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We will study effects of stresses on plants and see where it leads us
Course Plan We will study effects of stresses on plants and see where it leads us Phytoremediation Plant products Biofuels Effects of seed spacing on seed germination Effects of nutrient deprivation Effects of stresses Climate/CO2 change Non-coding RNAs Biotechnology Plant movements: flytraps, mimosa, soybeans Carnivorous plants Stress responses/stress avoidance Plant signaling (including neurobiology) Flowering? Hormones? Plant pathology? Plant tropisms and nastic movements Root growth responses Metal toxicity? Circadian rhythms? Effects of magnetic fields? Effects of different colors of light on plant growth?
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We will study effects of stresses on plants and see where it leads us
Learn about plant stress
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We will study effects of stresses on plants and see where it leads us
Learn about plant stress Pick some stresses to study
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We will study effects of stresses on plants and see where it leads us
Learn about plant stress Pick some stresses to study Decide which plants to study and how to assay the stress effects Radishes Onions Cucumbers Jalapenos Indian mustard Any more? Soybean or other beans Corn, sorghum to compare C4 vs C3 Wheat, barley, oats vs corn to compare C3 vs C4 grasses
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We will study effects of stresses on plants and see where it leads us
Learn about plant stress Pick some stresses to study Decide which plants to study and how to assay the stress effects What to measure? Biomass Total Height Leaf area Root/shoot
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We will study effects of stresses on plants and see where it leads us
Learn about plant stress Pick some stresses to study Decide which plants to study and how to assay the stress effects What to measure? Biomass Yield
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We will study effects of stresses on plants and see where it leads us
Learn about plant stress Pick some stresses to study Decide which plants to study and how to assay the stress effects What to measure? Biomass Yield Proteins, pigments
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We will study effects of stresses on plants and see where it leads us
Learn about plant stress Pick some stresses to study Decide which plants to study and how to assay the stress effects What to measure? Biomass Yield Proteins, pigments Secondary products
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We will study effects of stresses on plants and see where it leads us
Learn about plant stress Pick some stresses to study Decide which plants to study and how to assay the stress effects What to measure? Biomass Yield Proteins, pigments Secondary products Responses to stimuli Solar tracking Leaf closing Tropisms
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We will study effects of stresses on plants and see where it leads us
Learn about plant stress Pick some stresses to study Decide which plants to study and how to assay the stress effects What to measure? Biomass Yield Proteins, pigments Secondary products Responses to stimuli Solar tracking Leaf closing Tropisms Flowering
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Plant Stress Won Senator Proxmire’s “Golden Fleece” award for wasteful government spending: anything that affects plant health Water?
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Plant Stress Won Senator Proxmire’s “Golden Fleece” award for wasteful government spending: anything that affects plant health Water? Nutrients?
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Plant Stress Won Senator Proxmire’s “Golden Fleece” award for wasteful government spending: anything that affects plant health Water? Nutrients? Environment? Temp?
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Plant Stress Won Senator Proxmire’s “Golden Fleece” award for wasteful government spending Water? Nutrients? Environment? Temp? pCO2?
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Plant Stress Won Senator Proxmire’s “Golden Fleece” award for wasteful government spending Water? Nutrients? Environment? Temp? pCO2? Pollution? Ozone, other gases?
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Plant Stress Won Senator Proxmire’s “Golden Fleece” award for wasteful government spending Water? Nutrients? Environment? Temp? pCO2? Pollution? Ozone, other gases? Herbicides, eg Round-Up, Atrazine?
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Plant Stress Won Senator Proxmire’s “Golden Fleece” award for wasteful government spending Water? Nutrients? Environment? Temp? pCO2? Pollution? Ozone, other gases? Herbicides, eg Round-Up, Atrazine? Light?
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Plant Stress Won Senator Proxmire’s “Golden Fleece” award for wasteful government spending Water? Nutrients? Environment? Temp? pCO2? Pollution? Ozone, other gases? Herbicides, eg Round-Up, Atrazine? Light? Insects and other herbivores?
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Plant Stress Won Senator Proxmire’s “Golden Fleece” award for wasteful government spending Water? Nutrients? Environment? Temp? Pollution? Insects and other herbivores? Pathogens = bacteria, viruses, fungi
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WATER Plants' most important chemical most often limits productivity
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WATER Constantly lose water due to PS SPAC= Soil Plant Air Continuum moves from soil->plant->air Due to its special properties
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Water movement Diffusion: movement of single molecules down [] due to random motion until [ ] is even Bulk Flow: movement of groups of molecules down a pressure gradient Independent of ∆ [ ] ! How water moves through xylem How water moves through soil and apoplast
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Water potential Water moves to lower its potential Depends on: [H2O]: Ys (osmotic potential) Pressure Yp Gravity Yg Yw = Ys +Yp + Yg
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Water transport Path starts at root hairs Must take water from soil
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Water transport Path starts at root hairs Must take water from soil Ease depends on availability & how tightly it is bound Binding depends on particle size & chem
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Water transport Availability depends on amount in soil pores Saturation: completely full Field capacity: amount left after gravity has drained excess Permanent wilting point: amount where soil water potential is too negative for plants to take it up
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Water movement in plants
Water enters via root hairs mainly through apoplast until hits Casparian strip : hydrophobic barrier in cell walls of endodermis
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Water movement in plants
Water enters via root hairs mainly through apoplast until hits Casparian strip : hydrophobic barrier in cell walls of endodermis Must enter endodermal cell
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Water Transport Water enters via root hairs mainly through apoplast until hits Casparian strip : hydrophobic barrier in cell walls of endodermis Must enter endodermal cell Why flooded plants wilt!
