The Effect of Defoliating Tiller Leaves on the Crown Root Formation in the Main Stem of Rice Plants

[摘要] The growth of tillers was depressed by defoliating their leaves successively and the influence on the main stem was investigated with respect to the number of crown roots formed and to the size of stem parts as well. The number of 'dormant' root primordia increased in the main stems of treated plants as compared with that of untreated ones. In any shoot unit, the total number of crown roots, including the 'dormant' root primordia, also increased by the treatment. This increase depends on the number of the lower roots rather than that of the upper roots in the same shoot unit. In main stems, the surface area, the diameter and the length of root forming zones (stem parts, which form the upper or lower roots respectively, delimitted by the peripheral cylinder of vascular bundles) were examined. In each shoot unit (consisting of the upper and the lower root forming zones), or restrictedly in each lower root forming zone, these three parameters were found to be increased by the treatment. As to the upper root forming zone, however, no clear effect of the treatment was found. From the 5th to 10th shoot unit, there was close correlation between the number of crown roots and the surface area of root forming zone, with respect to the shoot unit, separately, to the upper or the lower root forming zone. On the other hand, no such correlation was recognized in the 11th, l2th and 13th shoot units.

[学科分类] 农业科学（综合）