Abstract
One of the deepwater rice (Oryza sativa L.), cultivar. 'Habiganj Aman VIII' was used as materials. Elongation ability of deepwater rice is closely related to the phase change of the main stem from the primary phase (short non-elongated internodes are formed) to the secondary phase (long elongated internodes are formed). Here, NNEI (number of non-elongated internodes) is used as a new index to evaluate the rate of the phase change of main stem and the primary tillers on the different positions of the main stem. The phase change of the primary tillers was closely related to that of main stem. NNEI was greater in the tillers at the lower position of the main stem. NNEI was zero in the tillers at the higher position of the main stem. These tiller buds are formed during the secondary phase and usually do not grow because of their dormancy which is due to apical dominance. However, when the tiller bud growth was released, the longer dormancy period was, the more NNEI in these tillers was found. In conclusion, the phase change of tillers is greatly influenced by that of the main stem. On the other hand, the NNEI seems to be dependent on the developmental stage of the tiller itself at the time of phase change in the main stem.
