क्लोरोप्लास्ट: Difference between revisions

 

 

क्लोरोप्लास्ट धाःगु खंग्वः युनानी खँग्वः ''क्लोरोस'' अर्थात वांगु व ''प्लास्ट'' अर्थात एन्टिटि स्वाना वःगु खंग्वः ख। क्लोरोप्लास्ट [[प्लास्टिड]] नां दूगु अर्‍ग्यानेल क्लासया छगू सदस्य ख।

 

क्लोरोप्लास्ट विभिन्न सेल अर्‍ग्यानेलय् छगू ख। साधारण कथं थ्व अर्‍ग्यानेलया पलिस्था [[इन्डोसिम्बायोटिक थियोरी|इन्डोसिम्बायोटिक]] [[सायनोब्याक्टेरिया]] (वा ब्लु-ग्रीन अल्गेइ)या कथं जूगु धैगु विश्वास दु। This was first suggested by [[Konstantin Mereschkowski|Mereschkowsky]] in 1905 <ref>{{cite journal | author= Mereschkowsky C | title= Über Natur und Ursprung der Chromatophoren im Pflanzenreiche | journal= Biol Centralbl | year=1905 | volume=25 | pages=593–604}} </ref> after an observation by Schimper in 1883 that chloroplasts closely resemble cyanobacteria. <ref>{{cite journal | author= Schimper AFW | title= Über die Entwicklung der Chlorophyllkörner und Farbkörper | journal= Bot. Zeitung | year=1883 | volume=41 | pages=105–14, 121–31, 137–46, 153–62}} </ref> All chloroplasts are thought to derive directly or indirectly from a single endosymbiotic event (in the [[Archaeplastida]]), except for ''[[Paulinella]] chromatophora'', which has recently acquired a photosynthetic cyanobacterial endosymbiont which is not closely related to chloroplasts of other eukaryotes.<ref>{{cite journal | title = Diversity and evolutionary history of plastids and their hosts | author = Patrick J. Keeling | url = http://www.amjbot.org/cgi/content/full/91/10/1481 | journal = American Journal of Botany | year = 2004 | volume = 91 | pages = 1481–1493 | doi = 10.3732/ajb.91.10.1481}}</ref> In that they derive from an endosymbiotic event, chloroplasts are similar to [[mitochondrion|mitochondria]] but chloroplasts are found only in [[plant]]s and [[protist]]a. The chloroplast is surrounded by a double-layered composite membrane with an intermembrane space; further, it has reticulations, or many infoldings, filling the inner spaces. The chloroplast has its own [[DNA]] which codes for redox proteins involved in electron transport in photosynthesis.

 

 

In some algae (such as the [[heterokont]]s and other protists such as [[Euglenozoa]] and [[Cercozoa]]), chloroplasts seem to have evolved through a secondary event of endosymbiosis, in which a eukaryotic cell engulfed a second eukaryotic cell containing chloroplasts, forming chloroplasts with three or four membrane layers. In some cases, such secondary [[endosymbiont]]s may have themselves been engulfed by still other eukaryotes, thus forming tertiary endosymbionts. In the alga ''Chlorella'', there is only one chloroplast, which is bell shaped.

In some groups of [[mixotrophic]] [[protist]]s such as the [[dinoflagellate]]s, chloroplasts are separated from a captured alga or diatom and used temporarily. These [[kleptoplasty|klepto chloroplasts]] may only have a lifetime of a few days and are then replaced.<ref name=Skovgaard>Skovgaard, A (1998) Role of chloroplast retention in a marine dinoflagellate. ''Aquatic Microbial Ecology'' 15, 293-301</ref>

 

 

Chloroplasts are observable morphologically as flat discs usually 2 to 10 micrometer in diameter and 1 micrometer thick. In land plants they are generally 5 μm in diameter and 2.3 μm thick. The chloroplast is contained by an envelope that consists of an inner and an outer phospholipid membrane. Between these two layers is the intermembrane space. A typical [[parenchyma]] cell contains about 10 to 100 chloroplasts.

