CHAPTER 5
OPERATION OF THE JUNIOR-PAM
Fo’
Minimum chlorophyll fluorescence yield in the presence of
open photosystem II reaction centers. The Fo’ is either calcu-
lated (see 6.1.2) or measured during far red illumination and
the actinic light switched off. Measuring of Fo’ fluorescence is
activated by ticking <Fo’-Mode> in Box (9).
Y(II)
Photochemical quantum yield of photosystem II; derived from
F’ and Fm’ measurements.
ETR
Electron transport rate (µmol electrons/(m
2
·
s) derived from
Y(II) and PAR.
PAR
Photosynthetic active radiation (µmol photons/(m
2
·
s).
Temp Temperature
(°C)
<Quench> data
These types of data quantify fluorescence quenching
caused by photochemical energy use or non-photochemical
energy dissipation. All fluorescence parameter related to non-
photochemical quenching require both, saturating pulse analy-
sis of the dark-acclimated and light-exposed leaf. Coefficients
of photochemical fluorescence (qP and qL) require fluores-
cence measurements with dark acclimated material only if Fo
is calculated (see 6.1.2).
qP
Coefficient of photochemical fluorescence quenching.
qL
Coefficient of photochemical fluorescence quenching assum-
ing that the many photosystem complexes form a combined
light-harvesting antenna so that an absorbed photon becomes
available for many reaction centers (lake model). In compari-
son, the qP is more consistent with separated light-harvesting
antennae of photosystems (puddle model).
qN
Coefficient of non-photochemical fluorescence quenching.
NPQ
Non-photochemical fluorescence quenching: quantification of
non-photochemical quenching alternative to qN calculations.
The extent of NPQ has been suggested to be associated with
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