トウモロコシ根系を構成する1次根の外部形態およびその伸長方向

抄録

The number, the diameter and the growing direction of primary roots (main nodal roots) on successive "shoot units" of corn grown under field conditions were investigated. The number and the basal diameter of primary roots of each "shoot unit" remained almost constant in the lower "shoot units", then increased remarkably towards the higher "shoot units". Such tendencies were also found in case of the stem diameter and the internode length along successive "shoot units". In any "shoot unit", therefore, there were close correlations among the root diameter, the stem diameter and the internode length. The primary roots were classified into the following three types according to their growing directions: 1) The primary roots of lower "shoot units", which emerged at the earlier growing stages, grew horizontally or somewhat obliquely. 2) The primary roots of the middle "shoot units" grew obliquely at first, then turned their direction vertically near the interface of top- and sub-soil, and finally reached the deepest soil layer. 3) The primary roots from the upper "shoot units", which emerged in the later growing stages of the plant, grew vertically, however, they did not reach as deep layer as the roots of the type 2. From these results, it is inferred that a growth correlations might exist among the morphological characters of primary roots, growing directions of them and stem characters in successive "shoot units".