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Chapters 35-39. All Plants… multicellular, eukaryotic, autotrophic, alternation of generations.

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Presentation on theme: "Chapters 35-39. All Plants… multicellular, eukaryotic, autotrophic, alternation of generations."— Presentation transcript:

1 Chapters 35-39

2 All Plants… multicellular, eukaryotic, autotrophic, alternation of generations

3 Alternation of Generations Sporophyte (diploid) produces haploid spores via meiosis Gametophyte (haploid) produce haploid gametes via mitosis Fertilization joins two gametes to form a zygote

4 Angiosperms Monocots vs. Dicots named for the number of cotyledons present on the embryo of the plant + monocots - orchids, corn, lilies, grasses + dicotsdicots - roses, beans, sunflowers, oaks

5 Plant Morphology Morphology (body form) shoot and root systems + inhabit two environments - shoot (aerial) + stems, leaves, flowers - root (subterranean) + taproot, lateral roots vascular tissues + transport materials between roots and shoots - xylem/phloem

6 Plant Anatomy Anatomy (internal structure) division of labor + cells differing in structure and function - parenchyma, collenchyma, sclerenchyma (below) - water- and food-conducting cells (next slide) Parenchyma St: “typical” plant cells Fu: perform most metabolic functions Collenchyma St: unevenly thickened primary walls Fu: provide support but allow growth in young parts of plants Sclerenchyma St: hardened secondary walls (LIGNIN) Fu: specialized for support; dead

7 Plant cell types Parenchyma cellsCollenchyma cells Cell wall Sclerenchyma cells

8 Plant cell types Xylem Phloem WATER-CONDUCTING CELLS OF THE XYLEM Vessel Tracheids Tracheids and vessels Vessel element Pits Tracheids SUGAR-CONDUCTING CELLS OF THE PHLOEM Companion cell Sieve-tube member Sieve-tube members: longitudinal view Sieve plate Nucleus Cytoplasm Companion cell

9 Water- and Food-conducting Cells XylemXylem (water) dead at functional maturity tracheids- tapered with pits vessel elements- regular tubes PhloemPhloem (food) alive at functional maturity sieve-tube members- arranged end to end with sieve plates & Companion cells

10 Plant Tissues Three Tissue Systems dermal tissue + epidermis (skin) - single layer of cells that covers entire body - waxy cuticle/root hairs vascular tissue + xylem and phloem - transport and support ground tissue + mostly parenchyma - occupies the space b/n dermal/vascular tissue - photosynthesis, storage, support

11 Plant Growth Meristems perpetually embryonic tissues located at regions of growth + divide to generate additional cells (initials and derivatives) - apical meristems (primary growth- length) + located at tips of roots and shoots - lateral meristems (secondary growth- girth)

12 Roots A root –Is an organ that anchors the vascular plant –Absorbs minerals and water –Often stores organic nutrients –Taproots found in dicots and gymnosperms –Lateral roots (Branch roots off of the taproot) –Fibrous root system in monocots (e.g. grass) Figure 35.3

13 Modified Roots Many plants have modified roots (a) Prop roots(b) Storage roots (c) “Strangling” aerial roots (d) Buttress roots(e) Pneumatophores (a) Prop roots (b) Storage roots

14 Primary Growth of Roots apical meristem + root cap + three overlapping zones - cell division - elongation - maturation

15 Stems A stem is an organ consisting of –Nodes (could be opposite or alternate) –Internodes

16 Modified Stems Rhizomes (d) Tubers (c) Bulbs Stolons (a) Storage leaves Stem Root Node Rhizome Root

17 Buds An axillary bud –Is a structure that has the potential to form a lateral shoot, or branch A terminal bud –Is located near the shoot tip and causes elongation of a young shoot Gardening tip: Removing the terminal bud stimulates growth of axillary buds

18 Primary Growth in Shoots apical meristem (1, 7) + cell division occurs + produces primary meristems - protoderm (4, 8) - procambium (3, 10) - ground meristem (5, 9) axillary bud meristems + located at base of leaf primordia leaf primordium (2, 6) + gives rise to leaves

19 The leaf Is the main photosynthetic organ of most vascular plants Leaves generally consist of Blade Stalk Petiole

20 Leaf Morphology In classifying angiosperms –Taxonomists may use leaf morphology as a criterion Petiole (a) Simple leaf (b) Compound leaf. (c) Doubly compound leaf. Axillary bud Leaflet Petiole Axillary bud Leaflet Petiole

21 Modified Leaves Tendrils Spines Storage leaves Bracts Reproductive leaves. The leaves of some succulents produce adventitious plantlets, which fall off the leaf and take root in the soil.

