2.5 Parameter definition and calculation
The parameter
Fv/Fm represented the maximum
photochemical efficiency of PSII. The probability that trapped exciton
by PSII moves an electron further than QA- was
expressed as ψo. The parameter φEo stood
for electron transport quantum yield. PIABS was the
performance index which integrated different phenomena related to PSII
activity.
A relative change (RCX) was used to determine the
variation of parameters from predawn to dusk as follows:
\(\text{RC}_{X}\left(\%\right)=\left(\frac{X_{o}-X_{p}}{X_{p}}\right)\times 100\%\)(1)
where Xp and Xo were the
values of Fv/Fm, ψo,
φEo and PIABS observed at predawn and
other time points in a day, respectively.