No footnotes date September 2009 Refimprove date September 2009 Photoperiodism is the physiological reaction of organisms to the length of day or night. It occurs in plant s and animal s. Photoperiodism can also be defined as the developmental responses of plants to the relative lengths of the light and dark periods. Here it should be emphasized that photoperiodic effects relate directly to the timing of both the light and dark periods. In plants Photoperiodic plant redirects here Many flowering plant s use a photoreceptor protein , such as phytochrome or cryptochrome , to sense seasonal changes in night length, or photoperiod, which they take as signals to flower. In a further subdivision, obligate photoperiodic plants absolutely require a long or short enough night before flowering, whereas facultative photoperiodic plants are more likely to flower under the appropriate light conditions, but will eventually flower regardless of night length. Photoperiodic flowering plants are classified as long day plants or short day plants , though the regulatory mechanism is actually governed by hours of darkness, not the length of the day. Modern biologists believe Citation needed date June 2010 that it is the coincidence of the active forms of phytochrome or cryptochrome, created by light during the daytime, with the rhythms of the circadian clock that allows plants to measure the length of the night. Other than flowering, photoperiodism in plants includes the growth of stems or roots during certain seasons, or the loss of leaves. Long day plants A long day plant requires fewer than a certain number of hours of darkness in each 24 hour period to induce flowering. These plants typically ... Xanthium Maize tropical cultivars only citation needed date November 2011 reason see Talk Photoperiodism ... based on photoperiodism at all they flower regardless of the night length. They may initiate flowering ... and D. Vince Prue, Photoperiodism in plants 2nd ed . Academic Press, 1997. Category Zoology Category ... more details
italic title Taxobox name Thyrassia penangae image Thyrassia penangae.jpg image width image caption Thyrassia penangae penangae image2 Thyrassia penangae rafflesi.jpg image2 width image2 caption Thyrassia penangae rafflesi regnum Animal ia phylum Arthropod a classis Insect a ordo Lepidoptera familia Zygaenidae genus Thyrassia species T. penangae binomial Thyrassia penangae binomial authority Frederic Moore Moore , 1859 synonyms Syntomis penangae small Moore, 1859 small Syntomis rafflesi small Moore, 1859 small Thyrassia rafflesi Thyrassia penangae is a species of moth in the Zygaenidae family. It is found in south east Asia , including Peninsular Malaysia and China . Subspecies Thyrassia penangae penangae Thyrassia penangae rafflesi small Moore, 1859 small External links http www.ncbi.nlm.nih.gov pubmed 19619555 Photoperiodism of diapause induction in Thyrassia penangae Lepidoptera Zygaenidae Category Animals described in 1859 Category Procridinae Zygaenidae stub ... more details
The plastochron or plastochrone index and the leaf plastochron index are ways of measuring the age of a plant dependent on morphological traits rather than on chronological age. Use of these indices removes differences caused by germination, developmental differences and exponential growth. Definitions The spatial pattern of the arrangement of leaves is called phyllotaxis phyllotaxy whereas the time between successive leaf initiation events is called the plastochron and the rate of emergence from the Bud Types of buds apical bud is the phyllochron . The plastochron ratio In 1951, F. J. Richards introduced the idea of the plastochron ratio and developed a system of equations to describe mathematically a centric representation using three parameters plastochron ratio, divergence angle, and the angle of the cone tangential to the apex in the area being considered. ref FJ Richards, Philos. Trans. R. Soc. London, Ser. B 235, 509 1951 . ref ref http aob.oxfordjournals.org content 39 3 455.short Orthostichy, Parastichy and Plastochrone Ratio in a Central Theory of Phyllotaxis ref Emerging Petiole botany phyllodes or leaf variants experience a sudden change from a high humidity environment to a more arid one. There are other changes they encounter such as variations in light level, Photoperiodism photoperiod and the gaseous content of the air. Some effects on the phyllochron plastochron ratio are discussed in the papers Effects of Higher Temperatures, Photoperiod and Seed Vernalisation on Development in Two Spring Wheats ref Effects of Higher Temperatures, Photoperiod and Seed Vernalisation on Development in Two Spring Wheats by H. M. Rawson and M. Zajac Aust. J. Plant Physiol., 1993, 20, 21 1 22 http www.publish.csiro.au ?act view file&file id PP9930211.pdf Rawson and Zajac ref and A functional structural model of the elongation of the grass leaf and of its relationships to the phyllochron . ref A functional structural model of the elongation of the grass leaf and of its r ... more details
