抄録
It is well known that "lion tail like roots" are fraquently formed in superficial roots, which develop near soil surface in the period from the initiation of young panicles to heading (fig. 1, S2-S4 and W2-W4). With a view to examine whether water mangement exerts any influence on the formation of this type of roots, several treatments viz. submerged, water percolated while it is kept under submerged condition, drained, alternately submerged and drained, are tried. The results obtained indicate that the submerged rice plant showed the largest extent of the formation. With the percolated as well as the drained, the formation was noticed to some extent. While with the alternately submerged and drained, no formation was found. With an increasing interest to see whether the rate of the formation of roots vary with using various forms of nitrogen, rice plants were grown in three nutrient treatments based on Kasugai's which differ only their nitrogen form viz. ammonium-nitrogen, nitrate-nitrogen and ammonium-nitrogen-nitrate-nitrogen (ammonium nitrogen was cganged to nitrate-nitrogen at the time of the initiation of young panicles). In these experiments it had been observed that the most abundant "lion tail like root" formation usually occurs when ammonium is the source of nitrogen. But no formation was noticed when nitrate supplies the nitrogen. As to the roots grown in the solution (ammonium-nitrogen-nitrate-nitrogen), the formation was recognized to a little extent. As it is well known 4, 12, 18, 17), under alternately submerged and drained soil condition, the form of nitrogen easily changes from ammonium-nitrogen to nitrate-nitrogen. From the results mentioned above, it may be apparent that "lion tail like root" formation has much to do with the form of nitrogen and that it is ammonium-nitrogen which is of importance for its formation.
