Unformatted text preview: Primary Growth of Stems Primary meristems Stems, like roots, grow in length by division and elongation of cells at their tips. The youngest cells of stems (but not roots) are organized into two zones: the tunica and the corpus . In the tunica, cell divisions are perpendicular to the stem axis and give rise to a sheet of tissue several layers thick that covers the outside of the tip. Cell divisions in the corpus are in all directions and produce an interior mass of cells. Derivatives of cells in both tunica and corpus continue to divide and produce three recognizable primary (transitional) meristems —protoderm, ground meristem, and procambium— which, as they elongate and differentiate, create the three primary tissue systems — dermal, ground (fundamental) , and vascular . Cell divisions of the apical meristem give rise to leaf primordia close to the tip and so consistently,...
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- Fall '08
- Plant stem, Cambium, separate vascular bundles, primitive vascular plants, discrete vascular bundles, solid vascular core