Abstract
In Southeast Asia, floating rice is grown in lowlying areas of Thailand, Vietnam, Cambodia and Burma. The floating rice plant is characterized by its ability to elongate at the internode in lag phases during the rise in water level. The lowest elongated internode (LEI) of the plant varied from one variety to another and from one country to another. The mean value of the LEI position was at internode 10.7 for Vietnam, 10.8 for Thailand, 11.1 for Cambodia and 12.3 for Burma. These values are larger than the mean value of Bangladesh floating rice varieties. Considering the presence of awns, the length/width ratio of grains, the acid phosphatase isozyme genotype, and other factors besides the elongation ability of the plants, floating rice in Southeast Asia seems to belong to a different ecotype group from Bangladesh floating rice. The former may be more evolved than the latter.
