Relationships Between Seedling Growth Rate and Yield of Maize Cultivars Under Normal and Water Stress Conditions

Effects of water stress on root and leaf growth rates and their relationships with yield under normal and water stress conditions were examined at the Greenhouse and Research Field of Faculty of Agriculture, Kerman University, Iran, using seven maize cultivars including SC-404, SC-704, BC-666, TC-647, DC-370, Jeta and Kordona. During a period of 14 days, water stress at -0.4 MPa was imposed by application of PEG-6000 to the seedlings. The root and leaf growth were measured every day. Leaf and root growth rates were expressed as the slope of the line fitted to the data of length and time. Results showed that water stress inhibited root and shoot growth in all cultivars. Differences were found among cultivars in terms of root and leaf growth rates. Differences were greater under normal compared with water stress condition. In a field experiment during 2007- 2008 growing season, yield performances of the same cultivars were measured under water stress and normal conditions. Correlation coefficients of yield with root (0.54), (0.10) and leaf (0.79), (0.32), (0.91), (0.63) growth rates were stronger under normal compared with water stress condition. Higher grain yield (mean of 10 plants per plot) of cultivars with higher growth rates under normal condition may be attributed to the higher growth rates at the early stages of growth. It could be also indicated that the higher growth rate ability of cultivars decreases when they are exposed to water stress condition.