Plant Function. (Freeman Chs 38 & 39) 04 March Videos 34.3, 39.1 browser. ECOL 182R UofA K. E. Bonine

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1 Plant Function (Freeman Chs 38 & 39) 04 March 2010 ECOL 182R UofA K. E. Bonine Videos 34.3, 39.1 browser 1

2 Lecture Schedule (middle third) 18 Feb KB Fungi, Ch31 23 Feb KB Prokaryotes & Protists, Ch28&29 25 Feb KB Plant Diversity, Form, Function, Ch30&40 2 Mar KB Plant Form and Function, Ch36&37 4 Mar KB Plant Function, Ch38&39 9 Mar KB Plant Ecology, Ch50,52,53 11 Mar KB Ecology, Ch50,52, Mar Spring Break 23 Mar KB Biology of the Galapagos Wikelski 2000 and 25 Mar KB - Part 2. Discussion and Review. 30 Mar KB - EXAM 2 2

3 Plants: Nutrition Etc. Ch 38 3

4 How do plants get nutrients they need? Usually from soil through roots. A few interesting exceptions ymnlpqnyi6g&feature=related 4

5 In addition to carbon dioxide and water, plants require essential nutrients. Most nutrients are available as ions dissolved in soil water and are taken up by roots. Do Fungi Fix Nitrogen? Nutrient absorption occurs via specialized proteins in plasma membranes of root cells. Most plants also obtain xxxxxxx or phosphorus from xxxxx associated with their roots. 5

6 Nutritional Requirements early 1600s, classic experiment by van Helmont mass of a growing plant comes from soil? water? (elsewhere?) 6

7 Hypothesis? Predictions? 7

8 Hypothesis? Predictions? RESULTS 8

9 Nutritional Requirements early 1600s, classic experiment by van Helmont mass of a growing plant comes from soil? mass of a growing plant comes from water? [Most of the mass of the tree actually comes from xxxxxxxxxxx in the atmosphere] 9

10 Which Nutrients Are Essential? An xxxxxxxx nutrient: required for both normal growth and reproduction and for a specific structure or metabolic function. There are 17 essential nutrients for most vascular plants. 10

11 Which Nutrients Are Essential? Classified based on whether from water &/or carbon dioxide versus from Essential nutrients available from H 2 O or CO 2 are xxxxxxxxxxxxxxxxxxxx and xxxxxxxxxxxxx They make up 96% of the plant. Soil elements can be divided into macronutrients and micronutrients. 11

12 Macronutrients are the building blocks of nucleic acids, proteins, carbohydrates, phospholipids, and other key molecules required in relatively large quantities. They are nitrogen (N) potassium (K) calcium (Ca) magnesium(mg) phosphorus (P) sulfur(s). 12

13 Which Nutrients Are Essential? Limiting nutrients are macronutrients that commonly act as limits on plant growth. xxxx andxx are often limiting nutrients. 13

14 Which Nutrients Are Essential? Micronutrients are required in very small quantities. Rather than acting as components of macromolecules, they usually function as cofactors for specific enzymes. Examples include: iron, zinc, boron, copper, and nickel. 14

15 studying nutritional deficiencies Hydroponic growth takes place in liquid cultures, without soil, so the availability of nutrients can be precisely controlled. 15

16 16

17 Copper? 17

18 Copper! 18

19 Soil Weathering the forces applied by rain, running water, and wind begins the process of building soil from solid rock. Particles derived from rocks are the first ingredient in soil. As organisms occupy the substrate, they add dead cells and tissues. This organic matter is called xxxxx Organic + Inorganic = Mature Soil 19

20 Soil Formation Begins with Erosion of Rock Wind Particles Freezing and thawing Water (rain) Organisms (plants, lichens, moss, fungi, animals, bacteria, archaea) Soil texture is categorized by particle size: Gravel Sand Particles (>2.0 mm) ( mm) Silt Clay Soil formation begins when wind, temperature changes, rain, and organisms break small particles off solid rock Solid rock Particles Particles ( mm) (<0.002 mm) Soil Succession 20

