Effect of low nitrogen stress on bleeding sap characters and root activity of maize cultivars with different low N tolerance

Objectives Insufficient nitrogen(N) supply impacts the growth and root activities of crops. Comparison of the bleeding characteristic responses of different low N tolerance maize cultivars will provide a theoretical basis for breeding of low N tolerant maize cultivars.

MethodsTwo low N tolerant cultivars (‘ZH311’ and ‘CD30’) and two low N sensitive cultivars (‘XY508’ and ‘SB2’) were used as tested materials, and a hydroponic experiment with four N supply levels of 0, 0.05, 0.5 and 5 mmol/L was conducted. The plant height, dry matter accumulation, and root activity were investigated at seedling stage of maize.

ResultsThe stem diameters, plant heights, leaf areas, SPAD values, dry biomass of seedlings were decreased with the decreased N supply levels. The bleeding sap intensity, transport speeds of free amino acid, nitrate N, soluble protein and soluble sugar were declined, and the concentrations of free amino acid, nitrate N in bleeding, and the total absorbing areas, actively absorbing areas and root activities were decreased in all the four tested cultivars. However, the decreased ranges of the above indices of the low N tolerant maize cultivars were much lower than those of the low N sensitive ones. With the increase of treating time, the concentrations of soluble protein and soluble sugar showed trends of increasing first and then decreasing. The increased ranges of the root-shoot ratios of the low N tolerant maize cultivars were much lower than those of low N sensitive cultivars, while the increased ranges of concentrations of soluble protein were much higher. The root activities, concentrations of soluble protein and soluble sugar of the low N tolerant maize cultivars were much higher than low N sensitive ones.

ConclusionsLow N tolerant cultivars can keep higher root activities, further promote absorptive capacity and transformation capacity of N. The low N tolerant cultivars can keep stronger carbon and N cycles to coordinate the nutrients and substances distribution of underground part and aboveground part and control the increase of the root-shoot ratio.