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Suggestions 1. Arabidopsis 2. Fast plant 3. Sorghum 4. Brachypodium distachyon 5. Amaranthus (C4 dicot)6. Quinoa 7. Kalanchoe 8. Venus fly traps 9. C3 vs C4 Atriplex 10. C3 vs C4 Flaveria 11. C3 vs C4 Panicum 12. M. crystallinum C3-CAM 13. P. afra C3-CAM 14 . P. oleracea C4-CAM Options 1. Pick several plants • C3, C4, CAM • Long Day, Short day, Day Neutral • Tropical, temperate, arctic • ????? Options 1. Pick several plants • C3, C4, CAM • Long Day, short day, Day neutral • Tropical, temperate, arctic • ????? 2. Pick one plant • Study many conditions • Study many variants/mutants • ????? Grading? Combination of papers, presentations & lab reports • 4 lab reports @ 2.5 points each • 5 assignments @ 2 points each • Presentation on global change and plants: 5 points • Research proposal: 10 points • Final presentation: 15 points • Poster: 10 points • Draft report 10 points • Final report: 30 points Assignment 1 1.Pick a plant that might be worth studying •Try to convince the group in 5-10 minutes why yours is best: i.e., what is known/what isn’t known WATER • Plants' most important chemical • most often limits productivity •Gives cells shape • Dissolves many chem: most biochem occurs in water •Constantly lose water due to PS (1000 H2O/CO2) Plant Water Uptake Water is drawn through plants along the SPAC, relying on adhesion & cohesion (&surface tension) to draw water from the soil into the air Drawn through plant by cohesion & adhesion Surface tension & adhesion in mesophyll creates force that draws water through the plant! Water potential Water moves to lower its potential Depends on: 1. [H2O]: Ys (osmotic potential) 2. Pressure Yp 3. Gravity Yg Yw = Ys +Yp + Yg Water potential Yw = Ys +Yp + Yg Yp (pressure potential) can be positive or negative • Usually positive in cells to counteract Ys • Helps plants stay same size despite daily fluctuations in Yw • Yp in xylem is negative, draws water upwards Yg can usually be ignored, but important for tall trees Water potential Measuring water potential Ys (osmotic potential) is “easy” • Measure concentration of solution in equilibrium with cells Water potential Measuring water potential Ys (osmotic potential) is “easy” • Measure concentration of solution in equilibrium with cells Yg (gravity potential) is easy: height above ground • -0.01 Mpa/m Water potential Measuring water potential Ys (osmotic potential) is “easy” • Measure concentration of solution in equilibrium with cells Yg (gravity potential) is easy: height above ground YP (pressure potential) is hard! • Pressure bomb = most common technique Water potential Measuring water potential Ys (osmotic potential) is “easy” • Measure concentration of solution in equilibrium with cells Yg (gravity potential) is easy: height above ground YP (pressure potential) is hard! • Pressure bomb = most common technique Others include pressure transducers, xylem probes Measuring water potential YP (pressure potential) is hard! • Pressure bomb = most common technique Others include pressure transducers, xylem probes Therefore disagree about H2O transport in xylem Water transport Therefore disagree about H2O transport in xylem • Driving force = evaporation in leaves (evapotranspiration) • Continuous H2O column from leaf to root draws up replacement H2O from soil (SPAC) Water transport Driving force = evaporation in leaves (evapotranspiration) • Continuous H2O column from leaf to root draws up replacement H2O • Exact mech controversial Water transport Driving force = evaporation in leaves (evapotranspiration) • Continuous H2O column from leaf to root draws up replacement H2O • Exact mech controversial Path starts at root hairs Water transport Path starts at root hairs • Must take water from soil Measuring water potential Path starts at root hairs • Must take water from soil • Ease depends on availability & how tightly it is bound Measuring water potential 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 Measuring water potential Must take water from soil • Ease depends on availability & how tightly it is bound • Binding depends on particle size & chem • Availability depends on amount in soil pores Measuring water potential Availability depends on amount in soil pores • Saturation: completely full Measuring water potential Availability depends on amount in soil pores • Saturation: completely full • Field capacity: amount left after gravity has drained excess Measuring water potential 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 Florigenic and antiflorigenic signaling pathways in Arabidopsis. Matsoukas I G et al. Plant Cell Physiol 2012;53:1827-1842 Transition to Flowering Adults are competent to flower, but need correct signals Very complex process! Can be affected by: • Daylength • Temperature (especially cold!) • Water stress • Nutrition • Hormones • Age Transition to Flowering Can be affected by daylength (photoperiodic pathway) • Mainly through CO protein stability Transition to Flowering Can be affected by daylength (photoperiodic pathway) • Mainly through CO protein stability • FKF1/GI bind CO & remove FT & CO inhibitor CDF in afternoon (controlled by clock & enhanced by blue l) Transition to Flowering Can be affected by daylength (photoperiodic pathway) • Mainly through CO protein stability • FKF1/GI bind CO & remove FT & CO inhibitor CDF in afternoon (controlled by clock & enhanced by blue