不同钾水平下外源铵对烟草幼苗根系生长及钾吸收的影响

Effects of exogenous ammonium on root growth and potassium uptake of tobacco under different potassium concentrations

为探明铵参与低钾胁迫下烟株根系的生长及吸钾机制,采用室内水培法,以“豫烟6号”为试验材料,研究了不同供钾水平下外源NH4+对烟株根系的生长生理和钾吸收速率的影响。结果表明,未添加外源NH4+时,低钾胁迫下烟株根系可溶性蛋白、根系活力、烟株各部位干重和钾含量均显著低于常钾水平。两种供钾水平下,随着外源NH4+浓度增加,烟株根系干重、根系扫描参数、钾积累量和钾最大吸收速率均呈下降趋势,但根系可溶性蛋白含量和根系活力则先上升后下降并在外源NH4+浓度为1 mmol/L时最大。外源NH4+可抑制植物根系高亲和及低亲和K+吸收系统,且NH4+浓度越大,钾吸收速率越低,其中溶液K+浓度为0.2和10 mmol/L时,N5.00较N0处理分别显著降低55.78%和37.68%。可见,低钾胁迫显著抑制烟株根系生长和钾吸收,而外源NH4+可抑制高亲和或低亲和的K+吸收系统,从而影响烟株的钾吸收速率和吸收量。

In order to reveal the mechanism of ammonium involvement in root growth and potassium uptake of tobacco plants under low potassium level,tobacco cultivar YUYAN6 was used as experimental material by indoor hydroponic method to study the growth,physiology and potassium absorption rate in tobacco roots under different potassium levels when external NH4+was supplied.The results showed that without exogenous NH4+under low potassium stress,dry matter accumulation and potassium concentration of shoot and root,together with activity of root and the soluble protein in tobacco plants were significantly lower than those of normal potassium level.The root dry weight,root scanning parameters,potassium accumulation and maximum potassium absorption in tobacco plant decreased with the increase of exogenous NH4+concentration,while the soluble protein content and activity of root firstly increased,followed by decreased,and reached the peak when the concentration of exogenous NH4+was 1 mmol/L.High affinity and low affinity K+absorption system of tobacco roots could be significantly inhibited by exogenous NH4+,and potassium absorption rate decreased with the increase of NH4+concentration.When K+concentration of solution was 0.2 and 10 mmol/L,the potassium absorption rate of N5.00 treatment decreased by 55.78%and 37.68%,compared with N0 treatment,respectively.Accordingly,low potassium stress significantly inhibited root growth and potassium absorption of tobacco plants,while exogenous NH4+could affect potassium absorption rate and amount of tobacco plants by inhibiting K+absorption system with high affinity or low affinity.