ACRONYMS AND EQUATIONS
CHAPTER 6
nisms: the yield of all other non-photochemical losses is given by the
parameter Y(NO). Finally, the yields of photochemistry and non-
photochemical losses equal 1:
Y(II)+Y(NPQ)+Y(NO)=1
6.3
Relative Electron Transport Rate (ETR)
Relative electron transport rates are calculated according to:
ETR = PAR · ETR-Factor · P
PS2
/P
PPS
· Y(II).
The basic idea of the ETR equation is to multiply, Y(II), the effective
photochemical quantum yield of PS II, by an estimate for the photon
flux density absorbed by PS II. The letter approximation uses three pa-
rameters which are explained below:
PAR
Photosynthetic active radiation
To calculate ETR, WinControl-3 uses the PAR values of the JUNIOR
PAM’s internal PAR list which apply only with a 400 mm fiber and a
distance between sample and fiber tip of 1 mm. For other illumination
conditions, the PAR entering ETR calculations does not apply. Also, de-
creased LED output after long-term use or defective light fiber might af-
fect the PPDF delivered by the JUNIOR-PAM. In any case, when exter-
nal light sources are used, the PPDF needs to be measured using an ap-
propriate quantum sensor. In the latter cases, ETR calculations requires
export of Y(II) data into a spread sheet program.
ETR-Factor
Absorptance of photons by photosynthetic pigments
The ETR-Factor corresponds to the ratio of photons absorbed by photo-
synthetic pigments to incident photons. The WinControl-3 default value
for the ETR-Factor is 0.84 which matches reasonably well the average
absorptance in the visible range (400-700 nm) of many green leaves.
However, at 450 nm, the peak wavelength of the JUNIOR-PAM actinic
light, leaf absorptance is close to 0.9, but the presence of anthocyanins
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