88-532: The Citrus Industry is a book consisting of five volumes of scientific and experimental information on all the citrus species and varieties , originals as well as hybrids . The book was produced by scientists associated with the University of California Citrus Experiment Station , and contains fundamental information on the variety description and cost effectiveness of growing, as well technical support for citrus cultivation . The name reflects its aim to support
176-519: A carboxysome – an icosahedral structure that contains the enzyme RuBisCO responsible for carbon fixation . Third, starch created by the chloroplast is collected outside the chloroplast. Additionally, like cyanobacteria, both glaucophyte and rhodophyte thylakoids are studded with light collecting structures called phycobilisomes . The rhodophyte, or red algae , group is a large and diverse lineage. Rhodophyte chloroplasts are also called rhodoplasts , literally "red chloroplasts". Rhodoplasts have
264-408: A chromatophore . While all other chloroplasts originate from a single ancient endosymbiotic event, Paulinella independently acquired an endosymbiotic cyanobacterium from the genus Synechococcus around 90 - 140 million years ago. Each Paulinella cell contains one or two sausage-shaped chloroplasts; they were first described in 1894 by German biologist Robert Lauterborn. The chromatophore
352-402: A diatom ( heterokontophyte )-derived chloroplast. These chloroplasts are bounded by up to five membranes, (depending on whether the entire diatom endosymbiont is counted as the chloroplast, or just the red algal derived chloroplast inside it). The diatom endosymbiont has been reduced relatively little—it still retains its original mitochondria , and has endoplasmic reticulum , ribosomes ,
440-421: A nucleomorph found between the second and third chloroplast membranes —the periplastid space , which corresponds to the green alga's cytoplasm. Dinoflagellates in the genus Lepidodinium have lost their original peridinin chloroplast and replaced it with a green algal derived chloroplast (more specifically, a prasinophyte ). Lepidodinium is the only dinoflagellate that has a chloroplast that's not from
528-436: A nucleomorph that superficially resembles that of the chlorarachniophytes . Cryptophyte chloroplasts have four membranes. The outermost membrane is continuous with the rough endoplasmic reticulum . They synthesize ordinary starch , which is stored in granules found in the periplastid space—outside the original double membrane, in the place that corresponds to the ancestral red alga's cytoplasm. Inside cryptophyte chloroplasts
616-569: A nucleus , and of course, red algal derived chloroplasts—practically a complete cell , all inside the host's endoplasmic reticulum lumen . However the diatom endosymbiont can't store its own food—its storage polysaccharide is found in granules in the dinophyte host's cytoplasm instead. The diatom endosymbiont's nucleus is present, but it probably can't be called a nucleomorph because it shows no sign of genome reduction , and might have even been expanded . Diatoms have been engulfed by dinoflagellates at least three times. The diatom endosymbiont
704-457: A plastid that conducts photosynthesis mostly in plant and algal cells . Chloroplasts have a high concentration of chlorophyll pigments which capture the energy from sunlight and convert it to chemical energy and release oxygen . The chemical energy created is then used to make sugar and other organic molecules from carbon dioxide in a process called the Calvin cycle . Chloroplasts carry out
792-441: A pyrenoid , triplet thylakoids, and, with some exceptions, four layer plastidic envelope with the outermost membrane connected to the endoplasmic reticulum . Like haptophytes, stramenopiles store sugar in chrysolaminarin granules in the cytoplasm. Stramenopile chloroplasts contain chlorophyll a and, with a few exceptions, chlorophyll c . They also have carotenoids which give them their many colors. The alveolates are
880-425: A chloroplast with three or four membranes —the two cyanobacterial membranes, sometimes the eaten alga's cell membrane, and the phagosomal vacuole from the host's cell membrane. The genes in the phagocytosed eukaryote's nucleus are often transferred to the secondary host's nucleus. Cryptomonads and chlorarachniophytes retain the phagocytosed eukaryote's nucleus, an object called a nucleomorph , located between
968-420: A double membrane with an intermembrane space and phycobilin pigments organized into phycobilisomes on the thylakoid membranes, preventing their thylakoids from stacking. Some contain pyrenoids . Rhodoplasts have chlorophyll a and phycobilins for photosynthetic pigments; the phycobilin phycoerythrin is responsible for giving many red algae their distinctive red color. However, since they also contain
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#17330924352141056-414: A group of common flagellated protists that contain chloroplasts derived from a green alga. Euglenophytes are the only group outside Diaphoretickes that have chloroplasts without performing kleptoplasty . Euglenophyte chloroplasts have three membranes. It is thought that the membrane of the primary endosymbiont host was lost (e.g. the green algal membrane), leaving the two cyanobacterial membranes and
