In an effort to evaluate the ability of maize inbreds to utilizeammonium-nitorgen (NH??+-N), seedlings were grownin sand culture andsupplemented with different amounts and forms of N. seedlings were harvestedat 28 days after planting an determined for gross differences in dry mass,activity of NH??+-assimilating enzymes. PEP carboxylase, and the ability totake up NH??+ ion. the results indicate that some inbreds retained the abilityto effectively utilize NH??+ , but they adapted various combination ofmechanisms to cope with NH??+ pressure and thereby allowed seedling growth anddevelopment in the presence of high NH??+ concentrations. Thus, plant breedersshould be able to exploit this variability and to creat hybrids with enhancedperformance under predominantly NH?? +-N conditions.

　　　　　為了評估玉米品種利用銨態氮肥的能力，首先將幼苗生長於沙盆中，並施加不同形式及不等量之氮源。播種28天後將幼苗收穫並分別測定其乾重量，銨離子同化酵素和PEPcarboxlyase的活性，以及根部吸收銨離子的能力。所得結果顥示有幾個品種頗具利用銨離子的能力，且可以在高濃度的銨離子情況下生長。由於這幾個品種似乎各自採取不同的機制，因此育種專家應可利用這些品種間的差異性，而交配出具有高效率利用銨離子的雜交種。