Growth of the shoot apex of Lupinus albus observed by surface photomicrography and histology

Abstract

Summary: Surface views of the shoot apex of Lupinus albus at various developmental stages, referred to as plastochron stages, were photographed by reflected light. A part of the apical surface was shown in a flat montage of surface photomicrographs. A part of the area photographed was then cut paradermally, and cell configurations in surface views were compared with those in sections. The cells derived from individual cells in the surface of the shoot apex of an embryo, referred to as“ initial cells”, remained for a time within the original walls, which were stretched and became thickened. Thus, the surface layer of the shoot apex of a young plant consisted of many packets of cells, “ primary cell groups”, encompassed by the thickened original walls, as revealed by surface photomicrographs and paradermal sections. As the plastochron stages proceeded, these cell groups became enlarged in area due to an increased number of derivatives by cell divisions, until the encompassing walls became stretched and obscure, due to increase in cell number. These cell groups proved to be useful for the study of growth in the shoot apex, and the analytical consideration of surface growth of the shoot apex was made.