A New Leaf Fluorescence Model

1. A New Leaf Fluorescence Model R. Pedrós1,2, Y. Goulas2, S. Jacquemoud1, J. Louis2, I. Moya2 1 Laboratoire Environnement et Développement,Université Paris 7 - Denis Diderot, Paris 2Groupe Photosynthèse et Télédétection,LURE-CNRS, Orsay Development of a Vegetation Fluorescence Canopy Model Final Project Presentation Meeting, ESTEC 17 March 2005

2. OBJECTIVE Model Reflectance and Transmittance Including FLUORESCENCE at LEAF level

3. FLUORESCENCE EXCITATION RADIATIVE TRANSFER CHOICE OF THE APPROACH FLUORESCENCE SOURCE * * * * FLUORESCENCE EMISSION * PHYSIOLOGICAL PARAMETERS * COMPARISON MODEL OUTPUT - MEASUREMENTS * PREDICTED REFLECTANCE AND TRANSMITTANCE CONCLUSIONS * * Development of a Vegetation Fluorescence Canopy Model Final Project Presentation Meeting, ESTEC 17 March 2005

4. THE PROSPECT MODEL + FLUORESCENCE SCATTERING * N: leaf internal structure * n: refractive index Variables that can be related to intrinsic fluorescence CHOICE OF THE APPROACH * Compromise between number of variables and easy inversion * Variables that can be measured or estimated CHOICE OF THE APPROACH

5. PROSPECT PLATE MODEL: Allen et al. (1969) N LAYERS MODEL: Stokes (1862) CHOICE OF THE APPROACH

6. PROSPECT PARAMETERS N - Number of layers Cab - Chlorophyll a+b content Cw - Water equivalente thickness Cm - Dry matter content CHOICE OF THE APPROACH

7. RADIATIVE TRANSFER

8. 1 1 n1 n2 2 SCATTERING Real refractive index of constituent i: ni() Snell’s law RADIATIVE TRANSFER

9. Transmission of isotropic radiation across an interface between two dielectrics: n1 = 1 and n2 = n integration over the solid angle  RADIATIVE TRANSFER

10. ABSORPTION Specific absorption coefficient of constituent i: ki() Water Chlorophyll a+b d Dry matter Beer law RADIATIVE TRANSFER

11. Light incident with an angle  Diffuse light With (0,kx) the incomplete gamma function: RADIATIVE TRANSFER

12. FLUORESCENCE EXCITATION

13. PLATE MODEL Total flux at position x given by: i12(x) + i24(x) + i42(x) FLUORESCENCE EXCITATION

14. i12(x) and i42(x) are propagating towards positive values of x: i24(x) is propagating towards negative value of x: The absorbed intensity is then: FLUORESCENCE EXCITATION

15. FLUORESCENCE EMISSION

16. FLUORESCENCE SOURCE PLATE MODEL FLUORESCENCE EMISSION

17. The UPWARD and DOWNWARD FLUORESCENCE signals of the plate are UPWARD FLUORESCENCE DOWNWARD FLUORESCENCE Difficulty: we haven’t found an analytical solution of the integrals thus numerical solution FLUORESCENCE EMISSION

18. NUMERICAL INTEGRATION Numerical solution is very high time consuming We can write with and FLUORESCENCE EMISSION

19. with a change of variable x = 1 – x we can show that The integration problem has been reduced to calculate For q1 we have found an analytical solution FLUORESCENCE EMISSION

20. kem kexc For the integration of q2 we have built a look-up table The interpolation reduces the calculation time in a factor 20with respect to the numerical integration FLUORESCENCE EMISSION

21. * FLUORESCENCE FOR 1 LAYER FLUORESCENCE FOR N LAYERS * Necessary to describe the complex structure of the leaf FLUORESCENCE EMISSION

22. FLUORESCENCE IN N LAYERS:Stokes model revisited FLUORESCENCE EMISSION

23. FLUORESCENCE OF N LAYERS FLUORESCENCE EMISSION

24. Solving the system Setting m = N  1 and n = 1 Thus we can calculate the upward and downward fluorescence of 2, 3,…, N layers recursively FLUORESCENCE EMISSION

25. Upward Fu(N) and downward Fd(N) fluorescence is a CUBE of dimensions3512115 5 layers: n=1,2,...,5 Significant variation in fluorescence The fluorescence for N real is “a slice” calculated by cubic interpolation 351 wavelengths of excitation [400, 750] @ 1 nm is required in PROSPECT 211 wavelengths of emission[640, 850] @ 1 nm FLUORESCENCE EMISSION

26. FLUORESCENCE SOURCE

27. FLUORESCENCE SOURCE Quantum efficiency Excitation spectrum of dx Emission spectrum of dx FLUORESCENCE SOURCE

28. QUANTUM EFFICIENCY Measured in a leaf at: lexc = 633 nm LASER lem = 758 nm SPECTRALON POSITION OF THE SAMPLE PHOTODIODE FILTER HOLDER Experiment designed at LURE laboratory FLUORESCENCE SOURCE

