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THE PLANT BODY

THE PLANT BODY. Meristems.  In flowering plants cells originate from regions of active cell division known as meristems.  The cells arising from meristems give rise to the many different cell types that make up a plant. Types of Meristems.  Primary Meristems (also called Apical

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THE PLANT BODY

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  1. THE PLANT BODY

  2. Meristems In flowering plants cells originate from regions of active cell division known as meristems. The cells arising from meristems give rise to the many different cell types that make up a plant

  3. Types of Meristems Primary Meristems (also called Apical Meristems) result in primary growth - growth in length Secondary Meristems result in secondary growth which in growth in width (increase in diameter)

  4. Apical meristems Also known as primary meristems Found at the tips of all roots and stems Contribute to the increase in length of the plant which is called primary growth Give rise to the leaves, and non-woody stems and roots

  5. Secondary Meristems Some plants have additional meristems that result in increases in diameter which is secondary growth. • Vascular cambium • cork cambium

  6. Multicellular Organisms In multicellular organisms, certain cells are specialized in structure and function Tissues are specialized cells that perform specific functions Plants composed of three basic tissues categories • Dermal • Ground • Vascular

  7. Dermal Tissue Dermal tissues are the outermost layers in a plant They protect the plant Two types of dermal tissues • Epidermis • Periderm

  8. Epidermis  Outermost layer In young plants and non-woody plants  Single layer of flatten cells  Cells secrete cutin which makes up the cuticle and prevents water loss Cuticle Epidermal Cell

  9. Trichomes  Hairs (trichomes) may be present on the epidermis.  Sometime abundant enough so leaves look fuzzy  Trichomes may also be glandular Hair Gland

  10. Guard Cells and Stomata Pores known as stomata (singular stoma) occur on epidermis Gases exchange occurs through stomata A pair of sausage-shaped cells, guard cells, regulate the opening and closing of the stomata

  11. Guard Cells and Stoma Guard Cell Stoma (opening)

  12. Periderm In woody plants when the tree increases in diameter, the epidermis cracks and is replaced by periderm The periderm consists: • Cork cells • Cork cambium

  13. Cork Cells Outer bark on mature trees Dead cells with walls containing suberin, a waterproofing fatty substance. Prevents water loss from underlying tissues Produced by cork cambium

  14. Ground tissues Major tissue of non-woody plant organs Perform a variety of functions The three types of ground tissue: • Parenchyma • Collenchyma • Sclerenchyma

  15. Parenchyma Almost any shape or size Loosely arranged with intercellular spaces Many different functions: • Photosynthetic cells in leaves and green stems • Storage cells in plant organs for starch, sugar, or water

  16. Parenchyma Cells Intercellular spaces

  17. Parenchyma Cells

  18. Collenchyma Support tissue in young plant organs Found in stems, leaves, and petals Elongated cells with unevenly thickened primary cell walls with the walls thickest at the corners Found tightly packed together just below the epidermis

  19. Collenchyma Cells Cross section showing uneven wall thickening Longitudinal view

  20. Sclerenchyma  Two cell types • fibers • sclereids. Non-living at maturity Thickened secondary walls

  21. Fibers Elongate cells Function in support Leaf and stem fibers from many plants used for cloth and rope.

  22. Sclereids Various shapes Functions • mechanical support and • protection Account for the hardness in nut shells and the grit of pear fruit

  23. Sclerenchyma X-section of fiber showing thick secondary wall Fiber Sclereid x-section showing thick secondary wall Sclereids

  24. Sclereids

  25. Vascular tissues Xylem - conducts water and minerals from the roots upward Phloem - transports organic materials (sugars) synthesized by the plant

  26. Xylem Cells conducting water - non-living • Tracheids - long thin cells with tapering walls and numerous pits • Vessel elements - short, wide, with horizontal end walls with large openings • Both cells have secondary walls Fibers - non-living - provide support Parenchyma cells - metabolic activity

  27. Tracheids and Vessels

  28. Xylem Cells from Oak Wood

  29. Primary and Secondary Xylem Primary xylem develops from the apical meristem Secondary xylem develops from the vascular cambium. In trees secondary xylem is very extensive

  30. Phloem Cell Types in phloem • Sieve Tube Members - transport sugars • Companion Cells - loading and unloading • Fibers - support • Parenchyma - metabolic activity Primary and Secondary phloem

  31. Sieve Tube Member • Living cells with only thin primary walls • End walls have sieve plates (large pores with large plasmodesmata) End wall with sieve plate

  32. Companion cells • Specialized parenchyma cell develops alongside a sieve tube member • Plasmodesmata connect it to sieve tube member • Loading and unloading sugars for transport

  33. Plant Tissues and Cells  Tissue Type  Dermal Epidermis Periderm  Ground Parenchyma Cell Types Function epidermal cells cork cells protection protection parenchyma cells storage, photosynthesis Collenchyma Sclerenchyma collenchyma cells support sclereids, fibers support, protection

  34. Plant Tissues and Cells  Tissue Type  Vascular Xylem Cell Types Function tracheids water vessel elements conduction fibers support parenchyma metabolism sieve tube transport member sugars companion cells fibers parenchyma metabolism Phloem loading support

  35. Plant Organs Stems • Support leaves • Conduct water and sugars Roots • Anchor the plant • Absorb water and minerals Leaves • Photosynthesis • Transpiration

  36. Herbaceous Dicot Stem Cross-section Vascular bundle P X Pith (parenchyma cells) Epidermis Cortex (parenchyma cells)

  37. Monocot Stem Epidermis Vascular bundle Scattered Vascular Bundles Ground Tissue

  38. Roots Epidermis Stele root hair Xylem Cortex Endodermis Phloem

  39. Leaf Epidermis X P Palisade Mesophyll (parenchyma) Veins Spongy mesophyll (parenchyma)

  40. Leaf from Ligustrum

  41. Secondary Growth in Dicots

  42. 5 Year Old Woody Dicot Stem Periderm (cork) One annual ring Cortex Secondary phloem Vascular Cambium 5 Years of Secondary Xylem

  43. Three Year Old Tree

  44. Dendrochronology Study of tree rings has added many fields of study Can tell us about past climates Can be used to date from archeological sites artifacts Tree ring research lab at the University of Arizona http://www.ltrr.arizona.edu/

  45. Summary Growth, replacement of cells, and asexual reproduction all depend on cell division Tissues are groups of cells that perform a common function Stems, roots and leaves are made up of three basic tissue types: dermal, ground, and vascular

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