Porphyra is a coldwater seaweed that grows in cold, shallow seawater. More specifically, it belongs tored algae phylum of laver species, comprising approximately 70 species. 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 sea vegetable productsnori and gim. There are considered to be 60 to 70 species of Porphyra worldwide and seven around Britain and Ireland where it has been traditionally used to produce edible sea vegetables on the Irish Sea coast. Porphyra is a chief source of plant-based vitamin B12.
Life cycle
Porphyra displays a heteromorphic alternation of generations. The thallus we see is the haploid generation; it can reproduce asexually by forming spores which grow to replicate the original thallus. It can also reproduce sexually. Both male and female gametes 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 diploid, 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 diploid stage of Porphyra was discovered by the British phycologistKathleen Mary Drew-Baker in 1949 for the European species Porphyra umbilicalis. It was later shown for species from other regions as well.
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, known as laver, rong biển, nori, amanori, zakai, gim, zǐcài, karengo, sloke or slukos. The marine red algaPorphyra has been cultivated extensively in many Asian countries as an edible seaweed used to wrap the rice and fish that compose the Japanese foodsushi and the Korean foodgimbap. In Japan, the annual production of Porphyra species is valued at 100 billion yen.
Species
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 ZealandPyropia rakiura and Pyropia virididentata, leaving only five species out of seventy still within Porphyra itself.