Avishag Kadman Zahavi lang he born 1922 in Haifa is an Israel i professor emeritus of Plant Physiology at Agricultural Research In Israel The Agricultural Research Organization .28ARO.29 The Volcani Center for Agricultural Research , Bet Dagan, Israel. She is best known for her close collaboration with her husband Amotz Zahavi , who developed together with her the so called Handicap principle , a sociobiology sociobiological approach to the theory of natural selection . A lifelong naturalist, Avishag Kadman met Amotz Zahavi at the Hebrew University of Jerusalem during their studies in the field of biology and married him in 1954. Since then, besides following her own field of research, she has collaborated with Amotz in the study of the Old World babbler babblers and in the development of his ideas, often serving as the devil s advocate . Her research interests are basic and applied aspects of the effects of light on plant development photoperiodism , phytochrome , photomorphogenesis . Since her retirement Avishag Kadman Zahavi has continued her research at the Yair center for agricultural research at Hatzeva . Avishag and Amotz Zahavi have two daughters and two grandchildren. Sources The biographical details were learned from the German edition of Amotz Zahavi & Avishag Zahavi The Handicap Principle A Missing Piece of Darwin s Puzzle. Oxford University Press, 1997, ISBN 978 0195100358 additional source http de.wikipedia.org w index.php?title Avishag Zahavi&diff 21362395&oldid 7255926 Naama Zahavi Ely, College of William and Mary, Williamsburg, VA, USA Persondata Metadata see Wikipedia Persondata . NAME Zahavi, Avishag ALTERNATIVE NAMES SHORT DESCRIPTION Israeli biologist DATE OF BIRTH 1922 PLACE OF BIRTH DATE OF DEATH PLACE OF DEATH DEFAULTSORT Zahavi, Avishag Category Evolutionary biologists Category Israeli biologists Category Living people Category 1922 births Israel botanist stub de Avishag Zahavi ... more details
italictitle Taxobox name Wyeomyia smithii image Wyeomyia smithii 1.jpg image caption Wyeomyia smithii larva magnified 40X regnum Animal ia phylum Arthropod a classis Insect a ordo Diptera familia Culicidae subfamilia Culicinae tribus Sabethini genus Wyeomyia species W. smithii binomial Wyeomyia smithii binomial authority Coquillett, 1901 Wyeomyia smithii , the pitcher plant mosquito , is an inquiline invertebrate found only in the phytotelma of the purple pitcher plant, Sarracenia purpurea . In this microcommunity of bacteria, rotifer s, protozoa , and midge s, W. smithii is the top level predator its presence determines the bacterial species diversity within the pitcher. ref name Peterson 2008 Peterson, C. N., Day, S., Wolfe, B. E., Ellison, A. M., Kolter, R., and Pringle, A. 2008 . A keystone predator controls bacterial diversity in the pitcher plant Sarracenia purpurea microecosystem. Environmental Microbiology , 10 9 2257 2266. ref Wyeomyia smithii is a model organism for the study of photoperiodism , the biotic process of controlling seasonal Biological life cycle life history events by measuring day length as a reliable predictor of the seasons. W. smithii enters a state of developmental arrest, larval diapause , that is initiated and maintained by short daylengths and averted or terminated by long daylengths ref name Bradshaw 1977 Bradshaw, W.E., Lounibos P. 1977 . Evolution of dormancy and its photoperiodic control in pitcher plant mosquitoes. Evolution 31 546 567. ref References Reflist Category Culicidae Category Sarracenia purpurea inquilines fly stub vi Wyeomyia smithii ... more details
, Velasco conducted research on the photoperiodism of the rice rice plant . Among his findings, which ... citation acknowledged, among others, his research in photoperiodism and on the physiology of the coconut ... more details
