The Vascular Pattern of a Rhizomatous Ginger (Alpinia speciosa L. Zingiberaceae). 1. The Aerial Axis and its Development

Abstract

Alpinia speciosa L. (Zingiberaceae) has a horizontal sympodially branching rhizome. The distal end of each sympodial unit develops vertically to form a determinate axis some three metres high bearing foliage leaves with sheathing bases, and terminating in an inflorescence. A transverse section of the aerial axis indicates that the vascular tissue of' scattered' vascular bundles is arranged in two distinct zones an inner system and an outer system, separated by a cylinder of undifferentiated tissue, the intermediate zone, retaining the features of a meristem. The multiplicity of terminology applied to this zone in the literature is clarified. The distribution and interconnection of the vascular system in the aerial stem are described together with a consideration of their development. The observations on which the descriptions are based were achieved by the 'optical shuttle' and 'surface' methods of serial cinematography. The presentation of such data in three-dimensional diagrammatic form is explained. The inner system of vascular bundles is found to have the simple basic design of that of a 'typical' palm stem a system of upwardly branching leaf traces with interconnections. The outer system of functional vascular bundles in Alpinia anastomoses freely and is considered to be equivalent to the anastomosing cortical system of non-conducting fibrous bundles present at the periphery of many palm stems. Communication between the two systems in the aerial stem of Alpinia is by means of an extensive bridging to the outer system from departing inner system leaf traces.