1. Plant Tissues
Chapter 28 Part 1

2. Impacts, Issues Drought Versus Civilization
Without plants, we would die – prolonged drought can destroy crops and civilizations

3. 28.1 Components of the Plant Body
The unique organization of tissues in flowering plants is part of the reason why they are the dominant group of the plant kingdom

4. The Basic Body Plan Shoots Roots
Aboveground plant parts such as stems, leaves, and flowers
Roots
Structures that absorb water and dissolved minerals, store food, and support the plant
Usually grow down and outward in the soil

5. Plant Tissue Systems Ground tissue system Vascular tissue system
Photosynthesis, storage, and structural support of other tissues
Vascular tissue system
Distributes absorbed water and mineral ions and products of photosynthesis
Dermal tissue system
Covers and protects exposed plant surfaces

6. Body Plan: Tomato Plant

7. shoot tip (terminal bud) lateral (axillary) bud young leaf
flower
node
internode
dermal tissue
node
vascular tissues
leaf
seeds in fruit
withered seed leaf (cotyledon)
ground tissues
stem
Figure 28.2
Body plan of a tomato plant (Lycopersicon esculentum). Its vascular tissues (purple) conduct water, dissolved minerals, and organic substances. They thread through ground tissues that make up most of the plant. Epidermis, a type of dermal tissue, covers root and shoot surfaces.
SHOOTS
ROOTS
primary root
lateral root
root hairs
root tip
root cap
Fig. 28-2, p. 476

8. Animation: Tissue systems of a tomato plant

9. Eudicots and Monocots
Flowering plants are divided into two classes with tissues organized into different patterns
Eudicots have two cotyledons (seed leaves)
Monocots have one cotyledon

10. Eudicots and Monocots

11. In seeds, two cotyledons (seed leaves of embryo)
Flower parts in fours or fives (or multiples of four or five)
Leaf veins usually forming a netlike array
Pollen grains with three pores or furrows
Vascular bundles organized in a ring in ground tissue B
Figure 28.3
Comparison of eudicots and monocots.
In seeds, one cotyledon (seed leaf of embryo)
Flower parts in threes (or multiples of three)
Leaf veins usually running parallel with one another
Pollen grains with one pore or furrow
Vascular bundles throughout ground tissue
Fig. 28-3, p. 477

12. Animation: Eudicots and monocots

13. Introducing Meristems
All plants tissues arise at meristems (regions of rapidly dividing, undifferentiated cells)
Growth in apical meristems at tips of shoots and roots (primary growth) increases length
In some plants, growth in lateral meristems (secondary growth) thickens roots and shoots

14. Apical and Lateral Meristems

15. Figure 28.4
Locations of apical and lateral meristems.
Fig. 28-4a, p. 477

16. shoot apical meristem (new cells forming)
cells dividing, differentiating
three tissue systems developing
three tissue systems developing
cells dividing, differentiating
root apical meristem (new cells forming)
Figure 28.4
Locations of apical and lateral meristems.
a Many cellular descendants of apical meristems are the start of lineages of differentiated cells that grow, divide, and lengthen shoots and roots.
Fig. 28-4a, p. 477

17. Figure 28.4
Locations of apical and lateral meristems.
Fig. 28-4b, p. 477

18. vascular cambium cork cambium thickening
Figure 28.4
Locations of apical and lateral meristems.
b In woody plants, the activity of two lateral meristems—vascular cambium and cork cambium—result in secondary growth that thickens older stems and roots.
Fig. 28-4b, p. 477

19. 28.2 Components of Plant Tissues
Different plant tissues form just behind shoot and root tips, and on older stem and root parts
Tissue systems are organized as simple tissues (one cell type) or complex tissues (two or more cell types)

20. Simple Tissues Parenchyma makes up most primary growth
Functions in secretion, storage, photosynthesis (mesophyll), and tissue repair
Collenchyma supports growing plant parts
Pectin provides flexibility
Sclerenchyma contains lignin for support
Cells (fibers, sclereids) are dead at maturity

21. Simple Tissues

22. collenchyma parenchyma Figure 28.7
Simple tissues. (a) Collenchyma and parenchyma from a supporting strand inside of a celery stem, transverse section. Sclerenchyma: (b) Fibers from a strong flax stem, tangential view. (c) Stone cells, a type of sclereid in pears, transverse section.
Fig. 28-7a, p. 479

23. lignified secondary wall
Figure 28.7
Simple tissues. (a) Collenchyma and parenchyma from a supporting strand inside of a celery stem, transverse section. Sclerenchyma: (b) Fibers from a strong flax stem, tangential view. (c) Stone cells, a type of sclereid in pears, transverse section.
Fig. 28-7c, p. 479

24. Complex Tissues: Vascular Tissues
Xylem carries water and ions through the plant
Consists of two types of cells that are dead at maturity: tracheids and vessel members
Lignin-filled secondary walls
Phloem conducts sugars, other organic solutes
Sieve tubes connect end to end at sieve plates
Companion cells load sugars into sieve tubes

25. Vascular Tissues

26. sieve plate of sieve-tube cell
one cell’s wall
sieve plate of sieve-tube cell
pit in wall
companion cell a b c
Figure 28.8
Simple and complex tissues in a stem. In xylem, (a) part of a column of vessel members, and (b) a tracheid. (c) One of the living cells that interconnect as sieve tubes in phloem.
parenchyma
vessel of xylem
phloem
fibers of sclerenchyma
Fig. 28-8, p. 479

27. Complex Tissues: Dermal Tissues
Epidermis
Usually a single outer layer of cells that secrete a waxy, protective cuticle
May contain specialized cells that form stomata for gas exchange
Periderm
Replaces epidermis in woody stems and roots

