1. Plant Structure, Growth, and Development
Chapter 35
Plant Structure, Growth, and Development

2. Concept 35.1: Plants have a hierarchical organization consisting of organs, tissues, and cells
Plants have organs composed of different tissues, which in turn are composed of different cell types
A tissue is a group of cells consisting of one or more cell types that together perform a specialized function
An organ consists of several types of tissues that together carry out particular functions
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3. The Three Basic Plant Organs: Roots, Stems, and Leaves
Basic morphology of vascular plants reflects their evolution as organisms that draw nutrients from below ground and above ground
Plants take up water and minerals from below ground
Plants take up CO2 and light from above ground
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4. Three basic organs evolved: roots, stems, and leaves
They are organized into a root system and a shoot system
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5. Reproductive shoot (flower)
Figure 35.2
Reproductive shoot (flower)
Apical bud
Node
Internode
Apical bud
Shoot system
Vegetative shoot
Axillary bud
Blade
Leaf
Petiole
Stem
Figure 35.2 An overview of a flowering plant.
Taproot
Root system
Lateral (branch) roots

6. Monocots and eudicots are the two major groups of angiosperms
Roots rely on sugar produced by photosynthesis in the shoot system, and shoots rely on water and minerals absorbed by the root system
Monocots and eudicots are the two major groups of angiosperms
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7. Roots A root is an organ with important functions: Anchoring the plant
Absorbing minerals and water
Storing carbohydrates
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8. Most monocots have a fibrous root system, which consists of:
Most eudicots and gymnosperms have a taproot system, which consists of:
A taproot, the main vertical root
Lateral roots, or branch roots, that arise from the taproot
Most monocots have a fibrous root system, which consists of:
Adventitious roots that arise from stems or leaves
Lateral roots that arise from the adventitious roots
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9. In most plants, absorption of water and minerals occurs near the root hairs, where vast numbers of tiny root hairs increase the surface area
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10. Figure 35.3
Figure 35.3 Root hairs of a radish seedling.

11. Figure 35.4a
Figure 35.4 Evolutionary adaptations of roots.
Prop roots

12. Figure 35.4b
Storage roots
Figure 35.4 Evolutionary adaptations of roots.

13. “Strangling” aerial roots
Figure 35.4c
Figure 35.4 Evolutionary adaptations of roots.
“Strangling” aerial roots

14. Pneumatophores Figure 35.4d
Figure 35.4 Evolutionary adaptations of roots.
Pneumatophores

15. Buttress roots Figure 35.4e
Figure 35.4 Evolutionary adaptations of roots.
Buttress roots

16. Stems A stem is an organ consisting of
An alternating system of nodes, the points at which leaves are attached
Internodes, the stem segments between nodes
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17. Apical dominance helps to maintain dormancy in most axillary buds
An axillary bud is a structure that has the potential to form a lateral shoot, or branch
An apical bud, or terminal bud, is located near the shoot tip and causes elongation of a young shoot
Apical dominance helps to maintain dormancy in most axillary buds
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18. Many plants have modified stems (e. g
Many plants have modified stems (e.g., rhizomes, bulbs, stolons, tubers)
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19. Rhizome Root Rhizomes Figure 35.5a
Figure 35.5 Evolutionary adaptations of stems.
Rhizomes

20. Storage leaves Stem Bulbs Figure 35.5b
Figure 35.5 Evolutionary adaptations of stems.
Stem
Bulbs

21. Stolon Stolons Figure 35.5c
Figure 35.5 Evolutionary adaptations of stems.
Stolons

22. Figure 35.5d
Figure 35.5 Evolutionary adaptations of stems.
Tubers

23. Leaves
The leaf is the main photosynthetic organ of most vascular plants
Leaves generally consist of a flattened blade and a stalk called the petiole, which joins the leaf to a node of the stem
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24. Monocots and eudicots differ in the arrangement of veins, the vascular tissue of leaves
Most monocots have parallel veins
Most eudicots have branching veins
In classifying angiosperms, taxonomists may use leaf morphology as a criterion
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25. Simple leaf Axillary bud Petiole Compound leaf Doubly compound leaf
Figure 35.6
Simple leaf
Axillary bud
Petiole
Compound leaf
Doubly compound leaf
Leaflet
Figure 35.6 Simple versus compound leaves.
Petiole
Axillary bud
Axillary bud
Petiole
Leaflet

