively or by active ejection.^[6] Microspores produce microgametophytes which the produce sperm. Megaspores produce reduced megagametophytes inside the spore wall. At maturity, the megaspore cracks open at the trilete suture to allow the male gametes to access the egg cells in the archegonia inside. The gametophytes of Isoetes appear to be similar in this respect to those of the extinct Carboniferous arborescent lycophytes Lepidodendron and Lepidostrobus.^[7]

Fern Gametophyte Development

Seed plants[edit]

The seed plants (gymnosperms and angiosperms) are endosporic and heterosporous. The gametophytes develop into multicellular organisms while still enclosed within the spore wall, and the megaspores are retained within the sporangium.^[8]

Heteromorphy[edit]

In plants with heteromorphic gametophytes, there are two distinct kinds of gametophytes. Because the two gametophytes differ in form and function, they are termed heteromorphic, from hetero- 'different' and morph 'form'. The egg producing gametophyte is known as a megagametophyte, because it is typically larger, and the sperm producing gametophyte is known as a microgametophyte. Gametophytes which produce egg and sperm on separate plants are termed dioicous.

In heterosporous plants (water ferns, some lycophytes, as well as all gymnosperms and angiosperms), there are two distinct sporangia, each of which produces a single kind of spore and single kind of gametophyte. However, not all heteromorphic gametophytes come from heterosporous plants. That is, some plants have distinct egg-producing and sperm-producing gametophytes, but these gametophytes develop from the same kind of spore inside the same sporangium; Sphaerocarpos is an example of such a plant.

In seed plants, the microgametophyte is called pollen. Seed plant microgametophytes consists of several (typically two to five) cells when the pollen grains exit the sporangium. The megagametophyte develops within the megaspore of extant seedless vascular plants and within the megasporangium in a cone or flower in seed plants. In seed plants, the microgametophyte (pollen) travels to the vicinity of the egg cell (carried by a physical or animal vector), and produces two sperm by mitosis.

In gymnosperms the megagametophyte consists of several thousand cells and produces one to several archegonia, each with a single egg cell. The gametophyte becomes a food storage tissue in the seed.^[9]

In angiosperms, the megagametophyte is reduced to only a few nuclei and cells, and is sometimes called the embryo sac. A typical embryo sac contains seven cells and eight nuclei, one of which is the egg cell. Two nuclei fuse with a sperm nucleus to form the endosperm, which becomes the food storage tissue in the seed.

See also[edit]

References[edit]

1. ^Sadava, David; Hillis, David; Heller, H. Craig; Berenbaum, May (2012). Life: The Science of Biology, Volume 1 (10th ed.). Macmillan. ISBN978-1464141225.
2. ^Bennici, Andrea (2008). 'Origin and early evolution of land plants'. Communicative & Integrative Biology. 1 (2): 212–218. doi:10.4161/cib.1.2.6987. ISSN1942-0889. PMC2686025. PMID19513262.
3. ^Budke, J.M.; Goffinet, B.; Jones, C.S. (2013). 'Dehydration protection provided by a maternal cuticle improves offspring fitness in the moss Funaria hygrometrica'. Annals of Botany. 111 (5): 781–789. doi:10.1093/aob/mct033. PMC3631323. PMID23471009.
4. ^Ralf Reski (1998): Development, genetics and molecular biology of mosses. In: Botanica Acta 111, pp 1-15.
5. ^Stewart, W.N.; Rothwell, G.W. (1993-02-26). Palaeobotany and the evolution of plants, second edition. Cambridge, U.K.: Cambridge University press. ISBN0521382947.
6. ^Schneller, Jakob; Gerber, Hans; Zuppiger, Alex (June 2008). 'Speed and force of spore ejection in Selaginella martensii'(PDF). Botanica Helvetica. 118 (1): 13–20. doi:10.1007/s00035-008-0814-6.
7. ^Brack-Hanes, S.D. (1978). 'On the megagametophytes of two Lepidodendracean cones'. Botanical Gazette. 139: 140–146. doi:10.1086/336979.
8. ^C.Michael Hogan (2010): Fern. Encyclopedia of Earth. National council for Science and the EnvironmentArchived November 9, 2011, at the Wayback Machine. Washington, DC
9. ^'Vascular Plants :: Description'. Digimuse.nmns.edu.tw. Archived from the original on 2014-05-22. Retrieved 2014-07-13.

The Fern Gametophyte Is Typically One