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Dermal Tissues
(General)
- •Complex Tissues
- •Located on surface of plant body
- •Types:
- –Epidermis
- –Periderm
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Epidermis
(thickness, covering, types)
- •Usually one layer thick on surface of leaves, stems, roots
- –Outermost layer of cells on primary plant body
- •Covered by a waxy cuticle on leaves and stems
- •Cell Types:
- –Epidermal cell proper (most prevalent)
- –Guard Cells
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Epidermal cell proper
- – generally parenchyma
- – shape varies (often tabular)
- –Most lack chlorophyll
- –Secrete waxy cuticle over leaves and stems of primary plant
- •Protects against evaporation and microbial invasion
- –In root- contain root hairs for water absorption
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Epidermis: Guard Cells
- –Paired, opening between is stomata
- –Regulates gas exchange
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Periderm
(covering/ function)
- •Outer covering on secondary plant body (stems and roots)
- – Replaces epidermis in these regions
- •Functions in protection
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Periderm composed of?
- –cork (outer bark); cork cells are dead at maturity and filled with suberin , a water-proofing substance
- –cork cambium (meristematic tissue)
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Vascular Tissues
- •Complex, conductive tissues of plant
- –Transport of water, minerals and food
- •Located throughout plant body
- •Types:
- –Xylem
- –Phloem
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Xylem
(Job, tissue, cells)
- •Transport of water and dissolved minerals upward through plant body
- –Continuous pathway from roots, stems and leaves
- •Complex tissue
- •Chief cells:
- –Trachieds
- –Vessel elements
- •Other cell types:
- –Parenchyma
- –Sclerenchyma
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Xylem
Chief cell: tracheids
- –Chief water conducting cells in most lower vascular plants (ferns, etc) and gymnosperms
- –Elongated cells with no protoplast or nuclei at maturity (dead)
- Secondary cell walls contain pits (holes in sec wall
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Xylem
vessel elements
- –Chief water conducting cells in higher plants
- –Elongated cells with no protoplast or nuclei at maturity
- –Secondary cell walls contain pits and perforations (hole in primary and sec wall)
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Phloem
- •Transport food up and down plant
- –Newly synthesized organic molecules
- •Complex tissue
- •Major cell types:
- –Sieve tube elements and companion cells
- –Sieve cells and albuminous cells
- •Other cell types:
- –sclerenchyma
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Phloem (sieve cells and tube elements)
- –Elongated cells, alive at maturity but lack most organelles
- –Contain sieve plates
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Phloem
albuminous and companion cells
- –Specialized parenchyma cells
- –Alive at maturity
- –Necessary for loading and unloading or organic material into or out of sieve cells and tube elements
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