Porphyra is a genus of coldwater that grow in cold, shallow seawater. More specifically, it belongs to red algae phylum of laver species (from which comes laverbread), comprising approximately 70 species.[Brodie, J.A. and Irvine, L.M. 2003. Seaweeds of the British Isles. Volume 1 Part 3b. The Natural History Museum, London.] It grows in the intertidal zone, typically between the upper intertidal zone and the splash zone in cold waters of temperate oceans. In East Asia, it is used to produce the seaweed products nori (in Japan) and gim (in Korea). There are considered to be 60–70 species of Porphyra worldwide[Kain, 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, Chichester ] and seven around Britain and Ireland, where it has been traditionally used to produce edible edible seaweed on the Irish Sea coast.[Hardy, F.G. and Guiry, M.D. 2006. A Check-list and Atlas of the Seaweeds of Britain and Ireland. British Phycological Society, London. ] The species Porphyra purpurea has one of the largest plastid known, with 251 genes.[ The Chlamydomonas Sourcebook: Organellar and Metabolic Processes Volum 2]
Life cycle
Porphyra displays a heteromorphic alternation of generations.
[ Porphyra life cycle ] The
thallus we see is the
Ploidy generation; it can reproduce asexually by forming
which grow to replicate the original thallus. It can also reproduce sexually. Both male and female
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, now
Ploidy, carposporangia after
mitosis produce spores (
) 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 as
Conchocelis rosea. That
Conchocelis was the
Ploidy stage of
Porphyra was discovered in 1949 by the British
phycology Kathleen Mary Drew-Baker for the
species
Porphyra umbilicalis.
It was later shown for species from other regions as well.
[Thomas, D. 2002. Seaweeds. The Natural History Museum, London. ]
Food
Most human cultures with access to Porphyra use it as a food or somehow in the diet, making it perhaps the most domesticated of the marine algae,
[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. ] known as
Laverbread, rong biển (Vietnamese),
nori (Japanese:海苔),
amanori (Japanese),
,
gim (
Korean language:김),
(
Standard Chinese:紫菜),
karengo,
sloke or
slukos.
The marine red alga
Porphyra has been cultivated extensively in many
countries as an
edible seaweed used to wrap the rice and fish that compose the Japanese food
sushi and the Korean food
gimbap. In Japan, the annual production of
Porphyra species is valued at 100 billion
Japanese yen (US$1 billion).
[Aoki, Y. and Kamei, Y. 2006 Preparation of recombinant polysaccharide-degrading enzymes from the marine bacterium, Pseudomonas sp. ND137 for the production of protoplasts of Porphyra yezoensis Eur. J. Phycol. 41: 321-328.]
P.umbilicalis is harvested from the coasts of Great Britain and Ireland, where it has a variety of culinary uses, including laverbread.
Vitamin B12
Porphyra contains vitamin B12 and one study suggests that it is the most suitable non-meat source of this essential vitamin.
In the view of the Academy of Nutrition and Dietetics, however, it may not provide an adequate source of B12 for
.
Species
Porphyra currently contains 57 confirmed species and 14 unconfirmed species.
Confirmed
Unconfirmed
Following a major reassessment of the genus in 2011, many species previously included in
Porphyra have been transferred to
Pyropia: for example
Pyropia tenera,
Pyropia yezoensis, and the species from New Zealand
Pyropia rakiura and
Pyropia virididentata, leaving only five species out of seventy still within
Porphyra itself.
See also
External links