l) • FKF1/GI controlled by circadian clock Transition to Flowering Can be affected by daylength • Mainly through CO protein stability • FKF1/GI bind CO & remove FT & CO inhibitor CDF in afternoon (controlled by clock & enhanced by blue l) • FKF1/GI controlled by circadian clock • PHYA & CRY also stabilize CO @ end of day Transition to Flowering Can be affected by daylength Can be affected by T • FLC blocks flowering in fall; after 20 days near 0˚C plants make COLDAIR ncRNA FLC blocks flowering in fall; after 20 days near 0˚C plants make COLDAIR ncRNA: Targets Polycomb Repressor Complex 2 to FLC locus & makes H3K27me3 -> silences gene Transition to Flowering Can be affected by daylength Can be affected by T • FLC blocks flowering in fall; after 20 days near 0˚C plants make COLDAIR ncRNA ->PRC2 silences FLC • Can then flower next spring Transition to Flowering Can be affected by daylength Can be affected by T • FLC blocks flowering in fall; after 20 days near 0˚C plants make COLDAIR ncRNA ->PRC2 silences FLC • Can then flower next spring • PIF4 activates flowering @ high T by inducing FT mRNA (ind of daylength) Transition to Flowering Can be affected by daylength Can be affected by T Can be affected by gibberellins (GA) Gibberellins Discovered by studying "foolish seedling" disease in rice • Kurosawa (1926): fungal filtrate causes these effects • Yabuta (1935): purified gibberellins from filtrates of Gibberella fujikuroi cultures • Discovered in plants in 1950s Gibberellins Discovered in plants in 1950s • "rescued" some dwarf corn & pea mutants • Made rosette plants bolt Gibberellins Discovered in plants in 1950s • "rescued" some dwarf corn & pea mutants • Made rosette plants bolt • Trigger adulthood in ivy & conifers • • • • • Gibberellins "rescued" some dwarf corn & pea mutants Made rosette plants bolt Trigger adulthood in ivy & conifers Induce growth of seedless fruit Promote seed germination Gibberellins • "rescued" some dwarf corn & pea mutants • Made rosette plants bolt • Trigger adulthood in ivy & conifers • Promote seed germination • >136 gibberellins (based on structure)! Gibberellins >136 gibberellins (based on structure)! • Most plants have >10 • Activity varies dramatically! Gibberellins >136 gibberellins (based on structure)! • Most plants have >10 • Activity varies dramatically! • Most are precursors or degradation products • GAs 1, 3 & 4 are most bioactive Gibberellin signaling Used mutants to learn about GA signaling •Many are involved in GA synthesis •Varies during development •Others hit GA signaling •Gid = GA insensitive • encode GA receptors •Sly = E3 receptors •DELLA (eg rga) = repressors of GA signaling Gibberellins GAs 1, 3 & 4 are most bioactive Act by triggering degradation of DELLA repressors Gibberellins GAs 1, 3 & 4 are most bioactive Made at many locations in plant Act by triggering degradation of DELLA repressors w/o GA DELLA binds & blocks activator (GRAS) Gibberellins Act by triggering degradation of DELLA repressors w/o GA DELLA binds & blocks activator bioactive GA binds GID1; GA-GID1 binds DELLA & marks for destruction Gibberellins Act by triggering degradation of DELLA repressors w/o GA DELLA binds & blocks activator bioactive GA binds GID1; GA-GID1 binds DELLA & marks for destruction GA early genes are transcribed, start GA responses Transition to Flowering Can be affected by gibberellins (GA) DELLA bind microRNA156 (miR156)-targeted SPL transcription factors, which promote flowering by activating miR172 and MADS box genes Transition to Flowering Can be affected by gibberellins (GA) DELLA bind microRNA156 (miR156)-targeted SPL transcription factors, which promote flowering by activating miR172 and MADS box genes GA triggers DELLA deg releasing SPL Transition to Flowering Can be affected by age (autonomous pathway) In young plants, SPL synthesis is blocked by high levels of miRNA156 : delays juvenile -> adult (OE delays it more) Transition to Flowering Can be affected by age (autonomous pathway) In young plants, SPL synthesis is blocked by high levels of miR156 : delays juvenile -> adult miR156 levels decay with age independently of other cues ->let SPL act Transition to Flowering Can be affected by age (autonomous pathway) In young plants, SPL synthesis is blocked by high levels of miR156 : delays juvenile -> adult miR156 levels decay with age independently of other cues ->let SPL act Tomato terminating flower mutants (tmf) flower early : TMF coordinates transition to flowering Transition to Flowering Can be affected by nutrition Pi deprivation induces miR399 Travels in phloem to repress PHO2, a neg regulator of Pi uptake Transition to Flowering Can be affected by nutrition Pi deprivation induces miR399 Travels in phloem to repress PHO2, a neg regulator of Pi uptake miR399 enhances TSF expression Transition to Flowering Can be affected by nutrition Pi deprivation induces miR399 Travels in phloem to repress PHO2, a neg regulator of Pi uptake miR399 enhances TSF expression Sucrose enhances miR399 expression (also many other genes) Transition to Flowering Can be affected by nutrition Pi deprivation induces miR399 Travels in phloem to repress PHO2, a neg regulator of Pi uptake miR399 enhances TSF expression Sucrose enhances miR399 expression (also many other genes) miR399 is Temp S! http://www3.syngenta.com/global/e-licensing/en/elicensing/Catalog/Pages/Chemicallyinducedsucrosemetabolismtocontrolplantflowering.aspx