Effect of ammonium nitrogen/nitric nitrogen on Al toxicity in rice.

In acidic soils,nitrification is depressed and ammonium nitrogen(NH4+-N) is the predominant inorganic N form,so Al3+ and NH4+-N often coexist in the soils.Investigating the interaction of Al3+ and nitrogen forms is helpful not only for well understanding the Al3+ resistance mechanisms of rice,but also for establishing theoretical bases of fertilization in acidic soils.In this study,two rice cultivars Wuyunjing7(Al3+-tolerant) and Yangdao6(Al3+-sensitive) were selected as materials to investigate the effects of different N forms on the Al3+ toxicity in rice through long-term(14 d) and short-term(24 h) experiments under hydroponic conditions.The inhibitory effects of Al3+ on biomass and root types of the two rice cultivars were significantly stronger in long-term NO3——N/Al3+ intermittent treatment than those in long-term NH+4-N/Al3+ intermittent treatment,and the Al3+ concentration in root was higher in NO3——N treatment than that in NH4+-N supply.In short-term N-Al treatment,the suppression of Al3+ on root elongation in NO3——N/Al3+ treatment was more significant than that in NH4+-N/Al3+ treatment,and the Al3+ treatment content in root tip of rice in NO3——N/Al3+ treatment was improved.To maintain a charge balance on the root surface,the concentration of cations(K+,Ca2+,Mg2+,Mn2+) in roots inereased when NO3——N was taken up.These results indicated that compared with NO3——N,NH4+-N alleviated Al3+ toxicity to rice and reduced Al3+ accumulation in the roots.