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Chapter 28: Plant Structure and Growth Overview: Are Plants Computers?
Your thoughts? © 2014 Pearson Education, Inc. 1
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Figure 28.2 A comparison of monocots and eudicots
Embryos One cotyledon Two cotyledons Leaf venation Veins usually netlike Veins usually parallel Stems Vascular tissue scattered Vascular tissue usually arranged in ring Roots Root system usually fibrous (no main root) Taproot (main root) usually present Figure 28.2 A comparison of monocots and eudicots Pollen Pollen grain with one opening Pollen grain with three openings Flowers Floral organs usually in multiples of three Floral organs usually in multiples of four or five 2
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Concept 28.1: Plants have a hierarchical organization consisting of organs, tissues, and cells
Recall: cells tissues organsorgan system organism Plants have a root system and a shoot system © 2014 Pearson Education, Inc. 3
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Reproductive shoot (flower) Apical bud
Figure 28.3 Reproductive shoot (flower) Apical bud Node Internode Apical bud Shoot system Vegetative shoot Blade Leaf Petiole Axillary bud Stem Taproot Figure 28.3 An overview of a flowering plant Lateral (branch) roots Root system 4
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Types of Roots in Vascular Plants
TAP ROOT FIBROUS ROOT ROOT HAIRS? MYCORRHIZAE? © 2014 Pearson Education, Inc. 5
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“Strangling” aerial roots
Figure 28.5 Storage roots Pneumatophores Figure 28.5 Evolutionary adaptations of roots “Strangling” aerial roots 6
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Stolon Rhizome Root Rhizomes Stolons Tubers Figure 28.6
Figure 28.6 Evolutionary adaptations of stems Tubers 7
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Spines Tendrils Storage leaves Stem Reproductive leaves Storage leaves
Figure 28.7 Spines Tendrils Figure 28.7 Evolutionary adaptations of leaves Storage leaves Stem Reproductive leaves Storage leaves 8
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Dermal, Vascular, and Ground Tissue Systems
Help make up the plant body Dermal tissue Vascular Tissue Ground Tissue © 2014 Pearson Education, Inc. 9
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Dermal tissue Ground tissue Vascular tissue Figure 28.8
Figure 28.8 The three tissue systems Dermal tissue Ground tissue Vascular tissue 10
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Common Types of Plant Cells
The major types of plant cells are Parenchyma Collenchyma Sclerenchyma Water-conducting cells of the xylem Sugar-conducting cells of the phloem Bozeman Biology= First Link; Crash Course Plants= Second Link Animation: Tour of a Plant Cell © 2014 Pearson Education, Inc. 11
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parenchyma collenchyma sclerenchyma © 2014 Pearson Education, Inc. 12
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chloroplasts (in Elodea leaf) (LM) 60 m
Figure 28.9a Figure 28.9a Exploring examples of differentiated plant cells (part 1: parenchyma cells with chloroplasts in Elodea leaf, LM) Parenchyma cells with chloroplasts (in Elodea leaf) (LM) 60 m 13
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(in Helianthus stem) (LM) 5 m
Figure 28.9b Figure 28.9b Exploring examples of differentiated plant cells (part 2: collenchyma cells in Helianthus stem, LM) Collenchyma cells (in Helianthus stem) (LM) 5 m 14
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Sclereid cells (in pear) (LM)
Figure 28.9c 5 m Sclereid cells (in pear) (LM) 25 m Cell wall Figure 28.9c Exploring examples of differentiated plant cells (part 3: sclerenchyma cells) Fiber cells (cross section from ash tree) (LM) 15
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xylem 100 m Vessel Tracheids Pits Tracheids and vessels
Figure 28.9d 100 m Vessel Tracheids xylem Pits Tracheids and vessels (colorized SEM) Figure 28.9d Exploring examples of differentiated plant cells (part 4: water-conducting cells of the xylem) Perforation plate Vessel element Vessel elements, with perforated end walls Tracheids 16
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Phloem Sieve-tube elements: longitudinal view (LM) 3 m Sieve plate
Figure 28.9e Sieve-tube elements: longitudinal view (LM) Phloem 3 m Sieve plate Sieve-tube element (left) and companion cell: cross section (TEM) Companion cells Sieve-tube elements Plasmodesma Sieve plate Figure 28.9e Exploring examples of differentiated plant cells (part 5: sugar-conducting cells of the phloem) 30 m Nucleus of companion cell 15 m Sieve-tube elements: longitudinal view Sieve plate with pores (LM) 17
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Concept 28.2: Meristems generate new cells for growth and control the developmental phases and life spans of plants A plant has indeterminate growth because of the presence of meristems Apical Lateral Some plant organs have determinate growth © 2014 Pearson Education, Inc. 18
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Primary growth in stems Epidermis
Figure 28.10 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 Lateral meristems Cork cambium Cork cambium Axillary bud meristem Periderm Pith Cortex Figure An overview of primary and secondary growth Primary phloem Secondary phloem Primary xylem Root apical meristems Secondary xylem Vascular cambium 19
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Apical bud Bud scale Axillary buds This year’s growth Leaf
Figure 28.11 Apical bud Bud scale Axillary buds This year’s growth (one year old) Leaf scar Bud scar Node One-year-old branch formed from axillary bud near shoot tip Internode Last year’s growth (two years old) Leaf scar Stem Figure Three years’ growth in a winter twig Bud scar Growth of two years ago (three years old) Leaf scar 20
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Gene Expression and Control of Cell Differentiation
