Dynamic Kinetic Characteristics of Different Ratios of Ammonium and Nitrate Absorbed by Banana Seedlings
Objective]Ammonium and nitrate and their interaction effect on N absorption by banana seedlings were studied to screen the optimum ratio of ammonium to nitrate for banana growth and efficient utilization of nitrogen.[Method] The NH4+-N, NO3--N and total nitrogen kinetics of N uptake by banana seedlings were studied by modified depletion method based on the principle of nutrient absorption kinetics in the solution culture with different ratios of ammonium to nitrate.[Result] Michaelis-Menten enzyme kinetic model or equation could be applied to describe the patterns of absorption of NH4+-N, NO3--N and total N by banana seedlings in all the treatments and the co-relationship coefficientr was at a significant level. When the rate of NH4+-N was at 10% and 70%, NH4+-N absorption rate increased with the NO3--N addition gradually. The maximum absorption rate (Vmax) of NH4+-N uptake reached the maximum of 55.56μmol·g-1·h-1, when the NH4+-N ratio increased to 70%. The NH4+-N absorption rate decreased again when the NH4+-N ratio was more than 70%. However, the rate of nitrate absorption of banana declined with the increase of NH4+-N. When the proportion of NH4+-N increased from 10% to 90%, the Vmax of NO3--N decreased by 2.62 times. Therefore, adding NH4+-N would significantly inhibit the banana seedlings to absorb NO3--N. There was no obvious effect of the ratio of ammonium to nitrate on affinity of banana root to NH4+-N and NO3--N. When ammonium to nitrate ratio was 3﹕7, the total nitrogen absorption rate was 83.33μmol·g-1·h-1, being the maximum rate and in favor of banana to take up nitrogen.[Conclusion] When the proportion of NH4+-N was lower than 70%, increase of NO3--N could enhance the banana seedlings to take up NH4+-N. When the ammonium ratio was more than 70%, increase of NO3--N would inhibit the banana seedlings to take up NH4+-N. Increasing ratio of NH4+-N could significantly inhibit the banana seedlings to absorb NO3--N. The optimum ratio of ammonium to nitrate being favor of nitrogen absorption was 3﹕7.
国家科技期刊平台
NSTL
万方数据
维普
