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Plant Cell Walls

Plant Cell Walls . Chapter 3. Where is the cell wall of plant cells located?. Inside the plasma membrane Outside the plasma membrane Between the plasma membranes of two adjacent cells. The Eukaryotic Plant Cell. cell wall plasma membrane cytoplasm various organelles

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Plant Cell Walls

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  1. Plant Cell Walls Chapter 3

  2. Where is the cell wall of plant cells located? • Inside the plasma membrane • Outside the plasma membrane • Between the plasma membranes of two adjacent cells

  3. The Eukaryotic Plant Cell • cell wall • plasma membrane • cytoplasm • various organelles • cytoplasmic streaming • nucleus • vacuole bound by tonoplast

  4. Cell Wall Functions • constrains protoplast expansion • gives turgidity to plant • determines size/shape of cell • cells classified largely based upon cell wall traits • contain enzymes, absorb, transport and secrete substances • play important role in defense • NOT JUST A CONTAINER BOUNDARY

  5. Primary Cell Walls • outside of the plasma membrane • deposited while cell grows • contain thin areas • primary pit fields • plasmodesmata connect cell-to-cell • (cytoplasmic connections) • shared with adjacent cell • middle lamella • joins primary cell walls of adjacent cells

  6. Plasmodesmata

  7. Chemistry of Primary Cell Walls • cellulose • glucose monomers • bundled into microfibrils • wound and coiled into macrofibrils • hemicelluloses • polysaccharides that limit cell wall extensibility • pectins • primary cell walls and middle lamella • give wall pliability; act as cement • glycoproteins • lignins • cutin • suberin • waxes

  8. determined by cellulose microfibril orientation Cell growth

  9. Secondary Cell Walls • formed inside the primary wall • different staining qualities than primary cell wall • very thick • not present in all cells • formed after cell growth • function in strength and water transport • abundant cellulose and hemicellulose • pectins and glycoproteins absent - thus not elastic • lignins common - gives hardness and rigidity

  10. dicot stem Pine stem dicot stem Basswood stem (angiosperm stem) monocot stem Secondary Cell Wall Examples • Vascular Tissue • xylem • vessel elements • tracheids (gymnosperms) • schlerenchyma fibers • phloem • schlerenchyma fibers • Ground Tissue • schlerenchyma fibers

  11. The primary cell wall of plant cells is located inside the plasma membrane. True False

  12. True False The secondary cell wall is located inside the plasma membrane.

  13. Plant body organization • Plant body • Systems • Shoot & root systems • Organs • Vegetative: root, stem, leaf • Reproductive: flower, fruit • Tissue Systems • Dermal, ground, vascular • Tissues • Cells

  14. Meristem classification: LOCATION FUNCTION • primary (formed first) • produce primary tissue systems • three types • protoderm • ground meristem • procambium • secondary (formed after 1°) • produce secondary tissue systems • two types • vascular cambium • cork cambium • apical • root tip & shoot tip • produce primary growth • lateral • to the side of stems and roots • produce secondary growth • intercalary • between mature tissues • help regenerate parts that are removed (grass leaves and herbivory)

  15. 1° Tissue Systems • Dermal tissue system • covers and protects plant surface • epidermis • Ground tissue system • parenchyma, collenchyma and sclerenchyma cells • mesophyll of leaves • young green stems (pith and cortex) • Vascular tissue system • conducts water and solutes (xylem) • conducts sugars (phloem) leaf stem root

  16. Plant body organization Tissues with cell types Simple • Parenchyma • Chlorenchyma • Sclerenchyma • Collenchyma Complex • Epidermis • Ground cells • Guard cells • Xylem • Vessel elements • parenchyma • Phloem • Sieve tube elements • Companion cells • Sclerenchyma fiber

  17. collenchyma parenchyma

  18. collenchyma

  19. sclerenchyma fibers sclerenchyma fibers

  20. vessel elements tracheid sclerenchyma fibers

  21. protoderm procambium ground meristem Primary Meristems • Forms primary tissue • Elongates root and shoot • types • protoderm • epidermis • procambium • primary xylem and phloem • ground meristem • pith and cortex of stems and root, mesophyll of leaves

  22. vascular cambium 2 xylem 2 phloem periderm Secondary Meristems • Forms secondary tissue • Growth in lateral direction • leads to increase in girth or circumference • wood in trees • 2 types • vascular cambium • secondary xylem • secondary phloem • cork cambium • periderm

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