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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
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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
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Figure 28.4 Root hairs of a radish seedling
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“Strangling” aerial roots
Storage roots Pneumatophores Figure 28.5 Evolutionary adaptations of roots “Strangling” aerial roots 4
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Stolon Rhizome Root Rhizomes Stolons Tubers
Figure 28.6 Evolutionary adaptations of stems Tubers 5
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Spines Tendrils Storage leaves Stem Reproductive leaves Storage leaves
Figure 28.7 Evolutionary adaptations of leaves Storage leaves Stem Reproductive leaves Storage leaves 6
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Dermal tissue Ground tissue Vascular tissue
Figure 28.8 The three tissue systems Dermal tissue Ground tissue Vascular tissue 7
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chloroplasts (in Elodea leaf) (LM) 60 m
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 8
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(in Helianthus stem) (LM) 5 m
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 9
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Sclereid cells (in pear) (LM)
Cell wall Figure 28.9c Exploring examples of differentiated plant cells (part 3: sclerenchyma cells) Fiber cells (cross section from ash tree) (LM) 10
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100 m Vessel Tracheids 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 11
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longitudinal view (LM) 3 m
Sieve-tube elements: longitudinal view (LM) 3 m Sieve plate Sieve-tube element (left) and companion cell: cross section (TEM) Companion cells Sieve-tube elements Plasmodesma Figure 28.9e Exploring examples of differentiated plant cells (part 5: sugar-conducting cells of the phloem) Sieve plate 30 m Nucleus of companion cell 15 m Sieve-tube elements: longitudinal view Sieve plate with pores (LM) 12
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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 13
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Apical bud Bud scale Axillary buds This year’s growth Leaf
(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 14
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and the cell remains hairless. Cortical cells
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. 15
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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 16
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(a) Root with xylem and phloem in the center (typical of eudicots)
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 17
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Emerging Epidermis lateral root 100 m Lateral root Cortex Vascular
Figure The formation of a lateral root (step 3) Vascular cylinder Pericycle 18
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Shoot apical meristem Leaf primordia Young leaf Developing vascular
strand Figure The shoot tip (LM) Axillary bud meristems 0.25 mm 19
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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) 20
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(a) Cross section of stem with vascular
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) 21
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(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 22
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Vascular cambium 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 23
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Growth ring Vascular ray Heartwood Secondary xylem Sapwood
Figure Anatomy of a tree trunk Vascular cambium Secondary phloem Bark Layers of periderm 24
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