1144-455: A high quantity of citric acid , which with other organic acids including ascorbic acid (vitamin C) give them their characteristic sharp taste. Citrus fruits are diverse in size and shape, as well as in color and flavor, reflecting their biochemistry; for instance, grapefruit is made bitter-tasting by a flavanone, naringin . Most commercial citrus cultivation uses trees produced by grafting
1232-456: A large group called chromalveolates . Today they are found in the haptophytes , cryptomonads , heterokonts , dinoflagellates and apicomplexans (the CASH lineage). Red algal secondary chloroplasts usually contain chlorophyll c and are surrounded by four membranes. Cryptophytes , or cryptomonads, are a group of algae that contain a red-algal derived chloroplast. Cryptophyte chloroplasts contain
1320-576: A linear furanocoumarin derived from psoralen . This claim has been confirmed for lime and bergamot . In particular, bergamot essential oil has a higher concentration of bergapten (3–3.6 g/kg) than any other Citrus -based essential oil. A systematic review indicates that citrus fruit consumption is associated with a 10% reduction of risk for developing breast cancer. Many citrus fruits, such as oranges , tangerines , grapefruits , and clementines , are generally eaten fresh. They are typically peeled and can be easily split into segments. Grapefruit
1408-422: A major clade of unicellular eukaryotes of both autotrophic and heterotrophic members. Many members contain a red-algal derived plastid. One notable characteristic of this diverse group is the frequent loss of photosynthesis. However, a majority of these heterotrophs continue to process a non-photosynthetic plastid. Apicomplexans are a group of alveolates. Like the helicosproidia , they're parasitic, and have
1496-412: A new chloroplast derived from a haptophyte endosymbiont, making these tertiary plastids. Karlodinium and Karenia probably took up different heterokontophytes. Because the haptophyte chloroplast has four membranes, tertiary endosymbiosis would be expected to create a six membraned chloroplast, adding the haptophyte's cell membrane and the dinophyte's phagosomal vacuole . However, the haptophyte
1584-544: A nonphotosynthetic chloroplast. They were once thought to be related to the helicosproidia, but it is now known that the helicosproida are green algae rather than part of the CASH lineage. The apicomplexans include Plasmodium , the malaria parasite. Many apicomplexans keep a vestigial red algal derived chloroplast called an apicoplast , which they inherited from their ancestors. Apicoplasts have lost all photosynthetic function, and contain no photosynthetic pigments or true thylakoids. They are bounded by four membranes, but
1672-563: A nucleomorph, their thylakoids are in stacks of three, and they synthesize chrysolaminarin sugar, which are stored in granules completely outside of the chloroplast, in the cytoplasm of the haptophyte. The stramenopiles , also known as heterokontophytes, are a very large and diverse group of eukaryotes. It inlcludes Ochrophyta —which includes diatoms , brown algae (seaweeds), and golden algae (chrysophytes) — and Xanthophyceae (also called yellow-green algae). Heterokont chloroplasts are very similar to haptophyte chloroplasts. They have
1760-472: A number of other functions, including fatty acid synthesis , amino acid synthesis, and the immune response in plants. The number of chloroplasts per cell varies from one, in some unicellular algae, up to 100 in plants like Arabidopsis and wheat . Chloroplasts are highly dynamic—they circulate and are moved around within cells. Their behavior is strongly influenced by environmental factors like light color and intensity. Chloroplasts cannot be made anew by
1848-684: A process called organellogenesis . Cyanobacteria are a diverse phylum of gram-negative bacteria capable of carrying out oxygenic photosynthesis . Like chloroplasts, they have thylakoids . The thylakoid membranes contain photosynthetic pigments , including chlorophyll a . This origin of chloroplasts was first suggested by the Russian biologist Konstantin Mereschkowski in 1905 after Andreas Franz Wilhelm Schimper observed in 1883 that chloroplasts closely resemble cyanobacteria . Chloroplasts are only found in plants , algae , and some species of
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#17330924352141936-403: A secondary plastid. These are called tertiary plastids . All primary chloroplasts belong to one of four chloroplast lineages—the glaucophyte chloroplast lineage, the rhodophyte ("red") chloroplast lineage, and the chloroplastidan ("green") chloroplast lineage, the amoeboid Paulinella chromatophora lineage. The glaucophyte, rhodophyte, and chloroplastidian lineages are all descended from
