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?

We will study effects of stresses on plants and see where it leads us Learn about plant stress

We will study effects of stresses on plants and see where it leads us Learn about plant stress Pick some stresses to study

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

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

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

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

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

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

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

Plant Stress Won Senator Proxmire’s “Golden Fleece” award for wasteful government spending: anything that affects plant health Water?

Plant Stress Won Senator Proxmire’s “Golden Fleece” award for wasteful government spending: anything that affects plant health Water? Nutrients?

Plant Stress Won Senator Proxmire’s “Golden Fleece” award for wasteful government spending: anything that affects plant health Water? Nutrients? Environment? Temp?

Plant Stress Won Senator Proxmire’s “Golden Fleece” award for wasteful government spending Water? Nutrients? Environment? Temp? pCO2?

Plant Stress Won Senator Proxmire’s “Golden Fleece” award for wasteful government spending Water? Nutrients? Environment? Temp? pCO2? Pollution? Ozone, other gases?

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?

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?

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?

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

WATER Plants' most important chemical most often limits productivity

WATER Constantly lose water due to PS SPAC= Soil Plant Air Continuum moves from soil->plant->air Due to its special properties

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

Water potential Water moves to lower its potential Depends on: [H2O]: Ys (osmotic potential) Pressure Yp Gravity Yg Yw = Ys +Yp + Yg

Water transport Path starts at root hairs Must take water from soil

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

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

Water movement in plants Water enters via root hairs mainly through apoplast until hits Casparian strip : hydrophobic barrier in cell walls of endodermis

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

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!

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

Water Transport Must enter endodermal cell Controls solutes Passes water & nutrients to xylem

Water Transport Passes water & nutrients to xylem Ys of xylem makes root pressure

Water Transport Passes water & nutrients to xylem Ys of xylem makes root pressure Causes guttation: pumping water into shoot

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

Water Transport Most water enters near root tips Xylem is dead! Pipes for moving water from root to shoot

Water Transport Most water enters near root tips Xylem is dead! Pipes for moving water from root to shoot Most movement is bulk flow

Water Transport Xylem is dead! Pipes for moving water from root to shoot Most movement is bulk flow adhesion to cell wall helps

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)

Water Transport Most movement is bulk flow adhesion to cell wall helps Especially if column broken by cavitation In leaf water passes to mesophyll

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

Water Transport In leaf water passes to mesophyll, then to air via stomates Driving force = vapor pressure deficit (VPD) air dryness

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

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

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

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

Water Transport Rate depends on pathway resistances stomatal resistance

Water Transport Rate depends on pathway resistances stomatal resistance Controlled by opening/closing

Water Transport Rate depends on pathway resistances stomatal resistance boundary layer resistance Influenced by leaf shape & wind

Consequences of water stress Reduced productivity

Consequences of water stress Reduced productivity Photosynthesis Cell expansion Wall synthesis

Responses to Water Stress roots make Abscisic Acid: transported to leaves and closes stomates

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)

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

Long term responses Hydrotropism genes guide root growth towards water

Flooding Short term effect is decreased root respiration due to anoxia Inhibits transport from roots, flooded plants may wilt!

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

Flooding Responses Turn on fermentation and alter metabolism Plants adapted to flooding may form aerenchyma

Flooding Responses Turn on fermentation and alter metabolism Plants adapted to flooding may form aerenchyma Plants adapted to submergence may grow to surface