Recent studies have shown that chloroplasts can be interconnected by tubular bridges called [[stromule]]s, formed as extensions of their outer membranes.<ref name=Köhler2000>Köhler RH & Hanson MR (2000) Plastid tubules of higher plants are tissue-specific and developmentally regulated. Journal of Cell Science 113, 81–89</ref><ref name=Gray2001>Gray JC, Sullivan JA, Hibberd JM & Hansen MR (2001) Stromules: mobile protrusions and interconnections between plastids. Plant Biology 3, 223–233</ref> Chloroplasts appear to be able to exchange proteins via stromules,<ref name=Köhler1997>Köhler RH, Cao J, Zipfel WR, Webb WW & Hanson MR (1997) Exchange of protein molecules through connections between higher plant plastids. Science 276, 1039–1042</ref> and thus function as a network.

 

Recently, chloroplasts have caught attention by developers of [[genetically modified plant]]s. In most flowering plants, chloroplasts are not inherited from the male parent,<ref>{{cite journal | quote = most angiosperm species inherit their chloroplasts maternally | doi = 10.1073/pnas.1430924100 | pmc = 166398 | year = 2003 | month = July | author = Stegemann, S; Hartmann, S; Ruf, S; Bock, R | title = High-frequency gene transfer from the chloroplast genome to the nucleus | volume = 100 | issue = 15 | pages = 8828–33 | pmid = 12817081 | journal = Proceedings of the National Academy of Sciences of the United States of America | url = http://www.pnas.org/cgi/pmidlookup?view=long&pmid=12817081 | format = Free full text }}</ref><ref name="ruf2007"/> although in plants such as pines, chloroplasts are inherited from males.<ref>{{cite journal | pmc = 41225 | quote = In the pines, the chloroplast genome is transmitted through pollen | journal = Proc Natl Acad Sci U S A. | date = 1995-08-15 | volume = 92 | issue = 17 | pages = 7759–7763 | doi = 10.1073/pnas.92.17.7759 | title = Polymorphic Simple Sequence Repeat Regions in Chloroplast Genomes: Applications to the Population Genetics of Pines | author = Powell, W. | pmid = 7644491 }}</ref> Where chloroplasts are inherited only from the female, [[transgene]]s in these plastids cannot be disseminated by [[pollen]]. This makes [[plastid transformation]] a valuable tool for the creation and cultivation of genetically modified plants that are biologically contained, thus posing significantly lower environmental risks. This [[biological containment]] strategy is therefore suitable for establishing the [[Co-existence of genetically modified and conventional crops and derived food and feed|coexistence of conventional and organic agriculture]]. The reliability of this mechanism has not yet been studied for all relevant crop species. However, the research programme [[Co-Extra]] recently published results for tobacco plants, demonstrating that the containment of transplastomic plants is highly reliable with a tiny failure rate of 3 in 1,000,000.<ref name="ruf2007">{{cite journal | author=Ruf S, Karcher D, Bock R | title=Determining the transgene containment level provided by chloroplast transformation | journal=PNAS | date=2007-04-24 | volume=104 | issue=17 | pages=6998–7002 | doi=10.1073/pnas.0700008104 | pmid=17420459 | pmc = 1849964 }}</ref>

 

*[[फोटोसिन्थेसिस]]

 

<references /></div>

 

*{{NCBI-scienceprimer}}

 

*[http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/Chloroplasts.html Chloroplasts] and [http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/L/LightReactions.html Photosynthesis: The Role of Light] from [http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/ Kimball's Biology Pages]

*[http://reference.allrefer.com/encyclopedia/C/chloropl.html Chloroplast, Botany]

*[http://www.coextra.eu/projects/project199.html Co-Extra research on chloroplast transformation]

 

 

[[af:Chloroplas]]

[[es:Cloroplasto]]

[[et:Kloroplast]]

[[fa:سبزدیسه]]

[[fi:Viherhiukkanen]]