These male and female sex cells, also known as eggs and sperm, unite during fertilization to form a diploid zygote. The angiosperm life cycle consists of a sporophyte phase and a gametophyte phase. In plants with vascular tissue systems, the sporophyte phase is the primary phase of the life cycle. Mature bryophytes have a single sporangium (spore-producing structure) on each sporophyte. The gametophye in non-vascular plants is the green, moss-like vegetation at the base of the plant. The male sex organ, the antheridium, is a saclike structure made up of a jacket of sterile cells one cell thick; it encloses many cells, each of which, when mature, produces one sperm. 3. Collectively, plants manifest a wide range of body plans, ranging from small multicellular structures to enormous trees. Final development of the male gametophyte, or microgametophyte, usually occurs on the soil prior to the release of biflagellate sperm. General rules for vascular plants are that the sporophyte generation is physically the larger, has a more complex developmental history, produces a greater range of cell types, and expresses a more diverse biochemistry; the gametophyte is often diminutive, reduced in the case of the angiosperms to a mere few cells. A gametophyte represents the sexual phase of the plant life. The gametophyte generation in these organisms consists of the green, leafy or moss-like vegetation located at the base of the plant. Water is needed for fertilization to take place as sperm swim toward the female reproductive organs (archegonia) and unite with the eggs. In plants, the gametophyte phase ends with the formation of a diploid zygote by sexual reproduction. When a sperm enters the field of the fluid diffused from the neck canal, it swims toward the site of greatest concentration of this fluid, therefore down the neck canal to the egg. The pollen grain germinates forming a pollen tube that extends downward to penetrate the ovary and allow a sperm cell to fertilize the egg. The egg remains in the base of the archegonium, ready for fertilization. The plant life cycle alternates between a gametophyte phase and a sporophyte phase in a cycle known as alternation of generations. The term gametophyte may refer to the gametophyte phase of the plant life cycle or to the particular plant body or organ that produces gametes. It is in the haploid gametophyte structure that gametes are formed. One gametophyte produces eggs, while the other produces sperm. The prothallium is the gametophyte phase in the fern's life cycle. The sporophyte generation is represented by the elongated stalks with spore-containing structures at the tip. Updates? The fertilized egg elongates and after a few cell divisions begins to differentiate. The alternation of generations illustrates an important principle, namely that cell lineages arising from single parental cells containing the same genetic potentiality may pursue mutually exclusive developmental patterns. In Selaginella, usually only four large megaspores are produced in a megasporangium. The life cycle of all tracheophytes (vascular plants), bryophytes (mosses and liverworts), and many algae and fungi is based on an alternation of generations, or different life phases: the gametophyte, which produces gametes, or sex cells, alternating with the sporophyte, which produces spores. The male gametophyte develops reproductive organs called antheridia (produce sperm) and the female gametophyte develops archegonia (produce eggs). Marchantia, Female Gametophyte Archegonium-bearing structures in a liverwort. The gametophyte structure of ferns is a heart-shaped plant called a prothallium. The development of the moss gametophyte illustrates the transition from a filamentous to a highly organized three-dimensional growth form. The gametophyte phase is the primary phase in non-vascular plants, such as mosses and liverworts. The plant life cycle has mitosis occurring in spores, produced by meiosis, that germinate into the gametophyte phase. The key difference between sporophyte and gametophyte is that the sporophyte is a diploid structure that participates in asexual reproduction while the gametophyte is a haploid structure that participates in sexual reproduction of plants.. Plants reproduce via asexual reproduction as well as via sexual reproduction. One form, the sporophyte, is created by the union of gametes (sex cells) and is thus diploid (contains two sets of similar chromosomes). Development of Male Gametophyte . Bailey, Regina. Non-vascular plants must live in moist habitats and rely on water to bring the male and female gametes together. ThoughtCo. The male spore will develop into a mature gametophyte that contains structures to make male gametes. In animal cells, haploid cells (gametes) are only produced by meiosis and only diploid cells undergo mitosis. Please refer to the appropriate style manual or other sources if you have any questions. The zygote develops into a diploid sporophyte, which represents the asexual phase of the cycle. Once an egg has been fertilized the development of the sporophyte begins. https://www.thoughtco.com/gametophyte-sexual-phase-4117501 (accessed March 14, 2021). The diploid sporophyte produces haploid spores (by meiosis) in specialized sacs called sporangia. Male microspores (sperm) form in microsporangia (pollen sacs) in the flower stamen. Conversely, certain features of animal cells are absent in plants. The second sperm fuses with the two polar bodies located in the center of the sac, producing the nutritive triploid endosperm tissue that will provide energy for the embryo's growth and development. This type of transition from simple to more complex growth form is accompanied by the synthesis of new kinds of ribonucleic acids (RNAs), presumably through the activation of genes that were not expressed during the early growth of the gametophyte. (2020, August 27). The prothallium produces both male and female reproductive organs, which form sperm and eggs respectively. Life cycle of a mossThe life cycle of bryophytes consists of an alternation of two stages, or generations, called the sporophyte and the gametophyte. The Pollen Grain: the Male Gametophyte. These male and female sex cells, also known as eggs and sperm, unite during fertilization to form a diploid zygote. "Gametophyte Generation of the Plant Life Cycle." Plant development, a multiphasic process in which two distinct plant forms succeed each other in alternating generations. 2. In seed producing plants, such as angiosperms and gymnosperms, the microscopic gametophyte generation is totally dependent upon the sporophyte generation. Kelp Forests - a Description. It may be noted, however, that, in the course of evolution, the capacity for this type of growth has not been lost, since it may be adopted by cells grown in tissue cultures in the laboratory. Other organisms, such as some algae and fungi, may spend most of their life cycles in the gametophyte phase. Development of Male Gametophyte Pollen grains display germination that is initiated in pollen sac which is referred to as precocious germination wherein a large central vacuole formation causes the nucleus to be pushed to one side post which the nucleus goes through mitosis that gives rise to two daughter nuclei. Higher plants sustain growth throughout life and, in this sense, are perpetually embryonic; animals, on the other hand, generally have a determinate period of growth, after which they are considered mature. By using ThoughtCo, you accept our, Gametophyte Generation in Non-vascular Plants. There's more about this in the REPRODUCTION SECTION. The expression of sporophytic genes must therefore be repressed in the gametophyte, probably from the time of spore formation (sporogenesis). The fertilized egg develops into a seed, which is the beginning of a new sporophyte generation. The heart-shaped prothallia produce gametes that unite to form a zygote, which develops into a new sporophyte plant. The term gametophyte may refer to the gametophyte phase of the plant life cycle or to the particular plant body or organ that produces gametes. The male gametophyte develops and reaches maturity in an immature anther. One cell is the tube cell, and the remaining cell/cells are the sperm cells. At maturity, the sporophyte produces Sporangia are found on the underside of the fern leaves and release spores into the environment. In seed-bearing plants, pollen is a male sperm-producing gametophyte and female sex cells are contained within plant ovules. Upon reaching the egg, the sperm burrows into its wall, and the egg nucleus unites with the sperm nucleus to produce the diploid zygote. Life cycle of a typical angiosperm. Although both plants and animals share the chemical basis of inheritance and of translation of the genetic code into structural units called proteins, plant development differs from that of animals in several important ways. The small plant, called a gametophyte, produces both male and female gametes. The mature haploid gametophyte then produces gametes by mitosis. When a spore germinates, it usually produces the protonema, which precedes the appearance of the more elaborately organized gametophytic plant, the gametophyte, which produces the sex organs. In the bryophytes, the gametophyte generation, rather than the sporophyte, is the more conspicuous. Once an egg and sperm meet, either from the same gametophyte or from different gametophytes, a zygote is formed. The gametophyte represents the sexual phase of the life cycle as gametes are produced in this phase. Gametophyte Generation in Vascular Plants. Unlike in non-vascular plants, the gametophyte and sporophyte phases in non-seed producing vascular plants are independent. In seed-bearing vascular plants, such as angiosperms and gymnosperms, the gametophyte is totally dependent on the sporophyte for development. The alternating generations typically have different forms (i.e., are heteromorphic); this is true for the bryophytes and for all vascular plants, including lower vascular plants (ferns and allies), angiosperms (flowering plants), and gymnosperms (conifers and allies). This colored scanning electron micrograph (SEM) shows pollen tubes (orange) on the pistil of a prairie gentian flower (Gentiana sp.). Each generation has a different physical form. The male gametophyte will develop via one or two rounds of mitosis inside the anther. Mosses and liverworts are also heterosporous, meaning that they produce two different types of spores. Within each pollen grain is a male gametophyte Most plants are heteromorphic, meaning that they produce two different types of gametophytes.