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Phototropism
Phototropism is the growth of an organism in response to a light stimulus. Phototropism is most often observed in plants, but can also occur in other organisms such as fungi. The cells on the plant that are farthest from the light contain a hormone called auxin that reacts when phototropism occurs. This causes the plant to have elongated cells on the furthest side from the light. Phototropism is one of the many plant tropisms or movements which respond to external stimuli. Growth towards a light source is called positive phototropism, while growth away from light is called negative phototropism. Negative phototropism is not to be confused with skototropism which is defined as the growth towards darkness, whereas negative phototropism can refer to either the growth away from a light source or towards the darkness. Most plant shoots exhibit positive phototropism, and rearrange their chloroplasts in the leaves to maximize photosynthetic energy and promote growth.Goyal, A., Szarzyn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phytochrome
Phytochromes are a class of photoreceptor in plants, bacteria and fungi used to detect light. They are sensitive to light in the red and far-red region of the visible spectrum and can be classed as either Type I, which are activated by far-red light, or Type II that are activated by red light. Recent advances have suggested that phytochromes also act as temperature sensors, as warmer temperatures enhance their de-activation. All of these factors contribute to the plant's ability to germinate. Phytochromes control many aspects of plant development. They regulate the germination of seeds (photoblasty), the synthesis of chlorophyll, the elongation of seedlings, the size, shape and number and movement of leaves and the timing of flowering in adult plants. Phytochromes are widely expressed across many tissues and developmental stages. Other plant photoreceptors include cryptochromes and phototropins, which respond to blue and ultraviolet-A light and UVR8, which is sensitive to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tropism
A tropism is a biological phenomenon, indicating growth or turning movement of a biological organism, usually a plant, in response to an environmental stimulus. In tropisms, this response is dependent on the direction of the stimulus (as opposed to nastic movements which are non-directional responses). Tropisms are usually named for the stimulus involved (for example, a phototropism is a reaction to sunlight). Tropisms occur in three sequential steps. First, there is a sensation to a stimulus. Next, signal transduction occurs. And finally, the directional growth response occurs. Tropisms are typically associated with plants (although not necessarily restricted to them). Where an organism is capable of directed physical movement (motility), movement or activity in response to a specific stimulus is more likely to be regarded by behaviorists as a '' taxis'' (directional response) or a '' kinesis'' (non-directional response). The Cholodny–Went model, proposed in 1927, is a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arabidopsis Thaliana
''Arabidopsis thaliana'', the thale cress, mouse-ear cress or arabidopsis, is a small flowering plant native to Eurasia and Africa. ''A. thaliana'' is considered a weed; it is found along the shoulders of roads and in disturbed land. A winter annual with a relatively short lifecycle, ''A. thaliana'' is a popular model organism in plant biology and genetics. For a complex multicellular eukaryote, ''A. thaliana'' has a relatively small genome around 135 megabase pairs. It was the first plant to have its genome sequenced, and is a popular tool for understanding the molecular biology of many plant traits, including flower development and light sensing. Description ''Arabidopsis thaliana'' is an annual (rarely biennial) plant, usually growing to 20–25 cm tall. The leaves form a rosette at the base of the plant, with a few leaves also on the flowering stem. The basal leaves are green to slightly purplish in color, 1.5–5 cm long, and 2–10 mm broad, wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Auxin Action
Auxins (plural of auxin ) are a class of plant hormones (or plant-growth regulators) with some morphogen-like characteristics. Auxins play a cardinal role in coordination of many growth and behavioral processes in plant life cycles and are essential for plant body development. The Dutch biologist Frits Warmolt Went first described auxins and their role in plant growth in the 1920s. Kenneth V. Thimann became the first to isolate one of these phytohormones and to determine its chemical structure as indole-3-acetic acid (IAA). Went and Thimann co-authored a book on plant hormones, ''Phytohormones'', in 1937. Overview Auxins were the first of the major plant hormones to be discovered. They derive their name from the Greek word αυξειν (''auxein'' – "to grow/increase"). Auxin is present in all parts of a plant, although in very different concentrations. The concentration in each position is crucial developmental information, so it is subject to tight regulation through both metab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Auxin
