I am using FluorPen FP 100 (PSI, CZ) for measuring OJIP transients of various Panicum antidotale grass accession collected from various locations to assess their potential for drought tolerance. Of various JIP-test parameters, computed parameters are Phi_Pav, Pi_Abs. I assume that these two parameters are related with performance index. However, on our manuscript the reviewer commented that you have to take measurements two times for the calculations of performance index which is most suitable.
as far I can guess the first task is knowing if fluorescence varies with stress. Usually it does with low temperature and herbicides, but plants have got a number of adaptations that maintain chloroplasts functions under osmotic variation. If the stress is occurring with drought and non optimal temperatures then you will notice a variation on Fv/Fm on dark adpted leaves that depends on photinhibition. whole plant tolrerance is at best evaluated by ex situ potted plant growth, in a controlled deficit. It is also important to record the age of leaves you use for fluorescence.
''the performance index that is calculated as:
(RC/ABS) × (ϕPo/(1 − ϕPo)) × ( o/(1 − o)), where,
RC is for reaction center; ABS is for absorption
flux; ϕPo is for maximal quantum yield for primary
photochemistry; and o is for the quantum yield
for electron transport'' Environmental and Experimental Botany 73 (2011) 64–72
The best information on performance index you can find in Strasser et al. Chapter 12. Analysis of the Chlorophyll a Fluorescence Transient, In: George C. Papageorgiou and Govindjee (eds): Chlorophyll Fluorescence: A Signature of Photosynthesis, © 2004 Kluwer Academic Publishers.
Hy dear Habib Athar
you can use of this article and words that i sent for you.
PIABS = (γRC/1- γRC) (φP0/1 - φP0) (ψEo/1- ψEo)
PITotal = PIABS . δR0/(1 - δR0)
φPo = TRo /JABS = 1 _ Fo/FM
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