Embed Size (px)
Citation preview
Ch. 2 Photosynthesis (Ps) and Light
CAM and Epiphytes• Epiphytes:
– Abundant tropical rain forests
CAM and Epiphytes• Spanish moss (Tillandsia
usneoides)• CAM plant:
Comparing C3, C4, CAM plants• Exs: many Orchidaceae
(esp. epiphytes)
Comparing C3, C4, CAM plants• CAM:
– Succulents (deserts)– Epiphytes (tropical/subtropical areas)
Comparing C3, C4, CAM plants• Trait C3 C4 CAM
• Max. Ps rate
Fig. 2.12
Comparing C3, C4, CAM plants• Trait C3 C4 CAM
• Max. growth rate• (optimal conditions)
Comparing C3, C4, CAM plants• Trait C3 C4 CAM
• Optimum Ps temp.• .
Fig. 2.11
Comparing C3, C4, CAM plants• Trait C3 C4 CAM
• Water use efficiency
(g CO2 gain per
Kg H2O lost)
Applied Aspects• What crops best hot areas?
sorghum
millet
Applied Aspect• Genetic engineering:
Applied Aspect• Ex: rice (C3 grass)
• Asia: 70% calories rice– 70% world’s poor Asian
• Put in– Yields up 10-30%
C3 variation (between species)• C3 plants
• Heliophytes:• Sciophytes:
Sciophyte: Who am I?Variation among C3 plants
C3 variation (within individual)• Sun vs. shade leaves• Sun leaves:
Quercus pagoda (cherrybark oak)
European beech
Sun Shade
Carbon isotope ratios• Isotope:• Ex: Carbon-12 (98.9% C)• Carbon-13• Carbon-14
Light vs. heavyCarbon dioxide
Enzyme affinity?
Carbon isotope ratios• Enzyme affinity
– If low, light CO2 used more (more discrimination)– If high, less discrimination
Carbon isotope ratios• Enzyme affinity
– If low, light CO2 used more (more discrimination)– If high, less discrimination
• Measure ratio? Delta C-13– Units:– More negative delta C-13 =
Carbon isotope ratios• Enzyme affinity CO2
– Rubisco: less– PEP carboxylase: more
• C3 delta C-13; -24 to -34 ppt• C4 delta C-13; -10 to -20 ppt
More negative = more discrimination
C4
SO WHAT??Commercial sugar (sucrose):• Sugar cane• Sugar beet
AHAH!ID sugar source delta C-13 ratio!
• C3: -24 to -34 ppt• C4: -10 to -20 ppt
Bernie Beet hands out sacksof white powder to kids.....
Bernie BeetFood webs….
Herbivore Feeding PreferencesEx., rhinos AfricaBlack rhino: more rare (3,600). Browses
Herbivore Feeding PreferencesWhite rhino: less rare (11,700). Grazes
Herbivore Feeding PreferencesRhino poaching: ID horn using delta C-13 ratio
Ch. 3 Water Relations & Energy Dynamics
Water relations• Plants need light (energy: Ch. 2)
• Plants need CO2 (carbon: Ch. 2)
• Plants need water (Ch. 3)
Water potential
Water potential• Water potential:
• “Tendency water to move”– Moves
• Symbol--Greek letter: psi
4 factors that influence water potential
Water Potential• Affected by:
– solutes: solute potential– symbolized– high solutes =
s
Water Potential• Affected by:
– pressure: pressure potential – symbolized – high pressure =
p
Water Potential• Affected by:
– charged surfaces (cell walls, clay particles): matric potential
– symbolized – More surfaces =
m
The Matrix potential
Water Potential• Affected by:
– gravity: gravitational potential– symbolized – Height increases, tendency move
g
Water Potential• Total water potential = sum all factors:
g= + + +total mps
Units?
Water Potential• Measurement relative: compared to
• = 0 megaPascals (MPa)
• megaPascal:
– 1 MPa = about 10 bars or 10 atmospheres
total
Water Potential• Water in plants/soil has solutes: so
What tissue in plant carries water?
Water transport• Xylem:
• What % water from soil remains in plant?
Water transport• Xylem: water
conducting tissue• How much water in
plant? <5%!
How water move?
?
Water transport• Transpiration:
• Moves by pull (under tension)
• Psi high soil & low air.
Water transport• Ex: • Soil:• Root xylem: • Stem xylem:
• Leaf xylem: • Air: -10 to -100 MPa
Water potential tour.....• Soil to air pathway
Fig. 3.2a
Soil water
• What determines psi soil?
g= + + +total mps
Soil water
• What determines psi soil?• gravitational potential:
• pressure potential:
g= + + +total mps
Soil water
• solute potential:
g= + + +total mps
Dauphin Island: salt marsh
Soil water
• matric potential:
g= + + +total mps