22 Leaf Anatomy Epidermal Tissue upper/lower epidermis guard cells (stomata) Ground Tissue mesophyll +palisade/spongy parenchyma Vascular Tissue veins + xylem and phloem

23 Key to labels Dermal Ground Vascular Guard cells Stomatal pore Epidermal cell 50 µm Surface view of a spiderwort (Tradescantia) leaf (LM) (b) Cuticle Sclerenchyma fibers Stoma Upper epidermis Palisade mesophyll Spongy mesophyll Lower epidermis Cuticle Vein Guard cells Xylem Phloem Guard cells Bundle- sheath cell Cutaway drawing of leaf tissues(a) VeinAir spacesGuard cells 100 µm Transverse section of a lilac (Syringa) leaf (LM) (c) Leaf Anatomy

24 Dermal tissue Ground tissue Vascular tissue The Three Tissue Systems: Dermal, Vascular, and Ground

25 Dermal Tissue –Protects plant from: Physical damage Pathogens H 2 O loss (Cuticle)

26 Vascular tissue –Carries out long-distance transport of materials between roots and shoots –Consists of two tissues, xylem and phloem

27 Ground Tissue –Includes various cells specialized for functions such as storage, photosynthesis, and support –Pith = ground tissue internal to the vascular tissue –Cortex = ground tissue external to the vascular tissue

28 Secondary Growth Lateral Meristems vascular cambium + produces secondary xylem/phloem (vascular tissue) cork cambium + produces tough, thick covering (replaces epidermis) secondary growth + occurs in all gymnosperms; most dicot angiosperms

29 The Vascular Cambium and Secondary Vascular Tissue The vascular cambium –Is a cylinder of meristematic cells one cell thick –Develops from parenchyma cells

30 2° Growth As a tree or woody shrub ages –The older layers of secondary xylem, the heartwood, no longer transport water and minerals The outer layers, known as sapwood –Still transport materials through the xylem

31 Cork Cambium Periderm protective coat of secondary plant body + cork cambium and dead cork cells - bark cork cambium produces cork cells



34 Minerals H2OH2O CO 2 O2O2 O2O2 H2OH2O Sugar Light A variety of physical processes –Are involved in the different types of transport Sugars are produced by photosynthesis in the leaves. 5 Sugars are transported as phloem sap to roots and other parts of the plant. 6 Through stomata, leaves take in CO 2 and expel O 2. The CO 2 provides carbon for photosynthesis. Some O 2 produced by photosynthesis is used in cellular respiration. 4 Transpiration, the loss of water from leaves (mostly through stomata), creates a force within leaves that pulls xylem sap upward. 3 Water and minerals are transported upward from roots to shoots as xylem sap. 2 Roots absorb water and dissolved minerals from the soil. 1 Roots exchange gases with the air spaces of soil, taking in O 2 and discharging CO 2. In cellular respiration, O 2 supports the breakdown of sugars. 7

35 The Central Role of Proton Pumps Proton pumps in plant cells –Create a hydrogen ion gradient –Contribute to membrane potential CYTOPLASM EXTRACELLULAR FLUID ATP H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ Proton pump generates membrane potential and H + gradient. – – – – – + + + + +

36 Plant cells use energy stored in the proton gradient and membrane potential –To drive the transport of many different cations + CYTOPLASM EXTRACELLULAR FLUID Cations (, for example) are driven into the cell by the membrane potential. Transport protein K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ – – – + + (Membrane potential and cation uptake – – + +

37 Figure 37.6b (b) Cation exchange in soil. Hydrogen ions (H + ) help make nutrients available by displacing positively charged minerals (cations such as Ca 2+ ) that were bound tightly to the surface of negatively charged soil particles. Plants contribute H + by secreting it from root hairs and also by cellular respiration, which releases CO 2 into the soil solution, where it reacts with H 2 O to form carbonic acid (H 2 CO 3 ). Dissociation of this acid adds H + to the soil solution. H 2 O + CO 2 H 2 CO 3 HCO 3 – + Root hair K+K+ Cu 2+ Ca 2+ Mg 2+ K+K+ K+K+ H+H+ H+H+ Soil particle – – – – – – – – –

38 Cotransport –A transport protein couples the passage of H + to anions H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ NO 3 – – – – + + + – – – + + + Cotransport of anions H+H+ of through a cotransporter. Cell accumulates anions (, for example) by coupling their transport to the inward diffusion