taxobox image Eendekroos dicht bijeen.JPG image caption Common Duckweed Lemna minor regnum Plantae unranked division Angiosperms unranked classes Monocots ordo Alismatales familia Araceae subfamilia Lemnaoideae Lemnoideae tribus Lemneae genus Lemna genus authority Carolus Linnaeus L. subdivision ranks Species subdivision About 13, including br Lemna gibba Gibbous Duckweed Lemna minor Common Duckweed Lemna minuta Least Duckweed Lemna trisulca Ivy Duckweed Lemna valdiviana Valdivia Duckweed Lemna is a genus of free floating aquatic plant s from the duckweed family. These rapidly growing plants have found uses as a Model organism model system for studies in community ecology, basic plant biology, in ecotoxicology , in production of biopharmaceutical s, and as a source of animal feeds for agriculture and aquaculture . Taxonomy and growth habits The duckweeds have been classified as a separate family, the Lemnaceae , but some researchers the Angiosperm Phylogeny Group AGP II consider the duckweeds members of the Araceae . Lemna species grow as simple free floating Thallus tissue thalli on or just beneath the water surface. Most are small, not exceeding 5 mm in length, except Lemna trisulca which is elongated and has a branched structure. Lemna thalli have a single root, which distinguishes them from related genus genera Spirodela and Landoltia The plants grow mainly by vegetative reproduction two daughter plants bud off from the adult plant. This form of growth allows very rapid colonisation of new water. Duckweeds are flowering plant s, and nearly all of them are known to reproduce sexually, flower ing and producing seed under appropriate conditions. Certain duckweeds e.g. L. gibba are photoperiodism long day plant s, while others e.g. L. minor are photoperiodism short day plant s. When Lemna invades a waterway, it can be removed mechanically, by the addition of herbivorous fish e.g. grass carp or treated with a herbicide . The rapid growth of duckweeds finds applicatio ... more details
insects or attract predators. ref name farmer1990 Light Main Photomorphogenesis photoperiodism ... to flower. see photoperiodism The seeds of many plants sprout only after they are exposed to light ... more details
Photomorphogenesis photoperiodism Many plant organs contain photo sensitive compounds phototropin .... These light sensors tell the plant if it s day or night, how long the day is photoperiodism , how ... more details
of light sensitive compounds that respond to the length of the night, a phenomenon known as photoperiodism ... the time of flower ing based on the length of day and night photoperiodism and to set circadian ... of the epicotyl or hypocotyl hook of dicot seedlings. Photoperiodism Image Poinsettia 2.jpg thumb The poinsettia is a short day plant, requiring two months of long nights prior to blooming. main Photoperiodism ..., which they take as signals to flower. This sensitivity to day length is termed photoperiodism . Broadly ... level. Day neutral plants do not initiate flowering based on photoperiodism, though some may use ... more details
plant named Albion ref Photoperiodism Day neutral Univ. of California 2006 Diamante Cal94.16 1 Alice ... PP10435 Strawberry plant Diamante ref Photoperiodism Day neutral Univ. of California 1991 Cal 87.112 ... Evita x Irvine Evie 2 Photoperiodism Day neutral Edward Vinson Ltd. U.K. 2006 Everglade J92D12 ... more details
Florigen or flowering hormone is the term used to describe the hypothesized hormone like molecules responsible for controlling and or triggering flowering in plants. Florigen is produced in the leaves and acts in the shoot apical meristem of bud s and growing tips. It is known to be graft transmissible and even functions between species. However, despite having been sought since the 1930s, the exact nature of florigen is still a mystery. Mechanism Central to the hunt for florigen is an understanding of how plants use seasonal changes in day length to mediate flowering, a mechanism known as photoperiodism . Plants which exhibit photoperiodism may be either short day or long day plants, which in order to flower require short days or long days respectively. Although plants in fact distinguish day length from night length. ref name Garner1920 cite journal author Garner W.W., Allard H.A. year 1920 title Effect of the relative length of day and night and other factors of the environment on growth and reproduction in plants journal Journal of Agricultural Research volume 18 pages 553 606 doi 10.1175 1520 0493 1920 48 415b EOTRLO 2.0.CO 2 issue 7 ref The current model suggests the involvement of multiple different factors. Research into florigen is predominately centred around the model organism and long day plant, Arabidopsis thaliana . Whilst much of the florigen pathways appear to be well conserved in other studied species, variations do exist. ref name Turck2008 cite journal author Turck, F., Fornara, F., Coupland, G. year 2008 title Regulation and Identity of Florigen FLOWERING LOCUS T Moves Centre Stage journal Annual Review of Plant Biology volume 59 pages 573 594 doi 10.1146 annurev.arplant.59.032607.092755 pmid 18444908 ref The mechanism may be broken down into three stages photoperiod regulated Initiation , signal Translocation via the phloem, and induction of Flowering at the shoot apical meristem. Initiation In Arabidopsis thaliana , the signal is initiated by t ... more details
