Abstract
The growth and dry matter production in the early to middle growth stage of Manaw Thu Kha (MTK), a high yielding rice cultivar in Myanmar, were studied in comparison with Japanese cultivars (JP), Koshihikari and Nipponbare. The pot experiments were carried out in spring and summer, in 2002 to 2004. The leaf emergence rate, number of stems and leaf area were greater in MTK than in JP. The difference in leaf emergence rate between MTK and JP was larger in spring than in summer. The leaf number on the main stem of MTK was apparently larger than that of JP at 30 days after transplanting. The number of tillers in MTK was about two times as large as that in JP in both seasons in 2004. The dry matter (DM) weight of MTK was similar to or lighter than that of JP in spring, but was heavier in summer. In 2004, which was hotter than common years, DM weight was heavier in MTK than in JP. The nitrogen content per unit leaf area (NCLA) was distinctly lower in MTK than in JP irrespective of season or year. The relative growth rate (RGR) of MTK was the same as or lower than that of JP in spring, but was the same as or higher than that of JP in summer. Then, net assimilation rate was lower in MTK than in JP in both seasons. In MTK, leaf area ratio (LAR) was high and specific leaf area (SLA) was large during the experiments, and NAR was positively correlated with NCLA that was negatively correlated with SLA. In MTK, RGR was higher than that in JP even in summer, when NAR was lower than that in JP. Thus, it was considered that high DM productivity of MTK depended on the high LAR resulting from the large of SLA.
