Jan_21 - Root System • Anchors the vascular plant •...

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Unformatted text preview: Root System • Anchors the vascular plant • Absorbs minerals and water • Often stores carbohydrates & nutrients Common root system types tap roots Fibrous Primary Root Structure - Longitudinal View Root tip is covered by root cap, protecting apical meristem as root pushes through soil. Root Tip Root hair Epidermis Cortex Vascular Cylinder Protoderm Ground Meristem Procambium Apical Meristem Root Cap Cell Cell division division Cell elongation Cell maturation Primary Root Cross Section Eudicot (or Gymnosperm) Root Hair Epidermis Cortex Monocot Endodermis Pericycle Phloem Xylem Root Endodermis Plasmodesmata Casparian Strip Epidermis Cortex Pericycle Endodermis Lateral Root Development Lateral roots arise from the pericycle outermost cell layer in the vascular cylinder Stem Anatomy ORGAN (STEM) TISSUES CELL TYPES Stem Apex A shoot apical meristem • is dome-shaped mass of dividing cells at the tip of the terminal bud • gives rise to 3 primary meristems: Protoderm Ground Meristem Procambium Stem Cross Section: Eudicots vs. Monocots In most eudicots (e.g., sunflower), vascular tissue consists of vascular bundles arranged in a ring Sunflower (eudicot) Xylem Phloem Epidermis Cortex Fibers Pith In most monocots (e.g., maize), vascular bundles are scattered throughout stem cross section Maize (monocot) Stem Secondary Growth (Eudicots) Epidermis Cortex Primary Primary Phloem Phloem Periderm Cork Cambium Secondary Secondary Phloem Phloem Primary Primary Xylem Xylem Secondary Secondary Xylem Xylem Vascular Cambium Woody Stem Structure • In woody plants, primary and secondary growth occur simultaneously but in different locations Vascular Cambium Cork Cambium Woody Stem Cross Section Heartwood Heartwood (non-functional xylem) (non-functional Sapwood Sapwood (functional xylem) (functional Vascular Vascular Cambium Cambium Phloem Cork Cambium Cork (outer Cork bark) bark) Bark Periderm Woody Stem Cross Section - Annual Rings Secondary xylem Late wood Early wood Secondary phloem Vascular cambium Cork cambium Cork Periderm Xylem ray Bark 0.5 mm 0.5 mm Composition of Dermal and Ground Tissues – Includes various cells specialized for functions such as storage, photosynthesis, and support – 3 common cell types: Collenchyma Parenchyma Sclerenchyma Cell Types in Vascular Tissues Phloem Sieve-tube Sieve-tube member member Companion cell Sieve plate Xylem Tracheid Vessel *Fibers and wood Fibers parenchyma also common parenchyma ...
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