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Plant tissues

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Plant tissues

  1. 1. Plant Tissues Chapter 26 Jin Hoe Huh March 28, 2005
  2. 2. Angiosperms – flowering plants <ul><li>The angiosperms are seed-bearing vascular plants </li></ul><ul><li>In terms of distribution and diversity, they are the most successful plants on Earth </li></ul><ul><li>The structure and function of this plant group help explain its success </li></ul>
  3. 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. 4. Plant Life Histories <ul><li>Annuals complete life cycle in one growing season </li></ul><ul><li>Biennials live for two seasons; flowers form in second season </li></ul><ul><li>Perennials grow and produce seeds year after year </li></ul>
  5. 5. Shoot System Root System <ul><li>Root system </li></ul><ul><li>anchors the plant </li></ul><ul><li>penetrates the soil and absorbs water and minerals </li></ul><ul><li>stores food </li></ul><ul><li>Shoot system </li></ul><ul><li>produces sugars by photosynthesis </li></ul><ul><li>carries out reproduction </li></ul>Shoot and Root Systems
  6. 6. water & minerals sugar SHOOT SYSTEM ROOT SYSTEM Shoot and root systems are interdependent
  7. 7. Plant Tissue Systems VASCULAR TISSUES GROUND TISSUES SHOOT SYSTEM ROOT SYSTEM EPIDERMIS <ul><li>Ground tissue system </li></ul><ul><li>Vascular tissue system </li></ul><ul><li>Dermal tissue system </li></ul>
  8. 8. Meristems – Where Tissues Originate <ul><li>Regions where cell divisions produce plant growth </li></ul><ul><li>Apical meristems </li></ul><ul><ul><li>Lengthen stems and roots </li></ul></ul><ul><ul><li>Responsible for primary growth </li></ul></ul><ul><li>Lateral meristems </li></ul><ul><ul><li>Increase width of stems </li></ul></ul><ul><ul><li>Responsible for secondary growth </li></ul></ul>
  9. 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. 10. Lateral Meristems vascular cambium  secondary vascular tissues periderm  cork cambium thickening Increases girth of older roots and stems Cylindrical arrays of cells
  11. 11. Simple Tissues <ul><li>Made up of only one type of cell </li></ul><ul><li>Parenchyma </li></ul><ul><li>Collenchyma </li></ul><ul><li>Sclerenchyma </li></ul>
  12. 12. collenchyma parenchyma sclerenchyma Morphology of three simple tissue types
  13. 13. Parenchyma: A Simple Tissue <ul><li>Comprises most of a plant’s soft primary growth </li></ul><ul><li>Cells are pliable, thin walled, many sided </li></ul><ul><li>Cells remain alive at maturity and retain capacity to divide </li></ul><ul><li>Mesophyll is a type of parenchyma that contains chloroplasts </li></ul>
  14. 14. Collenchyma: A Simple Tissue <ul><li>Specialized for support for primary tissues </li></ul><ul><li>Cells are elongated, with walls (especially corners) thickened with pectin </li></ul><ul><li>Makes stems strong but pliable </li></ul><ul><li>Cells are alive at maturity </li></ul>
  15. 15. Sc l er enchyma: A Simple Tissue <ul><li>Supports mature plant parts </li></ul><ul><li>Protects many seeds </li></ul><ul><li>Cells have thick, lignified walls and are dead at maturity </li></ul><ul><li>Two types: </li></ul><ul><ul><li>Fibers: Long, tapered cells </li></ul></ul><ul><ul><li>Sclereids: Stubbier cells </li></ul></ul>
  16. 16. Complex Tissues <ul><li>Composed of a mix of cell types </li></ul><ul><li>Xylem </li></ul><ul><li>Phloem </li></ul><ul><li>Epidermis </li></ul>
  17. 17. Xylem <ul><li>Conducts water and dissolved minerals </li></ul><ul><li>Conducting cells are dead and hollow at maturity </li></ul>vessel member tracheids
  18. 18. Phloem: A Complex Vascular Tissue <ul><li>Transports sugars </li></ul><ul><li>Main conducting cells are sieve-tube members </li></ul><ul><li>Companion cells assist in the loading of sugars </li></ul>sieve plate sieve-tube member companion cell
  19. 19. Epidermis: A Complex Plant Tissue <ul><li>- Covers and protects plant surfaces </li></ul><ul><li>- Secretes a waxy, waterproof cuticle </li></ul><ul><li>- In plants with secondary growth, periderm replaces epidermis </li></ul>