Auxins (plural of auxin ) are a class of plant hormones (or plant-growth regulators) with some morphogen-like characteristics. Auxins play a cardinal role in coordination of many growth and behavioral processes in plant life cycles and are essential for plant body development. The Dutch biologist Frits Warmolt Went first described auxins and their role in plant growth in the 1920s. Kenneth V. Thimann became the first to isolate one of these phytohormones and to determine its chemical structure as indole-3-acetic acid (IAA). Went and Thimann co-authored a book on plant hormones, ''Phytohormones'', in 1937. Overview Auxins were the first of the major plant hormones to be discovered. They derive their name from the Greek word αυξειν (''auxein'' – "to grow/increase"). Auxin is present in all parts of a plant, although in very different concentrations. The concentration in each position is crucial developmental information, so it is subject to tight regulation through both ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coleoptile
Coleoptile is the pointed protective sheath covering the emerging shoot in monocotyledons such as grasses in which few leaf primordia and shoot apex of monocot embryo remain enclosed. The coleoptile protects the first leaf as well as the growing stem in seedlings and eventually, allows the first leaf to emerge. Coleoptiles have two vascular bundles, one on either side. Unlike the flag leaves rolled up within, the pre-emergent coleoptile does not accumulate significant protochlorophyll or carotenoids, and so it is generally very pale. Some preemergent coleoptiles do, however, accumulate purple anthocyanin pigments. Coleoptiles consist of very similar cells that are all specialised to fast stretch growth. They do not divide, but increase in size as they accumulate more water. Coleoptiles also have water vessels (frequently two) along the axis to provide a water supply. When a coleoptile reaches the surface, it stops growing and the flag leaves penetrate its top, continuing to grow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cholodny–Went Model
In botany, the Cholodny–Went model, proposed in 1927, is an early model describing tropism in emerging shoots of monocotyledons, including the tendencies for the shoot to grow towards the light (phototropism) and the roots to grow downward (gravitropism Gravitropism (also known as geotropism) is a coordinated process of differential growth by a plant in response to gravity pulling on it. It also occurs in fungi. Gravity can be either "artificial gravity" or natural gravity. It is a general feat ...). In both cases the directional growth is considered to be due to asymmetrical distribution of auxin, a plant growth hormone. Although the model has been criticized and continues to be refined, it has largely stood the test of time. Basic model The model was independently proposed by the Russian scientist Nikolai Cholodny of the University of Kyiv in 1927 and by Frits Warmolt Went of the California Institute of Technology in 1928, both based on work they had done in 1926. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phycomyces
''Phycomyces'' is a genus of fungus in the Zygomycota phylum. They are known for their strong phototropism response and helical growth of the sporangium. The best studied species is '' Phycomyces blakesleeanus''. Asexual reproduction ''Phycomyces'' can reproduce via extension of mycelia, or by production of spores either asexually or sexually. The asexual cycle includes the formation of spore containing sporangia borne on the top of sporangiophores that may extend 10 to 15 cm above the surface of the fungal colony from which they emerged. The long filamentous sporangiophores respond to divergent environmental signals including light, gravity, wind, chemicals and adjacent objects. The sporangia contain vegetative spores with one to six haploid nuclei. These spores when dispersed can establish new colonies. Sexual reproduction ''Phycomyces'' have two mating types that are indistinguishable morphologically. The sexual cycle is thought to occur by the following steps. Two ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basipetal
This glossary of mycology is a list of definitions of terms and concepts relevant to mycology, the study of fungi. Terms in common with other fields, if repeated here, generally focus on their mycology-specific meaning. Related terms can be found in glossary of biology and glossary of botany, among others. List of Latin and Greek words commonly used in systematic names and Botanical Latin may also be relevant, although some prefixes and suffixes very common in mycology are repeated here for clarity. A B C D E F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cryptochrome
Cryptochromes (from the Greek κρυπτός χρώμα, "hidden colour") are a class of flavoproteins found in plants and animals that are sensitive to blue light. They are involved in the circadian rhythms and the sensing of magnetic fields in a number of species. The name ''cryptochrome'' was proposed as a ''portmanteau'' combining the '' chromatic'' nature of the photoreceptor, and the '' cryptogamic'' organisms on which many blue-light studies were carried out. The two genes ''Cry1'' and ''Cry2'' code the two cryptochrome proteins CRY1 and CRY2. In insects and plants, CRY1 regulates the circadian clock in a light-dependent fashion, whereas in mammals, CRY1 and CRY2 act as light-independent inhibitors of CLOCK- BMAL1 components of the circadian clock. In plants, blue-light photoreception can be used to cue developmental signals. Besides chlorophylls, cryptochromes are the only proteins known to form photoinduced radical-pairs '' in vivo''. These appear to enable some a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