26. Some plant species have evolved modified leaves that serve various functions
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27. Tendrils Spines Storage leaves Reproductive leaves Bracts Figure 35.7
Figure 35.7 Evolutionary adaptations of leaves.
Bracts

28. Dermal, Vascular, and Ground Tissues
Each plant organ has dermal, vascular, and ground tissues
Each of these three categories forms a tissue system
Each tissue system is continuous throughout the plant
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29. Dermal tissue Ground tissue Vascular tissue Figure 35.8
Figure 35.8 The three tissue systems.
Dermal tissue
Ground tissue
Vascular tissue

30. In nonwoody plants, the dermal tissue system consists of the epidermis
A waxy coating called the cuticle helps prevent water loss from the epidermis
In woody plants, protective tissues called periderm replace the epidermis in older regions of stems and roots
Trichomes are outgrowths of the shoot epidermis and can help with insect defense
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31. The two vascular tissues are xylem and phloem
The vascular tissue system carries out long-distance transport of materials between roots and shoots
The two vascular tissues are xylem and phloem
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
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32. 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
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33. Tissues that are neither dermal nor vascular are the ground tissue system
Ground tissue internal to the vascular tissue is pith; ground tissue external to the vascular tissue is cortex
Ground tissue includes cells specialized for storage, photosynthesis, and support
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34. Concept 35.2: Meristems generate cells for primary and secondary growth
A plant can grow throughout its life; this is called indeterminate growth
Some plant organs cease to grow at a certain size; this is called determinate growth
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35. Meristems are perpetually embryonic tissue and allow for indeterminate growth
Apical meristems are located at the tips of roots and shoots and at the axillary buds of shoots
Apical meristems elongate shoots and roots, a process called primary growth
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36. 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
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37. Primary growth in stems
Figure 35.11
Primary growth in stems
Epidermis
Cortex
Primary phloem
Shoot tip (shoot apical meristem and young leaves)
Primary xylem
Pith
Vascular cambium
Secondary growth in stems
Cork cambium
Lateral meristems
Cork cambium
Axillary bud meristem
Cortex
Periderm
Primary phloem
Figure An overview of primary and secondary growth.
Pith
Secondary phloem
Root apical meristems
Primary xylem
Vascular cambium
Secondary xylem

38. This year’s growth (one year old) Leaf scar
Figure 35.12
Apical bud
Bud scale
Axillary buds
This year’s growth (one year old)
Leaf scar
Node
Bud scar
One-year-old side branch formed from axillary bud near shoot tip
Internode
Last year’s growth (two year old)
Leaf scar
Stem
Figure Three years’ growth in a winter twig.
Bud scar
Growth of two years ago (three years old)
Leaf scar

39. Flowering plants can be categorized based on the length of their life cycle
Annuals complete their life cycle in a year or less
Biennials require two growing seasons
Perennials live for many years
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40. Concept 35.3: Primary growth lengthens roots and shoots
Primary growth produces the parts of the root and shoot systems produced by apical meristems
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41. 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 differentiation, or maturation
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42. Zone of differentiation Ground Root hair Vascular
Figure 35.13
Cortex
Vascular cylinder
Key to labels
Epidermis
Dermal
Zone of differentiation
Ground
Root hair
Vascular
Zone of elongation
Figure Primary growth of a root.
Zone of cell division (including apical meristem)
Mitotic cells
100 m
Root cap

