Lecture 5 Outline (Ch. 35)

2. Lecture 5 Outline (Ch. 35) • I. Overview – Plant Systems • II. Plant cell types & tissues • Cell Types: Parenchyma, Collenchyma, Sclerenchyma • 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. Setting the scene - animal bodies Cells  Tissues  Organs  Systems

5. 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

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

7. 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

8. What type of tissue transports fluids in plants? A. Dermal B. Roots C. Vascular D. Stems E. Ground

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

10. 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

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

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

13. Which is a plant cell type? A. secondary B. vascular C. ground D. collenchyma E. leaves

14. 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

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

16. 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

17. 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

18. 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

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

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

21. 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

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

23. 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

24. 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

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

26. 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

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

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

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

30. Apical bud Node Internode Apical bud Shoot system Vegetative shoot Axillary bud Stem Stems - Overview Stem: an organ made of • An alternating system of nodes, points at which leaves attach • Internodes, stem length between nodes • 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

31. Vasculature - Stems Phloem Xylem Ground tissue Sclerenchyma (fiber cells) Ground tissue connecting pith to cortex Pith Epidermis Key to labels Vascular bundles Cortex Epidermis Dermal Vascular bundle Ground 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) • In most monocot stems, the vascular bundles are scattered throughout the ground tissue, rather than forming a ring Dicot Monocot

32. 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

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

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

35. Leaves – Structure and Development • Leaves are several layers thick – each with different cell types

36. 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

37. Leaves Guard cells Key to labels Stomatal pore 50 µm Dermal Epidermal cell Ground Cuticle Sclerenchyma fibers Vascular Stoma (b) Surface view of a spiderwort (Tradescantia) leaf (LM) Upper epidermis Palisade mesophyll Spongy mesophyll Bundle- sheath cell Lower epidermis 100 µm Cuticle Xylem Vein Phloem Vein Air spaces Guard cells Guard cells (a) Cutaway drawing of leaf tissues (c) Cross section of a lilac (Syringa)) leaf (LM) • Leaf epidermis contains stomata - allow CO2 exchange • Stomata flanked by two guard cells,control open vs. closed

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

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

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

41. 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

42. length girth Plant Growth 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

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

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

45. Plant Growth Stem – Secondary Growth: primary phloem • thicker, stronger stems • Vascular Cambium: between primary xylem and phloem vascular cambium primary xylem epidermis • Produces inside stem: pith • A) Secondary xylem • moves H2O, inward • B) Secondary phloem • moves sugars, outward cortex primary xylem dividing vascular cambium primary phloem

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

47. A cross section of what tissue is pictured? A. Monocot root B. Dicot root C. Monocot stem D. Dicot stem

48. 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 different 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?)