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Plant tissues


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  • 1. Plant Tissues Chapter 26 Jin Hoe Huh March 28, 2005
  • 2. Angiosperms – flowering plants
    • The angiosperms are seed-bearing vascular plants
    • In terms of distribution and diversity, they are the most successful plants on Earth
    • The structure and function of this plant group help explain its success
  • 3. Flowering Plant Life Cycle Double fertilization Meiosis Meiosis microspores Female gametophyte pollination Mitosis without cytoplasmic division Two sperm s enter ovule Diploid Haploid
  • 4. Plant Life Histories
    • Annuals complete life cycle in one growing season
    • Biennials live for two seasons; flowers form in second season
    • Perennials grow and produce seeds year after year
  • 5. Shoot System Root System
    • Root system
    • anchors the plant
    • penetrates the soil and absorbs water and minerals
    • stores food
    • Shoot system
    • produces sugars by photosynthesis
    • carries out reproduction
    Shoot and Root Systems
  • 6. water & minerals sugar SHOOT SYSTEM ROOT SYSTEM Shoot and root systems are interdependent
    • Ground tissue system
    • Vascular tissue system
    • Dermal tissue system
  • 8. Meristems – Where Tissues Originate
    • Regions where cell divisions produce plant growth
    • Apical meristems
      • Lengthen stems and roots
      • Responsible for primary growth
    • Lateral meristems
      • Increase width of stems
      • Responsible for secondary growth
  • 9. Apical Meristems activity at meristems new cells elongate and start to differentiate into primary tissues procambium  primary vascular tissues protoderm  epidermis Cells that form at apical meristems : ground meristem  ground tissues Lengthen shoots and roots: SAM and RAM
  • 10. Lateral Meristems vascular cambium  secondary vascular tissues periderm  cork cambium thickening Increases girth of older roots and stems Cylindrical arrays of cells
  • 11. Simple Tissues
    • Made up of only one type of cell
    • Parenchyma
    • Collenchyma
    • Sclerenchyma
  • 12. collenchyma parenchyma sclerenchyma Morphology of three simple tissue types
  • 13. Parenchyma: A Simple Tissue
    • Comprises most of a plant’s soft primary growth
    • Cells are pliable, thin walled, many sided
    • Cells remain alive at maturity and retain capacity to divide
    • Mesophyll is a type of parenchyma that contains chloroplasts
  • 14. Collenchyma: A Simple Tissue
    • Specialized for support for primary tissues
    • Cells are elongated, with walls (especially corners) thickened with pectin
    • Makes stems strong but pliable
    • Cells are alive at maturity
  • 15. Sc l er enchyma: A Simple Tissue
    • Supports mature plant parts
    • Protects many seeds
    • Cells have thick, lignified walls and are dead at maturity
    • Two types:
      • Fibers: Long, tapered cells
      • Sclereids: Stubbier cells
  • 16. Complex Tissues
    • Composed of a mix of cell types
    • Xylem
    • Phloem
    • Epidermis
  • 17. Xylem
    • Conducts water and dissolved minerals
    • Conducting cells are dead and hollow at maturity
    vessel member tracheids
  • 18. Phloem: A Complex Vascular Tissue
    • Transports sugars
    • Main conducting cells are sieve-tube members
    • Companion cells assist in the loading of sugars
    sieve plate sieve-tube member companion cell
  • 19. Epidermis: A Complex Plant Tissue
    • - Covers and protects plant surfaces
    • - Secretes a waxy, waterproof cuticle
    • - In plants with secondary growth, periderm replaces epidermis
  • 20. Monocots and Dicots – same tissues, different features Parallel veins Netlike veins 3 pores 1 pore 4 or 5 floral parts 3 floral parts 1 cotyledon 2 cotyledons Vascular bundles dispersed Vascular bundles in ring
  • 21. Shoot Development ground meristem primary xylem pith procambrium cortex procambrium protoderm shoot apical meristem primary phloem
  • 22. Bud = undeveloped shoot of meristematic tissue Internode Leaves Axillary bud at node Longitudinal section of terminal bud
  • 23. Roots also have meristems
  • 24. Internal Structure of a Dicot Stem
    • - Outermost layer is epidermis
    • - Cortex lies beneath epidermis
    • - Ring of vascular bundles separates the cortex from the pith
    • - The pith lies in the center of the stem
  • 25. Internal Structure of a Monocot Stem
    • The vascular bundles are distributed throughout the ground tissue
    • No division of ground tissue into cortex and pith
  • 26. Dicots
    • Dicots and Monocots have different stem and root anatomies
    Ground tissue system Vascular tissue system Dermal tissue system Monocots
  • 27. Leaf Gross Structure petiole blade axillary bud node blade sheath node DICOT MONOCOT
  • 28. Adapted for Photosynthesis
    • Leaves are usually thin
      • High surface area-to-volume ratio
      • Promotes diffusion of carbon dioxide in, oxygen out
    • Leaves are arranged to capture sunlight
      • Are held perpendicular to rays of sun
      • Arrange so they don’t shade one another
  • 29. Leaf Structure UPPER EPIDERMIS PALISADE MESOPHYLL SPONGY MESOPHYLL LOWER EPIDERMIS one stoma cuticle O 2 CO 2 xylem phloem
  • 30. Mesophyll: Photosynthetic Tissue
    • A type of parenchyma tissue
    • Cells have chloroplasts
    • Two layers in dicots
      • Palisade mesophyll
      • Spongy mesophyll
  • 31. Parenchyma Collenchyma
  • 32. Leaf Veins: Vascular Bundles
    • Xylem and phloem – often strengthened with fibers
    • In dicots, veins are netlike
    • In monocots, they are parallel
  • 33. Root Systems
  • 34. Root Structure
    • Root cap covers tip
    • Apical meristem produces the cap
    • Cell divisions at the apical meristem cause the root to lengthen
    • Farther up, cells differentiate and mature
    root apical meristem root cap
  • 35. Internal Structure of a Root
    • Outermost layer is epidermis
    • Root cortex is beneath the epidermis
    • Endodermis, then pericycle surround the vascular cylinder
    • In some plants, there is a central pith
  • 36. pericycle phloem xylem root hair endodermis epidermis cortex
  • 37. Root Hairs and Lateral Roots
    • Both increase the surface area of a root system
    • Root hairs are tiny extensions of epidermal cells
    • Lateral roots arise from the pericycle and must push through the cortex and epidermis to reach the soil
    new lateral root
  • 38. Secondary Growth
    • Occurs in perennials
    • A ring of vascular cambium produces secondary xylem and phloem
    • Wood is the accumulation of these secondary tissues, especially xylem
  • 39. Secondary Growth
  • 40. Woody Stem periderm (consists of cork, cork cambium, and secondary cortex) secondary phloem BARK HEARTWOOD SAPWOOD vascular cambium
  • 41. Annual Rings
    • Concentric rings of secondary xylem
    • Alternating bands of early and late wood
    • Early wood
      • Xylem cells with large diameter, thin walls
    • Late wood
      • Xylem cells with smaller diameter, thicker walls
  • 42. Types of Wood
    • Hardwood (oak, hickory)
      • Dicot wood
      • Xylem composed of vessels, tracheids, and fibers
    • Softwood (pine, redwood)
      • Gymnosperm wood
      • Xylem composed mostly of tracheids
      • Grows more quickly