Roots213-page3 - There are slight pattern variations in the...

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Roots - 3 Root Structure: Root Tips and Meristem Each root tip has four easily defined zones: Root cap Protective layer of unspecialized parenchyma cells that are continuously worn away by moving through the soil as the root grows, and replaced by new root cap cells. The root cap cells are coated with mucigel, a slime sheath that helps to lubricate the root as it penetrates through soil. Cells of the central column of the root cap are positively geotropic, so that roots grow toward gravity. Amyloplasts, calcium ions and hormones all influence this growth direction. Meristem (Zone of Cell Division) The root tip meristem is comprised of the apical meristem initials and three derivative meristem zones (protoderm, procambium and ground meristem).
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Unformatted text preview: There are slight pattern variations in the meristem initials that are genetic. As roots mature the tip region of meristem becomes inactive and is called the quiescent zone. The active meristem is just above the quiescent zone. Zone of Elongation • Cells (in their fixed positions) elongate to reach mature dimensions in the region of elongation. The vacuole plays a major role in this process, using water pressure to push against the walls to stretch the cellulose fibers as the cells elongate. Virtually all increase in root length occurs in the elongation region. Zone of Maturation • Cells mature for their specific functions and tissues in the maturation region....
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