Abstract:

In order to elucidate the effects of nitrogen on growth and development in summer maize (Zea mays L.), the photosynthesis characteristics regulated by nitrogen application rates in summer maize was studied. The results indicated that the photosynthetic rate (P_n), cholorophyll content (Chl), soluble protein content (Pro), Hill reaction activity, Ca²⁺-ATPase activity, Mg²⁺-ATPase activity and PEPCase activity in lower leaf, ear leaf and upper leaf of summer maize cultivar (Ludan 50) all increased, with the increase of nitrogen application amount. With the growth progress, the P_n and pro in all tested leaves gradually decreased. The dynamic changes of Chl in leaves showed different patterns, with little changes at different assaying points in the lower leaf and a single peak curve in the ear leaf and upper leaf. There were different patterns on traits of Hill reaction activity, Ca²⁺-ATPase activity and Mg²⁺-ATPase activity, such as the pattern of gradually decrease, single peak curve and double peaks curve. The changes of PEPCase activities in the tested leaves all showed a curve with one peak with the growth progress. With the increase of nitrogen application amount, leaf source capacity, biomass and yield all increased. The results indicated that all photosynthetic characteristics, including P_n, and its related physiological and biochemical parameters could be improved based on application of suitable nitrogen amount. The Ca²⁺-ATPase activity is one of the important factors to affect the function of photoreaction system in maize. In the experiment, P_n was affected little by PEPCase and largely regulated by function of photo system and dark reaction system in the photosynthetic organ during the early and mid-growth stage. Meanwhile, It is suggested that leaf source capacity could be used as a criteria to evaluate the productivity of single plant in maize.

Key words: Summer maize (Zea mays L.), Nitrogen application rate, Photosynthetic rate, Photosynthetic parameter