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Chapter 35

Chapter 35. Plant Structure, Growth, and Development. LE 30-12ba. MONOCOTS. EUDICOTS. Orchid ( Lemboglossum rossii ). California poppy ( Eschscholzia california ). Eudicot Characteristics. Monocot Characteristics. Embryos. Two cotyledons. One cotyledon. LE 30-12bb. MONOCOTS.

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Chapter 35

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  1. Chapter 35 Plant Structure, Growth, and Development

  2. LE 30-12ba MONOCOTS EUDICOTS Orchid (Lemboglossum rossii) California poppy (Eschscholzia california) Eudicot Characteristics Monocot Characteristics Embryos Two cotyledons One cotyledon

  3. LE 30-12bb MONOCOTS EUDICOTS Pyrenean oak (Quercus pyrenaica) Leaf venation Veins usually netlike Veins usually parallel Stems Pygmy date palm (Phoenix roebelenii) Vascular tissue usually arranged in ring Vascular tissue scattered

  4. LE 30-12bc MONOCOTS EUDICOTS Lily (Lilium “Enchantment”) Roots Dog rose (Rosa canina), a wild rose Taproot (main root) usually present Root system usually fibrous (no main root)

  5. LE 30-12bd MONOCOTS EUDICOTS Barley (Hordeum vulgare), a grass Pea (Lathyrusner vosus, Lord Anson’s blue pea), a legume Pollen Pollen grain with one opening Pollen grain with three openings Flowers Anther Zucchini (Cucurbita Pepo), female (left), and male flowers Floral organs usually in multiples of three Floral organs usually in multiples of four or five Stigma Ovary Filament

  6. LE 35-2 Reproductive shoot (flower) Terminal bud Node Internode Terminal bud Shoot system Vegetable shoot Blade Leaf Petiole Axillary bud Stem Taproot Lateral roots Root system

  7. LE 35-4a Prop roots.

  8. LE 35-4b Storage roots.

  9. LE 35-4c “Strangling” aerial roots.

  10. LE 35-4d Buttress roots.

  11. LE 35-4e Pneumatophores.

  12. LE 35-5a Stolons.

  13. LE 35-5c Tubers.

  14. LE 35-5d Rhizomes. Node Rhizome Root

  15. LE 35-6a Simple leaf Petiole Axillary bud

  16. LE 35-6b Leaflet Compound leaf Petiole Axillary bud

  17. LE 35-6c Doubly compound leaf Leaflet Petiole Axillary bud

  18. LE 35-7a Tendrils.

  19. LE 35-7b Spines.

  20. LE 35-7c Storage leaves.

  21. The Three Tissue Systems: Dermal, Vascular, and Ground • Each plant organ has dermal, vascular, and ground tissues

  22. LE 35-8 Dermal tissue Ground tissue Vascular tissue

  23. In nonwoody plants, the dermal tissue system consists of the epidermis • In woody plants, protective tissues called periderm replace the epidermis in older regions of stems and roots

  24. The vascular tissue system carries out long-distance transport of materials between roots and shoots • The two vascular tissues are xylem and phloem

  25. Xylem conveys water and dissolved minerals upward from roots into the shoots • Phloem transports organic nutrients from where they are made to where they are needed

  26. The vascular tissue of a stem or root is collectively called the stele • In angiosperms the stele of the root is a solid central vascular cylinder • The stele of stems and leaves is divided into vascular bundles, strands of xylem and phloem

  27. Tissues that are neither dermal nor vascular are the ground tissue system • Ground tissue includes cells specialized for storage, photosynthesis, and support

  28. Common Types of Plant Cells • Like any multicellular organism, a plant is characterized by cellular differentiation, the specialization of cells in structure and function

  29. Some major types of plant cells: • Parenchyma • Collenchyma • Sclerenchyma • Water-conducting cells of the xylem • Sugar-conducting cells of the phloem

  30. LE 35-9 WATER-CONDUCTING CELLS OF THE XYLEM PARENCHYMA CELLS 100 µm Tracheids Vessel Parenchyma cells in Elodea leaf, with chloroplasts (LM) 60 µm Pits COLLENCHYMA CELLS Cortical parenchyma cells Tracheids and vessels (colorized SEM) 80 µm Vessel element Vessel elements with perforated end walls Tracheids SUGAR-CONDUCTING CELLS OF THE PHLOEM Collenchyma cells (in cortex of Sambucus, elderberry; cell walls stained red) (LM) Sieve-tube members: longitudinal view (LM) SCLERENCHYMA CELLS 5 µm Companion cell Sclereid cells in pear (LM) Sieve-tube member 25 µm Plasmodesma Sieve plate Cell wall Nucleus Cytoplasm Companion cell 30 µm 15 µm Fiber cells (transverse section from ash tree) (LM) Sieve-tube members: longitudinal view Sieve plate with pores (LM)

