evaluation of water and photosynthetic nitrogen use efficiency in two maize hybrids

water deficit and low nitrogen content of soil are the two major yield limiting factors in most maize (zea mays l.) producing areas. the objective of the current research was to evaluate the relationships between photosynthetic water and nitrogen use efficiency at different levels of soil moisture and nitrogen contents. a factorial experiment, based on completely randomized design with 3 replications was conducted in the greenhouse of college of agriculture, shiraz university in the spring and summer 2006. the treatments consisted of 4 different levels of soil moisture based on field capacity (1.2 fc, fc, 0.8 fc and 0.5 fc), soil nitrogen at two levels (180 and 60 kg ha-1) and 2 single crosses of maize hybrids (ksc 700 and ksc 704). the results revealed that ksc 700 had a higher photosynthetic water use efficiency compared to ksc 704 under the water and nitrogen stressed conditions, this being due to higher photosynthetic nitrogen use efficiency. furthermore, the present research indicated a negative correlation between photosynthetic water use efficiency and photosynthetic nitrogen use efficiency under water stress conditions. overall, it appears that ksc 700 hybrid might be superior under low water and nitrogen availability conditions, compaed to widely grown ksc 704 hybrid.