plant organs: stems chapter 7. learning objective 1 describe three functions of stems describe three...

Download Plant Organs: Stems Chapter 7. LEARNING OBJECTIVE 1 Describe three functions of stems Describe three functions of stems

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  • Slide 1
  • Plant Organs: Stems Chapter 7
  • Slide 2
  • LEARNING OBJECTIVE 1 Describe three functions of stems Describe three functions of stems
  • Slide 3
  • Stem Functions Support Support leaves and reproductive structures leaves and reproductive structures Conduct Conduct water, dissolved minerals, carbohydrates water, dissolved minerals, carbohydrates Produce new living tissues Produce new living tissues at apical meristems at apical meristems at lateral meristems (secondary growth) at lateral meristems (secondary growth)
  • Slide 4
  • Variation in Stems
  • Slide 5
  • LEARNING OBJECTIVE 2 Relate the functions of each tissue in an herbaceous stem Relate the functions of each tissue in an herbaceous stem
  • Slide 6
  • Tissues in Herbaceous Stems 1 Epidermis Epidermis protective outer layer protective outer layer covered by water-conserving cuticle covered by water-conserving cuticle Vascular tissues Vascular tissues Xylem conducts water and dissolved minerals Xylem conducts water and dissolved minerals phloem conducts dissolved carbohydrates (sucrose) phloem conducts dissolved carbohydrates (sucrose)
  • Slide 7
  • Tissues in Herbaceous Stems 2 Storage tissues Storage tissues Cortex and pith Cortex and pith ground tissue ground tissue
  • Slide 8
  • LEARNING OBJECTIVE 3 Contrast the structures of an herbaceous eudicot stem and a monocot stem Contrast the structures of an herbaceous eudicot stem and a monocot stem
  • Slide 9
  • Herbaceous Eudicot Stems Have vascular bundles arranged in a circle (in cross section) Have vascular bundles arranged in a circle (in cross section) Have a distinct cortex and pith Have a distinct cortex and pith
  • Slide 10
  • Monocot Stems Have scattered vascular bundles Have scattered vascular bundles Have ground tissue instead of distinct cortex and pith Have ground tissue instead of distinct cortex and pith
  • Slide 11
  • Monocot Stems
  • Slide 12
  • EpidermisGround tissue Vascular bundles Corn seedling (a) Cross section of a corn (Zea mays) stem, showing the scattered vascular bundles. (b) Close-up of a vascular bundle. The air space is where the first xylem elements formed. The entire bundle is enclosed in a bundle sheath of sclerenchyma for additional support. Bundle sheath Air space Xylem Phloem Ground tissue Fig. 7-4, p. 134
  • Slide 13
  • LEARNING OBJECTIVE 4 Distinguish between the structures of stems and roots Distinguish between the structures of stems and roots
  • Slide 14
  • Differences Between Stems and Roots 1 Unlike roots, stems have nodes and internodes, leaves and buds Unlike roots, stems have nodes and internodes, leaves and buds Unlike stems, roots have root caps and root hairs Unlike stems, roots have root caps and root hairs
  • Slide 15
  • KEY TERMS NODE NODE Area on a stem where one or more leaves is attached; stems have nodes, but roots do not Area on a stem where one or more leaves is attached; stems have nodes, but roots do not INTERNODE INTERNODE Stem area between two successive nodes Stem area between two successive nodes
  • Slide 16
  • KEY TERMS BUD BUD An undeveloped shoot that contains an embryonic meristem An undeveloped shoot that contains an embryonic meristem May be terminal (at tip of stem) or axillary (on side of stem) May be terminal (at tip of stem) or axillary (on side of stem)
  • Slide 17
  • A Woody Twig
  • Slide 18
  • Bud scale Terminal bud One years growth Terminal bud scale scars Axillary bud Leaf scar Node Internode Lenticels Terminal bud scale scars Bundle scars Fig. 7-2, p. 131
  • Slide 19
  • Differences Between Stems and Roots 2 Internally Internally herbaceous roots possess an endodermis and pericycle herbaceous roots possess an endodermis and pericycle stems lack a pericycle and rarely have an endodermis stems lack a pericycle and rarely have an endodermis
  • Slide 20
  • Differences Between Stems and Roots
  • Slide 21
  • LEARNING OBJECTIVE 5 Outline the transition from primary growth to secondary growth in a woody stem Outline the transition from primary growth to secondary growth in a woody stem List the two lateral meristems, and describe the tissues that arise from each List the two lateral meristems, and describe the tissues that arise from each
  • Slide 22
  • Primary Growth: Eudicot
  • Slide 23
