Transformation of Energy by Plants

1. Transformation of Energy by Plants

2. Efficiency - How well do plants utilize the solar input? • Ecological (or Lindeman) efficiency • (GPP/solar radiation) • wild and cultivated plants ~1.6%.

3. Assimilation efficiency - GPP/light absorbed • 8% at full light to 18% in dim light.

4. Light saturation point

5. Assimilation efficiency - GPP/light absorbed • 8% at full light to 18% in dim light. • Light saturation point • Bonner hypothesis • Many temperate leaves: • Adapted to low light conditions

6. Chlorophyll concentration From AJB 92(2) - Jan 05

7. Biochemical efficiency • molecules of glucose produced/amt. of light absorbed by the photosystems. • Photosynthesis is most often limited by CO2 concentrations

9. Solar radiation within the forest • PAR is light at 380-710 nm - about 40% of the total irradiation reaching the plants

10. Changes with seasons

14. Leaf Area Index (LAI) • (Surface area of leaves over given area of ground)/(area of ground itself)

15. LAI Leaf Area LAI LAI=4.01

16. Light attenuation Typical LAI for deciduous forest = 3 to 5; for coniferous forest = 2 to 4; tropical rain forest = 6 to 10

18. Color spectrum

19. Attenuation of PAR is dependent on: • LAI at a given level above the ground • Arrangement of leaves (multi- or monolayers) • Angle at which leaves are held to the horizontal. Very little light between 500 and 700 nm gets through the canopy.

20. Successional age • Eastern deciduous trees • # of layers also declines with successional age • Data from Henry Horn

21. Sunflects

22. Sunflects • Decrease as tree height & LAI increase • Short duration (1-30”) normally • Varies from 10-85% of daily photon flux density in a given area

23. Production

24. Sunflects • Decrease as tree height & LAI increase • Short duration (1-30”) normally • Varies from 10-85% of daily photon flux density in a given area • Leaf “induction” important for efficiency • As duration  efficiency of utilization 

26. Victoria Lily

27. Leaf Unit Placement • Placed under gaps in upper layer • Under upper leaves - can receive light from three sources: • Passed through other leaves • Reflected off other surfaces • Direct light passing through

28. Umbra (RDZ) • Shadow cast by circle • Distance for influence to be gone • ~70*diameter • Clear day • Sun @ zenith

29. Leaf angle • Umbra decreases as a leaf orientation moves toward vertical

30. Henry Horn’s hypothesis • Trees growing in the open • leaves arranged in depth in a random array • Small leaves; irregular shape • LAI>1

31. Open sun plants Northern Red Oak Choke Cherry

32. Henry Horn’s hypothesis • Understory trees in dense shade • Leaves nonrandom; short vertical distance • Regular shape; larger than leaves in open • LAI~=<1 • Single branch of a tree adapted to growth in the open should cast less shade than a single branch adapted for dim light.

33. Shade plants

34. Growth Rate • R=E*F • F is comprised of: • Ratio of leaf wt. To plant wt. (LWR) • Ratio of leaf area to leaf weight or specific leaf area (SLA) • LWR is fairly steady • SLA can change markedly if plant is moved from sun to shade

35. C3 vs. C4 Photosynthesis

36. C3 Mesophyll cell Mesophyll cell C4 Bundle sheath cell CAM Mesophyll cell

39. Larch (Larix)

40. N. Amer. Larch distribution

41. Larch Larch Red Maple Black Spruce Light absorption & height/radius ratio