39 H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ S S S S S Plant cells can also accumulate a neutral solute, such as sucrose ( ), by cotransporting down the steep proton gradient. S H+H+ – – – + + + – – + + – H+H+ H+H+ S + – Contransport of a neutral solute Cotransport –Is also responsible for the uptake of sucrose by plant cells

40 Water potential –Is a measurement that combines the effects of solute concentration and pressure –Determines the direction of movement of water Water –Flows from regions of high water potential to regions of low water potential

41 Quantitative Analysis of Water Potential The addition of solutes –Reduces water potential 0.1 M solution H2OH2O Pure water (a)

42 Negative pressure –Decreases water potential H2OH2O (d)

43 Application of physical pressure –Increases water potential H2OH2O (b) H2OH2O (c)

44 Aquaporin Proteins and Water Transport Aquaporins –Are transport proteins in the cell membrane that allow the passage of water –Do not affect water potential

45 Movement of fluid in the xylem & phloem is driven by pressure differences at opposite ends of the xylem vessels and sieve tubes Fluid Movement

46 Water and minerals ascend from roots to shoots through the xylem Plants lose an enormous amount of water through transpiration, the loss of water vapor from leaves and other aerial parts of the plant The transpired water must be replaced by water transported up from the roots

47 Pushing Xylem Sap: Root Pressure At night, when transpiration is very low –Root cells continue pumping mineral ions into the xylem of the vascular cylinder, lowering the water potential Water flows in from the root cortex –Generating root pressure

48 Root pressure sometimes results in guttation

49 Transpiration produces negative pressure (tension) in the leaf Which exerts a pulling force on water in the xylem, pulling water into the leaf The transpirational pull on xylem sap Is transmitted all the way from the leaves to the root tips and even into the soil solution Is facilitated by cohesion and adhesion

50 The stomata of xerophytes –Are concentrated on the lower leaf surface –Are often located in depressions that shelter the pores from the dry wind Lower epidermal tissue Trichomes (“hairs”) Cuticle Upper epidermal tissue Stomata 100  m

51 Translocation Is the transport of organic nutrients in the plant Phloem sap Is an aqueous solution that is mostly sucrose Travels from a sugar source to a sugar sink Translocation through Phloem

52 A sugar source Is a plant organ that is a net producer of sugar, such as mature leaves A sugar sink Is an organ that is a net consumer or storer of sugar, such as a tuber or bulb Sugar Source & Sink

53 Transpiration Lab

54 Control of Transpiration Photosynthesis-Transpiration Compromise guard cells help balance plant’s need to conserve water with its requirement for photosynthesis

55 Stomatal closing 1. Potassium ions move out of the vacuole and out of the cells. 2. Water moves out of the vacuoles, following potassium ions. 3. The guard cells shrink in size. 4. The stoma closes. Stomatal opening 1.Potassium ions move into the vacuoles. 2.Water moves into the vacuoles, following potassium ions. 3.The guard cells expand. 4.The stoma opens.

56 Plant nutrition Chapter 37

57 Plant Nutrition What does a plant need to survive? 9 macronutrients, 8 micronutrients + macro- required in large quantities - C, H, N, O, P, S, K, Ca, Mg + micro- required in small quantities - Fe, Cl, Cu, Mn, Zn, Mo, B, Ni + usually serve as cofactors of enzymatic reactions


59 The most common deficiencies –Are those of nitrogen, potassium, and phosphorus Phosphate-deficient Healthy Potassium-deficient Nitrogen-deficient

60 Remove only one macronutrient to see effects on plant

61 Soil Texture and Composition texture depends on size of particles + sand-silt-clay - loams: equal amounts of sand, silt, clay composition + horizons - living organic matter - A horizon: topsoil, living organisms, humus - B horizon: less organic, less weathering than A horizon - C Horizon: “parent” material for upper layers soil conservation issues + fertilizers, irrigation, erosion

62 A mixture of mineral particles, decaying organic material, living organisms, air, and water, which together support the growth of plants

63 Soil Bacteria and Nitrogen Availability Nitrogen-fixing bacteria convert atmospheric N 2 –plants absorb ammonium (NH 4 + ), nitrate (NO 3 - ) Atmosphere N2N2 Soil N2N2 N2N2 Nitrogen-fixing bacteria Organic material (humus) NH 3 (ammonia) NH 4 + (ammonium) H + (From soil) NO 3 – (nitrate) Nitrifying bacteria Denitrifying bacteria Root NH 4 + Soil Atmosphere Nitrate and nitrogenous organic compounds exported in xylem to shoot system Ammonifying bacteria