43. In angiosperm roots, the stele is a vascular cylinder
The primary growth of roots produces the epidermis, ground tissue, and vascular tissue
In angiosperm roots, the stele is a vascular cylinder
In most eudicots, the xylem is starlike in appearance with phloem between the “arms”
In many monocots, a core of parenchyma cells is surrounded by rings of xylem then phloem
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44. Core of parenchyma cells
Figure 35.14
Epidermis
Cortex
Endodermis
Vascular cylinder
Pericycle
Core of parenchyma cells
Xylem
100 m
Phloem
100 m
(a)
Root with xylem and phloem in the center (typical of eudicots)
(b)
Root with parenchyma in the center (typical of monocots)
50 m
Key to labels
Figure Organization of primary tissues in young roots.
Endodermis
Pericycle
Dermal
Xylem
Ground
Phloem
Vascular

45. Root with xylem and phloem in the center (typical of eudicots)
Figure 35.14aa
Epidermis
Key to labels
Cortex
Endodermis
Dermal
Vascular cylinder
Ground
Vascular
Pericycle
Xylem
Phloem
Figure Organization of primary tissues in young roots.
100 m
(a)
Root with xylem and phloem in the center (typical of eudicots)

46. 50 m Endodermis Pericycle Xylem Phloem Key to labels Dermal Ground
Figure 35.14ab
50 m
Endodermis
Pericycle
Xylem
Phloem
Key to labels
Figure Organization of primary tissues in young roots.
Dermal
Ground
Vascular

47. Core of parenchyma cells
Figure 35.14b
Epidermis
Key to labels
Cortex
Dermal
Endodermis
Ground
Vascular
Vascular cylinder
Pericycle
Core of parenchyma cells
Figure Organization of primary tissues in young roots.
Xylem
Phloem
100 m
(b)
Root with parenchyma in the center (typical of monocots)

48. Tissue Organization of Stems
Lateral shoots develop from axillary buds on the stem’s surface
In most eudicots, the vascular tissue consists of vascular bundles arranged in a ring
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49. Sclerenchyma (fiber cells) Ground tissue
Figure 35.17
Phloem
Xylem
Sclerenchyma (fiber cells)
Ground tissue
Ground tissue connecting pith to cortex
Pith
Epidermis
Key to labels
Epidermis
Cortex
Vascular bundles
Figure Organization of primary tissues in young stems.
Vascular bundle
Dermal
1 mm
1 mm
Ground
(a)
Cross section of stem with vascular bundles forming a ring (typical of eudicots)
(b)
Vascular
Cross section of stem with scattered vascular bundles (typical of monocots)

50. Tissue Organization of Leaves
The epidermis in leaves is interrupted by stomata, which allow CO2 and O2 exchange between the air and the photosynthetic cells in a leaf
Each stomatal pore is flanked by two guard cells, which regulate its opening and closing
The ground tissue in a leaf, called mesophyll, is sandwiched between the upper and lower epidermis
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51. Each vein in a leaf is enclosed by a protective bundle sheath
The vascular tissue of each leaf is continuous with the vascular tissue of the stem
Veins are the leaf’s vascular bundles and function as the leaf’s skeleton
Each vein in a leaf is enclosed by a protective bundle sheath
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52. Surface view of a spiderwort (Tradescantia) leaf (LM) Cuticle Stoma
Figure 35.18
Guard cells
Key to labels
Stomatal pore
Dermal
Ground
Epidermal cell
50 m
Vascular
Sclerenchyma fibers
(b)
Surface view of a spiderwort (Tradescantia) leaf (LM)
Cuticle
Stoma
Upper epidermis
Palisade mesophyll
Spongy mesophyll
Bundle- sheath cell
Figure Leaf anatomy.
Lower epidermis
100 m
Xylem
Vein
Cuticle
Phloem
Guard cells
Guard cells
Vein
Air spaces
(a) Cutaway drawing of leaf tissues
(c)
Cross section of a lilac (Syringa) leaf (LM)

53. Growth ring Vascular ray Heartwood Secondary xylem Sapwood
Figure 35.22
Growth ring
Vascular ray
Heartwood
Secondary xylem
Sapwood
Figure Anatomy of a tree trunk.
Vascular cambium
Secondary phloem
Bark
Layers of periderm

54. Figure 35.23
Figure Is this tree living or dead?