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Plant Organs Roots Stems Leaves Monocots vs. Eudicots Epidermal Tissue Vascular Tissue. Roots Organization Diversity Stems Organization Diversity Leaves Organization Diversity. Outline. Plant Organs. Roots

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  1. Plant Structure and Organization

  2. Plant Organs Roots Stems Leaves Monocots vs. Eudicots Epidermal Tissue Vascular Tissue Roots Organization Diversity Stems Organization Diversity Leaves Organization Diversity Outline

  3. Plant Organs • Roots • Generally, the root system is at least equivalent in size and extent to the shoot system • Anchors plant in soil • Absorbs water and minerals • Produces hormones • Root hairs: • Projections from epidermal root hair cells • Greatly increase absorptive capacity of root

  4. Organization of Plant Body

  5. Vegetative Organs of Several Eudicots

  6. Stems • Shoot system of a plant is composed of the stem, branches, and leaves • Stem is the main axis of a plant that elongates and produces leaves • Nodes occur where leaves are attached to the stem • Internode is region between nodes • Stem also has vascular tissue that transports water and minerals

  7. Leaves • Leaves are the major part of the plant that carries on photosynthesis • Foliage leaves are usually broad and thin • Blade - Wide portion of foliage leaf • Petiole - Stalk attaches blade to stem • Leaf Axil - Axillary bud originates • Tendrils - Leaves that attach to objects • Bulbs - Leaves that store food

  8. Monocot vs. Eudicot • Monocots (Single cotyledon) • Cotyledons act as transfer tissue • Root vascular tissue occurs in ring • Parallel leaf venation • Eudicots (Two cotyledons) • Cotyledons supply nutrients to seedlings • Root phloem located between xylem arms • Netted leaf venation

  9. Flowering Plants:Monocots or Eudicots

  10. Plant Tissues • Epidermal Tissues • Contain closely packed epidermal cells • Covered with waxy cuticle • Roots contain root hairs • Lower leaf surface contain stomata • Woody plants covered by cork

  11. Modifications of Epidermal Tissue

  12. Ground Tissue • Ground tissue forms bulk of a plant • Parenchyma cells: • Least specialized and are found in all organs of plant • Can divide and give rise to more specialized cells • Collenchyma cells: • Have thicker primary walls • Form bundles underneath epidermis • Flexible support to immature regions of the plant

  13. Ground Tissue Cells

  14. Ground Tissue • Sclerenchyma cells: • Have thick secondary walls impregnated with lignin • Most are nonliving • Primary function is to support mature regions of the plant • Fibers • Sclereids

  15. Vascular Tissue • Xylem transports water and minerals from the roots to the leaves • Tracheids • Long, with tapered ends • Pits in end walls • Vascular rays • Fibers • Vessel Elements • Larger, with perforated plates in their end walls

  16. Xylem Structure

  17. Ground Tissue • Sclerenchyma cells: • Have thick secondary walls impregnated with lignin • Most are nonliving • Primary function is to support mature regions of the plant • Fibers • Sclereids

  18. Vascular Tissue • Phloem transports sucrose and other organic compounds from the leaves to the roots • Sieve-tube members are conducting cells • Contain cytoplasm but no nuclei • Channels in end walls • Plasmodesmata extend from one cell to another through sieve plate

  19. Phloem Structure

  20. Organization of Roots • Root apical meristem • Located in the root tip • Protected by root cap • Primary meristems are in the zone of cell division • Zone of maturation contains fully differentiated cells

  21. Tissues of Eudicot Root • Epidermis • Cortex • Endodermis • Casparian Strip • Vascular Tissue • Pericycle

  22. Eudicot Roots

  23. Branching of Eudicot Root

  24. Organization of Monocots Roots • Monocot roots: • Ground tissue of root’s pith is surrounded by vascular ring • Have the same growth zones as eudicot roots, but do not undergo secondary growth

  25. Monocot Root

  26. Root Diversity • Primary root (taproot) - Fleshy, long single root, that grows straight down • Stores food • Fibrous root system - Slender roots and lateral branches • Anchors plant to soil • Adventitous roots - Roots develop from organs of the shoot system • Prop roots

  27. Root Diversity • Haustoria: • Rootlike projections that grow into host plant • Make contact with vascular tissue and extract water and nutrients • Mycorrhizas: • Associations between roots and fungi • Assist in water and mineral extraction • Root nodules - Contain nitrogen-fixing bacteria

  28. Root Diversity

  29. Organization of Stems • Shoot apical meristem • Produces new cells that elongate and increase stem length • Protected by terminal bud • Enveloped by leaf primordia • Specialized primary meristems • Protoderm • Ground Meristem • Procambium

  30. Woody Twig

  31. Shoot tip and Primary Meristems

  32. Herbaceous Stems • Mature nonwoody stems exhibit only primary growth • Outermost tissue covered with waxy cuticle • Stems have distinctive vascular bundles • Herbaceous eudicots - Vascular bundles arranged in distinct ring • Monocots - Vascular bundles scattered throughout stem

  33. Herbaceous Eudicot Stem

  34. Monocot Stem

  35. Woody Stems • Woody plants have both primary and secondary tissues • Primary tissues formed each year from primary meristems • Secondary tissues develop during first and subsequent years from lateral meristems

  36. Woody Stems • Woody stems have no vascular tissue, and instead have three distinct regions • Bark • Wood • Pith

  37. Secondary Growth of Stems

  38. Bark • Bark of a tree contains cork, cork cambium, and phloem • Bark can be removed, but it is harmful to the plant due to lack of organic nutrient transport • Cork cells are impregnated with suberin • Gas exchange is impeded except at lenticels

  39. Wood • Wood is secondary xylem that builds up year after year • Vascular cambium dormant during winter • Annual ring is made up of spring wood and summer wood • In older trees, inner annual rings, heartwood, no longer function in water transport

  40. Three-year-old Woody Twig

  41. Tree Trunk

  42. Stem Diversity • Stolons: • Above-ground horizontal stems • Produce new plants when nodes touch the ground • Rhizomes: • Underground horizontal stems • Contribute to asexual reproduction • Variations: • Tubers - Enlarged portions functioning in food storage • Corms - Underground stems that produce new plants during the next season

  43. Stem Diversity

  44. Leaf Diversity • Blade of a leaf can be simple or compound • Leaves are adapted to environmental conditions. • Shade leaves • Spines • Climbing leaves

  45. Leaf Structure

  46. Classification of Leaves

  47. Leaf Diversity

  48. Plant Organs Roots Stems Leaves Monocots vs. Eudicots Epidermal Tissue Vascular Tissue Roots Organization Diversity Stems Organization Diversity Leaves Organization Diversity Review

  49. Plant Structure and Organization

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