2021年10月30日土曜日

The original species seems to be L. serriola L., which is distributed from the eastern Mediterranean coast to Asia Minor. It is said that this is because only this species is freely crossed to produce seeds among several wild species closely related to lettuce. It seems that it is known from the mural painting that it was already used in Egypt around 4500 BC. Furthermore, it seems that it was introduced to Greece and Italy and became an important vegetable. However, I heard that all of these were non-heading lettuce. Heading lettuce seems to be known in Europe only in the middle of the 16th century. In China, around 600-900 AD, stalk lettuce, which is an unusual cultivar group that feeds on enlarged stalks, is being cultivated. It was introduced to Japan through China and seems to have been widely cultivated. At present, ball lettuce has become a common vegetable in Japan. Head lettuce has been introduced and cultivated as a western vegetable in the Meiji era. In addition, it was after World War II that the crisp head type that completely headed was cultivated, and it is considered to be a completely new vegetable. The head lettuce used today has been bred in Europe and the United States since the 16th century, and it seems that it has changed beyond imagination from its former form. Unlike traditional varieties, it prefers a cool climate and the optimum temperature for seed germination is 15 to 20 ° C, but the germination rate drops significantly after 25 ° C. Seeds also go dormant when the temperature rises.

It is a well-known fact that the green leaves of lettuce are rich in vitamin E. Vitamin E improves blood circulation, suppresses active oxyg...