Effects of iso-osmotic Ca(NO3)2 and NaCl treatment on photosynthesis in leaves of tomato

The effects of iso-osmotic Ca(NO3)2 and NaCl treatment on photosynthesis in leaves of tomato were studied. The results indicated chlorophyll content, net photosynthetic rate(Pn), stomatal conductance(Gs), intrnsic photochemical efficiency(Fv/Fm),quantum yield of PSII (ΦPSII), Fv/Fo and photochemical quenching(qP) were decreased by salt stress. However, the decreased degree of NaCl treatment was bigger than that of Ca(NO3)2 treatment. Intercellular CO2 concentration(Ci) was decreased by Ca(NO3)2 treatment, while was increased by NaCl treatment.So both of treatments caused stress to tomato plant, and NaCl stress was heavier than Ca(NO3)2 stress. We could conclude that stomatal limitation was a dominating factor of Pn decrease under Ca(NO3)2stress and non-stomatal limitation was a dominating factor of Pn reduction under NaCl stress.