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Antheridiogen
Antheridiogens are a class of chemicals secreted by fern gametophytes that have "been shown to influence production of male gametangia and thus mating systems in a large number of terrestrial fern species". Antheridiogens are only observed in homosporous fern species, as all gametophytes are potentially bisexual (have the ability to produce both archegonia and antheridia). Background The first study regarding antheridiogen was published by Walter Döpp in 1950. In this article, he explains the discovery of a molecule, which he titled "A-substanz", that caused premature formation of antheridia when agar media was reused after cultivation of ''Pteridium aquilinum.'' A majority of the studies regarding antheridiogen were done by two researchers, Ulrich Näf and H. Schraudolf. Sex-determination pathway The way in which antheridiogen determines sex in ferns is a "spatiotemporally split gibberellin synthesis pathway". Gibberellin is a group of hormones that control plant processes. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antheridiogen
Antheridiogens are a class of chemicals secreted by fern gametophytes that have "been shown to influence production of male gametangia and thus mating systems in a large number of terrestrial fern species". Antheridiogens are only observed in Spore, homosporous fern species, as all gametophytes are potentially bisexual (have the ability to produce both Archegonium, archegonia and Antheridium, antheridia). Background The first study regarding antheridiogen was published by Walter Döpp in 1950. In this article, he explains the discovery of a molecule, which he titled "A-substanz", that caused premature formation of antheridia when agar media was reused after cultivation of ''Pteridium aquilinum.'' A majority of the studies regarding antheridiogen were done by two researchers, Ulrich Näf and H. Schraudolf. Sex-determination pathway The way in which antheridiogen determines sex in ferns is a "spatiotemporally split gibberellin synthesis pathway". Gibberellin is a group of hormo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gametophyte
A gametophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the life cycles 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 reproduction of plants, 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 diploid zygote 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 that on germination produce a new generation of gametophytes. Algae In some multicellular green algae (''Ulva lactuca'' is one example), red algae and brown algae, sporophytes and gametophytes may be externally indistinguishable (isomorphic). In ''Ulva (genus), Ulv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pheromone
A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavior of the receiving individuals. There are ''alarm signal, alarm pheromones'', ''food trail pheromones'', ''sex pheromones'', and many others that affect behavior or physiology. Pheromones are used by many organisms, from basic unicellular prokaryotes to complex multicellular eukaryotes. Their use among insects has been particularly well documented. In addition, some vertebrates, plants and ciliates communicate by using pheromones. The ecological functions and evolution of pheromones are a major topic of research in the field of chemical ecology. Background The portmanteau word "pheromone" was coined by Peter Karlson and Martin Lüscher in 1959, based on the Greek φερω ''pheroo'' ('I carry') and ὁρμων ''hormon'' ('stimulating'). P ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ceratopteris Richardii
''Ceratopteris richardii'' is a fern species belonging to the genus ''Ceratopteris'', one of only two genera of the subfamily Parkerioideae of the family Pteridaceae. It is one of several genera of ferns adapted to an aquatic existence. ''C. richardii'' was previously regarded as being part of the species ''Ceratopteris thalictroides''. "C-Fern" This particular species is of special scientific interest because a patented strain, called "C-Fern", was developed as a scientific aid and teaching tool in biology in 1995. The use of "C-Fern" is facilitated by the fact that it grows readily in a cell-culture dish on agar media, reaching sexual maturity within 2–3 weeks of spore inoculation, with motile sperm cells being visible at this time. Over the course of about 6 weeks germination, sex determination and development of gametophytes, fertilization, embryogenesis, organogenesis, and sporophyte growth can all be observed, allowing an incredibly comprehensive study of the life cyc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fern
A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except the lycopods, and differ from mosses and other bryophytes 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. Ferns have complex leaves called megaphylls, that are more complex than the microphylls of clubmosses. Most ferns are leptosporangiate ferns. They produce coiled fiddleheads that uncoil and expand into fronds. The group includes about 10,560 known extant species. 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. Ferns first ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plant Reproduction
Plant reproduction is the production of new offspring in plants, which can be accomplished by sexual or asexual reproduction. Sexual reproduction produces offspring by the fusion of gametes, resulting in offspring genetically different from either parent. Asexual reproduction produces new individuals without the fusion of gametes, resulting in clonal plants that are genetically identical to the parent plant and each other, unless mutations occur. Asexual reproduction Asexual reproduction does not involve the production and fusion of male and female gametes. Asexual reproduction may occur through budding, fragmentation, spore formation, regeneration and vegetative propagation. Asexual reproduction is a type of reproduction where the offspring comes from one parent only, thus inheriting the characteristics of the parent. Asexual reproduction in plants occurs in two fundamental forms, vegetative reproduction and agamospermy. Vegetative reproduction involves a vegetative piece of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Woodwardia Radicans
