You should check all other parameters, like CO2 in the chloroplast, leaf mass per unit area, chlorophyll density and nitrogen density. Amax is taken from controls and is the light saturation capacity at a given Cc, LMA ND and any stress would reduce it. On the other side some stress can affect growth and produce denser leaves before affecting life duration, like in a sort of hypersensitive reaction. In this case leaf area duration is affected.

 A max should be always greater than A, A max usually measured under saturating light and [CO2]  and A should be measured at ambient [CO2].  Many other parameters can influence Amax , generally A max should be more than A under any circumstances. So kindly cross check your experimental conditions as well as your IRGA .

 Dear Guido Bongi and Madhan Sekhar,

Thank you for your explaination and advice.

I' check all my results again