作物の窒素代謝に関する研究 : 第20報 各時期別施肥 - ¹⁵N の Sink への転流と蓄積について

抄録

In the previous paper, it was revealed in rice plant that ¹⁵N-labelled ammonium nitrogen top-dressed at the flowering stage was more effectively absorbed and translocated into grain proteins as compared with ¹⁴N supplied as basal-dressing. On the basis of these data, it was estimated that the relative distribution of N to sink was 40∼50% for basal-dressing and ca. 70% for top-dressing. This report presents the results of two experiments which were conducted to examine the translocation rate of three sources of nitrogen supplied as basal-dressing, top-dressing I (at the spikelet initiation stage) and II (at the flowering stage) in combination with the treatments on removal of the upper or lower leaf blades at the flowering stage. The results obtained are as follows. 1. Most of the ¹⁵N from top-dressing I was distributed in the upper leaf blades and ears as sink, whereas the distribution of ¹⁵N from basal-dressing was found in the lower leaf blades and leaf sheath + culms. However, ¹⁵N top-dressed at the flowering stage was continuously translocated into sink during the ripening period and incorporated rapidly into reserve protein such as glutelin. 2. The transport into sink of ¹⁵N-labelled ammonium top-dressed at the flowering stage was more rapid than basal-dressed ¹⁵N, and even in the rice plant from which all leaf blades were removed at the flowering stage, the rate of ¹⁵N transported into sink increased up to 63% of the untreated plant. These results indicate that most of the ¹⁵N derived from top-dressing at the flowering stage was directly translocated into sink via culms from the roots.