遮光および下層施肥による水稲の地上部の生育と根の発育との関係

抄録

Root developmental phase was investigated in connection to the growth of the aerial parts of rice plants cultured under two treatments, shading and deep placement of Nitrogen fertilizer. 1. It has been reported that crown root emerges on the (n-3) -th node at the time of emergence of the N-th leaf (the node number on which the N-th leaf emerged is expressed as n). Root emergence was delayed by shading, and the interval was prolonged to 3.5 nodes. But, when shading was stopped, this delay of emergence was restored to 3 nodes. 2. The total area of the cross section of secondary xylem per single root was measured related with the node-locus at which the root emerged. The development of secondary xylem of the root which emerged under shading treatment was inferior to that without shading treatment. But the development of secondary xylem of the root which emerged after the end of shading treatment was superior to that without shading treatment. 3. When nitrogen was applied into lower-layer, the growth af rice was inferior to that without treatment at the early growing period, but it became superior at the late growing period. Similarly, the development of secondary xylem of the root which emerged at the early growing period was inferior, while that of root which emerged at the late growing period was superior.