Cellular differentiation depends on gene expression, but is determined by position Gene activation or inactivation depends on cell-to-cell communication For example, Arabidopsis root epidermis forms root hairs or hairless cells depending on the number of cortical cells it is touching © 2014 Pearson Education, Inc. 21
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and the cell remains hairless. Cortical cells
Figure 28.12 GLABRA-2 is expressed, and the cell remains hairless. Cortical cells GLABRA-2 is not expressed, and the cell will develop a root hair. Figure Control of root hair differentiation by a master regulatory gene (LM) 20 m The root cap cells will be sloughed off before root hairs emerge. 22
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Meristematic Control of the Transition to Flowering and the Life Spans of Plants
Flower formation requires plant to transition from vegetative growth to reproductive growth Reproductive growth= determinate Annuals? Perennials? Biennials? © 2014 Pearson Education, Inc. 23
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Concept 28.3: Primary growth lengthens roots and shoots
Primary growth arises from the apical meristems and produces parts of the root and shoot systems © 2014 Pearson Education, Inc. 24
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Primary Growth of Roots
The root cap protects the developing root Growth occurs just behind the root tip, in three zones of cells Zone of cell division Zone of elongation Zone of differentiation, or maturation Video: Root Time Lapse © 2014 Pearson Education, Inc. 25
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Cortex Vascular cylinder Dermal Ground Epidermis Vascular Zone of
Figure 28.13 Cortex Vascular cylinder Dermal Ground Epidermis Vascular Zone of differentiation Root hair Zone of elongation Figure Primary growth of a typical eudicot root Zone of cell division (including root apical meristem) Mitotic cells 100 m Root cap 26
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(a) Root with xylem and phloem in the center (typical of eudicots)
Figure 28.14 Epidermis Cortex Endodermis Vascular cylinder Pericycle Core of parenchyma cells Xylem 100 m Phloem (a) Root with xylem and phloem in the center (typical of eudicots) 100 m (b) Root with parenchyma in the center (typical of monocots) Endodermis Figure Organization of primary tissues in young roots Pericycle Xylem Phloem Dermal Ground Vascular 70 m 27
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Emerging Epidermis lateral root 100 m Lateral root Cortex Vascular
Figure Emerging lateral root Epidermis 100 m Lateral root Cortex Figure The formation of a lateral root (step 3) Vascular cylinder Pericycle 28
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Shoot apical meristem Leaf primordia Young leaf Developing vascular
Figure 28.16 Shoot apical meristem Leaf primordia Young leaf Developing vascular strand Figure The shoot tip (LM) Axillary bud meristems 0.25 mm 29
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LEAF ORGANIZATION Figure 28.17 Guard cells Stomatal pore 50 m Dermal
Epidermal cell Ground Cuticle Sclerenchyma fibers Vascular Stoma (b) Surface view of a spiderwort (Tradescantia) leaf (LM) Upper epidermis Palisade mesophyll Spongy mesophyll Figure Leaf anatomy Lower epidermis 100 m Bundle- sheath cell Cuticle Xylem Vein Phloem Guard cells Vein Air spaces Guard cells (a) Cutaway drawing of leaf tissues (c) Cross section of a lilac (Syringa) leaf (LM) 30
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STEM ORGANIZATION Sclerenchyma (fiber cells) Phloem Xylem
Figure 28.18 STEM ORGANIZATION Sclerenchyma (fiber cells) Phloem Xylem Ground tissue connecting pith to cortex Ground tissue Pith Epidermis Dermal Figure Organization of primary tissues in young stems Epidermis Cortex Ground Vascular bundles Vascular bundle Vascular 1 mm 1 mm (a) Cross section of stem with vascular bundles forming a ring (typical of eudicots) (b) Cross section of stem with scattered vascular bundles (typical of monocots) 31
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Concept 28.4: Secondary growth increases the diameter of stems and roots in woody plants
Secondary growth is characteristic of ______________and many _________, but not monocots Secondary growth occurs in: © 2014 Pearson Education, Inc. 32
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Figure 28.19 (a) Primary and secondary growth in a two-year-old woody stem Pith Primary xylem Vascular cambium Primary phloem Epidermis Cortex Cortex Epidermis Primary phloem Vascular cambium Vascular ray Growth Periderm Primary xylem Secondary phloem Cork cambium Vascular cambium Cork Pith Bark Secondary xylem Late wood Secondary xylem Early wood Secondary phloem Cork First cork cambium 1 mm Periderm (mainly cork cambia and cork) Growth Vascular ray Growth ring Figure Primary and secondary growth of a woody stem 1.4 mm (b) Cross section of a three-year- old Tilia (linden) stem (LM) Secondary phloem Most recent cork cambium Layers of periderm Secondary xylem Cork Bark 33
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The Vascular Cambium and Secondary Vascular Tissue http://bcs
The vascular cambium is a cylinder of meristematic cells one cell layer thick In cross section, the vascular cambium appears as a ring of initials (stem cells) The initials increase the vascular cambium’s circumference and add secondary xylem to the inside and secondary phloem to the outside © 2014 Pearson Education, Inc. 34
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The Vascular Cambium and Secondary Vascular Tissue
Growth Vascular cambium Secondary phloem Secondary xylem Figure Secondary growth produced by the vascular cambium After one year of growth After two years of growth Figure 28.20 35
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LAYERS OF A TREE COOKIE Growth ring Vascular ray Heartwood Secondary
xylem Sapwood Figure Anatomy of a tree trunk Vascular cambium Secondary phloem Bark Layers of periderm Figure 28.21 36
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