The Transverse Veins of the Wheat Leaf

Abstract

The histology and fine structure of the transverse veins that connect the longitudinal veins in the leaf of wheat (Triticum aestivum L. cv. Heron) are illustrated and discussed. The transverse veins consist of a single sieve tube and vessel, and two files of vascular parenchyma cells. They lack the mestome sheath and parenchyma sheath that is present around longitudinal veins except where they make connection with longitudinal veins. The vascular elements of the transverse veins are connected to metaxylem and metaphloem of the longitudinal veins and these connections are illustrated in sections. The tracheary elements have an unusual pattern of wall thickening. Experiments with ferric chloride solutions reveal that the vessel wall may severely restrict passage of solutes from the transpiration stream to the free space of the mesophyll.