21 What Factors Affect Nutrient Availability? + Cations + bind to soil particles -Anions -stay in solution. (Leaching: loss of nutrients via washing). Soil ph (lower ph ~ more H + ) acidic(low ph) or alkaline (high ph) 21

22 What Factors Affect Nutrient Availability? Cations tend to bind to soil particles, while anions stay in solution. The loss of nutrients via washing is called leaching. 22

23 Root Hairs Increase the Surface Area Available for Nutrient Absorption Zone of maturation Root hairs 23

24 Mechanisms of Nutrient Uptake Plant cell walls can be permeable: to ions small molecules some large molecules Membrane proteins allow only specific ions to cross the plasma membrane: highly selective 24

25 Establishing and Using a Proton Gradient Root-hair cells have proton pumps (H + - ATPases) in their plasma membranes that move nutrients into the cell against a strong concentration gradient. 25

26 Ions Enter Roots along Electrochemical Gradients Created by xxxxx Pumps Root hair Proton pumps establish an electrochemical gradient. Outside cell (positive) Proton pump Net positive charge Inside cell (negative) Net negative charge 26

27 Cations Enter Roots via xxxxxxxxxx Cations enter root hairs via channels. Proton pump Channel 27

28 Anions Enter Roots via xxxxxxxxxxxxxxx Anions enter root hairs via cotransporters. Proton pump Cotransporter 28

29 Cation vs Anion Nutrients Anions easier to get than cations But anions can leach out of sandy soils Anions better retained in clay soils Cationsoften bound to organic or inorganic soil particles Cation H + (proton) for Mg + or K + or Ca + etc. Plants facilitate by pumping H + out of root hairs 29

30 Cation H+ (proton) for Mg+ or K+ or Ca+ etc. Plants facilitate by pumping H+ out of root hairs 30

31 Review Fungi lecture Nutrient Transfer via Mycorrhizal Fungi Vast majority of plants take up nutrients through their root hairs But, most need more nitrogen and phosphorus Help from fungi that live in close association with their roots. These fungi are called mycorrhizae 31

32 Fungal hypha Plants provide sugars to mycorrhizae Soil The hyphae secrete enzymes that digest macromolecules. The hyphae than absorb the resulting ions Mycorrhizae provide nutrients to plants Cross section of plant root mycorrhizae provide xxxx and/or phosphorus to the plants in exchange for sugar. Review Fungi lecture Symbiotic Photosynthetic products mutualism 32

33 Not all soil ions are good for the plant In Salt-Tolerant Plants, an xxxx Concentrates Sodium in Vacuoles In the tonoplast, antiporters send H + out and Na + in. Proton gradient Cytoplasm Tonoplast Inside vacuole Proton pump Antiporter 33

34 Some species of plant have specialized methods of obtaining nutrients, including associations with nitrogen-fixing bacteria, parasitism, and carnivory. 34

35 See prokaryote lecture! Nitrogen Fixation Plants and other eukaryotes cannot use N 2 from the atmosphere. However, some xxxxxxx are able to absorb N 2 from the atmosphere and convert it to ammonia, nitrates, and nitrites in a process called nitrogen fixation. 35

36 See prokaryote lecture! Nitrogen Fixation Such bacteria often take up residence inside plant root cells. For example, members of the bacterial genus Rhizobium associate with plants in the pea family (legumes). Rhizobia (Rhizobium species and close relatives) are found in nodules on the roots of legumes and provide the plant with ammonia in return for sugar and protection 36

37 In Some Plants, Roots Form Nodules where Nitrogen-Fixing Bacteria Live Nodule in cross section See prokaryote lecture! Roots of pea plant Nodules 37

38 Nutritional Adaptations of Plants Mostplants use proton pumps as a mechanism for importing nutrients from the soil and/or acquire nutrients from symbioses. In addition, 99% of plants make their own sugars. Some plants don t follow these rules, some appear to live on: 1)xxx some 2) xxxxxxx others, some catch 3) 38

