Although Japan has a clear change of the seasons, the winter is mild, because it is surrounded by the sea. Even if it snows in the coastal area of the Japan Sea in the winter, it does not snow so heavily in the Pacific Ocean area. Because there is much rain in the summer and the air temperature and relative humidity are high, many horticultural crops are grown in the cool upland region, including the Hokkaido area. The Japanese islands are long from south to north covering north latitude 24° and 46°. Many indigenous vegetables such as water dropwort, japanese hornwort, wasabi, japanese butterbur, rakkyo, chinese chive, asatsuki, goldband lily, mioga ginger, and japanese pepper as well have been grown throughout ≈2000 years, being domesticated under selections and are now in modern Japan popular and important vegetables. Many variations have been produced under different climatic as well as soil conditions. Daikon, turnip, japanese bunching onion, komatsuna, kyona, taro, and eggplant have many variations in the growing areas. A lot of varieties are found particularly in daikon and turnip whose shape and color include small round, large round, long, and conical and white, green, and red, etc. Kyona and komatsuna belong to the same species, Brassica rapa, and also there are many useful variations as leaf vegetables in this species. Japanese bunching onion as an example has also many variations and in east Japan, the leaf sheaths are etiolated by hilling with soil during the winter and etiolated leaf sheaths are harvested in the spring, whereas in west Japan, the leaf sheaths are grown without hilling and green leaves are harvested. Those variations from indigenous vegetables are selected under every condition and various cultural methods were developed in growing areas. People have devised ways also how of cooking and using them depending on their eating habits as an established food culture.
Takashi Ikeda, Yukihiro Fujime, Satoshi Terabayashi, and Shuichi Date
Garlic (Allium sativum L.) calli in vitro were evaluated over a range of salt concentrations and by adding mannitol to culture medium with reduced salt to provide equivalent osmoticum. The water potential of the medium ranged from -0.27 to -0.73 MPa under the various salt and osmotic stress conditions. The percent increase in calli was highest in standard Murashige & Skoog (MS) medium and was reduced when MS salts were reduced but the water potential of medium was adjusted to that of standard MS medium by addition of mannitol. The water potential of callus tissue was similar to that of tissue culture media over a 20-fold range (10% to 200%) of MS concentrations. Turgor of callus tissue was not influenced by any stress conditions. These results indicate that the optimum concentration of salt and water status of medium for formation of garlic calli was provided by standard MS medium.