2024-466: A single endosymbiotic event around two billion years ago and these chloroplasts all share a single ancestor . It has been proposed this the closest living relative of the ancestral engulfed cyanobacterium is Gloeomargarita lithophora . Separately, somewhere about 90–140 million years ago, this process happened again in the amoeboid Paulinella with a cyanobacterium in the genus Prochlorococcus . This independently evolved chloroplast
2112-491: A small number of core ancestral species, including the citron, pomelo, and mandarin. Natural and cultivated citrus hybrids include commercially important fruit such as oranges, grapefruit , lemons, limes, and some tangerines . The multiple hybridisations have made the taxonomy of Citrus complex. Apart from these core species, Australian limes and the recently discovered mangshanyegan are grown. Kumquats and Clymenia spp. are now generally considered to belong within
2200-460: A wasp on one of the fruits. The impressionist Edouard Manet depicted a lemon on a pewter plate. In modern art, Arshile Gorky painted Still Life with Lemons in the 1930s. Citrus fruits "were the clear status symbols of the nobility in the ancient Mediterranean", according to the paleoethnobotanist Dafna Langgut. In Louisa May Alcott 's 1868 novel Little Women , the character Amy March states that "It's nothing but limes now, for everyone
2288-455: A wide range of appearance and fruit flavors. The large citrus fruit of today evolved originally from small, edible berries over millions of years. Citrus species began to diverge from a common ancestor about 15 million years ago, at about the same time that Severinia (such as the Chinese box orange ) diverged from the same ancestor. About 7 million years ago, the ancestors of Citrus split into
2376-485: Is a genus of flowering trees and shrubs in the family Rutaceae . Plants in the genus produce citrus fruits , including important crops such as oranges , mandarins , lemons , grapefruits , pomelos , and limes . Citrus is native to South Asia, East Asia, Southeast Asia, Melanesia , and Australia. Indigenous people in these areas have used and domesticated various species since ancient times. Its cultivation first spread into Micronesia and Polynesia through
2464-459: Is a pyrenoid and thylakoids in stacks of two. Cryptophyte chloroplasts do not have phycobilisomes , but they do have phycobilin pigments which they keep in the thylakoid space, rather than anchored on the outside of their thylakoid membranes. Cryptophytes may have played a key role in the spreading of red algal based chloroplasts. Haptophytes are similar and closely related to cryptophytes or heterokontophytes. Their chloroplasts lack
2552-422: Is highly reduced compared to its free-living cyanobacterial relatives and has limited functions. For example, it has a genome of about 1 million base pairs , one third the size of Synechococcus genomes, and only encodes around 850 proteins. However, this is still much larger than other chloroplast genomes, which are typically around 150,000 base pairs. Chromatophores have also transferred much less of their DNA to
2640-477: Is more commonly halved and eaten out of the skin with a spoon. Lemonade is a popular beverage prepared by diluting the juice and adding sugar. Lemon juice is mixed in salad dressings and squeezed over fruit salad to stop it from turning brown: its acidity suppresses oxidation by polyphenol oxidase enzymes. A variety of flavours can be derived from different parts and treatments of citrus fruits. The colourful outer skin of some citrus fruits, known as zest ,
2728-419: Is more complicated than that of the euglenophytes. The ancestor of chlorarachniophytes is thought to have been a eukaryote with a red algal derived chloroplast. It is then thought to have lost its first red algal chloroplast, and later engulfed a green alga, giving it its second, green algal derived chloroplast. Chlorarachniophyte chloroplasts are bounded by four membranes, except near the cell membrane, where
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2816-444: Is not connected to the endoplasmic reticulum. They contain a pyrenoid , and have triplet-stacked thylakoids. Starch is found outside the chloroplast. Peridinin chloroplasts also have DNA that is highly reduced and fragmented into many small circles. Most of the genome has migrated to the nucleus, and only critical photosynthesis-related genes remain in the chloroplast. Most dinophyte chloroplasts contain form II RuBisCO, at least
2904-483: Is often called a chromatophore instead of a chloroplast. Chloroplasts are believed to have arisen after mitochondria , since all eukaryotes contain mitochondria, but not all have chloroplasts. This is called serial endosymbiosis —where an early eukaryote engulfed the mitochondrion ancestor, and then descendants of it then engulfed the chloroplast ancestor, creating a cell with both chloroplasts and mitochondria. Many other organisms obtained chloroplasts from
2992-402: Is sucking them in their desks in schooltime, and trading them off for pencils, bead rings, paper dolls, or something else… If one girl likes another, she gives her a lime; if she’s mad with her, she eats one before her face, and doesn’t offer even a suck." Chloroplast A chloroplast ( / ˈ k l ɔːr ə ˌ p l æ s t , - p l ɑː s t / ) is a type of organelle known as