  • Sunflower Vascular bundles Pith Cortex Epidermis Cortex Phloem fiber cap Phloem Vascular cambium Xylem Pith ray Pith Vessel element Vascular bundle (a) Cross section of a sunflower (Helianthus annuus) stem, showing the organization of tissues. The vascular bundles are arranged in a circle. (b) Close-up of a vascular bundle. The xylem is toward the stems interior, and the phloem toward the outside. Each vascular bundle is capped by a batch of fibers for additional support. Fig. 7-3, p. 132
  • Slide 24
  • KEY TERMS VASCULAR CAMBIUM VASCULAR CAMBIUM A lateral meristem that produces secondary xylem (wood) to the inside and secondary phloem (inner bark) to the outside A lateral meristem that produces secondary xylem (wood) to the inside and secondary phloem (inner bark) to the outside
  • Slide 25
  • Secondary Growth Occurs in woody eudicots and conifers Occurs in woody eudicots and conifers Produced by vascular cambium Produced by vascular cambium between primary xylem and primary phloem between primary xylem and primary phloem
  • Slide 26
  • Vascular Cambium 1 Is not initially a solid cylinder of cells Is not initially a solid cylinder of cells becomes continuous when production of secondary tissues begins becomes continuous when production of secondary tissues begins
  • Slide 27
  • Vascular Cambium 2 Certain parenchyma cells between vascular bundles Certain parenchyma cells between vascular bundles retain ability to divide retain ability to divide connect to vascular cambium cells in each vascular bundle connect to vascular cambium cells in each vascular bundle form a complete ring of vascular cambium form a complete ring of vascular cambium
  • Slide 28
  • Dividing Vascular Cambium
  • Slide 29
  • Time Secondary xylem Secondary phloem Second division of vascular cambium forms a phloem cell. Division of vascular cambium forms two cells, one xylem cell and one vascular cambium cell. Vascular cambium cell when secondary growth begins. Vascular cambium cell 1X 2X 1P 2P 3X 4X Fig. 7-6, p. 136
  • Slide 30
  • KEY TERMS CORK CAMBIUM CORK CAMBIUM A lateral meristem that produces cork parenchyma to the inside and cork cells to the outside A lateral meristem that produces cork parenchyma to the inside and cork cells to the outside Cork cambium and the tissues it produces make up the outer bark of a woody plant Cork cambium and the tissues it produces make up the outer bark of a woody plant
  • Slide 31
  • Cork Cambium Arises near the stems surface Arises near the stems surface Is either a continuous cylinder of dividing cells or a series of overlapping arcs of meristematic cells that form from parenchyma cells in successively deeper layers of the cortex and, eventually, secondary phloem Is either a continuous cylinder of dividing cells or a series of overlapping arcs of meristematic cells that form from parenchyma cells in successively deeper layers of the cortex and, eventually, secondary phloem
  • Slide 32
  • Development: Woody Eudicot
  • Slide 33
  • (a) At the onset of secondary growth, vascular cambium arises in the parenchyma between the vascular bundles (that is, in the pith rays), forming a cylinder of meristematic tissue (blue circle in cross section). Pith Vascular cambium Cortex Epidermis Primary xylem Primary phloem Fig. 7-5a, p. 135
  • Slide 34
  • (b) Vascular cambium begins to divide, forming secondary xylem on the inside and secondary phloem on the outside. Remnant of primary xylem Remnant of pith Vascular cambium Periderm (outer bark) Secondary xylem (wood) Secondary phloem (inner bark) Remnant of epidermis Remnant of cortex Remnant of primary phloem Fig. 7-5b, p. 135
  • Slide 35
  • Secondary xylem (wood) Remnant of primary xylem Remnant of pith Vascular cambium Secondary phloem (inner bark) Periderm (outer bark; remnants of primary phloem, cortex, and epidermis are gradually crushed or torn apart and slough off) (c) A young woody stem. Vascular cambium produces more secondary xylem than secondary phloem. Fig. 7-5c, p. 135
  • Slide 36
  • 3-Year-Old Stem
  • Slide 37
  • (a) LM of cross section of basswood (Tilia americana) stem. Note the location of the vascular cambium between the secondary xylem (wood) and secondary phloem (inner bark). PithPrimary xylem Annual ring of secondary xylem Secondary xylem (wood) Vascular cambium Secondary phloem Periderm and remnants of primary phloem, cortex, and epidermis Expanded phloem ray Xylem ray Remains of epidermis Cork cambium Expanded phloem ray Cortex Secondary phloem Vascular cambium Secondary xylem (third year) Xylem rays Secondary xylem (first year) Primary xylem Pith (b) Sketch of a pie- shaped segment of the cross section. The primary phloem

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