Suggestions 1. Arabidopsis2. Fast plant 3. Sorghum4. Brachypodium distachyon 5. Amaranthus (C4 dicot)6. Quinoa 7. Kalanchoe8. Venus fly traps 9. C3 vs C4 Atriplex10. C3 vs C4 Flaveria 11. C3 vs C4 Panicum12. 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 2.5 points each 5 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 H 2 O/CO 2 )

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.[H 2 O]:  s (osmotic potential) 2.Pressure  p 3.Gravity  g  w =  s +  p +  g

Water potential  w =  s +  p +  g  p (pressure potential) can be positive or negative Usually positive in cells to counteract  s Helps plants stay same size despite daily fluctuations in  w  p in xylem is negative, draws water upwards  g can usually be ignored, but important for tall trees

Water potential Measuring water potential  s (osmotic potential) is “easy” Measure concentration of solution in equilibrium with cells

Water potential Measuring water potential  s (osmotic potential) is “easy” Measure concentration of solution in equilibrium with cells  g (gravity potential) is easy: height above ground Mpa/m

Water potential Measuring water potential  s (osmotic potential) is “easy” Measure concentration of solution in equilibrium with cells  g (gravity potential) is easy: height above ground  P (pressure potential) is hard! Pressure bomb = most common technique

Water potential Measuring water potential  s (osmotic potential) is “easy” Measure concentration of solution in equilibrium with cells  g (gravity potential) is easy: height above ground  P (pressure potential) is hard! Pressure bomb = most common technique Others include pressure transducers, xylem probes

Measuring water potential  P (pressure potential) is hard! Pressure bomb = most common technique Others include pressure transducers, xylem probes Therefore disagree about H 2 O transport in xylem

Water transport Therefore disagree about H 2 O transport in xylem Driving force = evaporation in leaves (evapotranspiration) Continuous H 2 O column from leaf to root draws up replacement H 2 O from soil (SPAC)

Water transport Driving force = evaporation in leaves (evapotranspiration) Continuous H 2 O column from leaf to root draws up replacement H 2 O Exact mech controversial

Water transport Driving force = evaporation in leaves (evapotranspiration) Continuous H 2 O column from leaf to root draws up replacement H 2 O 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  s of xylem makes root pressure

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

Water Transport Passes water & nutrients to xylem  s 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 ∆ H 2 O vapor pressure [H 2 O (g) ] & saturated H 2 O vapor pressure

Water Transport In leaf water passes to mesophyll, then to air via stomates Driving force = vapor pressure deficit (VPD) air dryness ∆ H 2 O vapor pressure [H 2 O (g) ] & saturated H 2 O vapor pressure saturated H 2 O 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 ∆ H 2 O vapor pressure [H 2 O (g) ] & saturated H 2 O vapor pressure saturated H 2 O vapor pressure varies with T, so RH depends on T VPD is independent of T: says how fast plants lose H 2 O 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:

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 )

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 ) 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 ) FKF1/GI controlled by circadian clock PHYA & CRY also stabilize 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 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!

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