Pfam box Symbol Phytochrome Name Phytochrome image 3G6O.pdb.jpg width caption Crystal Structure of Phytochrome. ref name pmid19720999 PDB 3G6O cite journal author Yang X, Kuk J, Moffat K title Crystal structure of P. aeruginosa bacteriaphytochrome PaBphP photosensory core domain mutant Q188L journal Proc.Natl.Acad.Sci.USA volume 106 pages 15639 15644 year 2009 pmid 1972099 doi 10.2210 pdb3g6o pdb ref Pfam PF00360 InterPro IPR013515 SMART Prosite SCOP TCDB OPM family OPM protein PDB Image Phytochrome sic a bsorbtion hide y .png thumb Oat phytochrome absorption spectrum Devlin, 1969 Phytochrome is a photoreceptor protein photoreceptor , a pigment that plant s use to detect light. It is sensitive to light in the red and far red region of the visible spectrum . Many flowering plant s use it to regulate the time of flowering based on the length of day and night photoperiodism and to set circadian rhythms . It also regulates other responses including the germination of seeds photoblasty , elongation of seedlings, the size, shape and number of leaf leaves , the synthesis of chlorophyll , and the straightening of the epicotyl or hypocotyl hook of dicot seedlings. It is found in the leaves of most plants. Biochemically, phytochrome is a protein with a bilin biochemistry bilin chromophore . Phytochrome has been found in most plants including all higher plants very similar molecules have been found in several bacteria . A fragment of a bacterial phytochrome now has a solved three dimensional protein structure . Other plant photoreceptors include cryptochrome s and phototropin s, which are sensitive to light in the blue and ultra violet regions of the spectrum. Structure Phytochrome consists of two identical chains A and B . Each chain has a PAS domain and GAF domain . The PAS domain serves as a signal sensor and the GAF domain is responsible for binding to cGMP and also senses light signals. Together, these subunits form the phytochrome region, which regulates physiological ch ... more details
File Seriola dumerili Florida.jpg thumb 300px right center An amberjack broodstock, Seriola dumerili center Broodstock , or broodfish , are a group of mature individuals used in aquaculture for breeding purposes. Broodstock can be a population of animals maintained in captivity as a source of replacement for, or enhancement of, seed and Fry fish fry numbers. ref name Waples & Do, 1994 Waples, R.S., and C. Do. 1994. Genetic risk associated with supplementation of Pacific salmonids Captive broodstock programs. Canadian Journal of Fisheries and Aquatic Science,51 1 , 310 329. ref These are generally kept in ponds or tanks in which environmental conditions such as Photoperiodism photoperiod , temperature and pH are controlled. Such populations often undergo conditioning to ensure maximum fry output. Broodstock can also be sourced from Wild fisheries wild populations where they are harvested and held in maturation tanks before their seed is collected for grow out to market size ref name Fast, 1994 Fast, A. W. 1994 . Effects of broodstock size and source on ovarian maturation and spawning on Penaeus monodon Fabricius from the Gulf of Thailand. Journal of the World Aquaculture Society, 25 1 , 41 49. ref or the juveniles returned to the sea to supplement natural populations. ref name Waples & Do, 1994 This method, however, is subject to environmental conditions and can be unreliable seasonally, or annually. ref name Fast, 1994 Broodstock management can improve seed quality and number through enhanced gonad al development and fecundity . ref name Izquierdo et al, 2001 Izquierdo, M. S., Fernandez Palacios, H. And Tacon, A. G. J. 2001 . Effect of broodstock nutrition on reproductive performance of fish. Aquaculture, 197, 25 42. ref Management Broodstock management involves manipulating environmental factors surrounding the broodstock to ensure maximum survival, enhance gonadal development and increase fecundity. ref name Izquierdo et al, 2001 Such conditioning is necessary to ... more details
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