Studies on Morphogenesis in Rice Plants. : 5. Histological observation on the maturing process of vascular bundles in culm.

Abstract

The mechanism of water conduction in the elongating vascular bundles was clarified with a histological observation on the maturing process of vascular bundle in the culm of rice plants. On a same horizontal plane, the first sieve tube of protophloem matures two days before the maturation of the first vessel of protoxylem in a large vascular bundle, which has in general about six protoxylem elements. During the period of elongation of each internode, old vessels and sieve tubes are destroyed, but new vessels of protoxylem and new sieve tubes of protophloem are formed one after another, and then, the elongating internode has always one or two active vessels and several active sieve tubes. The two vessels of metaxylem begin to work one or two days after the end of elongation. The tenth leaf, for example, is connected closely with the eighth leaf through the system of vascular bundles. When the eighth leaf has expanded entirely, the first elements of protoxylem and protophloem mature in the leaf traces between the two leaves, and the tenth leaf begins to grow rapidly at the same time.