Aspects of Vascular Anatomy and Differentiation of Vascular Tissues and Transfer Cells in Vegetative Nodes of Wheat

Abstract

Xylem transfer cells are strongly developed in the departing leaf traces of the mature wheat node. Their differentiation is initiated soon after the appearance of the first tracheary elements in these bundles. and wall ingrowth development reaches its peak just as the leaf to which the bundle belongs becomes fully expanded. It is suggested that the xylem transfer cells play an important role in redirecting solutes travelling in the xylem of the mature leaf to the developing leaves at the shoot apex. It is further suggested that they form an integral part of the normal xylem transpiration pathway, compensating for xylem restrictions and discontinuities in the mature node. Phloem transfer cells also appear very early in the differentiation of the nodal vasculature, although their function remains obscure.