Studies on Corresponded Relations between Plant Characters and Cultivation Methods : I. Distribution and natural environments of native millets in Gifu prefecture and temperature response of the seed germination

Abstract

This study was done to understand the corresponded relations between plant characters and cultivation methods by using the five native millets (Setaria italica Beauv., Panicum miliaceum L., Echinochloa utilis Ohwi et Yabuno, Sorghum bicolor Moench, Eleusine coracana Gaertn.) collected in Gifu prefecture in 1974 to 1975. As the first step for this purpose, the relations between plant characters and the environmental conditions in the places where authors had investigated to find the above materials was discussed in this paper. In addition to the discriptions of the geographical distribution and natural environmental conditions of collected samples, here are results of the seed germination test which was conducted under the various temperatures (15°C, 25°C, 35°C and 45°C). 1) Distribution and natural environments: Most of Echinochloa utilis were cultivated in Hida area which situated at the high elevation (500-1, 300 m) and Sorghum bicolor were distributed at the low or middle elevation (100-600 m) Mino area. Other two crops, i.e. Setaria italica and Panicum miliaceum had been grown over all areas of Gifu prefecture. Temperature, rainfall and water holding capacity of the soil in the sampling plots were investigated to grasp the environmental conditions of the crops and obtained main values were as follows: As to mean minimum temperature at the sowing time and accumulated temperature during cultivation period, the values of the sowed areas of Echinochloa utilis were the lowest (7-10°C, 2, 720-3, 920°C) and those of Sorghum bicolor were the highest (10-14°C, 3, 540-4, 150°C) of all the samples. Total rainfall during the same period was 1, 060-1, 750 mm in Echinochloa utilis, 1, 150-1, 750 mm in Panicum miliaceum, 1, 210-1, 750 mm in Setaria italica and Sorghum bicolor. Moisture ratios at pF=3.0 to determine water holding capacity of the soil were 17-32% in Panicum miliaceum, 16-42% in Setaria italica and Sorghum bicolor, 22-60% in Echinochloa utilis, respectively. Eleucine coracana showed the similar tendency to Sorghum bicolor on the above environmental conditions though thc number of cultivation examples for this crop was only three in this survey. 2) Germination test: Germination percentage of each strain reached almost 100% and average required days for germination was mostly one day at 25°C and 35°C. In the case of Echinochloa utilis, the germination rate and average required days for germination at 15°C was 42.8-88.0% and 4.1-4.8 days but those of Sorghum bicolor was 4.0-28.0% and 5.3-6.2 days respectively. On the other case of 45°C, Sorghum bicolor showed 85.2-96.0% of germination percentage, but those of Setaria italica and Panicum miliaceum were indicated 22.8-72.0% and 32.0-62.8% respectively. As far as plant growth at 8 days after germination was concerned, maximum values of plant height of Echinochloa utilis and Panicum miliaceum were found at 35°C and those of root length were gained at 25°C. In the case of Sorghum bicolor and Setaria italica, both of maximum values on plant height and root length were obtained at 25°C. On the while, dry matter weight of Sorghum bicolor was the heaviest in 35°C but those of the rest crops were maximum in 25°C. Among the strains of Echinochloa utilis, Setaria italica and Panicum miliaceum used in this experiment, it was tended that the dry matter weight of strains in the higher elevation was the heavier than those of lower elevation at 15°C. From the above results, it was manifest that the geographical distribution of the used native millets coincided with the plant character, their temperature response at the early growth stages including germination, and also suggested that the ability of crops for cold resistance was one of the most important factors to determine the crops cultivated in the high land.