28. Plant Cuticle

29. leaf surface cuticle epidermal cell photosynthetic cell Figure 28.9
A typical plant cuticle, with many epidermal cells and photosynthetic cells under it.
Fig. 28-9, p. 479

30. Flowering Plant Tissues

31. Studying Plant Parts: Tissue Specimens
Tissue specimens are cut along standard planes

32. radial: tangential: transverse: Figure 28.6
Terms that identify how tissue specimens are cut from a plant. Longitudinal cuts along a stem or root radius give radial sections. Cuts at right angles to the radius give tangential sections. Cuts perpendicular to the long axis of a stem or root give transverse sections—that is, cross-sections.
Fig. 28-6, p. 478

33. Tissues in a Buttercup Stem

34. sclerenchyma (fibers) parenchyma epidermis
Figure 28.5
Some tissues in a buttercup stem (Ranunculus).
xylem
phloem
Fig. 28-5, p. 478

35. 28.1-28.2 Key Concepts Overview of Plant Tissues
Seed-bearing vascular plants have a shoot system, which includes stems, leaves, and reproductive parts; most also have a root system
Such plants have ground, vascular, and dermal tissues
Plants lengthen or thicken only at active meristems

36. 28.3 Primary Structure of Shoots
Inside the soft, young stems and leaves of both eudicots and monocots, the ground, vascular, and dermal tissue systems are organized in predictable patterns

37. Behind the Apical Meristem
Terminal buds
Main zones of primary growth in shoots
Naked or encased in modified leaves (bud scales)
Form leaves at nodes
Lateral buds (axillary buds)
Dormant shoots in leaf axils
Form side branches, leaves, or flowers

38. Apical Meristem and Primary Growth

39. Figure 28.10
Stem of Coleus, a eudicot. (a–c) Successive stages of the stem’s primary growth, starting with the shoot apical meristem. (d) The light micrograph shows a longitudinal cut through the stem’s center. The tiers of leaves in the photograph below it formed in this linear pattern of development.
Figure It Out: What is the transparent layer of cells on the outer surface of b and c?
Answer: Epidermis
Fig (a-c), p. 480

40. immature leaf shoot apical meristem
a Sketch of the shoot tip in the micrograph at right, tangential
cut. The descendant meristematic
cells are color-coded orange .
b Same tissue region later on, after the shoot tip lengthened above it
Figure 28.10
Stem of Coleus, a eudicot. (a–c) Successive stages of the stem’s primary growth, starting with the shoot apical meristem. (d) The light micrograph shows a longitudinal cut through the stem’s center. The tiers of leaves in the photograph below it formed in this linear pattern of development.
Figure It Out: What is the transparent layer of cells on the outer surface of b and c?
Answer: Epidermis
primary phloem
primary xylem
cortex
pith
c Same tissue region later still, with lineages
of cells lengthening and differentiating
Fig (a-c), p. 480

41. Figure 28.10
Stem of Coleus, a eudicot. (a–c) Successive stages of the stem’s primary growth, starting with the shoot apical meristem. (d) The light micrograph shows a longitudinal cut through the stem’s center. The tiers of leaves in the photograph below it formed in this linear pattern of development.
Figure It Out: What is the transparent layer of cells on the outer surface of b and c?
Answer: Epidermis
Fig d (1), p. 480

42. youngest immature leaf
apical meristem
epidermis forming
lateral bud forming
Figure 28.10
Stem of Coleus, a eudicot. (a–c) Successive stages of the stem’s primary growth, starting with the shoot apical meristem. (d) The light micrograph shows a longitudinal cut through the stem’s center. The tiers of leaves in the photograph below it formed in this linear pattern of development.
Figure It Out: What is the transparent layer of cells on the outer surface of b and c?
Answer: Epidermis
vascular tissues forming
pith
Fig d (1), p. 480

43. Figure 28.10
Stem of Coleus, a eudicot. (a–c) Successive stages of the stem’s primary growth, starting with the shoot apical meristem. (d) The light micrograph shows a longitudinal cut through the stem’s center. The tiers of leaves in the photograph below it formed in this linear pattern of development.
Figure It Out: What is the transparent layer of cells on the outer surface of b and c?
Answer: Epidermis
Fig d (2), p. 480

44. Inside the Stem Vascular bundles
Multistranded cords of vascular tissues threaded lengthwise through ground tissues of all shoots
Two distinct patterns of vascular bundles
Eudicot stems: Cylinders run parallel with stem, divide ground tissue into cortex and pith
Monocot stems: Bundles distributed throughout ground tissue

45. Eudicot and Monocot Stems

46. Figure 28.11
Zooming in on a eudicot and a monocot stem.
Fig a, p. 481

47. companion cell in phloem
vessel in xylem
meristem cell
epidermis
cortex
vascular bundle
pith
Figure 28.11
Zooming in on a eudicot and a monocot stem.
sieve tube in phloem
companion cell in phloem
A Stem fine structure for alfalfa (Medicago), a eudicot
Fig a, p. 481

48. Figure 28.11
Zooming in on a eudicot and a monocot stem.
Fig b, p. 481

49. collenchyma sheath cell companion cell in phloem
air space
vessel in xylem
epidermis
vascular bundle
pith
Figure 28.11
Zooming in on a eudicot and a monocot stem.
sieve tube in phloem
companion cell in phloem
B Stem fine structure for corn (Zea mays), a monocot
Fig b, p. 481

50. Animation: Stem organization

51. Animation: Apical meristems

52. Animation: Cutting tissue specimens

53. Animation: Ground tissues

54. Animation: Vascular tissues