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SC.912.L.14.7Plant Structures and Functions. Plant Structures and Functions 1. Monocots vs. Dicots -Root structure and vasculature -Stem vasculature -Leaf.

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Presentation on theme: "SC.912.L.14.7Plant Structures and Functions. Plant Structures and Functions 1. Monocots vs. Dicots -Root structure and vasculature -Stem vasculature -Leaf."— Presentation transcript:

1 SC.912.L.14.7Plant Structures and Functions

2 Plant Structures and Functions 1. Monocots vs. Dicots -Root structure and vasculature -Stem vasculature -Leaf structure and vasculature 2. Plant tissues -Dermal (epidermis) -Vascular -Ground -Meristematic 3. Plant organs -Roots -Stems -Leaves -Flowers and Cones 4. Plant Growth -Meristems – apical, axillary, lateral -Vascular cambium vs. cork cambium

3 Plant Classification – Monocots vs. Dicots Basic categories of plants based on structure and function

4 Plant “bodies” Three Basic Plant Organs: Roots, Stems, and Leaves Plants, like multicellular animals, have organs composed of different tissues, which in turn are composed of cells Shoot system Leaf Stem Root system

5 Each plant organ has dermal, vascular, and ground tissues Each of these three categories forms a tissue system Plant Tissues Dermal tissue Ground tissue Vascular tissue

6 1) Dermal Tissue System Outer covering Protection 3) Ground Tissue System “Body” of plant Photosynthesis; storage; support 2) Vascular Tissue System “Vessels” throughout plant Transport materials Plant Tissues

7 Dermal Tissue System (Outer Covering of Plant): 1) Epidermal Tissue (epidermis): Forms outermost layer Cuticle: Waxy covering Reduces evaporation Inhibits microorganism invasion Root Hairs: extended root surface Increase absorption 2) Peridermal Tissue (periderm): Only in woody plants (“bark = dead cells”) Protection; support Plant Tissues - Dermis

8 Guard cells Stoma Epidermal cell Guard cells Stomata Epidermal cell Guard cells Stoma Epidermal cell Guard cells Stomata Epidermal cell 4 µm 200 µm 71 µm a.c. b. Plant Tissues - Dermis Paired sausage-shaped cells Flank a stoma – epidermal opening Passageway for oxygen, carbon dioxide, and water vapor Special Dermal Cells – Guard Cells

9 Plant Tissues - Dermis Special Dermal Cells – Trichomes & Root hairs Trichomes –Hairlike outgrowths of epidermis –Keep leaf surfaces cool and reduce evaporation Roots hairs –Tube extensions from epidermal cells –Greatly increase the root’s surface area for absorption

10 1) Xylem (dead at maturity): Plant Tissues - Vascular A)Tracheids: Narrow, tube-like cells B)Vessel Elements: Wide, tube-like cells

11 Vascular Transport System 1) Xylem (dead at maturity): - Moves water & minerals from roots to shoots Plant Tissues - Vascular

12 A)Sieve Tubes: Wide, tube-like cells B) Companion Cells: support and regulate sieve tubes 2) Phloem (living at maturity) Plant Tissues - Vascular

13 Vascular Transport System - Moves water, sugar, amino acids & hormones 2) Phloem (living at maturity) Plant Tissues - Vascular

14 Dicots Monocots Vasculature - Comparisons Monocots and dicots differ in the arrangement of vessels in the roots and stems Root Stem

15 Some major types of plant cells: –Parenchyma –Collenchyma –Sclerenchyma Plant Tissues – Ground Tissue Tissues that are neither dermal nor vascular are ground tissue 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

16 Plant Tissues - Ground Ground Tissue System (“Body” of Plant): Parenchyma 1) Parenchyma (most abundant): plant metabolism: Photosynthesis; hormone secretion; sugar storage Thin-walled cells; living Parenchyma cells in Elodea leaf,(w/chloroplasts)