39 Epiphytic Plants Epiphytes are plants that are adapted to grow in the absence of xxxx. They often grow on leaves or branches of trees. They absorb most of the water and nutrients they need from rainwater, dust, and particles that collect in their tissues or in the crevices of bark. 39

40 Epiphytes Are Adapted to Grow in the Absence of Soil Epiphytes grow on trees (e.g., Bromeliads). Epiphytes 40

41 Parasitic Plants Most parasitic plants make their own sugars through xxxxxxxxxxxx and tap into the vascular tissue of their hosts for water and essential nutrients. Some plant parasites are nonphotosynthetic and obtain all their nutrition from the host. There are at least 3000 species of parasitic plants 41

42 Some Plant Parasites Tap into the Xylem Tissue of Their Hosts Mistletoe haustoria penetrate host xylem and extract water and ions Mistletoe Host xylem Host tree Mistletoe 42

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44 cranberries peat BOGS mummies carnivores Why are these all found in the same habitat? -Stagnant water -Low oxygen levels -Acidic -Nutrient poor xxxxxxxxxxxxx Slow 44

45 Carnivorous Plants Carnivorous plants use modified leaves to trap insects and other animals, kill them, and absorb the prey s nutrients. Carnivorous species make their own carbohydrates via photosynthesis but use carnivory to supplement the nitrogen available in the environment, which is often lacking. 45

46 Sundews Have Modified Leaves with a Sticky Surface That Catches Insects 46

47 Venus fly trap - The Private Life of Plants - David Attenborough - BBC wildlife m/watch?v=ktigvtkdgw o&nr=1&feature=fvwp 47

48 Plant Sensory Systems (Freeman Ch39) 48

49 Plant Sensory Systems, Signals, and Responses Plants process information Environmental stimuli affect ability to grow and reproduce wavelength of light, photoperiod, time of day gravity, mechanical stimulation (touch or wind) disease-causing agents and herbivores. 49

50 Information Processing Monitoraspects of environment that affect fitness (survive & reproduce) Three steps: (1) a receptor cell receives an external signal (2) the receptor cell sends a signal to cells in another part of the plant (3) responder cells receive the signal and change activity appropriately. 50

51 STEPS IN INFORMATION PROCESSING External stimulus on receptor cell Internal signal 1. Receptor cell perceives external stimulus and transduces the information to an internal signal. Cell-cell signal 2. A hormone (cell-cell signal) released by the receptor cell travels throughout the body. Internal signal 3. Receptor cells receive the hormonal (cell-cell) signal, transduce it to an internal signal, and change activity. 51

52 Signal Transduction Signals from environment received by specialized protein (for that function). Receptor proteins change shape in response to a stimulus. This causes the information to change form from an external signal to an intracellular signal. This process is called 52

53 Signal transduction in a receptor cell often results in the release of a xxxxxxx that carries information to responder cells. A few examples 53

54 When sensory cells receive a stimulus, they transduce the signal and respond by producing hormones that carry information to target cells elsewhere in the body. Hormones produce a response by acting on target cells. 54

55 SIGNAL TRANSDUCTION 1. Signal Cell wall 2. Receptor protein changes in response to signal. Cell membrane Phosphorylation cascade ATP ADP ATP ADP ATP ATP ADP 3. Receptor or associated protein catalyzes phosphorylation reaction. 4. Phosphorylated protein triggers phosphorylation cascade (left) OR release of second messenger (right). Second messenger Vacuole Shoots bend specifically toward blue light. ADP 5. Phosphorylated proteins or second messenger initiate response. Nuclear envelope OR OR DNA 6. Activate or repress transcription. 6. Activate or repress translation. Nucleus 6. Change ion flow through channel or pump. 55

56 Blue Light: The Phototropic Response Plants sense and respond to specific, narrow range of wavelengths Any directed movement by an organism toward light is called xxxxxxxxx. Plants exhibit a phototropic response only to blue wavelengths Why blue light? 56

57 Photosynthesis Chlorophyll a and b Absorb Most Strongly in the Blue (and Red) Parts of the Visible Spectrum Chlorophyll b Chlorophyll a Different pigments absorb different wavelengths of light 57

