1. Plant Tissues and the Multicellular Plant Body
Chapter 5

2. LEARNING OBJECTIVE 1
Discuss the plant body, including the root system and shoot system

3. The Plant Body 1 Root system generally underground
obtains water and dissolved minerals for plant
usually anchors the plant firmly in place

4. The Plant Body 2 Shoot system Shoot system consists of
generally aerial
obtains sunlight and carbon dioxide for plant
Shoot system consists of
a vertical stem bearing leaves (main organs of photosynthesis)
flowers and fruits (reproductive structures)

5. The Plant Body 3 Buds (undeveloped embryonic shoots) develop on stems
Although separate organs (roots, stems, and leaves) exist in the plant, many tissues are integrated throughout the plant body, providing continuity from organ to organ

6. The Plant Body

7. Nodes (areas of leaf and axillary bud attachment)
Developing fruit
Nodes (areas of leaf and
axillary bud attachment)
Flower
Shoot
system
Axillary bud
Internode (area between
adjacent nodes)
Petiole Blade
Leaf
Stem
Figure 5.1: The primary plant body.
A plant body consists of a root system, usually underground, and a shoot system, usually aboveground. Shown is mouse-ear cress (Arabidopsis thaliana), a small plant in the mustard family that is a model plant for biological research. Arabidopsis is native to North Africa and Eurasia and has been naturalized (was introduced and is now growing in the wild) in California and the eastern half of the United States.
Rosette of
basal leaves
Root
system
Taproot
Branch roots
Fig. 5-1, p. 92

8. Rosette of basal leaves Shoot system Developing fruit
Nodes (areas of leaf and axillary bud attachment)
Axillary bud
Internode (area between adjacent nodes)
Flower
Petiole
Blade
Leaf
Figure 5.1: The primary plant body.
A plant body consists of a root system, usually underground, and a shoot system, usually aboveground. Shown is mouse-ear cress (Arabidopsis thaliana), a small plant in the mustard family that is a model plant for biological research. Arabidopsis is native to North Africa and Eurasia and has been naturalized (was introduced and is now growing in the wild) in California and the eastern half of the United States.
Taproot
Branch roots
Root system
Stepped Art
Fig. 5-1, p. 92

9. KEY TERMS GROUND TISSUE SYSTEM VASCULAR TISSUE SYSTEM
All tissues of the plant body other than vascular tissues and dermal tissues
VASCULAR TISSUE SYSTEM
Tissue system that conducts materials throughout the plant body
DERMAL TISSUE SYSTEM
Tissue system that provides an outer covering for the plant body

10. 3 Tissue Systems in Plant Body

11. Vascular tissue system
Dermal tissue system
Vascular tissue system
Ground tissue system
(a) Leaf
Dermal tissue system
Vascular tissue system
Ground tissue system
(b) Stem
Figure 5.2: The three tissue systems in the plant body.
This illustration shows the distribution of the ground tissue system, vascular tissue system, and dermal tissue system in the (a) leaves, (b) stems, and (c) roots of an herbaceous plant such as Arabidopsis.
Dermal tissue system
Vascular tissue system
Ground tissue system
(c) Root
Fig. 5-2, p. 94

12. LEARNING OBJECTIVE 2
Describe the ground tissue system (parenchyma tissue, collenchyma tissue, and sclerenchyma tissue) of plants

13. KEY TERMS PARENCHYMA CELL COLLENCHYMA CELL SCLERENCHYMA CELL
Relatively unspecialized plant cell; thin walled, may contain chlorophyll, loosely packed
COLLENCHYMA CELL
Living plant cell with moderately but unevenly thickened primary walls
SCLERENCHYMA CELL
Plant cell with extremely thick walls; provides strength and support to plant body

14. Ground Tissue System 1 Parenchyma tissue
Composed of living parenchyma cells with thin primary cell walls
Functions include photosynthesis, storage, and secretion

15. Parenchyma Cells

16. Parenchyma Cells

17. Vacuole
Nucleus
Onion
(a) Parenchyma cells from an epidermal peel of red onion (Allium cepa). The large vacuole contains pigmented material and occupies most of the cell. The nucleus and cytoplasmic strands are positioned under and on top of the vacuole, between it and the plasma membrane.
Figure 5.3: Parenchyma cells.
Fig. 5-3a, p. 96

18. Chloroplasts
Figure 5.3: Parenchyma cells.
(b) Some parenchyma cells contain chloroplasts, and their primary function is photosynthesis. These parenchyma cells are from a waterweed (Elodea) leaf.
Elodea
Fig. 5-3b, p. 96

19. Buttercup Starch grains
Figure 5.3: Parenchyma cells.
Buttercup
(c) Parenchyma cells often function in storage. These parenchyma cells are from a buttercup (Ranunculus) root. Note the starch grains filling the cells.
Fig. 5-3c, p. 96

20. Ground Tissue System 2 Collenchyma tissue
Composed of collenchyma cells with unevenly thickened primary cell walls
Provides flexible structural support

