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Ch. 2 Photosynthesis (Ps) and Light

This article explores the differences between C3, C4, and CAM plants in terms of their photosynthetic mechanisms, growth rates, temperature requirements, and water use efficiency. It also discusses the applied aspects of these plant types in hot climates and the potential for genetic engineering to enhance crop production. Additionally, the article touches upon the variation within C3 plants and the use of carbon isotope ratios for identifying sugar sources.

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Ch. 2 Photosynthesis (Ps) and Light

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  1. Ch. 2 Photosynthesis (Ps) and Light

  2. Comparing C3, C4, CAM plants

  3. CAM and Epiphytes • Epiphytes: plants on plants • Abundant tropical rain forests

  4. CAM and Epiphytes • Spanish moss (Tillandsia usneoides) • CAM plant: pineapple family (Bromeliaceae)

  5. Comparing C3, C4, CAM plants • Exs: many Orchidaceae (70% epiphytes!)

  6. Comparing C3, C4, CAM plants • CAM: • Succulents (deserts) • Epiphytes (tropical/subtropical areas)

  7. Comparing C3, C4, CAM plants • Trait C3 C4 CAM • Max. Ps rate Fig. 2.12

  8. Comparing C3, C4, CAM plants • Trait C3 C4 CAM • Max. growth rate • (optimal conditions)

  9. Comparing C3, C4, CAM plants • Trait C3 C4 CAM • Optimum Ps temp. Fig. 2.11

  10. Comparing C3, C4, CAM plants • Trait C3 C4 CAM • Water use efficiency (g CO2 gain per Kg H2O lost)

  11. Applied Aspects • What crops best hot areas? • Corn/maize • Sorghum • Millet millet sorghum

  12. Applied Aspect • Genetic engineering: C4 properties to C3 plants

  13. Applied Aspect • Ex: rice (C3 grass) • Asia: 70% calories rice • 70% world’s poor Asian • Add PEP carboxylase gene • Yields

  14. C3 variation (between species) • C3 plants • Heliophytes: adapted • Sciophytes: adapted Sciophyte: Who am I? Variation among C3 plants

  15. C3 variation (within individual) European beech • Sun vs. shade leaves • Sun lvs.: Shade Sun Quercus pagoda (cherrybark oak)

  16. Carbon isotope ratios • Isotope: different # neutrons • Ex: Carbon-12 (98.9% C) • Carbon-13 • Carbon-14 Light vs. heavy Carbon dioxide Enzyme affinity?

  17. Carbon isotope ratios • Enzyme affinity • Lo: light CO2 used more • Hi, less discrimination • Measure ratio? Delta C-13 • Units: parts per thousand (ppt)

  18. Carbon isotope ratios C4 • Enzyme affinity CO2 • Rubisco: • PEP carboxylase: • C3 delta C-13; -24 to -34 ppt • C4 delta C-13; -10 to -20 ppt • More negative = • more discrimination

  19. SO WHAT?? 2 main plant species used to produce sugar (Sucrose)?

  20. SO WHAT?? Commercial sugar (sucrose):

  21. AHAH! ID sugar source delta C-13 ratio! • C3: -24 to -34 ppt • C4: -10 to -20 ppt Bernie Beet hands out sacks of white powder to kids..... Bernie Beet Food webs….

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

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

  24. Herbivore Feeding Preferences Rhino poaching: ID horn by delta C-13 ratio

  25. Ch. 3 Water Relations & Energy Dynamics

  26. Water relations • Plants need light (energy: Ch. 2) • Plants need CO2 (carbon: Ch. 2) • Plants need H2O (Ch. 3) Water potential

  27. Water potential • Water potential: free energy • “Tendency H2O to move” • Moves hi to lo • Symbol--Greek letter: psi 4 factors influence water potential

  28. s Water Potential • Affected by: • solutes: solute potential • hi solutes = ___ tendency move

  29. p Water Potential • Affected by: • pressure: pressure potential • hi pressure = ___ tendency move

  30. m Water Potential • Affected by: • charged surfaces (cell walls, clay particles): matric potential • More surfaces = ______ tendency move The Matrix potential

  31. g Water Potential • Affected by: • gravity: gravitational potential • Height increases, tendency move _____

  32. p g m = + + + total s Water Potential • Total H2O potential = sum factors: Units?

  33. total Water Potential • Measurement relative: compared to standard conds. (pure H2O, sea level) • = 0 megaPascals (MPa) • megaPascal: metric system • 1 MPa = about 10 bars or 10 atmospheres

  34. Water Potential • H2O in plants/soil has solutes: NEGATIVE What tissue in plant carries H2O?

  35. Water transport • Xylem: H2O conducting tissue • % H2O remains in plant?

  36. Water transport • Xylem: H2O conducting tissue • H2O in plant? How water move? ?

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