3080-399: Is the peridinin -type chloroplast, characterized by the carotenoid pigment peridinin in their chloroplasts, along with chlorophyll a and chlorophyll c 2 . Peridinin is not found in any other group of chloroplasts. The peridinin chloroplast is bounded by three membranes (occasionally two), having lost the red algal endosymbiont's original cell membrane. The outermost membrane
3168-567: Is used as a flavouring in cooking. The whole of the bitter orange (and sometimes other citrus fruits) including the peel with its essential oils is cooked with sugar to make marmalade . By the 17th century, orangeries were added to great houses in Europe, both to enable the fruit to be grown locally and for prestige, as seen in the Versailles Orangerie . Some modern hobbyists grow dwarf citrus in containers or greenhouses in areas where
3256-674: The Austronesian expansion ( c. 3000 –1500 BCE). Later, it was spread to the Middle East and the Mediterranean ( c. 1200 BCE ) via the incense trade route , and from Europe to the Americas. Renowned for their highly fragrant aromas and complex flavor, citrus are among the most popular fruits in cultivation. With a propensity to hybridize between species, making their taxonomy complicated, there are numerous varieties encompassing
3344-707: The Philippines . This was followed by the spread of citrus species into Taiwan and Japan in the Early Pliocene (5.33 to 3.6 mya ), resulting in the tachibana orange ( C. tachibana ); and beyond the Wallace Line into Papua New Guinea and Australia during the Early Pleistocene (2.5 million to 800,000 years ago), where further speciation events created in the Australian limes . A fossil leaf from
3432-623: The Pliocene of Valdarno , Italy is described as † Citrus meletensis . In China, fossil leaf specimens of † Citrus linczangensis have been collected from late Miocene coal-bearing strata of the Bangmai Formation in Yunnan province. C. linczangensis resembles C. meletensis in having an intramarginal vein, an entire margin, and an articulated and distinctly winged petiole . Many cultivated Citrus species are natural or artificial hybrids of
3520-407: The amoeboid Paulinella . Mitochondria are thought to have come from a similar endosymbiosis event, where an aerobic prokaryote was engulfed. Approximately two billion years ago, a free-living cyanobacterium entered an early eukaryotic cell, either as food or as an internal parasite , but managed to escape the phagocytic vacuole it was contained in and persist inside
3608-445: The cell nucleus . With one exception (the amoeboid Paulinella chromatophora ), all chloroplasts can be traced back to a single endosymbiotic event . Despite this, chloroplasts can be found in extremely diverse organisms that are not directly related to each other—a consequence of many secondary and even tertiary endosymbiotic events . The first definitive description of a chloroplast ( Chlorophyllkörnen , "grain of chlorophyll")
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3696-665: The citron ( C. medica ) or a conifer tree ( Thuja ). The Latin word is related to the ancient Greek word for the cedar of Lebanon , κέδρος ( kédros ), perhaps from a perceived similarity of the smell of citrus leaves and fruit with that of cedar. Citrus plants are large shrubs or small to moderate-sized trees, reaching 5–15 m (16–49 ft) tall, with spiny shoots and alternately arranged evergreen leaves with an entire margin. The flowers are solitary or in small corymbs , each flower 2–4 cm (0.79–1.57 in) diameter, with five (rarely four) white petals and numerous stamens; they are often very strongly scented, due to
3784-421: The citrons ( Citrus medica ) of South Asia; the pomelos ( C. maxima ) of Mainland Southeast Asia ; the mandarins ( C. reticulata ), kumquats ( C. japonica ), mangshanyegan ( C. mangshanensis ), and ichang papedas ( C. cavaleriei ) of southeastern China; the kaffir limes ( C. hystrix ) of Island Southeast Asia ; and the biasong and samuyao ( C. micrantha ) of
3872-415: The euglenids and chlorarachniophytes . They are also found in one lineage of dinoflagellates and possibly the ancestor of the CASH lineage ( cryptomonads , alveolates , stramenopiles and haptophytes ) Many green algal derived chloroplasts contain pyrenoids , but unlike chloroplasts in their green algal ancestors, storage product collects in granules outside the chloroplast. The euglenophytes are
3960-422: The heme pathway. The most important apicoplast function is isopentenyl pyrophosphate synthesis—in fact, apicomplexans die when something interferes with this apicoplast function, and when apicomplexans are grown in an isopentenyl pyrophosphate-rich medium, they dump the organelle. The Chromerida is a newly discovered group of algae from Australian corals which comprises some close photosynthetic relatives of
4048-418: The nucleus of the host. Some of the cyanobacterial proteins were then synthesized by host cell and imported back into the chloroplast (formerly the cyanobacterium), allowing the host to control the chloroplast. Chloroplasts which can be traced back directly to a cyanobacterial ancestor (i.e. without a subsequent endosymbiotic event) are known as primary plastids (" plastid " in this context means almost
