Abstract
Using Asian deepwater rice (Oryza sativa L.) varieties from different countries, the elongation ability of the internodes was examined by increasing the water depth. When the seedlings reached the 10-11th or the 13-14th leaf stage, submergence treatment was initiated at the rate of 2 cm/day or 4 cm/day. In 25 varieties in which the LEI position corresponded to the 9th-10th Internode, plants of all varieties used could grow until the end of the treatments (ca. 190 cm water depth or 85 days in the2cm/day-and 280 cm or 65 days in the 4cm/day-submerged lots) . Differences in plant growth were not appreciable not only among varieties of the same country but also among varieties from different countries. In 17 varieties in which the LEI position corresponded to the 12th-13th internode, three varieties in the 2 cm/day-and 13 varieties in the 4 cm/day-submerged lots could not continue to grow until the end of the treatment. In those varieties, the elongation ability of the internodes especially in the lower position was lower than that of the varieties which could grow until the end of the treatment. In Asian deepwater rice, it appears that the earlier the growth stage at which internode elongation occurs, the higher the elongation ability of internodes is. Furthermore, in the deepwater rice varieties used, increase of the water depth by 4 cm per day may be the limit for the elongation ability of internodes.
