[Objective]In order to clarify the interaction between NH4+ and K+ uptake in rice roots at the seedling stage, and to lay a solid basis for fertilizer application in rice production, [Method] we conducted an hydroponic experiment under different NH4+ and K+ concentrations,and analyzed NH4+ and K+ uptake rate of rice roots at the seedling stage.[Result] When K+ concentration was less than 0.2 mmol/L, the K+ uptake curve through high-affinity transport system (HATS) in rice root followed the Michaelich-Menten equation. NH4+ decreased K+ uptake rate, the Vmax of K kept decreasing with the increase of NH4+ concentration, however, the effect of NH4+ on Km was relatively little. Compared with zero NH4+ treatment, the Vmax and Km of K+ uptake at the 1.62 mmol/L NH4+ application level decreased by 47.30%and 12.33% in rice variety Qilisimiao(QL), and by 39.21% and16.46% in rice variety Huke 3(HK3), respectively. When K+ concentration was higher than 0.5 mmol/L, it was mainly absorbed through low-affinity transport system(LATS), in which the uptake rate of K+ was kept increasing with the increase of K+ concentration, and NH4+ greatly decreased the uptake rate of K+-LATS at the same concentration of K+. The uptake rate of NH4+ was increased with the increase of NH4+ concentration, however, no significant difference was observed in NH4+ uptake rate under different concentrations of K+. [Conclusion] NH4+ reduced K+ uptake both through HATS and LATS of K+; and the effects of NH4+ on K+-HATS uptake were mainly due to the competition of NH4+ for K+-carrier at the cell membrane; K+ had no influence on NH4+ absorption. The interactions between NH4+ and K absorption in rice root at the seedling stage were mainly because NH4+ reduced K+ uptake.%[目的]为探讨水稻幼苗根系NH4+、K+吸收的交互作用,深化水稻养分吸收理论,[方法]采用溶液培养的方法,对低钾及高钾浓度下水稻在有铵和无铵时的K+吸收动力学特征进行了研究,对不同钾浓度下水稻根系NH4+的吸收速率进行了比较.[结果]1)当K+<0.2 mmol/L时,水稻根系通过高亲和转运系统吸收K+服从Michaelich-Menten动力学方程;NH4+的存在显著降低K+的最大吸收速率(Vmax),且降幅随着NH4+浓度的增加而增大;NH4+对水稻根表载体与K+的亲和力(Km)影响较小,在1.62 mmol/L NH4+浓度下,水稻品种齐粒丝苗和沪科3号的Km分别下降了12.33%和16.46%,远低于Vmax 47.30%和39.21%的降幅.2)当K+>0.5 mmol/L时,水稻根系K+低亲和转运系统发挥作用,K+吸收速率随浓度的增加而不断增加,呈不饱和特征;但在相同K+浓度下,水稻根系的K+吸收速率随NH4+浓度的增加而下降.3)水稻根系对NH4+的吸收速率随着NH4+浓度的增加而增加;在相同NH4+浓度下,水稻根系对NH4+的吸收速率受K+浓度的影响很小.[结论]NH4+抑制水稻苗期根系K+的高亲和转运和低亲和转运,NH4+对K+高亲和吸收的影响主要是由于铵竞争细胞膜上的钾载体所致;外界K+浓度的变化对水稻幼苗的NH4+吸收速率影响很小.水稻铵钾的交互作用主要表现在NH4+对K+吸收的抑制作用.
展开▼