4136-503: The photosynthetic pigments chlorophyll a , chlorophyll c 2 , beta -carotene , and at least one dinophyte-unique xanthophyll ( peridinin , dinoxanthin , or diadinoxanthin ), giving many a golden-brown color. All dinophytes store starch in their cytoplasm, and most have chloroplasts with thylakoids arranged in stacks of three. The fucoxanthin dinophyte lineages (including Karlodinium and Karenia ) lost their original red algal derived chloroplast, and replaced it with
4224-522: The rhodoplast lineage. The chloroplast is surrounded by two membranes and has no nucleomorph—all the nucleomorph genes have been transferred to the dinophyte nucleus . The endosymbiotic event that led to this chloroplast was serial secondary endosymbiosis rather than tertiary endosymbiosis—the endosymbiont was a green alga containing a primary chloroplast (making a secondary chloroplast). Secondary chloroplasts derived from red algae appear to have only been taken up only once, which then diversified into
4312-643: The Mediterranean by Arab traders around the 10th century CE. Sweet oranges were brought to Europe by the Genoese and Portuguese from Asia during the 15th to 16th century. Mandarins were not introduced until the 19th century. Oranges were introduced to Florida by Spanish colonists. In cooler parts of Europe, citrus fruit was grown in orangeries starting in the 17th century; many were as much status symbols as functional agricultural structures. The generic name Citrus originates from Latin , where it denoted either
4400-733: The apicomplexans. The first member, Chromera velia , was discovered and first isolated in 2001. The discovery of Chromera velia with similar structure to the apicomplexans, provides an important link in the evolutionary history of the apicomplexans and dinophytes. Their plastids have four membranes, lack chlorophyll c and use the type II form of RuBisCO obtained from a horizontal transfer event. The dinoflagellates are yet another very large and diverse group, around half of which are at least partially photosynthetic (i.e. mixotrophic ). Dinoflagellate chloroplasts have relatively complex history. Most dinoflagellate chloroplasts are secondary red algal derived chloroplasts. Many dinoflagellates have lost
4488-437: The blue-green chlorophyll a and other pigments, many are reddish to purple from the combination. The red phycoerytherin pigment is an adaptation to help red algae catch more sunlight in deep water —as such, some red algae that live in shallow water have less phycoerythrin in their rhodoplasts, and can appear more greenish. Rhodoplasts synthesize a form of starch called floridean starch , which collects into granules outside
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#17330924352144576-429: The cell. This event is called endosymbiosis , or "cell living inside another cell with a mutual benefit for both". The external cell is commonly referred to as the host while the internal cell is called the endosymbiont . The engulfed cyanobacteria provided an advantage to the host by providing sugar from photosynthesis. Over time, the cyanobacterium was assimilated, and many of its genes were lost or transferred to
4664-518: The center of origin of the genus Citrus is likely the southeast foothills of the Himalayas , in a region stretching from eastern Assam , northern Myanmar , to western Yunnan . It diverged from a common ancestor with Poncirus trifoliata . A change in climate conditions during the Late Miocene (11.63 to 5.33 mya ) resulted in a sudden speciation event . The species resulting from this event include
4752-415: The chloroplast (becoming nonphotosynthetic), some of these have replaced it though tertiary endosymbiosis. Others replaced their original chloroplast with a green algal derived chloroplast. The peridinin chloroplast is thought to be the dinophytes' "original" chloroplast, which has been lost, reduced, replaced, or has company in several other dinophyte lineages. The most common dinophyte chloroplast
4840-466: The chloroplast membranes fuse into a double membrane. Their thylakoids are arranged in loose stacks of three. Chlorarachniophytes have a form of polysaccharide called chrysolaminarin , which they store in the cytoplasm, often collected around the chloroplast pyrenoid , which bulges into the cytoplasm. Chlorarachniophyte chloroplasts are notable because the green alga they are derived from has not been completely broken down—its nucleus still persists as
4928-421: The chloroplast thylakoids are arranged in grana stacks. Some green algal chloroplasts contain a structure called a pyrenoid , that concentrate RuBisCO and CO 2 in the chloroplast, functionally similar to the glaucophyte carboxysome . There are some lineages of non-photosynthetic parasitic green algae that have lost their chloroplasts entirely, such as Prototheca , or have no chloroplast while retaining
