Abstract
An anatomical study was carried out on the development of large vascular bundles in the internode below the neck of panicle in rice plant, and on the mode of connection by vascular bundle between primary branch and secondary one or pedicel. Initial cells of the vascular bundles initiated at approximately the same time with differentiation of spikelet primordia in young panicle, and they differentiated phloem and primary xylem vessels connecting with the node of flag leaf and primary branches. The differentiation of every vascular element nearly preceded by the rapid growth of the young panicle. From those results, it was suggested that the development of young panicle had a correlation with the histogenesis of the large vascular bundles. By tracing acropetally the large vascular bundle of primary branch, it was observed that, in contrast with phloem, one of the metaxylem-1 connected with one of the metaxyrlem-2 of secondary branch and pedicel, which were classified by KAWATA et al., into different groups each otherby their morphological differences. This indicated that metaxylem-1 changed into metaxylem-2 at the connecting position of lateral branches in the primary branch. The conclusion of this experiment agreed with the view of KAWATA et al that metaxylem-1 and metaxylem-2 were morphogenetically continuous.
