Abstract
The relations between vascular bundles (Vb) in the peduncle and spike characters were investigated using 15 rice cultivars. The cultivars could be classified into two groups showing lower (<1.1) and higher (>1.4) ratios of the numbers of Vb to primary rachis branch (Rb), which were regarded as Japonica and Indica, respectively. The Vbs closely correlated with sink size; those in Japonica depending on the numbers of primary Rbs, and Indica on those of secondary Rbs. It was discussed that the balance of Vb and Rb was important to yielding abillty.
