Today, maize is one of the most important crops in the world. In addition, its range of uses is becoming increasingly wider (forage, food, oil, bioethanol and energy). Detection of physiological conditions of these plants is required in terms of precision crop production.

Potential (Fv/Fm) and actual photochemical efficiency of PSII (Yield) were measured with a PAM-2001 chlorophyll fluorometer on a maize (Zea mays L.) genotype at two different levels of nutrient supply in a field experiment. The investigation was set up early in the morning and at noon and in the case of younger (last fully developed) and older (leaf of the main cob) leaves. The values of Fv/Fm were around the optimum level in the case of both treatment and leaf ages early in the morning. Potential photochemical activity for most plants grown without stress is close to 0.83, lower values suggest that plants are growing under stress and that PSII reaction centers are damaged, which, in turn, is connected with reduced effectiveness of electron transport such as when plants are grown under excess light. The differences of the measured parameters between the treatments were more pronounced at noon. The actual photochemical activity values were more sensitive for treatments, leaf ages and environmental factors.

Keywords: photochemical activity, photosystem II, maize, nutrient supply, yield, Fv/Fm