Uptake characteristics of NO_3~--N and NH_4~+-N by different plant seedlings under the low pH condition

Effects of low medium pH on uptake rate of ammonium nitrogen and nitrate nitrogen by seedlings of different varieties of rice,wheat and maize were studied through solution culture method.Results indicated that the effects of medi- um pH on inorganic nitrogen uptake varied with plant species,varieties,and seedling ages.Majority of plant varieties ab- sorbed nitrate faster at low pH(4.0)than at near neutral pH(6.0),while uptake of ammonium was slower at pH 4.0 than at pH 6.0.The uptake rate of nitrate by rice roots decreased with the seedling ages,while that of ammonium increased. Roots of wheat and maize seedlings had increasing uptake rates of both nitrate and ammonium with the growth ages.