  31. Annuals (corn, wheat, beans) • Biennials (carrots, beats) • Perennials (Trees, shrubs, some grasses)

  32. Concept 35.2: Meristems generate cells for new organs • Apical meristems are located at the tips of roots and in the buds of shoots • Apical meristems elongate shoots and roots, a process called primary growth

  33. Lateral meristems add thickness to woody plants, a process called secondary growth • There are two lateral meristems: the vascular cambium and the cork cambium • The vascular cambium adds layers of vascular tissue called secondary xylem (wood) and secondary phloem • The cork cambium replaces the epidermis with periderm, which is thicker and tougher

  34. LE 35-10 Primary growth in stems Shoot apical meristems (in buds) Epidermis Cortex Primary phloem Primary xylem Vascular cambium Lateral meristems Pith Cork cambium Secondary growth in stems Periderm Cork cambium Pith Cortex Primary xylem Primary phloem Secondary xylem Root apical meristems Secondary phloem Vascular cambium

  35. In woody plants, primary and secondary growth occur simultaneously but in different locations

  36. LE 35-11 Terminal bud Bud scale Axillary buds Leaf scar This year’s growth (one year old) Node Stem Internode One-year-old side branch formed from axillary bud near shoot apex Leaf scar Last year’s growth (two years old) Scars left by terminal bud scales of previous winters Growth of two years ago (three years old) Leaf scar

  37. Concept 35.3: Primary growth lengthens roots and shoots • Primary growth produces the primary plant body, the parts of the root and shoot systems produced by apical meristems

  38. Primary Growth of Roots • The root tip is covered by a root cap, which protects the apical meristem as the root pushes through soil • Growth occurs just behind the root tip, in three zones of cells: • Zone of cell division • Zone of elongation • Zone of maturation Video: Root Growth in a Radish Seed (time lapse)

  39. LE 35-12 Vascular cylinder Cortex Epidermis Key Zone of maturation Root hair Dermal Ground Vascular Zone of elongation Apical meristem Zone of cell division Root cap 100 µm

  40. The primary growth of roots produces the epidermis, ground tissue, and vascular tissue • In most roots, the stele is a vascular cylinder • The ground tissue fills the cortex, the region between the vascular cylinder and epidermis • The innermost layer of the cortex is called the endodermis

  41. LE 35-13 Epidermis Cortex Vascular cylinder Endodermis Pericycle Core of parenchyma cells Xylem Phloem 100 µm 100 µm Transverse section of a typical root. In the roots of typical gymnosperms and eudicots, as well as some monocots, the stele is a vascular cylinder consisting of a lobed core of xylem with phloem between the lobes. Transverse section of a root with parenchyma in the center. The stele of many monocot roots is a vascular cylinder with a core of parenchyma surrounded by a ring of alternating xylem and phloem. Endodermis Key Dermal Pericycle Ground Vascular Xylem Phloem 50 µm

  42. Lateral roots arise from within the pericycle, the outermost cell layer in the vascular cylinder

  43. LE 35-14 100 µm Emerging lateral root Cortex Vascular cylinder Epidermis Lateral root

  44. Primary Growth of Shoots • A shoot apical meristem is a dome-shaped mass of dividing cells at the tip of the terminal bud • It gives rise to a repetition of internodes and leaf-bearing nodes

  45. LE 35-15 Apical meristem Leaf primordia Developing vascular strand Axillary bud meristems 0.25 mm

  46. Tissue Organization of Stems • In gymnosperms and most eudicots, the vascular tissue consists of vascular bundles that are arranged in a ring

  47. In most monocot stems, the vascular bundles are scattered throughout the ground tissue, rather than forming a ring

  48. LE 35-16 Phloem Xylem Ground tissue Sclerenchyma (fiber cells) Ground tissue connecting pith to cortex Pith Epidermis Key Vascular bundles Cortex Epidermis Dermal Vascular bundles Ground Vascular 1 mm 1 mm A monocot (maize) stem. Vascular bundles are scattered throughout the ground tissue. In such an arrangement, ground tissue is not partitioned into pith and cortex. (LM of transverse section) A eudicot (sunflower) stem. Vascular bundles form a ring. Ground tissue toward the inside is called pith, and ground tissue toward the outside is called cortex. (LM of transverse section)

  49. Tissue Organization of Leaves • The epidermis in leaves is interrupted by stomata, which allow CO2 exchange between the air and the photosynthetic cells in a leaf • The ground tissue in a leaf is sandwiched between the upper and lower epidermis • The vascular tissue of each leaf is continuous with the vascular tissue of the stem

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