MAIZE (Zea mays L.) HYBRID USE OF 15N-NITRATE ABSORBED VEGETATIVELY BY ROOTS

The use and mobilization of N absorbed at various vegetative growth stages by maize (Zea mays L.) roots have not been investigated by pulsing/chasing N. During this study two maize hybrids, B73 × LH39 (B×LH) and H93 × L10 (H×L), were evaluated in a greenhouse experiment for vegetative 15N absorption and subsequent utilization and mobilization. At 35 (EI) and 43 (EII) days after seed was planted (DAP), separate plants were given 99 atom % 15N as [Formula: see text] for 48 h. The experimental design was a randomized complete block with three replications. Plants were harvested at 38 DAP, 43 DAP, silking and physiological maturity (PM) for EI and at 46 DAP, 51 DAP, silking and PM for EII. Neither hybrid nor treatment differences were observed for uptake of 15N. Genotype B×LH remobilized more of the vegetatively absorbed N to the kernels than H×L (P ≤ 0.10). Initial deposition of 15N was in the leaves (60%), stalk (30%), and roots (10%) for EI and in the leaves (50%), stalk (40%) and roots (10%) for EII for both genotypes. Forty percent of the 15N in the plant (80, 12 and 8% from the leaves, roots and stalk) during EI was mobilized to reproductive tissue by PM, while 50% (60, 30 and 10% from the leaves, stalk and roots) was mobilized during EII. Thus, the later N is vegetatively absorbed by the maize plant, the more likely it will be translocated to the kernels.Key words: Nitrate, nitrogen, uptake, translocation, Zea mays L., maize