Regarding, Germination stress index was calculated using
Bouslama and Schapaugh (1984) equation.
PI=nd2 (1.0) + nd4 (0.8) + nd6 (0.6) + nd8 (0.4) +nd10 (0.2)
GSI= [PI, under stress condition / PI, under non-stress
condition]
Where nd2, nd4, nd6, nd8 and nd10: number of germinated seed
on second, fourth, sixth, eighth and tenth days, respectively.
if the experiment finished at 7th day, the equation will stop at which part
You would use PI = nd2 (1.0) + nd4 (0.8) + nd6 (0.6) + nd7 (0.5), but try to finish on an even day if you can :-)
i think we have to calculate, number of germinated seed that be added to before day. in the other hand, we only count germinated seed in d2 to d4 range.
d2: 2
d4: 3(5-2)
d6::4(9-5)
thus we don't have any germinated seed in d6-d8.
Dear Hoda Ali
You can also calculate germination rate (GR) under non-saline (GRc) and saline (GRs) conditions, separately, using the following equation:
GR = Σn / ΣDn
Where n is the number of seeds germinated on day D, and D is the number of days from the beginning of the test.
Then calculate germination stress index (GSI) as:
GSI = (GRs / GRc) × 100
Dear Hoda,
You can also use time to event models to calculate some indices along stress gradients. ED50 would be an possible indices along stress gradients.
Warm regrards,
Mehdi
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