  20. 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. 21. Shoot Development ground meristem primary xylem pith procambrium cortex procambrium protoderm shoot apical meristem primary phloem
  22. 22. Bud = undeveloped shoot of meristematic tissue Internode Leaves Axillary bud at node Longitudinal section of terminal bud
  23. 23. Roots also have meristems
  24. 24. Internal Structure of a Dicot Stem <ul><li>- Outermost layer is epidermis </li></ul><ul><li>- Cortex lies beneath epidermis </li></ul><ul><li>- Ring of vascular bundles separates the cortex from the pith </li></ul><ul><li>- The pith lies in the center of the stem </li></ul>
  25. 25. Internal Structure of a Monocot Stem <ul><li>The vascular bundles are distributed throughout the ground tissue </li></ul><ul><li>No division of ground tissue into cortex and pith </li></ul>
  26. 26. Dicots <ul><li>Dicots and Monocots have different stem and root anatomies </li></ul>Ground tissue system Vascular tissue system Dermal tissue system Monocots
  27. 27. Leaf Gross Structure petiole blade axillary bud node blade sheath node DICOT MONOCOT
  28. 28. Adapted for Photosynthesis <ul><li>Leaves are usually thin </li></ul><ul><ul><li>High surface area-to-volume ratio </li></ul></ul><ul><ul><li>Promotes diffusion of carbon dioxide in, oxygen out </li></ul></ul><ul><li>Leaves are arranged to capture sunlight </li></ul><ul><ul><li>Are held perpendicular to rays of sun </li></ul></ul><ul><ul><li>Arrange so they don’t shade one another </li></ul></ul>
  29. 29. Leaf Structure UPPER EPIDERMIS PALISADE MESOPHYLL SPONGY MESOPHYLL LOWER EPIDERMIS one stoma cuticle O 2 CO 2 xylem phloem
  30. 30. Mesophyll: Photosynthetic Tissue <ul><li>A type of parenchyma tissue </li></ul><ul><li>Cells have chloroplasts </li></ul><ul><li>Two layers in dicots </li></ul><ul><ul><li>Palisade mesophyll </li></ul></ul><ul><ul><li>Spongy mesophyll </li></ul></ul>
  31. 31. Parenchyma Collenchyma
  32. 32. Leaf Veins: Vascular Bundles <ul><li>Xylem and phloem – often strengthened with fibers </li></ul><ul><li>In dicots, veins are netlike </li></ul><ul><li>In monocots, they are parallel </li></ul>
  33. 33. Root Systems
  34. 34. Root Structure <ul><li>Root cap covers tip </li></ul><ul><li>Apical meristem produces the cap </li></ul><ul><li>Cell divisions at the apical meristem cause the root to lengthen </li></ul><ul><li>Farther up, cells differentiate and mature </li></ul>root apical meristem root cap
  35. 35. Internal Structure of a Root <ul><li>Outermost layer is epidermis </li></ul><ul><li>Root cortex is beneath the epidermis </li></ul><ul><li>Endodermis, then pericycle surround the vascular cylinder </li></ul><ul><li>In some plants, there is a central pith </li></ul>
  36. 36. pericycle phloem xylem root hair endodermis epidermis cortex
  37. 37. Root Hairs and Lateral Roots <ul><li>Both increase the surface area of a root system </li></ul><ul><li>Root hairs are tiny extensions of epidermal cells </li></ul><ul><li>Lateral roots arise from the pericycle and must push through the cortex and epidermis to reach the soil </li></ul>new lateral root
  38. 38. Secondary Growth <ul><li>Occurs in perennials </li></ul><ul><li>A ring of vascular cambium produces secondary xylem and phloem </li></ul><ul><li>Wood is the accumulation of these secondary tissues, especially xylem </li></ul>
  39. 39. Secondary Growth
  40. 40. Woody Stem periderm (consists of cork, cork cambium, and secondary cortex) secondary phloem BARK HEARTWOOD SAPWOOD vascular cambium
  41. 41. Annual Rings <ul><li>Concentric rings of secondary xylem </li></ul><ul><li>Alternating bands of early and late wood </li></ul><ul><li>Early wood </li></ul><ul><ul><li>Xylem cells with large diameter, thin walls </li></ul></ul><ul><li>Late wood </li></ul><ul><ul><li>Xylem cells with smaller diameter, thicker walls </li></ul></ul>
  42. 42. Types of Wood <ul><li>Hardwood (oak, hickory) </li></ul><ul><ul><li>Dicot wood </li></ul></ul><ul><ul><li>Xylem composed of vessels, tracheids, and fibers </li></ul></ul><ul><li>Softwood (pine, redwood) </li></ul><ul><ul><li>Gymnosperm wood </li></ul></ul><ul><ul><li>Xylem composed mostly of tracheids </li></ul></ul><ul><ul><li>Grows more quickly </li></ul></ul>

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