1. Ch. 2 Light and Photosynthesis (Ps)

2. Light Radiant energy (electromagnetic radiation) –Particle + wave Particle: torp

3. Light Wave: has Wavelength inversely

4. Light Visible light: 380-750 nanometers (nm) (nano=10 -9 )

5. Electromagnetic spectrum T/F: Plants green because chlorophyll absorbs green light

6. Electromagnetic spectrum 400-700 nm: Photosynthetically Active Radiation (PAR) –Drives Ps –Green least (why leaves green) Action spectrum for photosynthesis (Ps)

7. Radiation Helps determine IR: 750-10 6 nm. Objects > absolute 0 emit Gain energy from IR too Pred

8. IR “Infrared (IR) window” of leaves Transmit near IR (beyond visible): little Most visible IR window

9. IR Near IR transmitted through leaves (dashed line)

10. IR Use IR window (sense overstory)?? First: phytochrome

11. Phytochrome 2 forms (interconvertible) Pr absorbs R: converted to Pfr Pfr absorbs FR (near IR): converted to Pr Pfr active

12. IR 1) Ratio Pr:Pfr depends on ratio R:FR light 2) R:FR influenced by leaves –Leaves remove R, let FR through “IR window”

13. IR Ex, red alder (Alnus rubra) Germination sensitive to Pfr –Pfr high: –Pfr low:

14. IR Ex, red alder (Alnus rubra) In open: lots R light, lots Pfr

15. IR Ex, red alder (Alnus rubra) Under canopy: lots FR light, less Pfr

16. IR Plants may use phytochrome –1) shaded: stimulate etiolation (spindly, less chlorophyll) –2) info on canopy (deciduous forest) Trillium

17. Electromagnetic spectrum UV radiation: < 350 nm (to 1 nm)

18. UV Danger: Damage DNA (skin cancer!) Pigments (ex, flavonoids) absorb +DNA repair mechanisms Diamorpha smallii

19. Units (Intensity) ?

20. Units

21. PAR: Photosynthetic Photon Flux Density (PPFD) moles photons/sq. m/sec National Mole Day??

22. Units PPFD 1 mole photons = 1 Einstein So, Einsteins/sq. m/sec National Mole Day??

23. Light intensity variation Canopies patchy in

24. Light intensity variation Phenoseason: seasonal light change + canopy change Max. lite ground level Max. lite canopy top

25. Phenoseasons Ex, Eastern Deciduous Forest understory plants 4 strategies: 1) Spring herbs (“Ea”): emerge early Canopy leaf drop Canopy leaf expansion

26. Spring herbs Ex, Trillium

27. Spring herbs Ex, Erythronium (trout lily)

28. 2. Summer green herbs Emerge late spring, green summer, dormant fall “Us” Canopy leaf expansion Canopy leaf drop

29. Summer green herbs Ex, Uvularia sessilifolia (bellwort) Uvula??

30. Summer green herbs Ex, Uvularia sessilifolia (bellwort)

31. 3. Late-summer herbs Emerge summer, get early fall sun (Aa) Ex, Aster acuminatus (sharp-leaved aster) Canopy leaf expansion Canopy leaf drop

32. 4. Semievergreens Emerge late spring, green late: “Om” Ex, Oxalis montana (wood sorrel) Canopy leaf expansion Canopy leaf drop

33. Light variation Canopies patchy Question: Technical name for beam sunlight on forest floor?

34. Light variation Canopies patchy in space ______: beam sunlight on forest floor

35. Sunflecks: Good Useful (forest floor plants) –Some: 70% energy sunflecks

36. Sunflecks: Good Useful (forest floor plants) –Some: 70% energy sunflecks Ability to use: –Spring herbs (Trillium) respond –Summer green herbs (Uvularia) exploit

37. Sunflecks: Bad –Ex: shade-adapted Oxalis. Redwood forest ( Oxalis oregana-redwood sorrel) –Coast redwood (Sequoia sempervirens) Tallest tree: 368 ft. DBH 23 ft.!

38. Sunflecks: Bad O. oregana: Sunflecks damage Ps machinery

39. Sunflecks: Bad Sunflecks & drought stress Ex, regeneration Abies magnifica (CA red fir)

40. Sunflecks Ex, regeneration Abies magnifica (CA red fir) Seedling pattern from sunfleck pattern