21. Collenchyma Cells

22. Thick cell walls at corners of 4 cells
Cell's interior
Figure 5.4: Collenchyma cells.
Note the unevenly thickened cell walls that are especially thick in the corners, making the cell contents appear spherical in cross section. These collenchyma cells are from a water lily (Nymphaea) petiole.
Water lily
Fig. 5-4, p. 97

23. Ground Tissue System 3 Sclerenchyma tissue
Composed of sclerenchyma cells with both primary and secondary cell walls
Sclerenchyma cells are often dead at maturity, but provide structural support

24. Sclerenchyma Cells

25. Cherry Bamboo Fiber cells Parenchyma cell
Figure 5.5: Sclerenchyma cells.
(a) Sclereids from a cherry (Prunus avium) stone. The cell walls are extremely thick and hard, providing structural support.
(b) Long, tapering fibers and shorter parenchyma
cells from a bamboo (Bambusa) stem. The stem
was treated with acid to separate the cells.
Fig. 5-5, p. 97

26. LEARNING OBJECTIVE 3
Outline the structure and function of the vascular tissue system (xylem and phloem) of plants

27. Vascular Tissue System
Conducts materials throughout the plant body and provides strength and support
Xylem
Phloem

28. KEY TERMS
XYLEM
A complex vascular tissue that conducts water and dissolved minerals throughout the plant body
Actual conducting cells of xylem are tracheids and vessel elements

29. Xylem

30. Pits Tracheids White pine tree
Figure 5.6: Conducting cells in xylem tissue.
White pine tree
(a) Tracheids from a white pine (Pinus strobus) stem in longitudinal section (that is, cut lengthwise). These cells, which occur in clumps, transport water and dissolved minerals. Water passes readily from tracheid to tracheid through pits, thin places in the cell wall.
Fig. 5-6a, p. 98

31. Vessel elements Pumpkin plant
Figure 5.6: Conducting cells in xylem tissue.
Pumpkin plant
(b) Vessel elements from a pumpkin (Cucurbita mixta) stem in longitudinal section. The blue-stained regions are various patterns of the secondary walls in the vessel elements. Perforation plates are not visible in this micrograph.
Fig. 5-6b, p. 98

32. Adjacent perforation plates Southern magnolia
Figure 5.6: Conducting cells in xylem tissue.
Southern magnolia
(c) The end walls of vessel elements, called perforation plates, have large holes. Water
passes through the perforation plate from one vessel element to the next. Shown are adjacent perforation plates from a southern magnolia (Magnolia grandiflora) stem; in this species, the perforation plates are at an angle in longitudinal section.
Fig. 5-6c, p. 98

33. Pit Pairs

34. Pit Pairs

35. Pit Pairs

36. Pits Middle lamella Primary cell walls Permeable primary cell
wall pair
Tracheid
Simple
pit
Figure 5.7: Pit pairs.
Impermeable
secondary
cell walls
Cell A
Cell B
(a) A simple pit pair has an interruption in the secondary cell wall. The primary cell wall in a simple pit pair is permeable to water.
Fig. 5-7a, p. 101

37. (a) A simple pit pair has an interruption in the secondary cell
Primary
cell walls
Bordered
pit
Torus
Pit borders
Secondary
cell walls
Figure 5.7: Pit pairs.
Cell A
Cell B
(a) A simple pit pair has an interruption in the secondary cell
wall. The primary cell wall in a simple pit pair is permeable to
water.
Fig. 5-7b, p. 101

38. (c) (Left ) When water pressure is equal between the two
closes pit
Water
H2O
Cell A
Cell B
Cell A
Cell B
Figure 5.7: Pit pairs.
(c) (Left ) When water pressure is equal between the two
cells (A and B), the bordered pit is open, and water flow is
unrestricted. (Right ) When the pressure is greater in cell A
than in cell B, the torus, a thickening in the primary cell
walls, blocks the opening, restricting water movement
through the pit pair.
Fig. 5-7c, p. 101

39. KEY TERMS
PHLOEM
A complex vascular tissue that conducts food (carbohydrate) throughout the plant body
Conducting cells of phloem are sieve-tube elements assisted by companion cells

40. Phloem

41. at the end walls. The smaller cells are companion cells.
Sieve-tube
elements
Cross
section
Sieve
plate
Companion
cell
Squash leaves
Figure 5.8: Phloem tissue.
(a) Phloem tissue from a squash (Cucurbita) petiole in cross section. Note the
sieve plates, the end walls of the sieve-tube elements. Most sieve-tube elements
appear empty because they were sectioned in the middle of the cells rather than
at the end walls. The smaller cells are companion cells.
Fig. 5-8a, p. 102

42. Companion cell Sieve-tube element Longitudinal section Squash leaves
Figure 5.8: Phloem tissue.
Squash leaves
Sieve plate
(b) Phloem tissue from a squash (Cucurbita) petiole in longitudinal section.
Fig. 5-8b, p. 102

43. LEARNING OBJECTIVE 4
Describe the dermal tissue system (epidermis and periderm) of plants

44. Dermal Tissue System Outer protective covering of the plant body
Epidermis
Periderm

45. KEY TERMS EPIDERMIS Outermost tissue layer, usually one cell thick
Covers the primary plant body (leaves, young stems and roots)