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Water Transport Water enters via root hairs mainly through apoplast until hits Casparian strip : hydrophobic barrier in cell walls of endodermis Must enter endodermal cell Why flooded plants wilt! Controls solutes
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Water Transport Must enter endodermal cell Controls solutes Passes water & nutrients to xylem
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Water Transport Passes water & nutrients to xylem Ys of xylem makes root pressure
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Water Transport Passes water & nutrients to xylem Ys of xylem makes root pressure Causes guttation: pumping water into shoot
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Water Transport Passes water & nutrients to xylem Ys of xylem makes root pressure Causes guttation: pumping water into shoot Most water enters near root tips
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Water Transport Most water enters near root tips Xylem is dead! Pipes for moving water from root to shoot
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Water Transport Most water enters near root tips Xylem is dead! Pipes for moving water from root to shoot Most movement is bulk flow
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Water Transport Xylem is dead! Pipes for moving water from root to shoot Most movement is bulk flow adhesion to cell wall helps
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Water Transport Xylem is dead! Pipes for moving water from root to shoot Most movement is bulk flow adhesion to cell wall helps Especially if column is broken by cavitation (forms embolisms)
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Water Transport Most movement is bulk flow adhesion to cell wall helps Especially if column broken by cavitation In leaf water passes to mesophyll
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Water Transport Most movement is bulk flow adhesion to cell wall helps Especially if column broken by cavitation In leaf water passes to mesophyll, then to air via stomates
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Water Transport In leaf water passes to mesophyll, then to air via stomates Driving force = vapor pressure deficit (VPD) air dryness
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Water Transport In leaf water passes to mesophyll, then to air via stomates Driving force = vapor pressure deficit (VPD) air dryness ∆ H2O vapor pressure [H2O(g)] & saturated H2O vapor pressure
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Water Transport In leaf water passes to mesophyll, then to air via stomates Driving force = vapor pressure deficit (VPD) air dryness ∆ H2O vapor pressure [H2O(g)] & saturated H2O vapor pressure saturated H2O vapor pressure varies with T, so RH depends on T
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Water Transport In leaf water passes to mesophyll, then to air via stomates Driving force = vapor pressure deficit (VPD) air dryness ∆ H2O vapor pressure [H2O(g)] & saturated H2O vapor pressure saturated H2O vapor pressure varies with T, so RH depends on T VPD is independent of T: says how fast plants lose H2O at any T
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Water Transport In leaf water passes to mesophyll, then to air via stomates Driving force = vapor pressure deficit (VPD) air dryness Rate depends on pathway resistances
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Water Transport Rate depends on pathway resistances stomatal resistance
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Water Transport Rate depends on pathway resistances stomatal resistance Controlled by opening/closing
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Water Transport Rate depends on pathway resistances stomatal resistance boundary layer resistance Influenced by leaf shape & wind
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Consequences of water stress
Reduced productivity
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Consequences of water stress
Reduced productivity Photosynthesis Cell expansion Wall synthesis
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Responses to Water Stress
roots make Abscisic Acid: transported to leaves and closes stomates
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Responses to Water Stress
roots make Abscisic Acid: transported to leaves and closes stomates Slows photosynthesis and results in formation of Reactive Oxygen Species (ROS)
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Responses to Water Stress
roots make Abscisic Acid: transported to leaves and closes stomates Slows photosynthesis and results in formation of Reactive Oxygen Species (ROS) Plants adjust metabolism and turn on many genes
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Long term responses Hydrotropism genes guide root growth towards water
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Flooding Short term effect is decreased root respiration due to anoxia Inhibits transport from roots, flooded plants may wilt!
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Flooding Short term effect is decreased root respiration due to anoxia Inhibits transport from roots, flooded plants may wilt! Longer term also makes them more susceptible to many diseases
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Flooding Responses Turn on fermentation and alter metabolism Plants adapted to flooding may form aerenchyma
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Flooding Responses Turn on fermentation and alter metabolism Plants adapted to flooding may form aerenchyma Plants adapted to submergence may grow to surface
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