29. EXCITATION SPECTRUM dx is a thylakoid: membrane of the chloroplasts with Chl Commercial fluorimeter CARY ECLIPSE Measurement in relative units FLUORESCENCE SOURCE

30. LEAF LEVEL Qeff THYLAKOID LEVEL EXC(lexc) Spectral distribution of the quantum efficiency Possible as fluo lifetimes for leaf and chloroplast are aprox. the same + FLUORESCENCE SOURCE

31. FLUORESCENCE EMISSION SPECTRUM We need the spectral distribution of the fluorescence emission Meier (2000) after Gitelson et al. (1988) * A New Spetrum: * FLUORESCENCE SOURCE

32. Physical basis in the emission spectrum We can describe the transition F0 – FM: PSI to PSII contribution Introduction of the fluorescence spectra of the two photosystems Explain the enhancement effectEmerson (1958) FLUORESCENCE SOURCE

33. - F0 (minimal) : 40% - FM (maximal) : 10% - Fs (steady-state) : 35% Most of the variable fluorescence comes from PSII * PSI contribution to fluorescence is weak and constant * In 735 nm Agati et al. (2000) FLUORESCENCE SOURCE

34. CHOSEN PSI SPECTRUM LHC-Ispectrum Croce et al. (1996) The problems with detergents during extraction are reduced * The measurements in agreement with theory: * Absortion spectrum + Stepanov equation FLUORESCENCE SOURCE

35. CHOSEN PSII SPECTRUM BBY-granaRoom Temperature Franck et al. (2002) Spectra for various Chl contents * We choose the one with the minimun Chl concentration * FLUORESCENCE SOURCE

36. COMBINATION OF THE PSI AND PSII SPECTRA PSI PSII FLUORESCENCE SOURCE

37. COMBINATION OF PSI AND PSII Multiplied for a factor 5 because * PSII has 5 times more fluorescence yield than PSI t (PSII) = 0.5 ns lifetime t (PSI) = 0.1 ns t0 is 15-18 ns Stoichiometry of PSII to PSI reaction centers which is related to light conditions during growth * For high light its value is around 2 (Chow et al., 1988) This leads to PSII/PSI=10 for plants that grew with high light FLUORESCENCE SOURCE

38. COMBINATION OF PSI AND PSII PSII ELEMENTARY SPECTRUM PSIII(lem) MODEL PSI ELEMENTARY LEVEL LEAF LEVEL l excitation is 440 nm + FLUORESCENCE SOURCE

39. COMBINATION OF PSI AND PSII Elementary spectra Fluorescence spectra at leaf level l excitation is 440 nm The PSII/PSI stoichiometry is a physiological parameter FLUORESCENCE SOURCE

40. FLUORESCENCE MATRIX FLUORESCENCE SOURCE

41. FLUORESCENCE MATRIX l excitation l emission Dimensions 351 X 211 FLUORESCENCE SOURCE

42. PHYSIOLOGICAL PARAMETERS

43. FLUORESCENCE QUANTUM EFFICIENCY * STOICHIOMETRY OF PSI AND PSII * TEMPERATURE * LIGHT LEVEL * PHYSIOLOGICAL PARAMETERS

44. FLUORESCENCE QUANTUM EFFICIENCY 0 % 3-5 % 10 % No fluorescence Normal Maximum PHYSIOLOGICAL PARAMETERS

45. FLUORESCENCE QUANTUM EFFICIENCY The slope in 685 nm is greater than in 730 nm Qeff [0, 0.1] l emission PHYSIOLOGICAL PARAMETERS

46. STOICHIOMETRY OF PSI AND PSII 1:1 2.5:1 Low light Hight light Stoichiometry of PSII to PSI reaction centers which is related to light conditions during growth PSII:PSI PHYSIOLOGICAL PARAMETERS

47. It changes the shape of the elementary spectrum Sto [1, 2.5] STOICHIOMETRY OF PSI AND PSII FLUOintensity l emission PHYSIOLOGICAL PARAMETERS

48. TEMPERATURE Fluorescence increases as leaf temperature is decreased Linear relationship between F685 and F730and temperature * Is species dependent * Agati (1998) PHYSIOLOGICAL PARAMETERS

49. TEMPERATURE * Decreasing leaf temperature induces a reduction of the thylakoid membrane fluidity which inhibits the reoxidation of plastoquinones leading to an incrrease in the Chl F yield * There is a large reduction of the photochemical quenching at lower temperatures, while the NPQ is only slightly affected by temperature PHYSIOLOGICAL PARAMETERS

50. TEMPERATURE T [1, 26]ºC FLUOintensity l emission PHYSIOLOGICAL PARAMETERS