Resolve years of doubt: What is the relationship between nori and purple laver?

Don't rush to accuse the manufacturer of being unscrupulous. In modern Chinese contexts, although seaweed and laver are not the same thing, we can say that seaweed is a type of laver. The dark green, thin, and crispy seaweed sold on the Chinese market is mostly processed Pyropia yezoensis.

However, "laver" is not a single species but a general term for hundreds of species in the Bangiaceae family of red algae. Therefore, we can say that the seaweed sold in China is a type of laver, but not all laver is processed into seaweed. In addition to Pyropia yezoensis, China mainly cultivates Pyropia haitanensis. Pyropia haitanensis is a species endemic to China, and the specific epithet "haitanensis" in its scientific name originates from Haitan Island in Pingtan County, Fujian Province. In traditional classification, these two types of laver belonged to the genus Porphyra, but in recent years, researchers have reclassified them into the new genus Pyropia based on molecular evidence, and their scientific names have consequently changed.

Laver lives in the intertidal zone of coastal waters and is widely distributed along China's long coastline. Most of the laver produced in the northern coastal areas is Pyropia yezoensis, while Pyropia haitanensis is extensively cultivated in the south. Early settlers, striving for sustenance, recognized this easily collected delicious seaweed long ago. Volume 10 of "Qimin Yaoshu" quotes the "Records of the Seas of Wujun" stating, "All the mountains by the sea in Wudu are covered with laver," and mentions methods for pan-frying laver and making laver soup.

Since there is more than one type of laver, can they be distinguished on the dining table? There is a general method of distinction, as we mentioned earlier: Pyropia yezoensis is generally used to process into seaweed, and it usually appears as neatly cut, square, dried thin sheets in food. Pyropia haitanensis is consumed in a more traditional way, usually dried and processed into round discs for sale, and then floats in laver soup.

When laver is fresh, it exhibits varying shades of purplish-red due to the presence of phycoerythrin in its cells. Because phycoerythrin degrades quickly, except for very fresh laver which will be purplish-red, most laver, after processing, storage, and transportation, will only retain chlorophyll, making it appear green. If it is overheated or stored for too long, causing the chlorophyll to decompose as well, the laver will turn dark brown. Therefore, we can use the color of the laver to roughly judge its freshness.

In China, laver generally appears on coastal rocks every autumn and winter, and can be harvested from winter until late spring. However, the whereabouts of laver in summer have always been a mystery. In the late 19th century, the conchospores of laver and their filamentous stage after germination were discovered, but how they developed from the filamentous stage into laver could not be answered. In 1892, Batters named a filamentous marine red alga, Conchocelis rosea. By 1949, algologist Drew proved that Conchocelis rosea was the filamentous stage of laver. Subsequently, Japanese scholar Kurogi Mutsuo and Chinese scholar Zeng Chengkui published articles in 1953 and 1954 respectively, revealing the life cycle of laver.

In the life cycle of laver, there is an alternation of the haploid gametophyte generation and the diploid sporophyte generation. This phenomenon is called alternation of generations. The alternation of generations in laver is complex and varies among different species. Briefly speaking, the edible part of laver is its gametophyte generation – the thallus. The thallus produces male and female reproductive cells, which combine to form conchospores. The conchospores have a special developmental site in the natural environment – inside mollusk shells. When conchospores come into contact with shells, they burrow into the shells and develop into filamentous stages (Conchocelis). The process described above lasts from winter to early summer. During this period, the thallus is large and easily collected by people.

As summer arrives, the laver thallus completes its mission. The filamentous stage residing in mollusk shells releases conchospores. These conchospores attach to rocks and germinate, then undergo meiosis to grow into macroscopic thalli. In a sense, the laver we eat is actually an aggregate of its asexual reproductive cells. Therefore, the reason why living laver is not commonly seen in summer is simply because their thalli have not yet grown large. One of the biggest differences between Porphyra yezoensis and Porphyra haitanensis is the cells that make up the thallus. The thallus of Porphyra yezoensis possesses both male and female reproductive cells, while each thallus of Porphyra haitanensis generally releases only one type of cell, either male or female.

However, if we travel across the ocean to neighboring Japan, the relationship between nori and purple laver undergoes a major reversal. In Japanese cuisine, you can find more types of nori, some of which look quite different from the nori we have domestically. This is because Japan is the origin of the word "nori," and the species referred to by "nori" are different from those in modern Chinese contexts. Purple laver (zicai) from the red algae phylum is just one category. Therefore, it can be said that in Japanese, purple laver is a type of nori, but nori cannot be said to be purple laver.

The word "nori" (のり) appeared in Japanese literature as early as the early Nara period in the 8th century. In the "Hitachi Province Fudoki," it is recorded in Chinese characters: "An ancient saying goes: Emperor Wumu toured the coast and arrived at Naruhama. At that time, there was much dried nori on the shore, commonly called 'nori,' hence the name Norihama Village." Translated, it means Emperor Wumu (Yamato Takeru) toured a beach in present-day Ibaraki Prefecture, found a lot of nori (のり) drying on the beach, and named the place Nori Beach (のりはま), written in Chinese characters as Naruhama (のりはま). By the 10th century, in "Wamyō Ruijushō" and "Utsubo Monogatari," more specific types like sweet nori and purple nori appeared. Depending on the processing method, there are also distinctions like raw nori and sheet nori. What is generally called nori in China is sheet nori, which is dried purple laver processed into a paper-like form.

The scope of the Japanese word "nori" is broader than the Chinese word "nori." It includes not only two genera from the red algae family but also algae from the green algae phylum such as the Ulva genus (Ulva), Enteromorpha genus (Enteromorpha), and Prasiola japonica, as well as the prokaryotic cyanobacterium Aphanothece sacrum from the cyanobacteria phylum. Among these, purple laver, Ulva, and Enteromorpha have now achieved large-scale commercial cultivation.

The diversity of Japanese "nori" is often reflected in culinary manga. In the story of the 25th night of the second volume of "Midnight Diner," the "Aonori from the Shimanto River," symbolizing the bond between father and daughter, is actually Enteromorpha produced in the Shimanto River on Shikoku Island. It also has a Chinese character name, Suji Aonori, and is a high-quality ingredient in Japanese yakisoba and takoyaki. In addition to telling a touching story, the author conveys a message through the manga characters: "The aroma of Aonori from the Shimanto River is completely different." This is because authentic aonori should originally be made using species from the Enteromorpha genus. Due to limited production, some aonori in recent years uses artificially cultivated algae from the Ulva genus. In the eyes of Japanese people with sensitive taste buds, Ulva-based aonori is not as delicious as the authentic Enteromorpha-based aonori from the Shimanto River.