Interaction effects of light density and nitrogen on maize leaf pigments, chlorophyll fluorescence and energy transition

The effects of growth light density, nitrogen supply and its interaction on maize leaf pigments contents and chlorophyll fluorescence and energy transition was significant. Higher contents of chlorophyll a, chlorophyll b, total chlorophyll and carotenoid and a higher ratio of chlorophyll a/b was found in plant leaves grown under high light density (400 cmolm-2s-1).Under both light condition, the contents of various pigments mentioned above and the ratio of chlorophyll a/b increased first and then decreased with the increase of nitrogen supply, and the turning point of plants grown under low light density lay in the low level of nitrogen supply. Under higher nitrogen supply, the leaves of high light density had higher PSII efficiency, less nonphotochemistry, and more light energy absorbed by antennae was moved into the photochemistry course. The situation was in reversed under low light density, more light energy absorbed by antennae was dissipated in thermal or fluorescence through the antennae pigment. The least PSII efficiency was found in the nitrogen free treatment under high light density and in the highest nitrogen treatment under low light density, the suitable level of nitrogen supply was higher in plants grown under high light density than those under low light density. It was suggested that a attention must be pay to the balance between light and nitrogen condition in the canopy in order to get both a higher yield and a higher nitrogen efficiency.