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Models of fluorescence and photosynthesis for interpreting measurements of solar-induced chlorophyll fluorescence - PubMed

Models of fluorescence and photosynthesis for interpreting measurements of solar-induced chlorophyll fluorescence

C van der Tol et al. J Geophys Res Biogeosci. 2014 Dec.

Abstract

We have extended a conventional photosynthesis model to simulate field and laboratory measurements of chlorophyll fluorescence at the leaf scale. The fluorescence paramaterization is based on a close nonlinear relationship between the relative light saturation of photosynthesis and nonradiative energy dissipation in plants of different species. This relationship diverged only among examined data sets under stressed (strongly light saturated) conditions, possibly caused by differences in xanthophyll pigment concentrations. The relationship was quantified after analyzing data sets of pulse amplitude modulated measurements of chlorophyll fluorescence and gas exchange of leaves of different species exposed to different levels of light, CO2, temperature, nitrogen fertilization treatments, and drought. We used this relationship in a photosynthesis model. The coupled model enabled us to quantify the relationships between steady state chlorophyll fluorescence yield, electron transport rate, and photosynthesis in leaves under different environmental conditions.

Key points: Light saturation of photosynthesis determines quenching of leaf fluorescenceWe incorporated steady state leaf fluorescence in a photosynthesis model.

Keywords: chlorophyll fluorescence; electron transport; photosynthesis.

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Figures

Figure 1
Figure 1

A sample trace of a measurement of fluorescence from a leaf with a PAM fluorometer [after Maxwell and Johnson, 2000]. The measuring light is turned on at MB; saturating pulses (1 s) are applied at SP. Note that γ→0 during a SP while ν is unchanged. The experiment shows changes in fluorescence that occur when actinic light is provided. The fluorescence levels (F) are normalized to the Fo level. The photochemical yield of the leaf under dark adapted conditions formula image and after a period of illumination formula image. These arbitrary fluorescence levels can be related to absolute yields with the equations and probability constants shown in the boxes and the values of γ and ν. We used equations (8) and (9) to estimate KN and KP, respectively, and formula image and formula image.

Figure 2
Figure 2

Cotton data of (a) photochemical yield ΦP from gas exchange versus ΦP from PAM, (b) modeled [Collatz et al., 1991] versus measured photosynthesis, and (c) modeled versus measured (from gas exchange) ΦP.

Figure 3
Figure 3

The data and model results of the cotton experiment presented as formula image versus ΦP, with different symbols for driving variables. The lines are computed from the empirical KN(x) with temperature correction for 25°C (solid line) and 35°C (dashed line).

Figure 4
Figure 4

(top) Measurements of Fo/Fm at different temperatures for the cotton experiment (circles) and the tobacco experiment (squares). (bottom) Fm (open symbols) and Fo (closed symbols) at different temperature for the cotton experiment. Note that the values are relative, and the unit on the y axis is arbitrary

Figure 5
Figure 5

(top to bottom) Rate coefficients KP and KN versus relative light saturation of photosynthesis x, calculated from active fluorescence measurements of for cotton leaves exposed to varying irradiance, varying CO2 concentration, and varying temperature. Open symbols refer to low light conditions (Q < 800μmol m−2 s−2), crosses to high-temperature data (T > 35°C), and closed symbols to all other data. The solid line is an empirical model fit, and the dotted line is the theoretical value for KP if KN were always zero.

Figure 6
Figure 6

Similar to Figure 5 but for the other experiments: (1) tobacco leaves under different temperature and illumination and (2) grape and other C3 species subject to a drought experiment under full sunlight. The solid line represents the empirical fit of the cotton experiment, and the dashed line is calibrated to the drought experiment data.

Figure 7
Figure 7

Responses of KP (green) and KN for four different nitrogen treatments in maize (symbols). The lines represent the empirical fit for the cotton experiment.

Figure 8
Figure 8

Modeled versus measured photosynthesis A, fluorescence flux formula image, steady state fluorescence yield formula image, and maximum fluorescence yield formula image (clockwise). Circles refer to cotton, triangles to maize, and stars to tobacco.

Figure 9
Figure 9

Measured (open symbols) and modeled (closed symbols) responses of photosynthesis, maximum fluorescence yield, and steady state fluorescence yield of selected cotton leaves to temperature, leaf boundary layer CO2 concentration, and irradiance.

Figure 10
Figure 10

Selection of the cotton data for one light response curve (triangles) and one CO2 response curve at an incident PAR of 1400 μmol m−2 s−1 (circles), with CO2 gas exchange flux on the horizontal axis and fluorescence flux JP=ΦP·aPAR/2 from PAM data on the vertical axis. The lines are model results (cotton parameters for KN(x)) after coupling the PAM fluorescence model to the model of Collatz et al. [1991].

Figure 11
Figure 11

One-by-one sensitivity analysis of the modeled yields (fluorescence and photochemistry) and photosynthesis of a “standard” leaf to four input variables. The sensitivity was calculated for drought relation between x and KN. The parameters of the standard leaf were leaf boundary [CO2] = 380 ppm, aPAR = 1000μmol m−2s−1, leaf temperature T = 20°C, relative humidity RH = 70%, Vcmo=30μmol m−2 s−1, and Ball-Berry stomatal conductance parameter m = 8.

Figure 12
Figure 12

(top left) Modeled fluorescence yield ΦFt (top right)photochemical yield ΦP, (bottom left) photosynthesis A, and (bottom right) fluorescence flux JF, as functions of irradiance for the following values of maximum carboxylation capacity Vcmo: 10 (light gray), 30, 50, 70, and 90 (black) μmol m−2 s−1. The drought relation between x and KN was used.

Figure 13
Figure 13

Modeled responses of formula image, formula image, and ΦF to irradiance, (left) using the drought parameters for KN(x) and (right) using the cotton parameters for KN(x).

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