5016-729: The citations of their names are actually referring to this book. Citrus Ancestral species: Citrus maxima – Pomelo Citrus medica – Citron Citrus reticulata – Mandarin orange Citrus micrantha – a papeda Citrus hystrix – Kaffir lime Citrus cavaleriei – Ichang papeda Citrus japonica – Kumquat Important hybrids: Citrus × aurantiifolia – Key lime Citrus × aurantium – Bitter orange Citrus × latifolia – Persian lime Citrus × limon – Lemon Citrus × limonia – Rangpur Citrus × paradisi – Grapefruit Citrus × sinensis – Sweet orange Citrus × tangerina – Tangerine See also List of citrus fruits . Citrus
5104-458: The damaging citrus tristeza virus , while the aphid-like Asian citrus psyllid can carry the bacterium which causes the serious citrus greening disease . This threatens production in Florida, California, and worldwide. Citrus groves are attacked by parasitic Nematodes including citrus ( Tylenchulus semipenetrans ) and sheath nematodes ( Hemicycliophora spp.). Citrus plants can develop
5192-432: The deficiency condition chlorosis , characterized by yellowing leaves. The condition is often caused by an excessively high pH ( alkaline soil ), which prevents the plant from absorbing nutrients such as iron, magnesium , and zinc needed to produce chlorophyll . Some Citrus species contain significant amounts of furanocoumarins . In humans, some of these act as strong photosensitizers when applied topically to
5280-415: The desired fruiting cultivars onto rootstocks selected for disease resistance and hardiness. The trees are not generally frost hardy. They thrive in a consistently sunny, humid environment with fertile soil and adequate water. The colour of citrus fruits only develops in climates with a ( diurnal ) cool winter. In tropical regions with no winter at all, citrus fruits remain green until maturity, hence
5368-515: The earliest evidence are seeds recovered from the Hala Sultan Tekke site of Cyprus , dated to around 1200 BCE. Other archaeobotanical evidence includes pollen from Carthage dating back to the 4th century BCE; and carbonized seeds from Pompeii dated to around the 3rd to 2nd century BCE. The earliest complete description of the citron was written by Theophrastus , c. 310 BCE . Lemons, pomelos, and sour oranges were introduced to
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#17330924352145456-749: The early 21st century mainly by the increase in cultivation areas, improvements in transportation and packaging, rising incomes and consumer preference for healthy foods. In 2019–20, world production of oranges was estimated to be 47.5 million tonnes, led by Brazil, Mexico, the European Union, and China as the largest producers. Among the diseases of citrus plantations are citrus black spot (a fungus), citrus canker (a bacterium), citrus greening (a bacterium, spread by an insect pest), and sweet orange scab (a fungus, Elsinöe australis ). Citrus plants are liable to infestation by ectoparasites which act as vectors to plant diseases: for example, aphids transmit
5544-761: The genus Citrus associated with modern Citrus cultivars are the mandarin orange , pomelo , and citron . Almost all of the common commercially important citrus fruits (sweet oranges, lemons, grapefruit, limes, and so on) are hybrids between these three species, their main progenies, and other wild Citrus species within the last few thousand years. Citrus plants are native to subtropical and tropical regions of Asia, Island Southeast Asia , Near Oceania , and northeastern and central Australia. Domestication of citrus species involved much hybridization and introgression , leaving much uncertainty about when and where domestication first happened. A genomic, phylogenic, and biogeographical analysis by Wu et al. (2018) has shown that
5632-551: The genus Citrus . The false oranges, Oxanthera from New Caledonia , have been transferred to the Citrus genus on phylogenetic evidence. The earliest introductions of citrus species by human migrations was during the Austronesian expansion ( c. 3000 –1500 BCE), where Citrus hystrix , Citrus macroptera , and Citrus maxima were among the canoe plants carried by Austronesian voyagers eastwards into Micronesia and Polynesia . The citron ( Citrus medica )
5720-453: The locules, which provide nourishment to the fruit as it develops. The genus is commercially important with cultivars of many species grown for their fruit. Some cultivars have been developed to be easy to peel and seedless, meaning they are parthenocarpic . The fragrance of citrus fruits is conferred by flavonoids and limonoids in the rind. The flavonoids include various flavanones and flavones . The carpels are juicy; they contain
5808-553: The main genus, Citrus , and the genus Poncirus (such as the trifoliate orange ), which is closely enough related that it can still be hybridized with all other citrus and used as rootstock. These estimates are made using genetic mapping of plant chloroplasts . A DNA study published in Nature in 2018 concludes that the genus Citrus evolved in the foothills of the Himalayas , in the area of Assam (India), western Yunnan (China), and northern Myanmar . The three ancestral species in
