Porphyra is agenus of coldwaterseaweeds that grow in cold, shallowseawater. More specifically, it belongs tored algae phylum of laver species (from which comeslaverbread), comprising approximately 70 species.[2] It grows in theintertidal zone, typically between the upper intertidal zone and thesplash zone in cold waters oftemperate oceans. In East Asia, it is used to produce thesea vegetable productsnori (in Japan) andgim (in Korea). There are considered to be 60–70 species ofPorphyra worldwide[3] and seven around Britain and Ireland, where it has been traditionally used to produce ediblesea vegetables on theIrish Sea coast.[4] The speciesPorphyra purpurea has one of the largestplastidgenomes known, with 251 genes.[5]
Porphyra displays a heteromorphicalternation of generations.[6] Thethallus we see is thehaploid generation; it can reproduce asexually by formingspores which grow to replicate the original thallus. It can also reproduce sexually. Both male and femalegametes are formed on the one thallus. The female gametes while still on the thallus are fertilized by the released male gametes, which are non-motile. The fertilized, nowdiploid, carposporangia aftermitosis produce spores (carpospores) which settle, then bore into shells, germinate and form a filamentous stage. This stage was originally thought to be a different species of alga, and was referred to asConchocelis rosea. ThatConchocelis was thediploid stage ofPorphyra was discovered in 1949 by the BritishphycologistKathleen Mary Drew-Baker for theEuropean speciesPorphyra umbilicalis.[7] It was later shown for species from other regions as well.[2][8]
Most human cultures with access toPorphyra use it as a food or somehow in the diet, making it perhaps the most domesticated of the marine algae,[9] known aslaver,rong biển (Vietnamese),nori (Japanese:海苔),amanori (Japanese),[10]zakai,gim (Korean:김),[10]zǐcài (Chinese:紫菜),[10]karengo,sloke orslukos.[3] The marine red algaPorphyra has been cultivated extensively in manyAsian countries as anedible seaweed used to wrap the rice and fish that compose the Japanese foodsushi and the Korean foodgimbap. In Japan, the annual production ofPorphyra species is valued at 100 billionyen (US$1 billion).[11]
P.umbilicalis is harvested from the coasts of Great Britain and Ireland, where it has a variety of culinary uses, includinglaverbread.[12] In Hawaii, "the speciesP.atropurpurea is considered a delicacy, calledLimu luau".[12] Porphyra was also harvested by theSouthern Kwakiutl,Haida, Seechelt,Squawmish,Nuu-chah-nulth,Nuxalk,Tsimshian, andTlingit peoples of the North American Pacific coast.[12]
Porphyra containsvitamin B12 and one study suggests that it is the most suitable non-meat source of this essential vitamin.[13] In the view of the Academy of Nutrition and Dietetics, however, it may not provide an adequate source of B12 forvegans.[14]
Following a major reassessment of the genus in 2011, many species previously included inPorphyra have been transferred toPyropia: for examplePyropia tenera,Pyropia yezoensis, and the species from New ZealandPyropia rakiura andPyropia virididentata, leaving only five species out of seventy still withinPorphyra itself.[16]
^abGuiry, Michael D. (2012). Porphyra. In: Guiry, M.D. & Guiry, G.M. (2017). AlgaeBase. World-wide electronic publication, National University of Ireland, Galway (taxonomic information republished from AlgaeBase with permission of M.D. Guiry). Accessed through: World Register of Marine Species athttp://www.marinespecies.org/aphia.php?p=taxdetails&id=143808 on 2017-09-06
^abBrodie, J.A. and Irvine, L.M. 2003.Seaweeds of the British Isles. Volume 1 Part 3b. The Natural History Museum, London.ISBN1 898298 87 4
^abKain, J.M. 1991. Cultivation of attached seaweeds. in Guiry, M.D. and Blunden, G. 1992.Seaweed Resources in Europe: Uses and Potential. John Wiley and Sons, ChichesterISBN0-471-92947-6
^Hardy, F.G. and Guiry, M.D. 2006.A Check-list and Atlas of the Seaweeds of Britain and Ireland. British Phycological Society, London.ISBN3-906166-35-X
^Thomas, D. 2002.Seaweeds. The Natural History Museum, London.ISBN0-565-09175-1
^Mumford, T.F. and Miura, A. 4.Porphyra as food: cultivation and economics. in Lembi, C.A. and Waaland, J.R. 1988.Algae and Human Affairs. Cambridge University Press, Cambridge.ISBN0-521-32115-8
^Aoki, Y. and Kamei, Y. 2006 Preparation of recombinant polysaccharide-degrading enzymes from the marine bacterium,Pseudomonas sp. ND137 for the production of protoplasts ofPorphyra yezoensisEur. J. Phycol.41: 321-328.
^Melina V, Craig W, Levin S (2016)."Position of the Academy of Nutrition and Dietetics: Vegetarian Diets".J Acad Nutr Diet.116 (12):1970–1980.doi:10.1016/j.jand.2016.09.025.PMID27886704.S2CID4984228.Fermented foods (such as tempeh), nori, spirulina, chlorella algae, and unfortified nutritional yeast cannot be relied upon as adequate or practical sources of B-12.39,40 Vegans must regularly consume reliable sources— meaning B-12 fortified foods or B-12 containing supplements—or they could become deficient, as shown in case studies of vegan infants, children, and adults.
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