不同铵硝配比营养液对典型生菜硝酸盐吸收动力学的影响

利用100%NO3--N、10%NH4+-N+90%NO3--N、10%NH4+-N+100%NO3--N营养液来研究生菜吸收NO3-的动力学特征。结果表明,生菜吸收NO3-的速率随着营养液中NO3-浓度的增加而增加,增加的幅度随着营养液中NO3-浓度的增加而减少。NH4+-N的存在对生菜吸收NO3-有明显抑制作用。与100%NO3--N处理相比,生菜在10%NH4+-N+90%NO3--N1、0%NH4+-N+100%NO3--N处理中吸收NO3-的速率和Vmax有明显下降,Km有少量增加,但差异不显著。申选1号在有NO3--N的营养液中吸收NO3-的速率均大于耐热耐抽苔生菜,且随着营养液中NO3-浓度的增加,两者的差距逐渐加大。在NH4+-N的存在情况下,耐热耐抽苔生菜Vmax下降的程度大于申选1号,而Km增加的程度小于申选1号。

Effects of NH4+-N/NO-3N ratios on kinetics of nitrate uptake by two typical lettuce genotypes in hydroponics

Dryland crops generally favor NO-3-N,but some NH 4-N is usually beneficial to them.To determine the characteristics of nitrate uptake,two cultivars of lettuce(Lactuca sativa L.),Sx1 and Nrnct,were hydroponically grown in nutrient solution,i.e.100% NO-3-N,10% NH 4 -N 90% NO-3-N,10% NH 4 -N 100% NO-3-N.The results indicated that NO-3 uptake rate by lettuce increased with NO-3 content,while the increase rate decreased.Compared with the treatment of 100% NO-3-N,the rates of NO-3 uptake by lettuce decreased significantly in the treatments of 10% NH 4-N 90% NO-3N and 10% NH 4-N 100% NO-3N.This indicated that NH 4-N in nutrient solution had significant effects on the rates of NO-3 uptake.The Vmax of NO-3 uptake kinetics in the treatment of 100% NO-3-N was significantly higher than that of the treatments of 10% NH 4N 90% NO-3-N and 10% NH 4N 100% NO-3-N.The Km of NO-3 uptake kinetics in the treatment of 100% NO-3-N was lower than that of the treatments of 10% NH 4-N 90% NO-3-N and 10% NH 4-N 100% NO-3-N,but the difference was not significant.NH 4-N inhibited NO-3 uptake,mainly due to the higher Vmax.Different cultivars differed in nitrate uptake characteristics.The NO-3 uptake rate of Sx1 was higher than that of Nrnct in solution,and the difference increased with NO-3 content.When there was NH 4-N in nutrient solution,Vmax of Nrnct decreased more than that of Sx1,and Km of Nrnct increased less than that of Sx1.