17 Plant Tissues - Ground Collenchyma 2) Collenchyma: Thick-walled (uneven) ; living Offers support (flexible & strong) Ground Tissue System (“Body” of Plant): Collenchyma cells sunflower

18 Plant Tissues - Ground Sclerenchyma 3) Sclerenchyma: Thick, hard-walled; Dead Offer support (e.g. hemp fibers; nut shells) Ground Tissue System (“Body” of Plant): Sclereid cells in pear (LM) Fiber cells in ash tree Cell wall

19 Roots need sugars from photosynthesis; Shoots rely on water and minerals absorbed by the root system Roots - Overview Root Roles: - Anchoring the plant - Absorbing minerals and water - Storing organic nutrients

20 Taproots: Fibrous roots: Typical of dicots, primary root forms and small branch roots grow from it In monocots mostly, primary root dies, replaced by new roots from stem Roots - Comparisons

21 Roots – Structure and Development Four regions: –Root cap Protection, gravity detection –Zone of cell division Mitotic divisions –Zone of elongation Cells lengthen, no division –Zone of maturation Cells differentiate, outer layer becomes dermis

22 Roots – Structure and Development In maturation zone, Casparian strip forms – waterproof barrier material surrounding vasculature

23 Roots – Structure and Development 1250 µm Epidermis Primary phloem Primary xylem Pith Monocot Eudicot Endodermis Cortex Epidermis Primary xylem Pericycle Primary phloem 48 µm 385 µm 8 µm Endodermis Location of Casparian strip Endodermis Location of Casparian strip Cortex Pericycle

24 Prop roots “Strangling” aerial roots Storage roots Buttress roots Pneumatophores Roots – Many Plants Have Modified Roots Water storage

25 Stem: an organ made of –An alternating system of nodes, points at which leaves attach –Internodes, stem length between nodes Stems - Overview Axillary bud - structure that can form a lateral shoot, or branch Apical/terminal bud - located near the shoot tip, lengthens a shoot Apical dominance maintains dormancy in most nonapical buds Apical bud Node Internode Apical bud Shoot system Vegetative shoot Axillary bud Stem

26 Stems – Structure and Development Stems have all three types of plant tissue Grow by division at meristems –Develop into leaves, other shoots, and even flowers Leaves may be arranged in one of three ways

27 Stems - Comparisons Monocot Eudicot

28 Rhizomes Bulbs Storage leaves Stem Stolons Stolon Tubers Stems – Many Plants Have Modified Stems

29 The leaf is the main photosynthetic organ of most vascular plants Leaves - Overview Shoot system Leaf Blade Petiole Leaves generally have a flattened blade and a stalk called the petiole, which joins the leaf to a node of the stem

30 Leaves – Structure and Development Leaves are several layers thick – each with different cell types

31 Leaves – Structure and Development Most dicots have 2 types of mesophyll –Palisade mesophyll high photosynthesis –Spongy mesophyll air spaces for gas & water exchange Monocot leaves have 1 type of mesophyll

32 Most dicots have branch-like veins and palmate leaf shape Monocots have parallel leaf veins and longer, slender blades Leaves - Comparisons Monocots and dicots differ in the arrangement of veins, the vascular tissue of leaves

33 Tendrils Spines Storage leaves Reproductive leaves Bracts Leaves – Plants have modified leaves for various functions

34 Plant Growth: 1) Indeterminate: Grow throughout life 2) Growth at “tips” (length) and at “hips” (girth) Growth patterns in plant: 1) Meristem Cells: Dividing Cells 2) Differentiated Cells: Cells specialized in structure & role Form stable, permanent part of plant Plant Growth

35 1) Primary Growth: 1) Increased length 2) Specialized structures (e.g. fruits) 2) Secondary Growth: Responsible for increases in stem/root diameter Apical Meristems: Mitotic cells at “tips” of roots / stems Lateral Meristems: Mitotic cells “hips” of plant Plant Growth girth length

