BIOCHEMICAL CHANGES IN MAIZE SEEDLINGS EXPOSED TO DROUGHT STRESS CONDITIONS AT DIFFERENT NITROGEN LEVELS

Normally, under field conditions, maize seedlings are often exposed to early water stress. The objective of the present study was to evaluate the biochemical changes in maize seedlings exposed to drought stress at different nitrogen levels. Maize (Zea mays L.) hybrid SC 704 plants were grown in 18 kg pots containing the same soil from the field that maize is naturally growing. The treatments consisted of three soil moisture regimes (A: well-watered, i.e., control; B: watered at 50% field capacity; and C: watered at 10% field capacity) and three nitrogen levels [a: 0 control; b: 60; and c: 180 kg nitrogen (N)/ha]. In a factorial experiment based on randomized complete block (RCB) design, each treatment was replicated four times. The results of this study showed that mild drought stress increased the catalase (CAT) activity, however, severe stress decreased it. Moreover, nitrogen fertilizer significantly increased CAT activity when applied at highest level. Also, drought stress significantly increased the superoxide dismutase (SOD) activity. At the mild water stress level, peroxidase (POD) activity met its peak level, however, at sever water stress its activity was suppressed and even fell below the control level. Nitrogen fertilizer significantly increased the POD activity. Also, nitrogen application significantly increased proline concentration; however, there was no significant difference between 60 and 180 kg N/ha levels. Protein concentration was increased by water stress and the highest concentration of protein was occurred at mild water stress level, however, there was not statistically any significant difference between mild and sever water stress levels. In view of biochemical traits, further research is needed on clarifications and understanding of the interactions between nitrogen requirements of maize and drought stress.