46. Epidermis
Epidermis covering aerial parts secretes a wax layer (cuticle) that reduces water loss
Gas is exchanged between interior of shoot system and surrounding atmosphere through stomata

47. Epidermis

48. Epidermal cells Guard cells Stoma Spiderwort Fig. 5-9, p. 103
Figure 5.9: Epidermis.
This light micrograph shows the leaf epidermis of spiderwort (Tradescantia virginiana). Note the stomata, minute pores formed by guard cells (stained pink). Nuclei of all epidermal cells are stained a dark magenta.
Spiderwort
Fig. 5-9, p. 103

49. KEY TERMS
PERIDERM
Outermost layer of cells covering a woody stem or root (the outer bark that replaces epidermis when it is destroyed during secondary growth)

50. Periderm

51. Exterior environment Geranium Remnants of epidermis Cork cells
Figure 5.10: Periderm.
Formed by the cork cambium, periderm is the secondary plant body replacement for epidermis and makes up the outer bark of woody stems and roots. Some herbaceous eudicots, such as geranium (Pelargonium), form a limited periderm as they age. The cells of periderm are arranged in vertical stacks. Note that the cork cambium produces many layers toward the cell’s exterior but only a few layers toward the cell’s interior.
Cork cells
Periderm
Cork cambium
Cork
parenchyma
Cortex
(interior of stem)
Fig. 5-10, p. 103

52. LEARNING OBJECTIVE 5
Discuss what is meant by growth in plants and how it differs from growth in animals

53. Growth in Plants
Involves cell division, cell elongation, and cell differentiation
Plants grow only in specific areas (meristems) composed of cells that do not differentiate

54. Growth in Animals
Location of growth differs between plants and animals
When a young animal grows, all parts of its body grow, although not necessarily at the same rate

55. LEARNING OBJECTIVE 6
Distinguish between primary and secondary growth

56. KEY TERMS PRIMARY GROWTH
An increase in stem and root length due to the activity of apical meristems at the tips of roots and at the buds of stems

57. KEY TERMS APICAL MERISTEM BUD
An area of cell division at the tip of a stem or root in a plant; produces primary tissues
BUD
A dormant embryonic shoot that eventually develops into an apical meristem

58. Root Tip

59. Area of cell maturation Root hairs Area of cell Protoderm elongation
Ground meristem
Figure 5.11: The root tip.
A root cap protects the root apical meristem, where cells divide and thus increase in number. Farther from the tip is an area of cell elongation, where cells enlarge and begin to differentiate. The area of cell maturation has fully mature, differentiated cells. Note the root hairs in this area.
Procambium
Area of cell division
Apical
meristem
Root cap
Fig. 5-11, p. 105

60. Stem Tip

61. Older leaf Leaf primordia Apical meristem Older leaf Trichome Bud
primordium
Figure 5.12: The stem tip.
This longitudinal section through a terminal bud of coleus (Coleus) shows the stem apical meristem, leaf primordia, and bud primordia.
Coleus
Fig. 5-12, p. 106

62. Stem Tip Development

63. Immature leaf Stem apical meristem Area of cell division Procambium
Protoderm
Procambium
Ground meristem
Area of cell
elongation
Epidermis
Figure 5.13: Development in the stem tip.
This diagram shows the kinds of cells in the area of cell division, the area of cell elongation, and the area of cell maturation. The three primary meristems (protoderm, procambium, and ground meristem) in the area of cell elongation give rise to the mature cell types in the area of cell maturation. (Procambium cells shown in the area of cell maturation—between the primary xylem and primary phloem—may give rise to vascular cambium later in development.)
Area of cell
maturation
Cortex
Procambium
Pith
Primary xylem
Primary phloem
Fig. 5-13, p. 106

64. KEY TERMS SECONDARY GROWTH
An increase in a plant’s stem and root girth due to the activity of lateral meristems (the vascular cambium and cork cambium)

65. Secondary Growth Woody plants have secondary growth
In addition to primary growth
Secondary growth is localized, typically as long cylinders of active growth throughout the lengths of older stems and roots

66. KEY TERMS LATERAL MERISTEM
An area of cell division on the side of a vascular plant; the two lateral meristems (vascular cambium and cork cambium) give rise to secondary tissues

67. Lateral Meristems and Secondary Growth

68. Inner bark (secondary phloem)
Outer bark (periderm)
Inner bark (secondary phloem)
Figure 5.14: Lateral meristems and secondary growth.
The vascular cambium, a thin layer of cells sandwiched between the wood and bark, produces secondary vascular tissues: the wood, which is secondary xylem, and inner bark, which is secondary phloem. The cork cambium produces the periderm, the outer bark tissues that replace the epidermis in the secondary plant body.
Wood
(secondary xylem)
Bark
Surface of vascular cambium
Fig. 5-14, p. 107

69. Animation: Tissue Systems of a Tomato Plant
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70. Animation: Root Organization
root_structure.swf
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71. Animation: Shoot Differentiation
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72. Transport in Plants: Animations