5896-685: The membranes are not connected to the endoplasmic reticulum . Other apicomplexans like Cryptosporidium have lost the chloroplast completely. Apicomplexans store their energy in amylopectin granules that are located in their cytoplasm, even though they are nonphotosynthetic. The fact that apicomplexans still keep their nonphotosynthetic chloroplast around demonstrates how the chloroplast carries out important functions other than photosynthesis . Plant chloroplasts provide plant cells with many important things besides sugar, and apicoplasts are no different—they synthesize fatty acids , isopentenyl pyrophosphate , iron-sulfur clusters , and carry out part of
5984-656: The nucleus of their hosts. About 0.3–0.8% of the nuclear DNA in Paulinella is from the chromatophore, compared with 11–14% from the chloroplast in plants. Similar to other chloroplasts, Paulinella provides specific proteins to the chromatophore using a specific targeting sequence. Because chromatophores are much younger compared to the canoncial chloroplasts, Paulinella chromatophora is studied to understand how early chloroplasts evolved. Green algae have been taken up by many groups in three or four separate events. Primarily, secondary chloroplasts derived from green algae are in
6072-410: The pericarp is the mesocarp, which in citrus fruits consists of the white, spongy albedo or pith. The innermost layer of the pericarp is the endocarp. This surrounds a variable number of carpels , shaped as radial segments. The seeds, if present, develop inside the carpels. The space inside each segment is a locule filled with juice vesicles , or pulp. From the endocarp, string-like "hairs" extend into
6160-434: The plant cell and must be inherited by each daughter cell during cell division, which is thought to be inherited from their ancestor—a photosynthetic cyanobacterium that was engulfed by an early eukaryotic cell. Chloroplasts evolved from an ancient cyanobacterium that was engulfed by an early eukaryotic cell. Because of their endosymbiotic origins, chloroplasts, like mitochondria , contain their own DNA separate from
6248-403: The presence of essential oil glands. The fruit is a hesperidium , a specialised berry with multiple carpels , globose to elongated, 4–30 cm (1.6–11.8 in) long and 4–20 cm (1.6–7.9 in) diameter, with a leathery rind or "peel" called a pericarp . The outermost layer of the pericarp is an "exocarp" called the flavedo , commonly referred to as the zest . The middle layer of
6336-451: The primary chloroplast lineages through secondary endosymbiosis—engulfing a red or green alga with a primary chloroplast. These chloroplasts are known as secondary plastids . As a result of the secondary endosymbiotic event, secondary chloroplasts have additional membranes outside of the original two in primary chloroplasts. In secondary plastids, typically only the chloroplast, and sometimes its cell membrane and nucleus remain, forming
6424-585: The production and release of ethylene is gradual. According to the UN Food and Agriculture Organization , world production of all citrus fruits in 2016 was 124 million tonnes, with about half of this production as oranges. At US $ 15.2 billion equivalent in 2018, citrus trade makes up nearly half of the world fruit trade, which was US$ 32.1 billion that year. According to the United Nations Conference on Trade and Development , citrus production grew during
6512-443: The red and green chloroplasts. This early divergence is supported by both phylogenetic studies and physical features present in glaucophyte chloroplasts and cyanobacteria, but not the red and green chloroplasts. First, glaucophyte chloroplasts have a peptidoglycan wall, a type of cell wall otherwise only in bacteria (including cyanobacteria). Second, glaucophyte chloroplasts contain concentric unstacked thylakoids which surround
6600-561: The resting cells of Haematococcus pluvialis . Green chloroplasts differ from glaucophyte and red algal chloroplasts in that they have lost their phycobilisomes , and contain chlorophyll b . They have also lost the peptidoglycan wall between their double membrane, leaving an intermembrane space. Some plants have kept some genes required the synthesis of peptidoglycan, but have repurposed them for use in chloroplast division instead. Chloroplastida lineages also keep their starch inside their chloroplasts. In plants and some algae,
6688-428: The rhodoplast, in the cytoplasm of the red alga. The chloroplastida group is another large, highly diverse lineage that includes both green algae and land plants . This group is also called Viridiplantae , which includes two core clades— Chlorophyta and Streptophyta . Most green chloroplasts are green in color, though some aren't due to accessory pigments that override the green from chlorophylls, such as in
6776-405: The same ancestral endosymbiotic event and are all within the group Archaeplastida . The glaucophyte chloroplast group is the smallest of the three primary chloroplast lineages as there are only 25 described glaucophyte species. Glaucophytes diverged first before the red and green chloroplast lineages diverged. Because of this, they are sometimes considered intermediates between cyanobacteria and
