Origin of Nodes and Internodes in Plant Shoots. II. Models of Node and Internode Origin from One Layer of Cells

In the promeristem of some plant apices there are two layers'ofcells giving rise to the plant shoot. The first layer on thesurface forms the protoderm, and developing from it the epidermis;it is easily distinguished when there are phenolic compoundsexclusively in that layer, e.g. Crataegus, Vitis. The secondlayer may divide periclinally (a process here called differentiatingdivision) producing, successively, node and internode mothercell layers. Mitoses can start from the central part and continueradially or, more commonly, from leaf primordia and continuecentripetally. The number of periclinal divisions in that layerdetermines how many nodes and internodes the shoot will have.Differences in the number of cell divisions in these two motherlayers lead to the formation of long internodes and short nodes Nodes, internodes, idioblasts, phenolics, development, Crataegus, Vitis