Abstract: The genotypic differences in efficiency of absorption,utilization and transportation of phosphors(P) in two maize hybrid combination(SD1、SD-2),and their responses to low P in root structure and their physio-biochemical mechanisms were studied in hydroponics culture in P-deficiency condition.The results showed that compared with SD-1-CK、SD-2-CK,SD-1 and SD-2 had higher P absorption and utilization efficiency.Under low P condition,the root dry weight,length,surface area,and average root number for the two cultivars increased obviously,while the average root diameter decreased.The two combination had larger root total uptake area and active areas,showing longer Imax,but lower Km and Cmin values in the P absorption kinetics.In this experiment,the higher P uptake efficiency of SD-1 and SD-2 depended on more extensive root systems,larger root surface area,stronger root activity and affinity for P nutrition.