64 Nutritional Adaptations Symbiotic Relationships symbiotic nitrogen fixation + Legume root nodules contain bacteroids (Rhizobium bacteria) - mutualistic relationship - Crop rotation (Legumes mycorrhizae + symbiotic associations of fungi and roots - mutualistic relationship parasitic plants + plants that supplement their nutrition from host - mistletoe, dodder plant, Indian pipe carnivorous plants + supplement nutrition by digesting animals

65 Mycorrhizae and Plant Nutrition Mycorrhizae –Are modified roots consisting of mutualistic associations of fungi and roots The fungus –Benefits from a steady supply of sugar donated by the host plant In return, the fungus –Increases the surface area of water uptake and mineral absorption and supplies water and minerals to the host plant

66 Unusual nutritional adaptations in plants Staghorn fern, an epiphyte EPIPHYTES PARASITIC PLANTS CARNIVOROUS PLANTS Mistletoe, a photosynthetic parasite Dodder, a nonphotosynthetic parasite Host’s phloem Haustoria Indian pipe, a nonphotosynthetic parasite Venus’ flytrap Pitcher plants Sundews Dodder


68 Phytoremediation Poplars remove nitrates Mustard removes uranium


70 Pesticide Levels (ppb) in Ground Water Before & After Phytoremediation Activities Wetlands

71 Uptake of Soil Solution Symplastic Route continuum of cytosol based on plasmodesmata Apoplastic Route continuum of cell walls and extracellular spaces Lateral transport of soil solution alternates between apoplastic and symplastic routes until it reaches the Casparian strip

72 Casparian Strip A belt of suberin (purple) that blocks the passage of water and dissolved minerals.


74 Plant Reproduction Sporophyte (diploid) produces haploid spores via meiosis Gametophyte (haploid) produce haploid gametes via mitosis Fertilization joins two gametes to form a zygote

75 An overview of angiosperm reproduction Anther at tip of stamen Filament Anther Stamen Pollen tube Germinated pollen grain (n) (male gametophyte) on stigma of carpel Ovary (base of carpel) Ovule Embryo sac (n) (female gametophyte) FERTILIZATION Egg (n) Sperm (n) Petal Receptacle Sepal Style Ovary Key Haploid (n) Diploid (2n) (a) An idealized flower. (b) Simplified angiosperm life cycle. See Figure 30.10 for a more detailed version of the life cycle, including meiosis. Mature sporophyte plant (2n) with flowers Seed (develops from ovule) Zygote (2n) Embryo (2n) (sporophyte) Simple fruit (develops from ovary) Germinating seed Seed Carpel Stigma

76 Mechanisms That Prevent Self- Fertilization Stigma Anther with pollen Stigma Pin flowerThrum flower The most common anti-selfing mechanism in flowering plants Is known as self-incompatibility, the ability of a plant to reject its own pollen

77 Preventative Selfing Some plants –Reject pollen that has an S-gene matching an allele in the stigma cells Recognition of self pollen –Triggers a signal transduction pathway leading to a block in growth of a pollen tube

78 Double Fertilization pollen grain lands on stigma + pollen tube toward ovule + both sperm discharged down the tube - egg and one of the sperm produce zygote - 2 polar nuclei and sperm cell produce endosperm + ovule becomes the seed coat + ovary becomes the fruit

79 Seed Structure and Development

80 Foliage leaves Cotyledon Hypocotyl Radicle Epicotyl Seed coat Cotyledon Hypocotyl Cotyledon Hypocotyl The radicle –Is the first organ to emerge from the germinating seed In many eudicots –A hook forms in the hypocotyl, and growth pushes the hook above ground

81 Monocots –Use a different method for breaking ground when they germinate The coleoptile –Pushes upward through the soil and into the air Foliage leaves Coleoptile Radicle


83 Tropisms Growth toward or away from a stimulus Gravitropism (Gravity) Phototropism (Light) Thigmotropism (Touch)

84 Etiolation The stems of plants raised in the dark elongate much more rapidly than normal, a phenomenon called etiolation.

85 Figure 39.3 CELL WALL CYTOPLASM 1 Reception 2 Transduction 3 Response Receptor Relay molecules Activation of cellular responses Hormone or environmental stimulus Plasma membrane Signal Transduction Pathway

86 Plant hormones help coordinate growth, development, and responses to stimuli Hormones –Are chemical signals that coordinate the different parts of an organism


88 Photoperiod, the relative lengths of night and day + Is the environmental stimulus plants use most often to detect the time of year

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