58 Auxin: Phototropic Hormone The sensory and response cells in phototropism are not the same. Blue light is sensed at the tip of a coleoptile (protected shoot) and info is then transmitted to lower cells. Auxin (a hormone) is produced at the tip of the coleoptile, is transported to the area of bending, and acts as a signal Auxin promotes cell xxxxxxxx in the shoot. 58

59 Photoperiodism & Flowering Flowering in response to changes in day length triggered by red/far-red light. Photoperiodism is any response by an organism that is based on xxxxxxxxxx, the relative lengths of day and night. In plants, the ability to measure photoperiod is important because it allows the plant to respond to seasonal changes in climate and the correlated availability of resources and pollinators. 59

60 Different Species Respond to Photoperiod in Different Ways How do plants respond to differences in day length? 60

61 Youth, Maturity, and Aging: The Growth Responses Controlling growth in response to changes in age or environmental conditions (one of the most basic aspects of information processing in plants). Hormonesplay a key role in regulating 61

62 Cytokinins & Cell Division Cytokinins are a group of plant hormones that promote cell division. Cytokinins are synthesized in root tips, young fruits, seeds, growing buds, and other developing organs. Cytokinins regulate growth by xxxxxxx the xxxxxx that keep the cell cycle going. In the absence of cytokinins, cells arrest at the G 1 checkpoint in the cell cycle and cease growth. 62

63 Cytokinins Affect the Cell Cycle Mitosis M G 2 DIVISION G 1 S INTERPHASE Cytokinins promote expression of genes that start S phase (DNA synthesis). Without cytokinins, cells remain in G 1 and do not divide 63

64 Gibberellins and ABA: Growth and Dormancy Two types of hormones are responsible for initiating and terminating growth in plants in response to changes in environmental conditions: gibberellins xxxxxxx growth, abscissic acid (ABA) xxxxxx growth. 64

65 Gibberellins Stimulate Shoot Elongation Gibberellic acid (GA) is a gibberellin that appears to promote cell elongation and to increase rates of cell division in roots. 65

66 Gibberellins and ABA Interact during xxxxxxxxxxxx and Germination Many plants produce seeds that have to undergo a period of drying or a period of cold, wet conditions before they are able to germinate in response to warm, wet conditions. In many plants, ABA is the signal that inhibits seed germination, and gibberellins are the signal that triggers embryonic development. 66

67 Video 34.3 Germination of soybean plants 67

68 During seed germination, gibberellins activate production of a-amylase, a digestive enzyme that breaks the bonds between sugar units of starch. This releases sugars to the growing embryo. 68

69 ABA Closes Guard Cells in Stomata In most plants, stomata open in response to blue light, allowing gas exchange during photosynthesis. When stomata are open, water can be lost; if the roots cannot replace water lost at the leaves, then the stomata close. ABA from xxxxxxxx is transported to leaves, resulting in the xxxxxxx of stomata. Therefore, this signal overrides that from the blue-light receptors. 69

70 xxxxxx and Senescence Senescence= regulated aging process. The gaseous hormone ethylene is strongly associated with three aspects of senescence in plants: 1) x 2) flower fading 3) abscission. 70

71 The abscission zone is a region of the leaf petiole that becomes more sensitive to ethylene as auxin levels drop. As a result, it degrades first and the leaf breaks off at this point. 71

72 Leaves Drop in Response to Signals from Auxin and Ethylene LEAF SENESCENCE AND ABSCISSION Healthy leaf Age, drought, temperature, day length, etc. reduce auxin production from leaf Senescent leaf Abscised leaf A protective layer has formed to seal stem where leaf was attached Abscission zone 1. High auxin: Cells in abscission zone are insensitive to ethylene. Leaf functions normally. 2. Low auxin: Cells in abscission zone become more sensitive to ethylene, leading to leaf senescence. 3. Leaf detaches at the abscission zone. 72

