Photon Systems Instruments AquaPen-C AP 110-C, Instruction Manual

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Measuring the optical density of growing cultures is a common method to quantify various important culture parameters like cell
concentration, biomass production or changes in the cell morphology. The cuvette version of the AquaPen measures OD at two
wavelengths 680 and 720nm.
AquaPen measures:
Ft - Instantaneous Chlorophyll Fluorescence
F
t
is equivalent to F
0
if the sample is dark-adapted.
QY - Quantum Yield
QY is a measure of the Photosystem II efficiency. QY is equivalent to F
v
/F
m
in dark-adapted samples and to F
v '
/F
m '
in light-adapted
samples.
OJIP - Chlorophyll Fluorescence Induction Kinetics
The OJIP curves show major changes that occur during exposure of a sample to high irradiance (see more in chapter 5.1.3).
NPQ - Non-Photochemical Quenching
The NPQ protocol is used to quantify photochemical and non-photochemical quenching. The measurement should be performed
with a dark-adapted sample. (see More in chapter 5.1.4).
LC - Light Curve
Photosystem II Quantum Yield estimated from fluorescence that is measured sequentially at several different light levels. More in
chapter 5.1.5.
OD - Optical Density* at 680 nm and 720 nm. (AP-C only)
Optical density at 680 nm represents light scattering and chlorophyll absorption. Optical density at 720 nm represents light
scattering that corresponds to cell density. More in chapter 5.2.
*Optical density is defined as
OD = -Log(I/Io) - where "Io" is the irradiance that is transmitted through the cuvette filled with medium without algae or cyanobacteria.
This quantity must be measured as the reference. "I" is the irradiance transmitted through the cuvette with algal or cyanobacterial
suspension in which the OD is measured. "Log" is the decadic logarithm of the I/Io ratio. Thus, the optical density OD=1 means that the
light at the respective wavelength
is attenuated by the algae or cyanobacteria 10 times relative to the reference. With OD=2, the
attenuation relative to the reference is 100 times.