6864-473: The same thing as chloroplast ). Chloroplasts that can be traced back to another photosynthetic eukaryotic endosymbiont are called secondary plastids or tertiary plastids (discussed below). Whether primary chloroplasts came from a single endosymbiotic event or multiple independent engulfments across various eukaryotic lineages was long debated. It is now generally held that with one exception (the amoeboid Paulinella chromatophora ), chloroplasts arose from
6952-452: The second and third membranes of the chloroplast. All secondary chloroplasts come from green and red algae . No secondary chloroplasts from glaucophytes have been observed, probably because glaucophytes are relatively rare in nature, making them less likely to have been taken up by another eukaryote. Still other organisms, including the dinoflagellates Karlodinium and Karenia , obtained chloroplasts by engulfing an organism with
7040-426: The secondary host's phagosomal membrane. Euglenophyte chloroplasts have a pyrenoid and thylakoids stacked in groups of three. The carbon fixed through photosynthesis is stored in the form of paramylon , which is contained in membrane-bound granules in the cytoplasm of the euglenophyte. Chlorarachniophytes are a rare group of organisms that also contain chloroplasts derived from green algae, though their story
7128-478: The separate chloroplast genome, as in Helicosporidium . Morphological and physiological similarities, as well as phylogenetics , confirm that these are lineages that ancestrally had chloroplasts but have since lost them. The photosynthetic amoeboids in the genus Paulinella —P. chromatophora, P. micropora, and marine P. longichromatophora— have the only known independently evolved chloroplast, often called
7216-449: The skin, while others interact with medications when taken orally in the grapefruit juice effect . Due to the photosensitizing effects of certain furanocoumarins, some Citrus species cause phytophotodermatitis , a potentially severe skin inflammation resulting from contact with a light-sensitizing botanical agent followed by exposure to ultraviolet light. In Citrus species, the primary photosensitizing agent appears to be bergapten ,
7304-493: The success of the citrus industry in all means. It is considered the Bible of citrus farming. The book was originally published between the years 1943-1948, which is its first edition. It was revised in the 1960s by Walter Reuther with major reconstruction, and republished starting in 1976-1989. The Second Edition is much updated, but some interesting material was removed. Many of the mentioned are classical abbreviation authors, and
7392-480: The tropical "green oranges". The terms 'ripe' and 'mature' are widely used synonymously, but they mean different things. A mature fruit is one that has completed its growth phase. Ripening is the sequence of changes within the fruit from maturity to the beginning of decay. These changes involve the conversion of starches to sugars, a decrease in acids, softening, and s change in the fruit's colour. Citrus fruits are non- climacteric and respiration slowly declines and
7480-406: The weather is too cold to grow it outdoors; Citrofortunella hybrids have good cold resistance. Lemons appear in paintings, pop art, and novels. A wall painting in the tomb of Nakht in 15th century BC Egypt depicts a woman in a festival, holding a lemon. In the 17th century, Giovanna Garzoni painted a Still Life with Bowl of Citrons , the fruits still attached to leafy flowering twigs, with
7568-529: Was also introduced early into the Mediterranean basin from India and Southeast Asia. It was introduced via two ancient trade routes: an overland route through Persia , the Levant and the Mediterranean islands; and a maritime route through the Arabian Peninsula and Ptolemaic Egypt into North Africa. Although the exact date of the original introduction is unknown due to the sparseness of archaeobotanical remains,
7656-605: Was given by Hugo von Mohl in 1837 as discrete bodies within the green plant cell. In 1883, Andreas Franz Wilhelm Schimper named these bodies as "chloroplastids" ( Chloroplastiden ). In 1884, Eduard Strasburger adopted the term "chloroplasts" ( Chloroplasten ). The word chloroplast is derived from the Greek words chloros (χλωρός), which means green, and plastes (πλάστης), which means "the one who forms". Chloroplasts are one of many types of organelles in photosynthetic eukaryotic cells. They evolved from cyanobacteria through
7744-534: Was heavily reduced, stripped of a few membranes and its nucleus, leaving only its chloroplast (with its original double membrane), and possibly one or two additional membranes around it. Fucoxanthin-containing chloroplasts are characterized by having the pigment fucoxanthin (actually 19′-hexanoyloxy-fucoxanthin and/or 19′-butanoyloxy-fucoxanthin ) and no peridinin. Fucoxanthin is also found in haptophyte chloroplasts, providing evidence of ancestry. Some dinophytes, like Kryptoperidinium and Durinskia , have
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