Evaluation of Maize Inbreds for Vegetative Nitrate Uptake and Assimilation

Abstract

Twelve maize (Zea mays L.) inbred lines were cultured under hydroponic conditions in a controlled environment room for evaluation of NO₃^--N uptake, subsequent translocation patterns and utilisation. Prior to harvest (8-10-leaf stage), inbred roots were exposed to 24 h of 10 atom % ¹⁵NO₃^--N. Differences for N contents and biomass were determined. Root dry weight (RDW) was significantly correlated (r = 0.93) with root surface area. Significant inbred differences were found when N content in the plant was based on RDW.

When based on ¹⁵N during the 24 h, the amount of N absorbed varied between 30 and 71 mg per plant for the inbreds. Uptake rates ranged between 8.7 and 14.4 mg g^-1 day^-1 RDW. Nitrogen uptake over the 24 h based on RDW and total plant-N contents based on RDW were significantly (P< 0.001) correlated, implying that uptake rates were constant up to mid-vegetative stages for these genotypes. Of the ¹⁵N absorbed, between 30 and 61% was reduced by the inbreds and the amount reduced varied with plant tissue. The total amount reduced ranged between 0.72 and 1.25 mg g^-1 dry weight.