Ch. 2 Photosynthesis (Ps) and Light

CAM and Epiphytes Epiphytes: –Abundant tropical rain forests

CAM and Epiphytes Spanish moss (Tillandsia usneoides) CAM plant:

Comparing C 3, C 4, CAM plants Exs: many Orchidaceae (esp. epiphytes)

Comparing C 3, C 4, CAM plants CAM: –Succulents (deserts) –Epiphytes (tropical/subtropical areas)

Comparing C 3, C 4, CAM plants TraitC 3 C 4 CAM Max. Ps rate Fig. 2.12

Comparing C 3, C 4, CAM plants TraitC 3 C 4 CAM Max. growth rate (optimal conditions)

Comparing C 3, C 4, CAM plants TraitC 3 C 4 CAM Optimum Ps temp.. Fig. 2.11

Comparing C 3, C 4, CAM plants TraitC 3 C 4 CAM Water use efficiency (g CO 2 gain per Kg H 2 O lost)

Applied Aspects What crops best hot areas? sorghum millet

Applied Aspect Genetic engineering:

Applied Aspect Ex: rice (C 3 grass) Asia: 70% calories rice –70% world’s poor Asian Put in –Yields up 10-30%

C 3 variation (between species) C 3 plants Heliophytes: Sciophytes: Sciophyte: Who am I? Variation among C 3 plants

C 3 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. heavy Carbon dioxide Enzyme affinity?

Carbon isotope ratios Enzyme affinity –If low, light CO 2 used more (more discrimination) –If high, less discrimination

Carbon isotope ratios Enzyme affinity –If low, light CO 2 used more (more discrimination) –If high, less discrimination Measure ratio? Delta C-13 –Units: –More negative delta C-13 =

Carbon isotope ratios Enzyme affinity CO 2 –Rubisco: less –PEP carboxylase: more C 3 delta C-13; -24 to -34 ppt C 4 delta C-13; -10 to -20 ppt More negative = more discrimination C4C4

SO WHAT?? Commercial sugar (sucrose): Sugar cane Sugar beet

AHAH! ID sugar source delta C-13 ratio! C 3 : -24 to -34 ppt C 4 : -10 to -20 ppt Bernie Beet hands out sacks of white powder to kids..... Bernie Beet Food webs….

Herbivore Feeding Preferences Ex., rhinos Africa Black rhino: more rare (3,600). Browses

Herbivore Feeding Preferences White rhino: less rare (11,700). Grazes

Herbivore Feeding Preferences Rhino poaching: ID horn using delta C-13 ratio

Ch. 3 Water Relations & Energy Dynamics

Water relations Plants need light (energy: Ch. 2) Plants need CO 2 (carbon: Ch. 2) Plants need water (Ch. 3) 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