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Lecture 5 Outline (Ch. 35) I. Overview – Plant Systems

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2 Lecture 5 Outline (Ch. 35) I. Overview – Plant Systems
II. Plant cell types III. Tissues A. Dermal B. Vascular C. Ground III. Plant organs A. Roots B. Stems C. Leaves IV. Plant Growth A. Meristems B. Primary vs. secondary V. Preparation for next lecture

3 Plant Structure, Growth, Development
Plants are notably different from animals: SA:V ratio Mobility Growth Response to environment Cell structure

4 Cells  Tissues  Organs  Systems
Setting the scene - animal bodies Cells  Tissues  Organs  Systems

5 Plant Cell Types Plant cell structure recap Cell wall, plasmodesmata
Primary wall (some have secondary wall), middle lamella

6 Plant Cell Types 1) Parenchyma (most abundant):
Flexible, thin-walled cells; living plant metabolism: Photosynthesis; hormone secretion; sugar storage Parenchyma cells in Elodea leaf,(w/chloroplasts) thin wall permeable to gasses large central vacuole able to divide and differentiate

7 Plant Cell Types 2) Collenchyma: Able to elongate
Thick-walled (uneven); living Offers support (flexible & strong) Able to elongate Grouped in strands, lack secondary wall Collenchyma cells sunflower

8 Plant Cell Types 3) Sclerenchyma: Thick, hard-walled; Dead
Offer support (e.g. hemp fibers; nut shells) Thick secondary walls with lignin Rigid (cannot elongate) Two types – sclereids and fibers Sclereid cells in pear (LM) Fiber cells in ash tree Cell wall

9 Plant Tissues 1) Dermal Tissues Outer covering Protection
2) Vascular Tissues “Vessels” throughout plant Transport materials 3) Ground Tissues “Body” of plant Photosynthesis; storage; support Three basic cell types: Parenchyma Collenchyma Sclerenchyma

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

11 Plant Systems Dermal tissue Ground Vascular Each plant organ has dermal, vascular, and ground tissues Each of these three categories forms a system Roots Shoots Vascular

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

13 Plant Tissues - Dermis Special Dermal Cells – Trichomes & Root hairs
Hair-like 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

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

15 Plant Tissues - Vascular
Vascular tissues made up of multiple cell types: Arranged in multiple bundles or central cylinder Xylem – water and nutrients Phloem – dissolved sugars and metabolites

16 Plant Tissues - Vascular
1) Xylem (dead at maturity): water and minerals roots to shoots Tracheids: Narrow, tube-like cells Vessel Elements: Wide, tube-like cells Fibers

17 Plant Tissues - Vascular
1) Xylem: Tracheids: - Most vascular plants - Long, thin, tapered ends, lignified secondary walls - Water moves cell to cell through pits Vessel elements: - Wider and shorter - Perforation plates ends of vessel elements - water flows freely though perforation plates

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

19 Plant Tissues - Vascular
2) Phloem (living at maturity) - Moves water, sugar, amino acids & hormones Sieve tube elements/members • Living parenchyma • Long narrow cells stack end to end • Pores in end walls (sieve plates) • Lack most cellular structures including: • Distinct vacuole, Some cytoskeletal elements, Nucleus, Ribosomes Companion Cells: • Adjacent to every sieve tube element • Non-conducting. • Regulate both cells • Connected by numerous plasmodesmata

20 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

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

22 Plant Organs: Roots - Comparisons
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

23 Plant Organs: 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

24 Plant Organs: Roots – Structure and Development
In maturation zone, Casparian strip forms – waterproof barrier material surrounding vasculature

25 Plant Organs: Roots – Vasculature
Epidermis Cortex Endodermis Vascular cylinder Pericycle Core of parenchyma cells Xylem Phloem Dermal Ground Vascular Key to labels 50 m 100 m (a) (b) Root with parenchyma in the center Root with xylem and phloem in the center Dicot Monocot

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

27 Plant Organs: Stems - Overview
Apical bud Node Internode Apical bud Shoot system Vegetative shoot Axillary Stem Stem: an organ made of Alternating nodes, points of leaf attachment Internodes, stem length between nodes Axillary bud - can form a lateral shoot/branch Apical(terminal) bud - near the shoot tip, lengthens a shoot Apical dominance maintains dormancy in most non-apical buds

28 Vasculature - Stems In most monocot stems, the vascular bundles are scattered throughout the ground tissue, rather than forming a ring Phloem Xylem 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 Cross section of stem with scattered vascular bundles (typical of monocots) (b) bundles tissue Dicot Monocot

29 Stems – Many Plants Have Modified Stems
Rhizomes Bulbs Storage leaves Stem Stolons Stolon Tubers Figure 35.5 Modified stems

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

31 Leaves – Structure Leaves are several layers thick – different cell types Key to labels Dermal Ground Vascular Cuticle Xylem Phloem Sclerenchyma fibers Stoma Upper epidermis Palisade mesophyll Spongy mesophyll Lower epidermis Vein Guard cells

32 Plant Organs: Leaves Leaf epidermis contains stomata - allow CO2 exchange Stomata flanked by two guard cells, control open vs. closed

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

34 Leaves – Plants have modified leaves for various functions
Tendrils Spines Storage leaves Figure 35.7 Modified leaves Reproductive leaves Bracts

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

36 Plant Growth 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

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

38 Plant Growth in woody plants
Two lateral meristems: vascular cambium and cork cambium Pith Primary xylem Vascular cambium Primary phloem Cortex Epidermis thicker, stronger stems Vascular Cambium: between primary xylem and phloem

39 Plant Growth Stem – Secondary Growth: Produces inside stem:
Pith Primary xylem Vascular cambium Primary phloem Cortex Epidermis Vascular ray Growth Secondary xylem Secondary phloem First cork cambium Cork Produces inside stem: A) Secondary xylem moves H2O, inward B) Secondary phloem moves sugars, outward

40 Plant Growth Vascular Cambium: Pith Primary xylem Vascular cambium
Primary phloem Cortex Epidermis Vascular ray Growth Secondary xylem Secondary phloem First cork cambium Cork Bark Most recent cork cambium Layers of periderm

41 Things To Do After Lecture 5…
Reading and Preparation: Re-read today’s lecture, highlight all vocabulary you do not understand, and look up terms. Ch. 35 Self-Quiz: #1, 3, 6, 7 (correct answers in back of book) Read chapter 35, focus on material covered in lecture (terms, concepts, and figures!) Skim next lecture. “HOMEWORK” (NOT COLLECTED – but things to think about for studying): Compare and contrast monocots and dicots. List the different types of plant cells and describe which tissues and organs they make up, including roles for each organ. Explain the difference between apical and lateral meristems and how growth occurs. Discuss the composition of bark and it’s function for plants (do all plants have this tissue?)

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