水曲柳幼苗根系吸收不同形态氮的动力学特征

Kinetic Characteristics of Different Forms of Absorbing Nitrogen in Root System of Fraxinus mandshurica Rupr. Seedling

采用常规耗竭法研究水曲柳幼苗根系吸收不同形态氮素特征的结果表明:二年生水曲柳幼苗根系对NO3-和NH4+离子的亲和力比一年生幼苗要小许多,二年生幼苗对氮素的吸收优势比较明显;苗木根系吸收NH4+离子的最大吸收速率(Imax)均大于对NO3-的吸收,而米氏常数(Km)则相反;在低浓度范围内随着NO3-浓度的增加,根系吸收NO3-的速率增大并趋稳定;NH4+的存在明显抑制根系对NO3-吸收,其对一年生幼苗的影响大于二年生幼苗。

The method of conventional exhaustion was carried out to study the kinetic characteristics of nitrogen absorption in root system of Fraxinus mandschurica seedling. The results indicated that appetency of NO3- and NH4＋ in biennial seedling were less than those of annual seedling, in addition biennial seedling were more adept at nitrogen absorption. The maximum absorption rate （Imax） of NH4＋ were larger than that of NO3-, and Michaelis constant （Km） were opposite. Within low concentration, absorption rate of root systems increased firstly, and then tended to steady. Root system NO3 absorption were obviously restrained by NH4＋, and which influeced annual seedling more than biennial seedling.