2009 Volume 78 Issue 2 Pages 203-208
The rice cultivar Oochikara and its short root near isogenic line IL-srt1 were grown at different planting densities and under different nitrogen fertilizer regimes to reveal the effect of short root on the growth of rice plant through the comparison of growth responses between the cultivar and the line. In both Oochikara and IL-srt1, shoot dry weight (SDW) per hill and spike number per hill (SN) lineally decreased with increasing planting density and lineally increased with increasing nitrogen supply. The SDW per hill and SN of IL-srt1 grown at low planting densities or under high nitrogen regimes sometimes exceeded those of Oochikara grown at high planting densities or under low nitrogen regimes. The SDW per hill was closely correlated with SN rather than SDW per stem in both experiments. On the other hand, the SDW per hill and SN were significantly correlated with the root length per hill (RL) in the density experiments, but not in the nitrogen experiments. The differences in SDW per hill and SN between Oochikara and IL-srt1 tended to increase with decreasing planting density, probably because the difference in the size of rooting zone increased with decreasing planting density. In nitrogen experiments, however, the differences in SDW per hill and SN between Oochikara and IL-srt1 were about the same under all nitrogen regimes, probably because the pot size limits the elongation of root. These results suggested that the short root and its narrow rooting zone limit the SDW per hill and SN by affecting tiller survival through suppression of water and nutrient supply.
