Growth analysis of contrasting cultivars of zea mays l. At different rates of nitrogen supply

The effects of nitrogen supply on the growth and nitrogen contents of four cultivars of Zea mays L. of different origins were examined under water-culture conditions at the seedling stage. Seedlings of cultivars CNI A12, LG11, Tusa Fina, and UNPHU XC301 were grown under three different relative addition rates of nitrogen. Growth parameters were determined by means of functional growth analysis conducted on 10 to 19 d-old seedlings. No differences in relative growth rates were found among cultivars when nitrogen supply was high. However, at the lowest rate of nitrogen supply, Tusa Fina and LG11 showed lower relative growth rates than CNIA12 and UNPHU XC301, where relative growth rates were sustained even at the lowest rate of nitrogen supply, due to a higher unit leaf rate. The higher unit leaf rate of these two cultivars corresponds directly to higher leaf and plant nitrogen contents. High positive correlations were found between plant nitrogen contents and both relative growth rate and unit leaf rate. The results suggest a potential for selection of genotypes with improved performance under conditions where high rates of nitrogen-fertilizer application are too costly or not desirable.