36 Shoot apical meristem Leaf primordia Young leaf Developing vascular strand Axillary bud meristems Plant Growth

37 Shoot tip (shoot apical meristem and young leaves) Lateral meristems: Axillary bud meristem Vascular cambium Cork cambium Root apical meristems Primary growth in stems Epidermis Cortex Primary phloem Primary xylem Pith Secondary growth in stems Periderm Cork cambium Cortex Primary phloem Secondary phloem Pith Primary xylem Secondary xylem Vascular cambium Plant Growth Two lateral meristems: vascular cambium and cork cambium

38 Stem – Secondary Growth: thicker, stronger stems Vascular Cambium: between primary xylem and phloem primary phloem vascular cambium primary xylem epidermis cortex pith primary xylem primary phloem dividing vascular cambium Plant Growth Produces inside stem: A) Secondary xylem - moves H 2 O, inward B) Secondary phloem - moves sugars, outward

39 Plant Growth primary phloem dividing vascular cambium new secondary xylem new secondary phloem primary xylem secondary phloem primary phloem vascular cambium primary xylem secondary xylem pith cortex Secondary growth Vascular Cambium: Vascular cambium Growth Secondary xylem After one year of growth After two years of growth Secondary phloem Vascular cambium XX X X X X P P P P C C C C C C C C C C C C C

40 Stem – Secondary Growth: Dead at maturity Protection Cork Cambium: Located under outer surface; produces periderm Plant Growth Growth ring Vascular ray Secondary xylem Heartwood Sapwood Bark Vascular cambium Secondary phloem Layers of periderm

41 annual ring early xylem late xylem heartwood (xylem) sapwood (xylem) vascular cambium phloem Stem – Secondary Growth: Sapwood = Young xylem, water Heartwood = Old xylem, support Seasonal Growth = annual rings Secondary phloem = grows outward older phloem crushed Plant Growth

42 RESULTS Ring-width indexes 2 1.5 0.5 1 0 16001700180019002000 Year Plant Growth Using dendrochronology to study climate

43 Plant Growth Living tree or dead tree?

44 Epidermis Cortex Endodermis Vascular cylinder Pericycle Core of parenchyma cells Xylem Phloem 100 µm Root with xylem and phloem in the center (typical of eudicots) (a) Root with parenchyma in the center (typical of monocots) (b) 100 µm Endodermis Pericycle Xylem Phloem Key to labels Dermal Ground Vascular Plant Growth - Roots

45 PhloemXylem Sclerenchyma (fiber cells) Ground tissue connecting pith to cortex Pith Cortex 1 mm Epidermis Vascular bundle Cross section of stem with vascular bundles forming a ring (typical of eudicots) (a) Key to labels Dermal Ground Vascular Cross section of stem with scattered vascular bundles (typical of monocots) (b) 1 mm Epidermis Vascular bundles Ground tissue In most monocot stems, the vascular bundles are scattered throughout the ground tissue, rather than forming a ring Plant Growth - Stems

46 Plant Growth - Leaves Leaf epidermis contains stomata - allow CO 2 exchange Stomata flanked by two guard cells, control open vs. closed The ground tissue in a leaf, called mesophyll, fills the middle Key to labels Dermal Ground Vascular Cuticle Sclerenchyma fibers Stoma Bundle- sheath cell Xylem Phloem (a) Cutaway drawing of leaf tissues Guard cells Vein Cuticle Lower epidermis Spongy mesophyll Palisade mesophyll Upper epidermis Guard cells Stomatal pore Surface view of a spiderwort (Tradescantia) leaf (LM) Epidermal cell (b) 50 µm 100 µm VeinAir spacesGuard cells Cross section of a lilac (Syringa)) leaf (LM) (c)

47 Plant Structures and Functions Summary 1. Monocots vs. Dicots -Root structure and vasculature -Stem vasculature -Leaf structure and vasculature 2. Plant tissues -Dermal (epidermis) -Vascular -Ground 3. Plant organs -Roots -Stems -Leaves 4. Plant Growth -Meristems – apical, axillary, lateral -Vascular cambium vs. cork cambium


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