''Woodwardia radicans'', the chain fern, European chain fern or rooting chainfern, is a species of fern in the family Blechnaceae, mainly found in Macaronesia and southwestern Europe, but is also found in southern Italy and Crete. Growing to tall by broad, it is evergreen with arching fronds. The pinnae have curved, finely-toothed segments. The plant derives its common name from the linked sori on the undersides of the fronds. The specific epithet ''radicans'' means "with stems that take root", referring to rooting plantlets appearing at the tips of the fronds. This plant is cultivated as an ornamental, and in the UK has gained the Royal Horticultural Society's Award of Garden Merit. Unlike its hardier cousin ''Woodwardia unigemmata ''Woodwardia unigemmata'', the jewelled chain fern, is a species of evergreen fern native to Eastern Asia from the Himalayas to China, Japan and the Philippines. Growing to tall by broad, it bears pinnately-divided fronds which emerge red and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromosome
A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are the histones. These proteins, aided by chaperone proteins, bind to and condense the DNA molecule to maintain its integrity. These chromosomes display a complex three-dimensional structure, which plays a significant role in transcriptional regulation. Chromosomes are normally visible under a light microscope only during the metaphase of cell division (where all chromosomes are aligned in the center of the cell in their condensed form). Before this happens, each chromosome is duplicated ( S phase), and both copies are joined by a centromere, resulting either in an X-shaped structure (pictured above), if the centromere is located equatorially, or a two-arm structure, if the centromere is located distally. The joined copies are now called si ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Environmental Sex Determination
Environmental sex determination is the establishment of sex by a non-genetic cue, such as nutrient availability, experienced within a discrete period after fertilization. Environmental factors which often influence sex determination during development or sexual maturation include light intensity and photoperiod, temperature, nutrient availability, and pheromones emitted by surrounding plants or animals. This is in contrast to genotypic sex determination, which establishes sex at fertilization by genetic factors such as sex chromosomes. Under true environmental sex determination, once sex is determined, it is fixed and cannot be switched again. Environmental sex determination is different from some forms of sequential hermaphroditism in which the sex is determined flexibly after fertilization throughout the organism’s life. Adaptive Significance Environmental sex determination is similar to certain forms of sexual selection in that there are oftentimes different and opposing sel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hormone
A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required for the correct development of animals, plants and fungi. Due to the broad definition of a hormone (as a signaling molecule that exerts its effects far from its site of production), numerous kinds of molecules can be classified as hormones. Among the substances that can be considered hormones, are eicosanoids (e.g. prostaglandins and thromboxanes), steroids (e.g. oestrogen and brassinosteroid), amino acid derivatives (e.g. epinephrine and auxin), protein or peptides (e.g. insulin and CLE peptides), and gases (e.g. ethylene and nitric oxide). Hormones are used to communicate between organs and tissues. In vertebrates, hormones are responsible for regulating a variety of physiological processes and behavioral activities such as diges ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prothallus
A prothallus, or prothallium, (from Latin ''pro'' = forwards and Greek ''θαλλος'' (''thallos'') = twig) is usually the gametophyte stage in the life of a fern or other pteridophyte. Occasionally the term is also used to describe the young gametophyte of a liverwort or peat moss as well. In lichens it refers to the region of the thallus that is free of algae. The prothallus develops from a germinating spore. It is a short-lived and inconspicuous heart-shaped structure typically 2–5 millimeters wide, with a number of rhizoids (root-like hairs) growing underneath, and the sex organs: archegonium (female) and antheridium (male). Appearance varies quite a lot between species. Some are green and conduct photosynthesis while others are colorless and nourish themselves underground as saprotrophs. Alternation of generations Spore-bearing plants, like all plants, go through a life-cycle of alternation of generations. The fully grown sporophyte, what is commonly referred to as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gibberellin
Gibberellins (GAs) are plant hormones that regulate various developmental processes, including stem elongation, germination, dormancy, flowering, flower development, and leaf and fruit senescence. GAs are one of the longest-known classes of plant hormone. It is thought that the selective breeding (albeit unconscious) of crop strains that were deficient in GA synthesis was one of the key drivers of the "green revolution" in the 1960s, a revolution that is credited to have saved over a billion lives worldwide. History The first inroads into the understanding of GAs were developments from the plant pathology field, with studies on the ''bakanae'', or "foolish seedling" disease in rice. Foolish seedling disease causes a strong elongation of rice stems and leaves and eventually causes them to topple over. In 1926, Japanese scientist Eiichi Kurosawa identified that foolish seedling disease was caused by the fungus ''Gibberella fujikuroi.'' Later work at the University of Tokyo sho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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