Abstract
Summary Investigations were performed on the interrelation between the photoprotective role of the xanthophyll cycle and levels of N-supply in maize plants (Zea mays L. cv. Maya). Plants were grown in non-fertilised and fertilised plots, while the latter were supplied with 30, 60, 90, 120 and 150 kg ha−1 NH4NO3 and grown under natural conditions in the field. The photosynthetic carbon assimilation of plants with higher N-supply, as compared to that of plants with lower N-supply, showed no significant differences, although a peak of the CO2 assimilation rate was observed at 60 and 90 kg N ha−1 treatment levels. Maize plants with lower N-supply had a lower leaf Chl-content than plants with higher N-supply, which was accompanied by a reduced rate of photochemical efficiency of photosystem II and a high thermal energy dissipation activity, measured as non-photochemical fluorescence quenching. Plants supplied with lower doses of N were detected to have a greater fraction of xanthophyll cycle pool in the form zeaxanthin and antheraxanthin. With reduction of the N-supply levels an increase in the ratio of xanthophyll cycle pigments as related to total Chl was observed. These results suggest that with the decrease of N-supply there is an increasing need to dissipate the excess light energy in the chloroplasts of maize leaves through xanthophyll cycle.
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