73 Overview Plant Growth Regulators (1) A single hormone often affects many different target tissues. This means there can be an array of responses to the same intercellular signal. (2) In most cases, several hormones affect the same response. Hormones do not work independently they xxxxxxx with each other. 73

74 Gravity: The Gravitropic Response xxxxxxxx is the ability of plants to move in response to gravity. Roots grow down and shoots grow up or out. 74

75 Auxin as the Gravitropic Signal Root cap cells that sense changes in the direction of gravitational pull respond by changing the distribution of auxin in the root tip. 75

76 AUXIN AS THE GRAVITROPIC SIGNAL Auxin distribution Gravity 1. Normal distribution of auxin in vertical root prior to disturbance. The Auxin Auxin 2. Root tip moved into horizontal position. 3. Gravity-sensing cells actively redistribute the auxin more goes to bottom side. Redistribution Hypothesis for Gravitropism 4. Asymmetric auxin distribution inhibits cell growth on lower side and stimulates growth on upper side, leading to bending. 76

77 Auxin's Overall Role Auxin: controls growth via phototropism, gravitropism, and apical dominance. Auxin has other important effects as well: Fruit development is influenced by auxin produced by seeds within the fruit. Falling auxin concentrations are involved in xxxxxxxx (the shedding of leaves and fruits) associated with xxxxxxxxx (aging). 77

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79 How Do Plants Sense and Respond to Pathogens? If a pathogen invades a plant, the plant mounts a defense called the hypersensitive response (HR). HR causes the rapid and localized death of cells surrounding the site of infection, xxxxxx the pathogen. Other Responses too 79

80 Video 39.1 Lepidopteran larvae feeding on leaves 80

81 Herbivory xxxxxxxxxxxxxxxxxxx = toxins (Primary metabolites involved in homeostasis and typical cellular function) Tobacco makes nicotine Harmful to many herbivores 81

82 Secondary Metabolites Hormones/Pheromones Mimic juvenile hormone; stop molt to adult Attract your herbivore s insect prey! Warnother plants to mobilize their defensive cascades Poisons Disrupt nervous system of herbivore nicotine Disrupt digestive system of herbivore proteinase inhibitors 82

83 How Do Plants Sense and Respond to Herbivore Attack? Many plant seeds and storage organs contain proteinase xxxxxxxx, proteins that block the enzymes found in the mouths and stomachs of animals that digest proteins. When a herbivore ingests a large dose of a proteinase inhibitor, it gets sick. As a result, herbivores learn to detect and avoid plant tissues containing high concentrations of these proteins. 83

84 Pheromones Released from Plant Wounds Recruit Help from Wasps A xxxxxxxx is an organism that is free living as an adult but parasitic as a larva. Because parasitoids (for example, a wasp egg laid in a caterpillar's body) kill their host, parasitoid attacks limit the amount of damage that herbivores do to plants. Pheromones are chemical messengers synthesized by an individual and released into the environment that elicit a response from a different individual. Plants produce wasp attractant pheromones in 84 response to attack by caterpillars.

85 Parasitoid wasp 85

86 Attract the herbivore s xxxx! 86

87 Secondary Metabolites 87

88 grapes/wine Tannins oak leaves 88

89 Milkweeds Secrete a poisonous latex 89

90 Swallowtail butterflies incorporate milkweed toxins into their own tissues for defense (via bird learning) 90

91 Milkweeds Some herbivores learn to disable the defense (cut the latex supply lines, then eat the leaf!) Secrete a poisonous latex Another example of an 91

92 Cyanide (CN) Cyanide is a very rapidly acting toxin (used by communes for suicide!). In plants, CN is combined with sugar as a cyanogenic glycoside. Precursors, stored in vacuoles, get together in cytosol if plant is damaged by wilting, crushing, or chewing. More than 1000 plant species have cyanide in some form. 92

93 Aspirin! Salicylic Acid common in plants Well-studied in Willows (Salix) Used to combat many pathogens (e.g., viruses) Methyl salicylate, a related compound aka oil of wintergreen Volatilizes to signal other plants (~pheromone) to defend selves 93