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Flowering Plants ANGIOSPERMS Angiosperm Diversity • The two main groups of angiosperms are monocots (one cotyledon) and dicots (two cotyledons) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Monocots • More than one-quarter of angiosperm species are monocots Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-13e Orchid Fig. 30-13e1 Pygmy date palm (Phoenix roebelenii) Fig. 30-13f Fig. 30-13g Barley Anther Stigma Ovary Filament Dicots • More than two-thirds of angiosperm species are eudicots Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-13h California poppy Fig. 30-13i Pyrenean oak Fig. 30-13j Dog rose Fig. 30-13k Snow pea Fig. 30-13l Zucchini flowers Fig. 30-13n Monocot Characteristics Eudicot Characteristics Embryos Two cotyledons One cotyledon Leaf venation Veins usually parallel Veins usually netlike Stems Vascular tissue scattered Vascular tissue usually arranged in ring Fig. 30-13o Monocot Characteristics Eudicot Characteristics Roots Taproot (main root) usually present Root system usually fibrous (no main root) 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 • Three basic organs evolved: roots, stems, and leaves • They are organized into a root system and a shoot system • Roots rely on sugar produced by photosynthesis in the shoot system, and shoots rely on water and minerals absorbed by the root system Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 35-2 Reproductive shoot (flower) Apical bud Node Internode Apical bud Vegetative shoot Leaf Shoot system Blade Petiole Axillary bud Stem Taproot Lateral branch roots Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Root system Roots • Roots are multicellular organs with important functions: – Anchoring the plant – Absorbing minerals and water – Storing organic nutrients Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 35-14a1 Epidermis Key to labels Cortex Dermal Endodermis Ground Vascular Pericycle Stele Xylem 100 µm Phloem (a) Root with xylem and phloem in the center (typical of eudicots) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 35-14 Epidermis Cortex Endodermis Pericycle Core of parenchyma cells Xylem 100 µm Phloem 100 µm (a) Root with xylem and phloem in the center (typical of eudicots) (b) Root with parenchyma in the center (typical of monocots) Endodermis Pericycle Key to labels Dermal Ground Vascular Xylem Phloem 50 µm 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 35-17 Phloem Xylem Sclerenchyma (fiber cells) Ground tissue Ground tissue connecting pith to cortex Pith Epidermis Key to labels Cortex Epidermis Vascular bundle Dermal Vascular bundles Ground 1 mm (a) Cross section of stem with vascular bundles forming a ring (typical of eudicots) Vascular 1 mm (b) Cross section of stem with scattered vascular bundles (typical of monocots) Fig. 35-17a Phloem Xylem Sclerenchyma (fiber cells) Ground tissue connecting pith to cortex Pith Key to labels Cortex Epidermis Vascular bundle Dermal Ground 1 mm (a) Cross section of stem with vascular bundles forming a ring (typical of eudicots) Vascular Fig. 35-17b Ground tissue Epidermis Key to labels Dermal Vascular bundles Ground Vascular 1 mm (b) Cross section of stem with scattered vascular bundles (typical of monocots) In most monocot stems, the vascular bundles are scattered throughout the ground tissue, rather than forming a ring 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Monocots and dicots differ in the arrangement of veins, the vascular tissue of leaves – Most monocots have parallel veins – Most dicots have branching veins • In classifying angiosperms, taxonomists may use leaf morphology as a criterion Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 35-6 (a) Simple leaf Petiole Axillary bud Leaflet (b) Compound leaf Petiole Axillary bud (c) Doubly compound leaf Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Leaflet Petiole Axillary bud Fig. 35-6a (a) Simple leaf Petiole Axillary bud Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 35-6b Leaflet (b) Compound leaf Petiole Axillary bud Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Venation Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Monocot leave Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Tissue Organization of Leaves • The epidermis in leaves is interrupted by stomata, which allow CO2 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Below the palisade mesophyll in the upper part of the leaf is loosely arranged spongy mesophyll, where gas exchange occurs • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 35-18 Guard cells Key to labels Dermal Ground Cuticle Vascular 50 µm Stomatal pore Epidermal cell Sclerenchyma fibers Stoma (b) Surface view of a spiderwort (Tradescantia) leaf (LM) Upper epidermis Palisade mesophyll 100 µm Spongy mesophyll Bundlesheath cell Lower epidermis Cuticle Xylem Vein Phloem (a) Cutaway drawing of leaf tissues Guard cells Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Vein Air spaces Guard cells (c) Cross section of a lilac (Syringa)) leaf (LM) Concept 35.4: Secondary growth adds girth to stems and roots in woody plants • Secondary growth occurs in stems and roots of woody plants but rarely in leaves • The secondary plant body consists of the tissues produced by the vascular cambium and cork cambium • Secondary growth is characteristic of gymnosperms and many eudicots, but not monocots Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 35-19 (a) Primary and secondary growth in a two-year-old stem Epidermis Cortex Primary phloem Pith Primary xylem Epidermis Vascular cambium Primary phloem Cortex Vascular cambium Primary xylem Pith Vascular ray Primary xylem Secondary xylem Vascular cambium Secondary phloem Primary phloem First cork cambium Cork Periderm (mainly cork cambia and cork) Secondary phloem Vascular cambium Late wood Secondary xylem Early wood Primary phloem Vascular cambium Secondary xylem Primary xylem Cork cambium Periderm Cork Secondary Xylem (two years of production) Vascular cambium Secondary phloem Most recent cork cambium 0.5 mm Secondary phloem Bark Bark Cork Layers of periderm Pith Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 0.5 mm Vascular ray Growth ring (b) Cross section of a three-yearold Tilia (linden) stem (LM) • The vascular tissue system carries out longdistance 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Annuals complete their life cycle in a year or less • Biennials require two growing seasons • Perennials live for many years Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Assignments 1. Exclude e 2. Exclude c 3. All but we are using Coleus stems 4. Exclude b and j Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings